MATTER AND CONSCIOUSNESS third edition
p a u | |v|_ c h u r c h la n d
M atter and Consciousness
MATTER AND CONSCIOUSNESS
third edition
Paul M . Churchland
A Bradford Book The MIT Press Cam bridge, Massachusetts London, England
© 1984, 1988, 2013 Massachusetts Institute o f Technology First edition published 1984 by the MIT Press All rights reserved. No part o f this book m ay be reproduced in any form by any electronic or m echanical means (including photocopying, recording, or inform ation storage and retrieval) w ithout perm ission in writing from the publisher. MIT Press books may be purchased at special quantity discounts for business or sales prom otional use. For inform ation, please email special_
[email protected] or write to Special Sales Department, The MIT Press, 55 Hayward Street, Cambridge, MA 02142. This book was set in Stone Sans and Stone Serif by Toppan Best-set Premedia Limited, Hong Kong. Printed and bound in the United States o f America. Library o f Congress Cataloging-in-Publication Data Churchland, Paul M., 1 9 4 2 M atter and consciousness / Paul M. Churchland.—Third edition. pages
cm
"A Bradford book." Includes bibliographical references and index. ISBN 978-0-262-51958-8 (pbk. : alk. paper) 1. Philosophy o f mind. 2. Intellect. 3. Consciousness. 4. Cognition. 5. Artificial intelligence. 6. Neurology. I . Title. B F431.C 47
2013
128'.2— dc23 2012049084 10
9
8
7
6
5
4
3
2
1
Contents
Preface to the 2013 Edition
vii
Preface to the 1988 Edition
ix
Preface to the 1984 Edition
xi
1
W h at Is This Book About?
1
2
The Ontological Problem (the M ind-B ody Problem) 1
3
11
11
2
Philosophical Behaviorism
3
Reductive Materialism (the Id e n tity Theory)
4
Functionalism
5
Eliminative Materialism
36 40
63
The Semantical Problem 1
4
Dualism
73 87
D efinition by Inner Ostension
87
2
Philosophical Behaviorism
3
The Theoretical N etw ork Thesis and Folk Psychology
4
Intentionality and the Propositional Attitudes
The Epistemological Problem
91
111
1
The Problem of O ther Minds
2
The Problem of Self-Consciousness
111 119
103
93
Contents
5
6
7
The M ethodological Problem Idealism and Phenomenology
2
M ethodological Behaviorism
3
The C ognitive/C om putational Approach
4
M ethodological Materialism
Artificial Intelligence
135 142 147
153
157
1
Computers: Some Elementary Concepts
2
Program ming Intelligence: The Piecemeal Approach
Neuroscience
160
191
1
Neuroanatom y: The Evolutionary Background
2
Neurophysiology and Neural Organization
3
Neuropsychology
191 201
221
4
C ognitive N eurobiology
5
AI Again: C om puter Models of Parallel Distributed
Processing 8
135
1
226
241
Expanding Our Perspective
261
1
The D istribution of Intelligence in the Universe
2
The Expansion of Introspective Consciousness
Index
283
261 278
167
Preface to the 2013 Edition
Since the original edition of this text appeared, the several sci ences that bear on the philosophical issues surrounding the mind have continued to make gratifying progress, as was only to be expected. In addition, the philosophical literature has becom e enriched by a number of arresting thought experiments that try to move the debate forward—but, perhaps surprisingly, aw ay from materialism, in one direction or another. For example, the inaccessibly alien subjective experience of Thomas Nagel 's bat, the residual phenom enal ignorance of Frank Jackson 's scientifi cally om niscient neuroscientist Mary, the missing inner life of David Chalmers's otherwise hum anlike zom bies, and the absence of any real semantic content in the inner states of Joh n Searle' s Chinese-speaking room have all becom e icons of philosophical resistance. They have all raised new doubts (or old doubts in a new form) about the prospects of comprehensive explanatory success for the research programs of com putational artificial intelligence and cognitive neurobiology—that is, for the prospects of a purely physicalist account of all m ental phenom ena. Even so, the com putational and cognitive sciences continue to make relentless and illum inating progress in accounting for diverse cognitive phe nom ena, as this new edition will also try to highlight.
viii
Preface to the 2013 Edition
In sum, the intellectual situation is now even more engaging and taut with controversy than it was thirty years ago, when the issues compelled me to write the first edition of this text. My hope is that this new and relevantly augmented edition will allow both teachers and students to delve yet a few layers more deeply into the philosophical and scientific issues that shape our current understanding of the M ind and its place in Nature. I com m end their evaluation to your own native intelligence, whatever its ultimate nature—physical or nonphysical.
Preface to the 1988 Edition
I have been much gratified by the kind reception given the first edition of this small book, especially where it concerned the sec tions on neuroscience, cognitive science, and artificial intelli gence. As it happens, these sections are the focus of most of the changes and additions in the revised edition. The motive for change is the dramatic progress that continues to be made in these disciplines and their expanding relevance to issues in the philosophy of mind. These research results bear directly on ques tions such as: what are the basic elements of cognitive activity? How are they im plemented in real physical systems? And how is it that living creatures perform some cognitive tasks so swiftly and easily, where computers do them only badly or n ot at all? A central conviction of the first edition was that issues in the philosophy of mind are n ot independent of the theoretical and experimental results of the natural sciences. That view has not changed. But developments in the sciences have. This new edition attempts to make some of the more striking of these results accessible and intelligible to a wider audience. Their philosophical significance, as I see it, lies in the support they tend to give to the reductive and the eliminative versions of materialism. But my opinion is only one of m any alternatives. I invite you to make your own judgment.
Preface to the 1984 Edition
Philosophers usually write their books for other philosophers, and express parenthetical hopes that the book will prove useful to students and lay readers as well. Such hopes are usually vain. In hopeful contrast, I have written this book primarily and explic itly for people who are n ot professionals in philosophy, or in artificial intelligence, or in the neurosciences. It is the im agina tion of the general reader, and of the student, that I am here aiming to capture. I do indeed have subsidiary hopes that this compact volume will prove useful, as a comprehensive summary and source book, to my professional colleagues and to advanced graduate students. But I did n ot write this book for them . I have written it for newcomers to the philosophy of mind. This book was first conceived during a recent undergraduate course in the philosophy of mind, taught with the aid of familiar and long-standard texts. Since so m uch has happened in this field in the last fifteen years, those standard texts and anthologies are now badly dated. And while some good anthologies of very recent work are now available, they are too advanced and too expensive to be used easily with undergraduates. At the end of that course, I resolved to write a more suitable and more accessible text, free of fossilized issues, swift with historical summary, and bristling with the new developments. This volume is the result.
xii
Preface to the 1984 Edition
It was written during the summer of 1982, mostly at our cottage retreat on Moose Lake in the M anitoba wilderness, where the unearthly loons voiced nightly amusement at my labors. And it was completed in mid-autumn at the Institute for Advanced Study in Princeton, whose resident flock of Canada geese gave similar commentary. I have occasionally profited, however, from more substantial inspiration and instruction. I must thank first m y friend and col league, Larry Jordan, for taking me into his neurophysiology lab during 1981/82, for making me a part of his m arathon Wednes day Experiments, and for being the agent of so m uch entertain m ent and priceless instruction. I must thank fellow philosophers Daniel D ennett and Stephen Stich for arranging m y participation in a number of professional gatherings both in the United States and in England, and for all that they have taught me during our m any pleasant and useful encounters. I am in debt to my friend and colleague M ichael Stack, for what is now a decade of fruitful discussion concerning the m ind and its place in nature. And I must thank above all my wife and professional colleague Patricia Smith Churchland, who has taught me more about the m ind/ brain than any philosopher living. Finally, my thanks to Ken Warmbrod, Ned Block, Bob Rich ardson, Amélie Rorty, Cliff Hooker, and David Woodruff Smith for their various encouragements, and for their valuable criti cisms of the initial draft. And I am forever indebted to the Institute for Advanced Study for the facilities with w hich to complete this work, and for the opportunity to launch several other more theoretical pursuits. Paul M. Churchland Princeton, NJ, 1983
1
W hat Is This Book About?
The curiosity of Man, and the cunning of his Reason, have revealed much of what Nature held hidden. The structure of spacetime, the constitution of matter, the m any forms of energy, the nature of life itself; all of these mysteries have becom e open books to us. To be sure, deep questions remain unanswered and revolutions await us still, but it is difficult to exaggerate the explosion in scientific understanding we hum ans have fash ioned over the past 500 years. Despite this general advance, a central mystery remains largely a mystery: the nature of conscious intelligence. That is what this book is about. If conscious intelligence were still totally mysterious, there would be no useful book for me to write. But encouraging prog ress has indeed been made. The phenom ena to be penetrated are now the com m on focus of a variety of related fields. Philosophy has been joined by psychology, artificial intelligence, neurosci ence, ethology, and evolutionary theory, to nam e the principals. All of these sciences have made contributions to what used to be a purely philosophical debate, and all of them promise much more to come.
2
Chapter 1
This book is an introduction to the m ain elements of the current philosophical/scientific debate—to the m ajor issues, to the competing theories, to the most im portant arguments and evidence. In the last thirty years, philosophy itself has made significant progress on the nature of mind: m ainly by unravel ing the nature of the mind's self-knowledge, but also by provid ing a clearer conception of the possible alternative theories of m ind between which we must finally choose, and by clarifying what sorts of evidence are needed if we are to make a reasoned choice between them. More im portant still, the empirical sciences m entioned have provided a steady flow of evidence relevant to the making of such a rational choice. Psychology has taught us some surprising things about the penetration and reliability of our introspective knowledge. (This is an im portant matter, since some theories of m ind rely heavily on what self-conscious introspection is sup posed to reveal.) The fields of cognitive psychology and artificial intelligence have produced provocative models of cognition, which, when 'brought to life' within a suitably programmed computer, m im ic closely some of the complex activities of goaldriven intelligence. The neurosciences have begun to unravel the vast microsystem of interconnected brain cells or neurons that, in living creatures, appears to execute those activities. Ethology has given us new insights into the continuities, and discontinuities, relating hum an intelligence with the intelligence of other crea tures. And evolutionary theory has revealed the long and intricate selective processes from which conscious intelligence has slowly emerged. The evidence is still ambiguous, however, and a choice among the relevant theories has not yet been made, so the reader of this book will have the pleasure and excitem ent of joining an intellectual adventure that is still very much in progress.
W h a t Is This Book About?
3
The discussion here opens with the m ost obvious of the ques tions in this area. W hat is the real nature of m ental states and processes? In what medium do they take place, and how are they related to the physical world? W ith regard to the mind, these questions address what philosophers call the ontological problem . (In philosophical language, an 'ontological question' is just a question about what things really exist, and about what their essential nature is.) This problem is more widely known as the m in d-bodyproblem , and very probably you are already fam il iar with the m ost basic division in views here. On the one hand, there are m aterialist theories of mind, theories w hich claim that what we call m ental states and processes are merely sophisti cated states and processes of a com plex physical system: the brain. On the other hand, there are dualist theories of mind, theories which claim that m ental states and processes are not merely states and processes of a purely physical system, but constitute a distinct kind of phenom enon that is essentially nonphysical in nature. Many of us bring strong convictions to an issue such as this, and m any will think that the choice between these alternatives is easy or obvious, but it is wise to keep an open m ind here, whatever your convictions, at least until you have explored the lay of the land. There are at least five radically different versions of dualism, for example, and a comparable number of materialist theories, all very different from one another as well. There are not two theories here from w hich we must choose, but more like ten! And some of them have been formulated only recently. The purpose of chapter 2 is to lay out all of these theories, one by one, and try to evaluate the strengths and weaknesses of each. Any decision made on the strength of chapter 2 alone will be premature, however, since there are a number of other
4
Chapter 1
compelling problems with which the m ind-body problem is thoroughly intertwined. One of these is the sem antical p roblem . Where or how do our ordinary com m on-sense terms for m ental states get their m ean ings? W hat would count as an adequate definition or analysis of those very special concepts that we apply to ourselves and to other creatures with conscious intelligence? One suggestion— perhaps the m ost plausible one initially—is that one learns the m eaning of a term like "pain" or "sensation of w arm th" simply by attaching the relevant term to the relevant kind of mental state, as it is experienced in one' s own case. But this view leads to a number of problems, one of w hich may already have occurred to you at some point or other. How can you be sure that the inner sensation, to w hich your friend (say) has attached the term "pain," is qualitatively the same as the inner sensation to w hich you have attached the term? Perhaps your friend's inner state is radically different from yours, qualitatively, despite its being hooked up to behav ior, speech, and causal circumstances in the very same ways it is hooked up in you. Your friend would thus behave in all respects as you do, despite the hidden internal difference. The problem is that this skeptical worry, once raised, seems im pos sible to settle, because it appears entirely impossible that anyone should ever have direct experience of someone else's mental states, and nothing less than such experience would settle the issue. If this is so, then it appears that none of us knows, or can know, what meanings the m any terms for m ental states have for other people, if indeed they have any m eaning at all. One can know only what m eaning they have for oneself. This is a
W h a t Is This Book About?
5
very odd conclusion to reach about a m ajor segment of our language. The purpose of language, after all, is public com m u nication within a shared network of understanding. A competing theory of m eaning suggests a different source for the meanings of our ordinary psychological vocabulary. To learn the m eaning of the term "pain," it is claimed, is to learn that pain is a state that is often caused by bodily damage, a state that in turn causes other inner states such as mild unhappiness or outright panic, a state that causes characteristic sorts of behavior such as wincing, nursing, and moaning. In short, the essential feature of pain is said to be a network o f causal relations that connects any pain to a variety of other things, especially to publicly observable things. Materialists of all persuasions tend to prefer this latter approach to meaning, partly because it leaves wide open the possibility that m ental states are really physical states. There is no problem in supposing a purely physical state to have the appropriate kinds of causal connections essential to being a pain. And this approach does n ot land us swiftly in skepticism. On the other hand, it does seem to give short shrift to the inner, introspectible aspect of our m ental states, the aspect on which the first approach to m eaning was centered. Dualists, under standably, have tended to prefer that first approach to meaning, despite its apparently skeptical consequences. The introspectible or 'subjectively evident' qualities of our m ental states represent for them some of the very essence of mentality, an essence that is thought to be beyond merely physical explanation. You can appreciate already that no solution to the m in d body problem will rest easy without a simultaneous solution to the semantical problem. Chapter 3 will exam ine the major
6
Chapter 1
alternative solutions in detail, of w hich again there are several. One of them will require a thum bnail sketch of some elem en tary concepts in contemporary philosophy of science, so you may look forward to some novel and unexpected theoretical suggestions. These issues lead naturally enough to the epistemological problem . (Epistemology is the study of what knowledge is, and where it comes from.) This problem has two parts to it, both very perplexing. The first arises swiftly from a worry already discussed: on what grounds has one the right to assume that other humans, for example, enjoy the same family of mental states as oneself, or indeed, that they enjoy any m ental states a t all? Granted, the assumption that they do is one of the deepest assumptions one makes. But what exactly are the ratio nal grounds for that assumption? To justify that assumption, what one needs to know is that the behavior of others is causally connected, in the same ways, to inner states of the same kind as those to w hich one' s own behavior is connected. One needs to know, for example, that what is caused by a hammer blow and what causes a loud "ouch!" is the sam e in others as in oneself. But that would again seem to require the impossible: the direct subjective experience of someone else's m ental states. This is called the problem o f other minds, and it is n ot merely a skeptical conundrum about our fellow humans. The problem begins to look less frivolous or academic when one starts to ask seriously after the mental lives of the great apes, or domestic dogs, or dolphins. Do they have genuine consciousness? And the current explosion in computer technology promises a new location for the problem. How can we distinguish a truly con scious intelligence from a com plex physical system built to resemble a thinking being in all of its behavior, verbal and
W h a t Is This Book About?
7
em otional behavior included? Would there b e a difference? How could we tell? In sharp contrast to the opacity of the mental life of people other than oneself is the transparency of one' s own m ental life. Each of us is self-conscious. W hat is the nature of that curious access you have to the contents of your own mind, but to no other? How is it you are able to tell, without looking at your behavior, what you feel, think, and desire? We take it for granted, this capacity for introspection, but it is a m ost extraordinary and enigmatic talent to have. A great deal has been claimed for it by various thinkers: infallibility, by some; the feature that dis tinguishes m ind from matter, by others. And it does present a daunting challenge to any materialist who aspires to explain it. Here, some findings in psychology will prove relevant. W hat a successful account of introspection requires, and whether a materialist approach can ever provide such an account, will be addressed in chapter 4. As I hope it will be clear by the time you have half of this book behind you, the nature of m ind is not a purely philosophical question, but a deeply scientific question as well. To say this is n ot to beg any questions as to which of the alternative theories will ultimately be vindicated. But I do mean to assert that empiri cal research will weigh heavily, or even decisively, in determining the outcome. W hich raises the question: what is the proper approach or m ethodology to pursue in constructing a 'science of the m ind'? Here again there are differences. Should a science of conscious intelligence actively seek continuity with the network of established natural sciences (physics, chemistry, biology, and so on)? Or should it claim a discontinuous autonom y on grounds of some unique feature? (Even some materialists— the function alists—have answered yes to this latter question.) W hat sorts of
8
Chapter 1
data should it admit as legitimate? Introspection? Physical behav ior? Neurophysiology? These issues make up the m ethodological problem , and they are pointed toward the future. The shape of future theories hangs on these issues. Chapter 5 is devoted to their exploration. An introductory text m ight well draw to a close after that discussion, but I have included here three additional chapters. As this book is written, the great m ajority of professional phi losophers and scientists in this area are clustered around only two or three of the alternative possible solutions to the m in d body problem, and their tentative com m itm ents on that score find expression in two especially active research programs con cerning cognitive phenom ena. The first is the fairly recently formed field of artificial intelligence, or A I for short. To what extent (we may ask) is it possible to simulate or recreate the essential features of conscious intelligence with suitably pro grammed computers? A preliminary answer is, "To a very impressive extent," although AI researchers will be the first to admit that several basic problems remain stubbornly unsolved. The second research program is the fast-growing field of the several neurosciences, those sciences concerned with empirical study of the brain and nervous system. W hat light (we may ask) is thrown by neurophysiology, neurochemistry, comparative neuroanatomy, and com putational neurobiology on such matters as m ental illness, learning, three-dimensional (stereo) vision, and the mental life of dolphins? The answer is, "Considerable light," although neuroscientists will be the first to admit that they have only scratched the surface. I have included these chapters to provide at least an instructive sampling of the research currently under way in these fields. They are certainly not adequate to introduce an
W h a t Is This Book About?
9
aspiring computer scientist or neuroscientist to these fields. But they will provide some real understanding of how empirical research bears on the philosophical issues discussed in this text. (That is im portant because, as I hope to make clear, m ost of these philosophical issues are ultimately empirical in character. They will be decided by the comparative success and the relative progress displayed by alternative scientific research programs.) These chapters will also provide a lasting conceptual framework from w hich to address future developments concerning the mind. And they may whet your appetite for more empirical and theoretical inform ation. If they do only that, they will have served their purpose. The concluding chapter is overtly speculative, as befits a concluding chapter, and it opens with an attem pt to estimate the distribution of conscious intelligence in the universe at large. Intelligence appears likely to be a fairly widespread phe nom enon in the universe, and all advanced instances of it will inevitably face the problem of constructing a useful conception of just what intelligence ss. That process of self-discovery, to judge from our own case, need not be an easy one. Neither will it be completed in a short period, if indeed it can ever be truly com pleted. But progress is still possible, here, as elsewhere in the hum an endeavor; and we must be prepared to contemplate revolutions in our conception of what we are, just as we have successfully navigated repeated revolutions in our conception of the universe that we call home. The final section scouts the consequences of such a conceptual revolution for the contents of hum an self-consciousness in particular. This concludes my set of promissory notes. Let us now turn to the issues themselves.
2
The Ontological Problem (the Mind-Body
Problem)
W hat is the real nature of mental states and processes? In what medium do they take place, and how are they related to the physical world? Will my consciousness survive the disintegration of my physical body? Or will it disappear forever as m y brain ceases to function? Is it possible that a purely physical system such as a computer could be constructed so as to enjoy real con scious intelligence? Where do minds come from? W hat are they? These are some of the questions we shall confront in this chapter. W hich answer we should give to them depends on which theory of m ind proves to be the m ost reasonable theory on the evidence, to have the greatest explanatory power, pre dictive power, coherence, and simplicity. Let us exam ine the available theories, and the considerations that weigh for and against each. 1
Dualism
The dualistic approach to mind encompasses several quite dif ferent theories, but they are all agreed that the essential nature of conscious intelligence resides in som ething nonphysical, in
12
Chapter 2
som ething forever beyond the scope of sciences like physics, neurophysiology, and computer science. Dualism is n ot the m ost widely held view in the current philosophical and scien tific community, but it is the m ost com m on theory of m ind in the public at large, it is deeply entrenched in most of the world's popular religions, and it has been the dom inant theory of mind for m ost of Western history. It is thus an appropriate place to begin our discussion. Substance Dualism
The distinguishing claim of this view is that each m ind is a distinct nonphysical thing, an individual 'package' of nonphysi cal substance, whose identity is independent of any physical body to w hich it may be temporarily ' attached'. M ental states and activities derive their special character, on this view, from their being states and activities of this unique, nonphysical kind of substance. This leaves us wanting to ask for som ething more in the way of a positive characterization of this proposed mind-stuff. It is a frequent com plaint with the substance dualist' s approach that his characterization of it is so far almost entirely negative. We are told what it isn't, but not what it is. This need n ot be a fatal flaw, however, since we no doubt have much to learn about the underlying nature of mind, and perhaps the deficit here can eventually be made good. On this score, the philosopher René Descartes (1596-1650) has done as m uch as anyone to provide a positive account of the nature of the proposed mind-stuff, and his views are worthy of examination. Descartes theorized that reality divides into two basic kinds of substance. The first is ordinary physical matter, and the essen tial feature of this kind of substance was said to be that it is
The Ontological Problem
13
extended in space: any instance of it has length, breadth, and height, and occupies a determinate position in space. He dubbed it res extensa (extended substance). Descartes did not attempt to play down the im portance of this kind of matter. On the contrary, he was one of the most imaginative physicists of his time, and he was an enthusiastic advocate of what was then called "the m echanical philosophy." But there was one isolated corner of reality he thought could not be accounted for in terms of the m echanics of matter: the conscious reason of humankind. This was his motive for propos ing a second and radically different kind of substance, a sub stance that has no spatial extension or spatial position whatever, a substance whose essential feature is the activity of thinking. He dubbed this second kind of matter res cogitans (thinking sub stance). This view is known as Cartesian dualism. As Descartes saw it, the real you is not your material body, but rather a nonspatial thinking substance, an individual unit of mind-stuff quite distinct from your material body. This n o n physical m ind is in systematic causal interaction with your body, to be sure. The physical state of your body's sense organs, for example, causes visual/auditory/tactile experiences in your mind. And the desires and decisions of your nonphysical mind cause your body to behave in purposeful ways. Its two-way causal connections to your m ind are what make your particular body yours, and not someone else' s. The main reasons offered in support of this view were straightforward enough. First, Descartes thought that he could determine, by direct introspection alone, that he was essentially a thinking substance and nothing else. And second, he could n ot imagine how a purely physical system could ever use language in a relevant way, or engage in m athem atical reasoning, as
14
Chapter 2
any normal hum an can. W hether these are good reasons, we shall discuss presently. Let us first notice a difficulty that even Descartes regarded as a problem. If 'mind-stuff' is so utterly different from 'matter-stuff' in its nature—different to the point that it has no mass whatever, no shape whatever, and no position anywhere in space— then how is it possible for my m ind to have any causal influence on my body at all? As Descartes him self was aware (he was one of the first to formulate the law of the conservation of m om entum in any physical system), ordinary matter in space behaves according to rigid laws, and one cannot get bodily movem ent (= m om en tum) from nothing. How, then, is his utterly insubstantial 'think ing substance' to have any causal influence on ponderous matter? How can two such different things be in any sort of causal contact? Descartes proposed a very subtle m aterial substance— which he called "anim al spirits"—to convey the mind's influence to the brain and to the body in general. But this does n ot provide us with a solution, since it leaves us with the same problem with which we started: how som ething ponderous and spatial (even 'animal spirits ' ) can causally interact with som ething entirely nonspatial—Descartes' supposed res cogitans. In any case, the basic principle of division used by Descartes is no longer as plausible as it was in his day. It is now neither useful nor accurate to characterize ordinary matter as thatw hich-has-extension-in-space. Electrons, for example, are bits of matter, but our best current theories describe the electron as a point-particle with no extension whatever. And according to quantum theory, it even lacks a determinate position. Moreover, according to Einstein's theory of gravity, an entire star can achieve this same status if a complete gravitational collapse reduces it to a singularity. If there truly is a division between
The Ontological Problem
15
mind and body, it appears that Descartes failed to put his finger on the dividing line. Such difficulties with Cartesian dualism provide a motive for considering a less radical form of substance dualism, and that is what we find in a view I shall call popular dualism . This is the theory that a person is literally a 'ghost in a m achine' , where the m achine is the hum an body, and the ghost is a spiritual substance, quite unlike physical matter in its internal constitu tion, but fully possessed of spatial properties even so. In particu lar, minds are com m only held to be inside the bodies they control: inside the head, on m ost views, in intim ate contact with the brain. This view need not have the difficulties of Descartes ' . The m ind is right there in spatial contact with the brain, and their causal interaction can perhaps be understood in terms of their exchanging energy of a form that our science has n ot yet rec ognized or understood. Ordinary matter, you will recall, is just a form or m anifestation of energy. (You may think of a grain of sand as a great deal of energy condensed or frozen into a small package, according to Einstein's famous equation, E = mc2.) Perhaps mind-stuff is a well-behaved form or m anifestation of energy also, but a different form of it. It is thus possible that a dualism of this alternative sort be consistent with the familiar laws concerning the conservation of m om entum and energy. This is fortunate for dualism, since those laws are very well established indeed. This view will appeal to m any for the further reason that it at least holds out the possibility (though it certainly does not guarantee) that the m ind m ight survive the death of the body. It does n ot guarantee the m ind' s survival because it remains possible that the peculiar form of energy here supposed to
16
Chapter 2
constitute a m ind can be produced and sustained only in con junction with the highly intricate form of matter we call the brain, and must disintegrate when the brain disintegrates. So the prospects for surviving bodily death are quite unclear even on the assumption that popular dualism is true. But even if survival were a clear consequence of the theory, there is a pitfall to be avoided here. Its promise of survival m ight be a reason for wishing dualism to be true, but it does n ot constitute a reason for believing that it is true. Regrettably, and despite the exploit ative blatherings of the supermarket tabloids (TOP DOCS PROVE LIFE AFTER DEATH!!!), we possess no such evidence. As we shall see later in this section, when we turn to evalu ation, positive evidence for the existence of this novel, nonm a terial, thinking substance is in general on the slim side. This has moved m any dualists to articulate still less extreme forms of dualism, in hopes of narrowing further the gap between theory and available evidence. Property Dualism
The basic idea of the theories under this heading is that, while there is no substance to be dealt with here beyond the physical brain, the brain has a special set of properties possessed by no other kind of physical object. It is these special properties that are nonphysical: hence the term property dualism. The properties in question are the ones you would expect: the property of being in pain, of having a sensation of red, of thinking that P, of desiring that Q, and so forth. These are the properties that are characteristic of conscious intelligence. They are held to be nonphysical in the sense that they can never be reduced to or explained solely in terms of the concepts of the familiar physical sciences. They will require a w holly new and autonomous sci
The Ontological Problem
17
ence—the ' science of m ental phenom ena' —if they are ever to be adequately understood. From here, im portant differences among the several positions emerge. Let us begin with what is perhaps the oldest version of property dualism: epiphenom enalism . This term is rather a m outhful, but its m eaning is simple. The Greek prefix "epi-" means "above," and the position at issue holds that mental properties are not a part of the physical phenom ena in the brain that ultim ately determine our physical behavior, but rather ride 'above the fray' of such physical activity. M ental properties are thus epiphenom ena. They are held to just appear or emerge when the growing brain passes a certain level of complexity. But there is more. The epiphenom enalist holds that while m ental phenom ena are caused to occur by the various activities w ithin the brain, they do not have any causal effects in turn. They are entirely im potent with respect to causal effects on the physi cal world. They are mere epiphenomena. (To fix our ideas, a vague metaphor may be helpful here. Think of our conscious m ental states as little sparkles of shim mering light that dance over the wrinkled surface of the brain, but w hich have no causal effects on the brain in return.) This means that the universal conviction that one' s actions are determined by one' s desires, decisions, and volitions is false! Rather, one's actions are exhaus tively determined by physical events within the brain, w hich events also cause the epiphenom ena we call desires, decisions, and volitions. There is therefore a constant conjunction between volitions and physical actions. But according to the epiphenomenalist, it is mere illusion that the former cause the latter. W hat could motivate such a strange view? In fact, it is not too difficult to understand why someone m ight take it seriously. Put yourself in the shoes of a neuroscientist who is concerned
18
Chapter 2
to trace the origins of behavior back up the m otor nerves to the active cells in the motor cortex of the cerebrum, and to trace in turn their activity into inputs from other parts of the brain, and from the various sensory nerves. She finds a thoroughly physical system of awesome structure and delicacy, and much intricate activity, all of it unambiguously chem ical or electrical in nature, and she finds no hin t at all of any nonphysical inputs of the kind that substance dualism proposes. W hat is she to think? From the standpoint of her researches, hum an behavior is exhaustively a function of the activities of the physical brain. And this opinion is further supported by her confidence that the brain has precisely the behavior-controlling features it does exactly because those features have been ruthlessly selected for during the brain's long evolutionary history. In sum, the seat of hum an behavior appears entirely physical in its constitution, in its origins, and in its actual internal activities. On the other hand, our neuroscientist has the testim ony of her own introspection to account for as well. She can hardly deny that she has experiences, beliefs, and desires, nor that they are connected in som e way with her behavior. One bargain that can be struck here is to admit to the reality of mental properties, as nonphysical properties, but demote them to the status of causally im potent epiphenom ena that have nothing to do with the causal or scientific explanation of hum an and animal behav ior. This is the position the epiphenom enalist takes, and you can now appreciate the rationale behind it. It is a bargain struck between the desire to respect a rigorously scientific approach to the explanation of behavior, and the desire to respect, non eth e less, the testim ony of one' s own introspection. The epiphenom enalist' s 'dem otion' of m ental properties—to causally im potent by-products of physical brain activity—has
The Ontological Problem
19
seemed too extreme for most property dualists, and a theory closer to the convictions of com m on sense has enjoyed some what greater popularity. This view, which we may call interactionist property dualism , differs from the previous view in only one essential respect: the interactionist asserts that m ental states do indeed have causal effects on the brain, and thereby, on behavior. The m ental properties of the brain are an integrated part of the overall causal fray, in systematic interaction with the brain' s physical states and properties. One' s actions, therefore, are held to be caused by one 's desires and volitions after all. As before, m ental properties are here said to be emergent properties, properties that do not appear at all until ordinary physical matter has managed to organize itself, through the evolutionary process, into a system of sufficient complexity. Examples of properties that are emergent in this sense would be the property of being solid, the property of being colored, and the property of being alive. All of these require atomic and molecular matter to be suitably organized before they can be displayed. W ith this much, any materialist will agree. But any property dualist makes the further claim that mental states and properties are irreducible, in the sense that they are n ot just organizational features of physical matter, as are the three exam ples cited. M ental states, by contrast, are held to be novel properties beyond prediction or explanation by the physical sciences. This last condition—the irreducibility of m ental properties— is an im portant one, since this is what makes the position a dualist position. But it sits poorly with the join t claim that m ental properties emerge from nothing more than the organi zational achievements of physical matter. If that is how mental properties are produced, then one would expect a physical
20
Chapter 2
account of them to be possible, even inevitable. The sim ultane ous claim of evolutionary emergence and irreducibility is prima facie puzzling, if not self-contradictory. A property dualist is not absolutely bound to insist on both claims. He could let go of the thesis of evolutionary emergence, and claim that m ental properties are fundam ental properties of reality, properties that have been here since the universe's incep tion, properties on a par with such properties as length, mass, charge, time, and other fundamental properties. There is even an historical precedent for a position of this kind. In the early 1900s, it was still widely believed that electromagnetic phenom ena (such as electric charge, magnetic attraction, and electro magnetic waves) were just an unusually subtle m anifestation of purely m echanical phenom ena. Most scientists thought that an explanatory reduction of electromagnetics to m echanics was more or less in the bag. They thought that radio waves, for example, would turn out to be just traveling oscillation or waves in a very subtle jellylike aether that filled space everywhere. But the aether turned out not to exist! And so electromagnetic prop erties turned out to be fundamental properties in their own right, and we were forced to add electric charge to the existing list of fundamental properties (mass, length, and temporal duration). Perhaps mental properties enjoy a status like that of electro magnetic properties: irreducible, but not emergent. Such a view may be called elemental-property dualism , and it has the advan tage of clarity over the im mediately previous view. Unfortu nately, the parallel with electromagnetic phenom ena has one very obvious failure. Unlike electromagnetic properties, which are displayed at all levels of reality from the subatomic level on up, and from the earliest stages of the cosmos to the present,
The Ontological Problem
21
m ental properties are displayed only in large physical systems that have evolved a superlatively com plex internal organization, a process that has taken over ten billion years. The factual and historical case for the evolutionary emergence of m ental proper ties through the progressive organization of matter is extremely strong. They do n ot appear to be basic or elem ental at all. This returns us, therefore, to the issue of their irreducibility. W hy should we accept this m ost basic of the dualist' s claims? W hy be a dualist in the first place? Arguments fo r Dualism
Here we shall examine some of the main considerations com m only offered in support of dualism. Criticism will be post poned for a m om ent so that we may appreciate the collective force of these supporting considerations. A major source of dualistic convictions is the religious belief many of us bring to these issues. Each of the world 's major religions is in its way a theory about the cause or purpose of the universe, and hum ankind 's place w ithin it, and m any of them are com m itted to the notion of an im m ortal soul— that is, to some form of substance dualism. Supposing that one is consis tent in one' s beliefs, to consider disbelieving dualism is to con sider disbelieving one' s religious heritage, and some of us find that difficult to do. Call this the argument from religion. A more universal consideration is the argument from introspec tion. The fact is, when you center your attention on the contents of your conscious, you do not clearly comprehend a neural network pulsing with electrochem ical activity: rather, you apprehend a flux of thoughts, sensations, desires, and emotions. It seems that m ental states and properties, as revealed in intro spection, could hardly be more different from physical states
22
Chapter 2
and properties if they tried. The verdict of introspection, there fore, seems strongly on the side of some form of dualism— on the side of property dualism, at a minimum. A cluster of im portant considerations can be collected under the argument from irreducibility. Here one points to a variety of m ental phenom ena where it seems clear that no purely physical explanation could possibly account for what is going on. Des cartes has already cited our capacity to use language in a way that is relevant to our changing circumstances, and he was impressed also with our faculty of Reason, particularly as it is displayed in our capacity for m athem atical reasoning. These abilities, he thought, must surely be beyond the capacity of any purely physical system. More recently, the introspectible quali ties of our sensations (sensory 'qualia') and the meaningful contents of our thoughts and beliefs have also been cited as phenom ena that will forever resist explanatory reduction to the physical. Consider, for example, seeing the color or smelling the fragrance of a rose. A physicist or chem ist m ight know every thing about the molecular structure of the rose, and of the hum an brain, argues the dualist, but that knowledge would not enable her to predict or anticipate the subjective quality of these inexpressible experiences. Finally, parapsychological phenom ena are occasionally cited in favor of dualism. Telepathy (mind reading), precognition (seeing the future), telekinesis (thought control of material objects), and clairvoyance (knowledge of distant objects) are all deeply awkward to explain within the normal confines of psy chology and physics. If these phenom ena are real, they might well be reflecting the superphysical nature that the dualist ascribes to the mind. Trivially they are m ental phenom ena, and
The Ontological Problem
23
if they are also forever beyond physical explanation, then at least some m ental phenom ena must be irreducibly nonphysical. Collectively, these considerations may seem compelling. But there are serious criticisms of each, and we must examine them as well. Consider first the argument from religion. There is cer tainly nothing wrong in principle with appealing to a more general framework or theory that bears on the case at issue, which is what the appeal to religion amounts to. But the appeal can be only as good as the scientific credentials of the religion(s) being appealed to, and here the appeals tend to fall down rather badly. In general, attempts to decide scientific questions by appeal to religious orthodoxy have a very sorry history. That the stars are other suns, that the Earth is not the unm oving center of the universe, that the Earth is billions of years old, that life is a physico-chemical phenom enon; all of these crucial insights were strongly and sometimes viciously resisted because the dom inant religion of the time happened to think otherwise. Giordano Bruno was burned at the stake for teaching the first view; Galileo was forced by threat of torture in the Vatican 's basem ent to recant the second view; the firm belief that disease was a punishm ent visited by demonic spirits permitted public health practices that brought chronic and deadly plagues to most of the cities of Europe; and the age of the Earth and the evolution of life were forced to fight an uphill battle against religious prejudice even in an age of supposed enlightenm ent. History aside, the almost universal opinion that one' s own religious convictions are the reasoned outcome of a dispassion ate and unprejudiced evaluation of all of the m ajor alternatives is almost demonstrably false for hum anity in general. If that really were the genesis of m ost people' s religious convictions,
24
Chapter 2
then one would expect the m ajor faiths to be distributed more or less randomly or evenly across the globe. But in fact they show an overwhelmingly strong tendency to cluster. Christian ity is centered in Europe and the Americas, Islam in Africa and the Middle East, Hinduism in India, and Buddhism in Eastern Asia. W hich illustrates what we all suspected anyway: that social forces are the primary determinants of religious belief for people in general. To decide scientific questions by appeal to local reli gious orthodoxy would therefore be to put social forces in place of empirical evidence. For all these reasons, professional scien tists and philosophers concerned with the nature of m ind (or with any other topic) do their best to keep religious appeals out of the discussion entirely. They may have psychological force, but they have no evidential force. The argument from introspection is a much more interesting argument, since it tries to appeal to the direct experience of everyman. But the argument is deeply suspect, in that it assumes that our faculty of inner observation or introspection reveals things as they really are in their innerm ost nature. This assump tion is suspect because we already know that our other forms of observation—sight, hearing, touch, and so on— do no such thing. The red surface of an apple certainly does n ot look like a matrix of molecules reflecting photons at predom inantly long wavelengths, but that is what it is. The sound of a flute does not sound like a sinusoidal compression wave train in the atm o sphere, but that is what it is. The warmth of the summer air does not feel like the mean kinetic energy of m illions of tiny molecules, but that is what it is. If one 's pains and hopes and beliefs do not introspectively seem like the electrochem ical states of a neural network (one' s brain), that may be only because our faculty of introspection, like our other senses, is n ot sufficiently
The Ontological Problem
25
penetrating to reveal such hidden details. W hich is just what one would expect anyway. The argument from introspection is therefore entirely w ithout force, unless we can somehow argue that the faculty of introspection is quite different from all other forms of observation. On the face of it, the only difference would seem to be that its focus is on states inside the skin, whereas our other sensory faculties focus on states outside the skin. W hy that should make any philosophical difference needs to be explained, since what is inside my skin is already known to be m y brain and nervous system. The argument from irreducibility presents a more serious challenge to materialism, but here also its force is less than first impression suggests. Consider first our capacity for m athem ati cal reasoning w hich so impressed Descartes. The last thirty years have made available, to anyone with fifteen dollars to spend, electronic calculators whose capacity for m athem atical reasoning—the calculational part at least—far surpasses that of any normal hum an. The fact is, in the centuries since Descartes' writings, philosophers, logicians, m athematicians, and com puter scientists have managed to isolate the general principles of m athem atical reasoning, and electronics engineers have created machines that compute in accord with those principles. The result is a handheld object that would have astonished Descartes. This outcome is impressive not just because machines have proved capable of some of the capacities boasted by hum an reason, but because some of those achievements invade areas of hum an reason that past dualistic philosophers have held up as forever closed to mere physical devices. Although debate on the matter remains open, Descartes' argument from the hum an use of language is equally dubious. The notion of a computer language is by now a comm onplace:
26
Chapter 2
consider BASIC, FORTRAN, APL, LISP, C+, JAVA, and so on. Granted, these artificial 'languages' are much simpler in struc ture and content than hum an natural language, but the differ ences may be differences only of degree, and n ot of kind. As well, the theoretical work of Noam Chomsky and the ' genera tive grammar' approach to linguistics have done a great deal to explain the hum an capacity for language use in terms that invite simulation by computers. I do not mean to suggest that truly conversational computers are just around the corner. (Although the newly popular 'app' called "Siri" is rather impres sive.) We have a great deal yet to learn, and fundamental prob lems left to solve (mostly having to do with our capacity for inductive and theoretical reasoning). But recent progress here does nothing to support the claim that language use must be forever impossible for a purely physical system. On the contrary, such a claim now appears rather arbitrary and dogmatic, as we shall see in more detail in chapter 6. The next issue here is also a live problem: how can we pos sibly hope to explain or to predict the intrinsic qualities of our sensations, or the specific semantical content of our beliefs and desires, in purely physical terms? This is a major challenge to the materialist. But as we shall see in later sections, active research programs are already underway on both problems, and positive suggestions are being explored in some detail. It is in fact not impossible to imagine how such explanations m ight go, though materialists cannot yet pretend to have solved either problem. Until they do, the dualist will retain a bargaining chip here, but that is about all. W hat the dualists need in order to establish their case is the conclusion that a physical reduction is outright impossible (and n ot just yet-to-be-achieved), and that is a conclusion they have failed to establish. Rhetorical
The Ontological Problem
27
questions, like the one that opens this paragraph, do n ot con stitute arguments. And it is equally difficult, note well, to imagine how the relevant phenom ena could be explained or predicted solely in terms of the substance dualist 's nonphysical mindstuff. The explanatory problem here—concerning both subjec tive qualia and semantical content—is a m ajor challenge to everybody, n ot just to the materialist. On this issue, then, we have a rough standoff. The final argument in support of dualism urged the existence of parapsychological phenom ena such as telepathy and teleki nesis, the point being that such m ental phenom ena are (a) real, and (b) beyond purely physical explanation. This argument is really another instance of the argument from irreducibility dis cussed above, and as before, it is not entirely clear that such phenom ena, even if real, must forever escape a purely physical explanation. For example, the materialist can already suggest a possible explanation for telepathy. On his view, thinking is an electrical activity in the brain. But according to standard elec trom agnetic theory, such changing m otions of electric charges w ithin the brain must produce electromagnetic waves radiating from the brain in all directions, waves that will contain detailed inform ation about the very electrical activities that produced them . Such waves can, as they encounter other brains, have specific effects on their internal electrical activities, that is, on their thinking. Call this the ' radio transmitter/receiver ' theory of telepathy. I do not for a m om ent suggest that this theory is true: the electromagnetic waves emitted by a brain are fantastically weak (billions of times weaker than the ever-present background elec trom agnetic flux produced by commercial radio stations), and they are almost certain to be hopelessly jumbled together as
28
Chapter 2
well. This is one reason why, in the absence of systematic, com pelling, and repeatable evidence for telepathy, one must doubt that it really exists. But it is significant that the materialist has the theoretical resources to suggest a detailed possible explana tion of telepathy, if it were real, which is more than any dualist has so far done. It is not at all clear, then, that the materialist must be at an explanatory disadvantage in these matters. Quite the reverse. Put the preceding aside, if you wish, for the main difficulty with the argument from parapsychological phenom ena is much, m uch simpler. Despite the endless pronouncem ents and anec dotes in the popular press, and despite a steady trickle of serious research on such things, there is no significant or trustworthy evidence that such phenom ena even exist. The wide gap between popular conviction on this matter, and the actual evidence, is som ething that itself calls for research. For there is n ot a single 'parapsychological' effect that can be repeatedly or reliably pro duced in any laboratory suitable equipped to perform and control the experiment. Not one. Honest researchers have repeatedly been hoodwinked by 'psychic' charlatans with skills derived from the magician's trade, and the history of the subject is largely a history of gullibility, prejudicial selection of evi dence, poor experimental controls, and outright fraud by the occasional researcher as well. If someone really does discover a repeatable parapsychological effect, then we shall have to reevaluate the situation. But as things stand, there is nothing here to support a dualist theory of mind. Upon critical evaluation, the arguments in support of dualism lose m uch of their force. But we are not yet done: there are argu m ents against dualism, and these also require exam ination.
The Ontological Problem
29
Arguments against Dualism
The first argument against dualism urged by the materialists appeals to the greater simplicity of the materialist view. It is a principle of rational m ethodology that, if all else is equal, the simpler of two com peting hypotheses should be preferred. This principle is sometimes called "Ockham 's Razor"— after William of Ockham, the medieval philosopher who first enunciated it—and it can also be expressed as follows: "Do n ot multiply entities beyond what is strictly necessary to explain the phe nom ena." The materialist postulates only one kind of substance (physical matter) and one class of properties (physical proper ties), whereas the dualist postulates two kinds of substance and/ or two kinds of properties. And to no evident explanatory advantage, charges the materialist. This is n ot yet a decisive point against dualism, since neither dualism nor materialism can yet explain all of the phenom ena to be explained. But the objection does have some force, espe cially since there is no doubt at all that physical matter exists (and plays a substantial role in our internal cognitive activities), while spiritual matter remains a primitive, tenuous, and explan atorily feeble hypothesis. If the dualistic hypothesis brought us some definite explana tory advantage obtainable in no other way, then we would happily violate the initial preference for simplicity, and we would be right to do so. But it does not, claims the materialist. In fact, the advantage is just the other way around, he argues, and this brings us to a second objection to dualism: the relative explana tory impotence of dualism as compared to modern materialism. Consider, very briefly, the explanatory resources already available to the neurosciences. We know that the brain exists
30
Chapter 2
and what it is made of. We know m uch of its microstructure: how the neurons are organized into systems and how distinct systems are connected to one another, to the m otor nerves going out to the muscles, and to the sensory areas of the brain com ing in from the peripheral sensory neurons in the eyes, ears, skin, and so forth. We know m uch of their microchemistry: how the neurons fire tiny electrochem ical pulses along their various fibers, and how they make other cells in downstream popula tions fire also, or cease firing. We know some of how this activity processes sensory inform ation, selecting salient or relevant bits to be sent on to higher systems for analysis. And we know some of how such activity initiates and coordinates bodily behavior. Thanks m ainly to neurology (the branch of m edicine concerned with brain pathology), we know a great deal about the correla tions between damage to various parts of the brain, and various behavioral and cognitive deficits from w hich the victims suffer in consequence. There are a great m any isolated deficits— some gross, some subtle—that are familiar to neurologists (inability to speak, or read, or to understand speech, or to recognize faces, or to add/subtract, or to move a certain limb, or to store com prehended inform ation in long-term memory, and so on). And their appearance is closely tied to occurrence of damage to very specific subsystems of the brain. Nor are we limited to cataloging traumas. The growth and development of the brain's microstructure is som ething that neu roscience has explored in detail, and such development appears to be the basis of various kinds of learning by the organism. Learn ing, that is (including moral and social learning), involves lasting chem ical and microphysical changes in the brain. In sum, the neurosciences can tell us a great deal about the brain, about its constitution and the physical laws that govern it. They can
The Ontological Problem
31
already explain much of our behavior in terms of the structural, chemical, and electrical properties of the brain; and they command the theoretical resources adequate to explain a good deal more as our explorations continue. (We shall take a closer look at neurophysiology and neuropsychology in chapter 7.) Compare now what the neuroscientist can tell us about the brain, and what she can do with that knowledge, with what the dualist can tell us about spiritual substance, and what he can do with those assumptions. Can the dualist tell us anything about the internal constitution of mind-stuff? Of the nonm ate rial elements that make it up? Of the nonphysical laws that govern their behavior? Of the m ind 's structural connections with the body? Of the m anner of the m ind 's operations? Can he explain hum an capacities and pathologies in terms of its structures and defects? The fact is, the dualist can do none of these things because no detailed theory of mind-stuff has ever even been formulated. Compared to the rich resources and the explanatory successes of current materialism, dualism is n ot so m uch a theory of m ind as it is an empty space waiting for a genuine theory of m ind to be put in it. Thus argues the materialist. But again, this is n ot a com pletely decisive point against dualism. The dualist can admit that the brain plays a major role in the administration of both perception and behavior— on his view, the brain is the mediator between the m ind and the body—but he may attempt to argue that the materialist 's current successes and future explanatory prospects concern only the 'meditative' functions of the brain, not the central capacities of the nonphysical mind, capacities such as reason, em otion, and consciousness itself. On these latter topics, he may argue, both dualism and materialism cur rently draw a blank.
32
Chapter 2
But this reply is n ot a very good one. So far as the capacity for reasoning is concerned, m achines already exist that execute sophisticated deductive and m athem atical calculations that would take a hum an a lifetime to execute. And so far as the other two mental capacities are concerned, studies of such things as depression, motivation, attention, and sleep have revealed m any interesting and suggestive facts about the neuro chem ical and neurodynamical basis of both em otion and con sciousness. The central capacities of the mind, no less than the peripheral, have been addressed with systematic profit by various materialist research programs. In any case, the (substance) dualist's attempt to draw a sharp distinction between the uniquely ' m ental' capacities proper to the nonm aterial mind, and the merely meditative capacities of the physical brain, prompts an argument that comes close to being an outright refutation of (substance) dualism. If there really is a distinct entity in w hich reasoning, em otion, and consciousness take place, and if that entity is dependent on the brain for nothing more than sensory experiences as input and volitional executions as output, then one would expect reason, em otion, and consciousness to b e relatively invulnerable to direct control or pathology by m anipulation or dam age to the brain. But in fact the exact opposite is true. Alcohol, narcotics, or senile degeneration of neural activity will impair, cripple, or even destroy one's capacity for rational thought. Psychiatry knows of hundreds of em otion-controlling chemicals (lithium salts, chlorpromazine, amphetamine, cocaine, and so on) that do their work when vectored into the brain. And the vulnerabil ity of consciousness to anesthetics, to caffeine, and to some thing as simple as a sharp blow to the head, shows its very close dependence on neural activity in the brain. All this makes
The Ontological Problem
33
perfect sense if reason, em otion, and consciousness are activities of the brain itself. But it makes very little sense if they are activi ties of som ething else entirely. We may call this the argument from the neural dependence of all known m ental phenom ena. Property dualism, note, is not threatened by this argument, since, like materialism, property dualism reckons the physical brain as the seat of all mental activity. We shall conclude this section, however, with an argu m ent that cuts against both varieties of dualism. It is called the argument from evolutionary history. W hat is the origin of a com plex and sophisticated species such as ours? W hat, for that matter, is the origin of the dolphin, the mouse, or the housefly? Thanks to the fossil record, com parative anatomy, and the biochem istry of proteins and nucleic acids, there is no longer any significant doubt on this matter. Each existing species is a surviving type from a number of varia tions on an earlier type of organism. Each earlier type is in turn a surviving type from a number of variations on a still earlier type of organism. And so on down the branches of the evolu tionary tree until, some three billion years ago, we find a trunk of just one or a handful of very simple organisms. Those organ isms, like their more com plex and various offspring, are just self-repairing, self-replicating, energy-driven molecular struc tures. (That evolutionary trunk has its own roots in an earlier era of purely chem ical evolution, in which the molecular ele ments of life were themselves pieced together, randomly, by energy arriving from the Sun, or perhaps from the Earth's m olten core.) The m echanism of development that has struc tured this intricate and very old tree has two main elements: (1) the occasional blind or accidental variation, usually quite small, in types of reproducing creature, and (2) the selective survival
34
Chapter 2
of some of these modified types due to the relative reproductive advantage enjoyed by individuals of those types. Over periods of geological time, such a process of natural selection can produce an enormous variety of organisms, some of them very complex indeed. The initial case for this theory stemmed, of course, from Charles Darwin, who noted that distinct species tended to cluster into distinct 'families' of vaguely similar characteristics, as if they all shared a com m on ancestor species somewhere in the distant past. And this guess was further encouraged by his detailed understanding of the process of artificial selection long practiced on hum an farms, the process by w hich the varieties of current dom estic creatures— such as diverse dogs, cattle, chick ens, sheep, and so on (and corn and wheat and rice, for that matter)—were originally and fairly recently developed. As the years went by, Darwin' s insightful guess here was subsequently reinforced by our unfolding discovery of the Earth' s deep-time fossil record, and its frozen testim ony to the treelike develop m ent of ever more various and com plex species of plants and animals. These data were sufficient, even in the late 1800s, to win over the bulk of the scientific community. But since the recent discovery of DNA and the development of techniques to divine the entire genome of any given creature, we have a new and independent way of tracking the details of the Earth' s evo lutionary history. This is because the distinct and characteristic genome of any given species can be compared, for similarities and differences, to the genome of any other species. And so we can construct abstract trees of such similarities and differences, on the assumption that highly similar genomes bespeak a recent com m on ancestor genome, whereas very different genomes bespeak a genetic divergence a very long time in the past. W hat
The Ontological Problem
35
is charming, and evidentially significant, is that the speculative tree produced by Darwin's body-similarity analysis, and the evident developmental tree independently revealed in the fossil record, and the still more recent tree independently revealed by genom ic analysis, are all identical. Given the com plexity of the trees at issue, m ost people outside of the scientific academy are quite unaware of this extraordinary convergence of evidence. But it is real, and it is stunning. For purposes of our discussion, the im portant point about the standard evolutionary story is that the hum an species and all of its features are the w holly physical outcome of a wholly physical process. Like all but the simplest of organisms, we have a nervous system. And for the same reason: a nervous system permits the discriminating guidance of behavior. But a nervous system is just an active matrix of cells, and a cell is just an active matrix of molecules. We are notable only in that our nervous system is more com plex and powerful than those of our evolu tionary brothers and sisters. Our inner nature differs from that of simpler creatures in degree, but not in kind. If this is the correct account of our origins, then there seems neither need, nor room, to fit any nonphysical substances or properties into our scientific account of ourselves. We are creatures of matter. And we should learn to live with that fact. Arguments like these have moved most (but n ot entirely all) of the professional com m unity to embrace some form of m ate rialism. This has not produced much unanimity, however, since the differences between the several materialist positions are even wider than the differences that separate the various forms of dualism. The next four sections explore these more recent positions, and the difficulties that they, too, confront.
36
Chapter 2
Suggested Readings
On Substance Dualism Descartes, René. The Meditations, m editation II. Descartes, René. Discourse on Method, part 5. Eccles, Sir Jo h n C., with Sir Karl Popper. The Self and Its Brain. New York: Springer-Verlag, 1977.
On Property Dualism Margolis, Joseph. Persons and Minds: The Prospects o f Nonreductive Mate
rialism. Dordrecht, Holland: Reidel, 1978. Nagel, Thomas. "W hat Is It Like to Be a Bat?" Philosophical Review 83 (1974). Reprinted in Readings in Philosophy o f Psychology, vol. I, ed. N. Block (Cambridge, MA: Harvard University Press, 1980). Jackson, Frank. "Epiphenom enal Qualia." Philosophical Quarterly 32 (127) (April 1982).
2
Philosophical Behaviorism
Philosophical behaviorism reached the peak of its influence during the first and second decades after World War II. It was jointly motivated by at least three intellectual fashions. The first m oti vation was a reaction against dualism. The second m otivation was the Logical Positivists' idea that the m eaning of any sen tence was ultim ately a matter of the observable circumstances that would tend to verify or confirm that sentence. And the third m otivation was a general assumption that most, if n ot all, philosophical problems are a result of linguistic or conceptual confusion, and are to be solved (or dissolved) by careful analysis of the language in w hich the problem is expressed.
The Ontological Problem
37
In fact, philosophical behaviorism is not so m uch a theory of what m ental states are (in their inner nature) as it is a theory about how to analyze or understand the vocabulary we use to talk about them . Specifically, the claim is that our talk about em otions and sensations and belief and desires is not talk about ghostly inner episodes, but is rather a shorthand way of talking about actual and potential patterns o f behavior. In its strongest and m ost straightforward form, philosophical behaviorism claims that any sentence about a person 's m ental state can be paraphrased, without loss of meaning, into a long and com pli cated sentence about what observable behavior would result if the person were in this, that, or the other observable circumstance. A helpful analogy here is the dispositional property, being soluble. To say that a particular sugar cube is soluble is n ot to say that the sugar cube enjoys some ghostly inner state. It is just to say that i f the sugar cube were put in water, then it would dissolve. More strictly, "x is water soluble" is equivalent by definition to "if x were put in unsaturated water, then x would dissolve." This is one example of what is called an "operational defini tio n ." The term "soluble" is defined in terms of certain opera tions or tests that would reveal whether or n ot the term actually applies to the case to be tested. According to the behaviorist, a similar analysis holds for m ental states such as "wants a Caribbean holiday," save that the analysis is m uch richer. To say that Anne wants a Caribbean holiday is to say that (1) if asked whether that is what she wants, she would answer yes, and (2) if given new holiday brochures
38
Chapter 2
for Jamaica and Japan, she would peruse the ones from Jamaica first, and (3) if given a ticket on this Friday 's flight to Jamaica, she would go, and so on and so on. Unlike solubility, claims the behaviorist, m ost m ental states are m ultitracked dispositions. But dispositions they remain. There is therefore no point in worrying about the 'relation' between the mind and the body, on this view. To talk about Marie Curie's mind, for example, is not to talk about some 'thing' that she ' possesses'; it is to talk about certain of her extraordinary capacities and dispositions. The m ind-body problem, concludes the behaviorist, is a pseudoproblem. Behaviorism is clearly consistent with a materialist concep tion of hum an beings. Material objects can have dispositional properties, even multitracked ones, so there is no necessity to embrace dualism to make sense of our psychological vocabulary. (It should be pointed out, however, that behaviorism is strictly consistent with dualism also. Even if philosophical behaviorism were true, it would remain possible that our multitracked dis positions are grounded in immaterial mind-stuff rather than in molecular structures. This is not a possibility that m ost behaviorists took seriously, however, for the m any reasons outlined at the end of the preceding section.) Philosophical behaviorism, unfortunately, had two major flaws that made it awkward to believe, even for its defenders. It evidently ignored, and even denied, the 'inner' qualitative aspect of our m ental states. To have a pain, for example, seems to be not merely a matter of being inclined to moan, to wince, to take an aspirin, and so on. Pains also have an intrinsic quali tative nature (a horrible one) that is revealed in introspection, and any theory of mind that ignores or denies such qualia is simply derelict in its duty.
The Ontological Problem
39
This problem received much attention from behaviorists, and serious attempts were made to solve it. The details take us deeply into semantical problems, however, so we shall postpone further discussion of this difficulty until chapter 3. The second flaw emerged when behaviorists attempted to specify in detail the multitracked disposition said to constitute any given m ental state. The list of conditions necessary for an adequate analysis of "wants a Caribbean holiday," for example, seemed not just to be long, but to be indefinitely or even infi nitely long, with no finite way to specify the elem ents to be included. And no term can be well-defined whose definiens is open-ended and unspecific in this way. Further, each condition of the long analysis was suspect on its own. Supposing that Anne does want a Caribbean holiday, conditional (1) above will be true only if Anne isn' t secretive about her holiday fantasies; conditional (2) will be true only if she isn' t already bored with the Jam aica brochures; conditional (3) will be true only if she doesn't believe that the Friday flight will be hijacked; and so forth. But to repair each conditional by adding in the relevant qualification would be to reintroduce a series of plainly mental elements into the business end of the definition, and we would no longer be defining the m ental solely in terms of publicly observable circumstances and behavior. So long as behaviorism seemed the only alternative to dualism, philosophers were prepared to struggle with these flaws in hopes of repairing or defusing them . However, three more materialist theories rose to prom inence during the late fifties and sixties, and the flight from behaviorism was swift. (I close this section with a cautionary note. The philosophical behaviorism discussed above is to sharply distinguished from the m ethodological behaviorism that enjoyed such wide influence in
40
Chapter 2
psychology for the first two-thirds of the tw entieth century. In its bluntest form, this latter view urges that any new theoretical terms invented by the science of psychology should b e operation ally defined, in order to guarantee that psychology m aintains a firm and perm anent contact with observable reality. Philosophi cal behaviorism, by contrast, claims that all of the common-sense psychological terms in our prescientific vocabulary already get whatever m eaning they have from (tacit) operational definitions. The two views are logically distinct, and the scientific m ethodol ogy m ight be a wise one, for new theoretical terms, even though the correlative analysis of common-sense m ental terms is wrong.) Suggested Readings Ryle, Gilbert. The Concept o f Mind, chapters I and V. London: H utchin son, 1949. Malcolm, Norman. "W ittgenstein's Philosophical Investigations." Philo sophical Review 47 (1956). Reprinted in The Philosophy o f Mind, ed. V. C. Chappell (Englewood Cliffs, NJ: Prentice-Hall, 1962).
3
Reductive Materialism (the Identity Theory)
Reductive m aterialism , more com m only known as the identity theory, is the m ost straightforward of the several materialist theories of mind. Its central claim is simplicity itself: Mental states are physical states of the brain. That is, each type of m ental state or process is numerically identical with (is one and the very same thing as) some type of physical state or process w ithin the brain or central nervous system. At present, we do not know enough about the intricate functionings of the brain actually to state the relevant identities—save in a few compara-
The Ontological Problem
41
tively simple and obvious cases—but the identity theory is com mitted to the view that brain research will eventually reveal them all. (Partly to help us evaluate that claim, we shall examine current brain research in chapter 7.) Historical Parallels
As the identity theorist sees it, the result here predicted has familiar parallels elsewhere in our scientific history. Consider sound. We now know that sound is just a train of compression waves traveling through the air, and that the qualitative prop erty of being high pitched, for example, is just the property of having a high oscillatory frequency. We have learned that light is just electromagnetic waves, and our best current theory says that the color of an object is identical with a triplet of reflec tance efficiencies the object has, rather like a musical chord that it strikes, although the 'notes' are struck in electrom agnetic waves instead of in sound waves. We now appreciate that the warmth or coolness of a body is just the energy of m otion of the molecules that make it up: warmth is identical with high average molecular kinetic energy, and coolness is identical with low average molecular kinetic energy. We know that lightning is identical with a sudden large-scale discharge of electrons between clouds, or between clouds and the ground. W hat we now think of as 'm ental states', argues the identity theorist, are identical with brain states in exactly the same way. Intertheoretic Reduction
These illustrative parallels are all cases of successful intertheoretic reduction. That is, they are all cases where a new and very powerful theory turns out to entail a set of propositions and principles that mirror perfectly (or almost perfectly) the propositions and
42
Chapter 2
principles of some older theory or conceptual framework. The relevant principles entailed by the new theory have the same collective structure as the corresponding principles of the old framework, and they apply in exactly the same cases. The only difference is that, where the old principles contained (for example) the notions of "heat," "is h o t," and "is cold," the new principles contain instead the notions of "total molecular kinetic energy," "has a high mean molecular kinetic energy," and "has a low mean molecular kinetic energy." If the new framework is far better than the old at explaining and predicting phenom ena, then we have excellent reason for believing that the theoretical terms of the new theory are the terms that describe reality correctly. But if the old framework worked adequately, so far as it went, and if it parallels a portion of the new theory in the systematic way described, then we may properly conclude that the old terms and the new terms refer to the very same things, or express the very same properties. We conclude that we have apprehended the very same reality that is incom pletely described by the old framework, but with a new and more penetrating conceptual framework. And we announce what philosophers of science call "intertheoretic identities": light is electromagnetic waves, temperature is mean molecular kinetic energy, and so forth. The examples of the preceding two paragraphs share one more im portant feature. They are all cases where the things or properties on the receiving end of the reduction are observable things and properties w ithin our com m on-sense conceptual framework. They show that intertheoretic reduction can and often does occur not only between conceptual frameworks in the theoretical stratosphere: com m on-sense observables can also b e reduced. There would therefore be nothing particularly sur
The Ontological Problem
43
prising about a reduction of our familiar introspectible mental states to physical states of the brain. All that would be required is that an explanatorily successful neuroscience develop to the point where it entails a suitable ' mirror image ' of the assump tions and principles that constitute our com m on-sense concep tual framework for mental states, an image where brain-state terms occupy the positions held by m ental-state terms in the assumptions and principles of com m on sense. If this (admit tedly rather demanding) condition were met, then, as in the historical cases cited, we would be justified in announcing a successful reduction, and in asserting the identity of mental states with brain states. Arguments fo r th e Identity Theory
W hat reasons does the identity theorist have for believing that neuroscience will eventually achieve the strong conditions nec essary for the reduction of our ' folk' psychology? There are at least four reasons, all directed at the conclusion that the correct account of human-behavior-and-its-causes must reside in the physical neurosciences. We can point first to the purely physical origins and the ostensibly physical constitution of each individual hum an. One begins as a genetically programmed m onocellular organization of molecules (a fertilized ovum), and one develops from there by the accretion of further molecules whose structure and in te gration is controlled by the inform ation coded in the DNA molecules of the cell nuclei. The result of such a process would be a purely physical system whose behavior arises from its inter nal operations and its interactions with the rest of the physical world. And those behavior-controlling internal operations are precisely what the neurosciences are about.
44
Chapter 2
This argument coheres with a second argument. The origins of each type of animal also appear to be exhaustively physical in nature. The argument from evolutionary history discussed earlier (p. 33) lends further support to the identity theorist 's claim, since evolutionary theory provides the only serious explanation we have for the behavior-controlling capacities of the brain and central nervous system. Those systems were selected for because of the m any advantages (ultimately, the reproductive advantage) held by the creatures whose behavior was thus controlled. Once again, our behavior appears to have its basic causes in neural activity. The identity theorist finds further support in the argument, discussed earlier, from the neural dependence of all known mental phenom ena (see p. 32). This is precisely what one should expect, if the identity theory is true. Of course, systematic neural depen dence is also a consequence of property dualism, but here the identity theorist will appeal to considerations of simplicity. W hy admit two radically different classes of properties and operations if the explanatory job can be done by one? A final argument derives from the growing success of the neurosciences in unraveling the nervous systems of m any crea tures and in explaining their behavioral capacities and deficits in terms of the structures discovered. The preceding arguments all suggest that neuroscience should be successful in this endeavor, and the fact is that the continuing history of neuro science bears them out. Especially in the case of very simple creatures (as one would expect), progress has been rapid. And progress has also been made with humans, though for obvious moral reasons exploration must be more cautious and circum spect. In sum, the neurosciences have a long way to go, but
The Ontological Problem
45
progress to date provides substantial encouragem ent for the identity theorist. Even so, these arguments are far from decisive in favor of the identity theory. No doubt they do provide an overwhelming case for the idea that the causes of hum an and animal behavior are essentially physical in nature, but the identity theory claims more than just this. It claims that neuroscience will discover a taxonom y of neural states that stand in a one-to-one correspon dence with the m ental states of our com m on-sense taxonomy. Claims for intertheoretic identity will be justified only if such a systematic m atch-up can be found. But nothing in the preced ing arguments guarantees that the old and the new frameworks will m atch up in this way, even if the new framework is a roaring success at explaining and predicting our behavior. Furthermore, there are arguments from other positions w ithin the materialist camp to the effect that such convenient match-ups are rather unlikely. Before exploring those, however, let us examine some more traditional objections to the identity theory. Arguments against the Identity Theory
We may begin with the argument from introspection discussed earlier. Introspection reveals a domain of thoughts, sensations, and emotions, not a domain of electrochem ical impulses in a neural network. M ental states and properties, as revealed in introspection, appear radically different from any neurophysiological states and properties. How could they possibly be the very same things? The answer, as we have already seen, is "Easily." In discri m inating red from green, sweet from sour, and h ot from cold, our external senses are actually discriminating between subtle
46
Chapter 2
electromagnetic, stereochemical, and micromechanical proper ties of physical objects. But our senses are not sufficiently pene trating to reveal on their own the detailed nature of those intricate and submicroscopic properties. That requires theoretical research and experimental exploration with specially designed instru ments. The same lim itation is presumably true of our 'inner' sense as well. Introspection may discriminate efficiently between a great variety of neural states, w ithout being able to reveal on its own the detailed nature of the states being discriminated. Indeed, it would be faintly miraculous if it did reveal them, just as miraculous as if unaided sight were to reveal the existence of interacting electric and magnetic fields whizzing by with an oscil latory frequency of a m illion billion hertz and a wavelength of less than a m illionth of a meter. For despite ' appearances', that is what light is. The argument from introspection, therefore, is quite w ithout force. You can 't expect introspection, all by itself, to reveal such microphysical details. The next objection argues that the identification of mental states with brain states would com m it us to statements that are literally unintelligible, to what philosophers have called "cate gory errors," and the proposed identification is therefore a case of sheer conceptual confusion. We may begin the discussion by noting a most im portant requirement on num erical identity. It is called "Leibniz' Law," and it states that two items, a and b, are num erically identical (i.e., a = b) if and only if any property had by either one of them is also had by the other. This law suggests a way of refuting the identity theory: find some prop erty that is true of brain states, but not of mental states (or vice versa), and the theory would be exploded. Spatial properties were often cited to this end. Brain states and processes must of course have some specific spatial location:
The Ontological Problem
47
in the brain as a whole, or in some part of it. And if mental states are identical with brain states, then they must have the very same spatial location. But it is literally meaningless, runs the argument, to say that m y feeling of pain is located in my ventral thalamus, or that m y belief-that-the-sun-is-a-star is located in the temporal lobe of my left cerebral hemisphere. Such claims are as meaningless as the claim that the num ber 5 is green, or that love weighs twenty grams. Trying the same move from the other direction, some have argued that it is senseless to ascribe the various sem antic proper ties to physical brain states. Our thought and beliefs, for example, have meaning, a specific propositional content; they are either true or false; and they can enjoy relations such as mutual consistency and entailm ent. If thoughts and beliefs were brain states, then all of these sem antic properties would have to be true of brain states. But it is senseless, runs the argument, to say that some resonance in my association cortex is true, or logically entails some other resonance close by, or has the meaning that P. Neither of these moves has the same bite it did twenty or thirty years ago, since familiarity with the identity theory and growing awareness of the brain's role in cognition have tended to reduce the feelings of semantic oddity produced by the claims at issue. But even if they still struck all of us as sem antically confused, this would carry little weight. The claim that a sound has a wave length, or that light has a frequency, must have seemed equally unintelligible in advance of the conviction that both sound and light are wave phenom ena. (See, for example, Bishop Berkeley's eighteenth-century dismissal of the idea that sound is a vibratory m otion of the air, in Dialogue I of his Three Dialogues. The objec tions are voiced by Philonous.) The claim that warmth can be
48
Chapter 2
measured in kilogram-meters2 per second2 would have seemed equally sem antically perverse before we came to understand that temperature is mean molecular kinetic energy. And Copernicus' sixteenth-century claim that the Earth moves also struck people as absurd to the point of perversity. It is not difficult to appreciate why. Consider the following argument: Copernicus' claim that the Earth moves is sheer conceptual confusion. For consider what it m eans to say that something moves: "x m oves" means "x changes position relative to the Earth." Thus, to say that the Earth moves is to say that the Earth changes position relative to itself! W hich is absurd. Copernicus' position is therefore a plain abuse of language. The meaning analysis here invoked m ight well have been correct, but all that would have m eant is that the speaker should set about changing his meanings. The fact is, any language em bod ies a rich network of assumptions about the structure of the world, and if a sentence S provokes intuitions of semantic oddness, that is often because S violates one or more of those background assumptions. But one cannot always reject S for that reason alone, since the overthrow of those background assump tions may be precisely what the emerging facts require. The 'abuse' of accepted modes of speech is often an essential feature of real scientific progress! Perhaps we shall just have to get used to the idea that mental states have anatom ical locations and brain states have semantic properties. W hile charge of sheer senselessness can be put aside, the identity theorist does owe us some account of exactly how physi cal brain states can have sem antic properties. The account cur rently being explored can be outlined as follows. Let us begin by asking how it is that a particular sentence (= utterance type)
The Ontological Problem
49
has the specific propositional content it has: the French sen tence "La pomme est rouge," for example. Note first that a sentence is always an integrated part of an entire system of sen tences: a language. Any given sentence enjoys m any relations with countless other sentences: it entails m any sentences, is entailed by m any others, is consistent with some, is inconsistent with others, provides confirm ing evidence for yet others, and so forth. And speakers who use that sentence within that lan guage draw inferences in accord with those relations. Evidently, each sentence (or each set of equivalent sentences) enjoys a unique pattern of such entailm ent relations: it plays a distinct inferential role in a com plex linguistic economy. Accordingly, we say that the French sentence "La pomme est rouge" has the propositional content, the apple is red, because the sentence "La pomme est rouge" plays the sam e role in French that the sen tence "The apple is red" plays in English. To have the relevant propositional content is just to play the relevant inferential role in a cognitive economy, according to this suggestion. Returning now to types of brain states, there is no problem in principle in assuming that one's brain is the seat of a com plex inferential econom y in w hich types of brain states are the roleplaying elements. According to the theory of m eaning just sketched, such states would then have propositional content, since having content is n ot a matter of whether the contentful item is a pattern of sound, a pattern of letters on paper, a set of raised Braille bumps, or a pattern of neural activity. W hat matters is the inferential role that the item plays in the relevant representational economy. Propositional content, therefore, seems w ithin the reach of brain states after all. We began this subsection with an argument against m aterial ism that appealed to the qualitative nature of our m ental states,
50
Chapter 2
as revealed in introspection. The next critical argument appeals to the simple fact that they are introspectible at all. 1. My m ental states are introspectively known by me as states of m y conscious self. 2. My brain states are not introspectively known by me as states of my conscious self. Therefore, by Leibniz' Law (that num erically identical things must have exactly the same properties), 3. My m ental states are n ot identical with m y brain states. This, in my experience, is the m ost beguiling form of the argument from introspection, seductive of freshmen and faculty alike. But it is a straightforward instance of a well-known fallacy, w hich is clearly illustrated in the following parallel arguments. 1. M uhammad Ali is widely known as a heavyweight champion. 2. Cassius Clay is not widely known as a heavyweight champion. Therefore, by Leibniz' Law, 3. M uhammad Ali is n ot identical with Cassius Clay. Or, 1. Aspirin is recognized by Jo h n to be a pain reliever. 2. Acetylsalicylic acid is not recognized by Jo h n to be a pain reliever. Therefore, by Leibniz' Law, 3. Aspirin is not identical with acetylsalicylic acid. Despite the truth of the relevant premises, both conclusions are false. The identities at issue are entirely real. W hich means that both arguments are invalid. The problem is that the
The Ontological Problem
51
so-called property ascribed in premise (1), and withheld in premise (2), consists only in the subject item 's being recognized, perceived, or known as something-or-other by somebody-or-other. But such apprehension is not a genuine property of the subject item i tself, fit for divining identities, since one and the same subject may be successfully recognized under one name or description, and yet fail to be recognized under another (accu rate and coreferential) description. Bluntly, Leibniz' Law is not valid for these bogus 'properties'. The attempt to use them as above commits what logicians call an intensional fallacy. The premises may reflect, not the failure of certain objective identi ties, but only our continuing failure to appreciate those very identities. A different version of the preceding style of argument must also be considered, since it may be urged that one' s brain states are more than merely not (yet) known by introspection: they are n ot knowable by introspection under any circumstances. Thus, 1. My m ental states are knowable by introspection. 2. My brain states are not knowable by introspection. Therefore, by Leibniz' Law, 3. My m ental states are n ot identical with m y brain states. Here the critic of the identity theory will insist that being knowable by introspection is a genuine property of a thing, and that this modified version of the argument is therefore free of the 'intensional fallacy' illustrated above. Let us agree that it is. But now the identity theorist is in a position to insist that this new argument contains a false premise—premise (2). For if m ental states are indeed brain states, then it is really brain states that we have been introspecting all along,
52
Chapter 2
though without fully appreciating what they are. And if we can learn to think of and recognize those states under their familiar m entalistic descriptions, then we can certainly learn to think of and recognize them under their more penetrating neurophysiological descriptions. At the very least, premise (2) simply begs the question against the identity theorist. The mistake is amply illus trated by the following parallel argument: 1. Temperature is knowable by feeling. 2. Mean molecular kinetic energy is not knowable by feeling. Therefore, by Leibniz' Law, 3. Temperature is n ot identical with mean molecular kinetic energy. But this identity, at least, is long established and this argument is clearly unsound. The culprit, as above, is premise (2). Just as one can learn to feel that the summer air is about 70°F, or 21°C, so one can learn to feel that the mean KE of its molecules is about 6.2 x 10-21 joules, for whether we realize it or not, that is what our native discriminatory m echanisms are keyed to. Perhaps our brain states are similarly accessible, if we learn the relevant theoretical vocabulary, and if we learn to spontane ously apply the relevant terms. (The introspectibility of brain states is addressed again in chapter 8.) Consider now a more intuitively appealing argument against the identity theory, one based on the presumably quite alien subjective experience of the bat. Bats, you will recall, emit extremely high-pitched squeaks as they fly through the air, so as to locate insects flying in the immediate vicinity. Those (to us) inaudible sounds bounce off those insects and the various returning echoes are picked up by the bat's exquisitely sensitive
The Ontological Problem
53
auditory system. The sonic profile of the returning echo, its return time, and the direction from w hich it comes allow the bat to 'hear' exactly where the insect is located in space, which way it is flying, and even what type of insect it is. This allows the bat to swiftly zero in on its target, all the time increasing the frequency of its sonarlike squeaks, ultim ately to devour the unlucky insect right out of the air. W hat would it be like to possess, and use, such an extraordi nary sensory system? W hat would it be like to actually experience the alien echo-locating process undergone by the marauding bat? Since we are not bats, we cannot of course know what it is like for the bat itself. We lack both the alien sensory apparatus and the alien brain circuitry that supports the bat' s decidedly alien auditory experiences. We are n ot built to have those kinds of experience. Our im aginations are thus crippled by our own experiential limitations. More
importantly,
says the
contemporary
philosopher
Thomas Nagel (who is responsible for this now famous thought experiment), no am ount of physics or neuroanatom y or cogni tive neurobiology will ever make good on this deficit. These physical sciences may tell us how the bat' s sensory system actu ally succeeds in its echo-locating task—that is, they may explain how the system works—but even com plete knowledge of the neurophysical details will fail to tell you what it is like, for the b a t, says Nagel. That subjective reality is apparently beyond the reach of the physical sciences. The identity theory, accordingly, is doomed to hit a brick wall where the phenom enal or qualita tive character of experience is concerned. Most people find this a hugely compelling argument, at least initially. But before you get too enthusiastic, note that an exactly
54
Chapter 2
parallel argument will also serve to ' show' that the ' subjective reality' here at issue is forever beyond the explanatory powers of dualism as well! Observe. Suppose we possess a detailed scientific theory of the nature and operations of a marvelous nonphysical substance called ectoplasm , a substance that constitutes the m ind of any con scious creature, hum ans and bats included. This ectoplasmic science may tell us how the bat' s sensory system and ectoplasm ic cognitive activity actually succeed in their echo-locating task—that is, it may provide an explanation of how this n o n physical system works—but even complete knowledge of the ectoplasmic details will fail to tell you what it is like, phenom enologically, for the bat. That subjective reality is apparently beyond the reach of the ectoplasmic sciences as well! Of course, we do not yet possess any such detailed ectoplasm ic theory of cognition, one ready to compete with modern cognitive neurobiology. (That is one of the problems with dualism.) But it is at least an irony that, if we did, an argument parallel to Nagel 's argument against the identity theory would also serve to shoot substance dualism down in flames. The parallel is more than merely ironic. The parallel illus trates that the problem facing any presumptive scientific theory here is not the virtue or vice of its peculiar subject m atter (neural m echanisms versus ectoplasmic processes). The problem facing both approaches is that any scientific theory, no matter what its proposed ontology, will be a system of discursive knowledge, whereas the target phenom enon here is a paradigm case of experiential or phenom enological knowledge, a fundam entally dif ferent ' orm of knowledge. Discursive knowledge requires, for example, that the cognizer possess a language, whereas phenom enological knowledge requires nothing of the sort. The former
The Ontological Problem
55
kind of knowledge may indeed tell us a great deal about the latter kind of knowledge. But no am ount of discursive knowl edge will ever constitute a case of phenom enological knowledge. This latter kind of knowledge deploys quite different neural mechanisms for its realization than the neural mechanism s that sustain our discursive understandings. It is no surprise, then, that no am ount of discursive knowledge, on any topic (let alone brain theory), will actually produce in you the quite dif ferent form of knowledge that the bat has concerning its own experiences. W hat is required to achieve that end is the m uch more demanding condition that the complete neurophysiological theory of bat-cognition be true o f you. That would do it, for you would then be a functioning bat. But simply knowing that theory isn' t remotely enough to make it actually true of you, even if the theory itself is both accurate and complete. Once again, some instructive parallels may drive the point home. Knowing the complete theory of superconductivity doesn't m ake you a superconductor. (That would require that the relevant theory be 'rue o f you.) Knowing the complete theory of what pregnancy is doesn' t m ake you pregnant. (That would require that the relevant theory of what pregnancy is currently be true o f you.) Knowing the complete theory of schizophrenia doesn't m ake you a schizophrenic. (That would require that the relevant psychiatric theory currently be true o f you.) Similarly, knowing the complete theory of bat-style cognition wouldn' t m ake you a bat-style cognizer. Nagel's argument imposes a wholly unreasonable demand on any adequate theory of bat-style cog nition, and the failure of any conceivable neuroscientific theory to m eet that demand is entirely without significance. You can't expect background discursive scientific knowledge to constitute
56
Chapter 2
current sensory experience. They are quite different animals. You can expect that the former will describe the latter, and in great explanatory detail, but as we shall see in a later chapter, current neuroscientific theories can already do that, and in revealing detail. Consider now a similar argument, again based on the introspectible qualities of our sensations. Here the sensations at issue are visual sensations, and their possessor is a hum an rather than a bat. Let us imagine (invites the philosopher Frank Jackson, the author of this thought experiment) a future neuro scientist named Mary. Mary has been raised in a room that has been scrupulously constructed to display no colors a t all save those that range from white, through the various shades of gray, to black. Her entire world looks to her as it would in an oldfashioned black-and-white movie. Nevertheless, she is scientifi cally inclined, pursues the study of neuroscience from within her room, and ultimately becomes the world' s premier expert on the brain's visual system. In particular, she knows everything physical there is to know about the ways in w hich color inform a tion is processed in normal hum an brains. But since she has been completely color-deprived all her life, as we have just sup posed, there will remain som ething she does not know about certain sensations, namely, w hat it is like to actually have a sensation-of-red. Therefore, concludes Jackson, complete knowledge of the physical facts of visual perception and its related brain activity still leaves som ething out. Accordingly, materialism cannot give an adequate account of all m ental phenomena, and the identity theory must be false. The logical parallel with Nagel' s bat-argument is extremely close, and so (the identity theorist will argue) is the underlying fallacy here at work, namely an equivocation on two entirely
The Ontological Problem
57
distinct kinds of knowledge. Concerning Mary's utopian knowl edge of the brain, "knows" means som ething like "has mastered the relevant set of discursive neuroscientific sentences." But concerning her (missing) knowledge of what it is like to have a sensation-of-red, "knows" means som ething like "has a prelinguistic representation of redness in her m echanisms for intro spective discrim ination." It is indeed true that one m ight have the former without having the latter. But, as we saw above, the identity theorist is n ot com m itted to the idea that having knowl edge in the former sense automatically constitutes having knowledge in the second sense. The identity theorist can admit a duality, or even a plurality, of different types o f knowledge without thereby com m itting him self to a duality in types o f things know n. The difference between a person who knows all about the visual cortex but has never enjoyed a sensation-of-red, and a person who knows no neuroscience but knows well the sensation-of-red, may reside n ot in w hat is respectively known by each (brain states by the former, nonphysical qualia by the latter), but rather in the different type, or m edium , or level of representation that each has of exactly the same thing: brain states. Mary 's undoubted deficit, accordingly, is entirely without any ontological or metaphysical significance. One can see this im m e diately by noting that our color-deprived Mary will be equally ignorant of w hat it is like to actually have a neural activation pattern of <50% , 90% , 50% > across the color-opponent neurons in her cortical area M4 (this what happens when a normal person sees red), for that is precisely the form of brain activity that her truncated experience has denied her. Does her ignorance here entail that the relevant activation pattern is nonphysical? Of course not. But the parallel inference in the former case is no better. Indeed, it is no different.
58
Chapter 2
In sum, there are pretty clearly more ways of 'having knowl edge' than just having mastered a set of scientific sentences, and the materialist can freely admit that one has 'knowledge' of sensations in a way that is utterly independent of the neurosci ence that one may or may not have learned. Animals, including humans, evidently have a prelinguistic mode of sensory recogni tion. This does not mean that sensations are beyond the reach of the physical sciences. It just means that the brain uses more modes or media of representation than the mere storage of sentences. W hich should have been obvious going in. A more recent argument against the identity theory, also m otivated by the worry that purely physical facts are inadequate to explain the existence of conscious phenom enal qualia, is the Zom bie Thought Experiment proposed in 1996 by the philosopher David Chalmers. We can perfectly well im agine, he claims, a species of cognitive creatures who are physically identical to us humans, down to the last synaptic connection and neurotrans m itter molecule, but who are completely devoid of any internal qualitative phenom enal experiences. They behave in all of the same ways that we do—because their physical constitutions interact with the physical world in the same ways that our own constitutions do—but they have no phenom enal consciousness at all. The 'lights are out ' inside them . They are, as it were, zombies. The conceivability of such qualia-free creatures, according to Chalmers, illustrates that the intrinsic or essential features of our conscious phen om enal states are entirely distinct from the causal/relational/functional/structural features that are so essen tial to the physical states of the brain. For it is plainly possible, at least, to have the latter without the former. In vain, then, could we hope to identify the phenom enal states with anything
The Ontological Problem
59
drawn from the domain of physical states. The essential natures of the former lie outside of, or beyond, the essential natures of the latter. There may well be natural laws that causally connect the two kinds of states, such that, under circumstances beyond our current understanding, certain kinds of neurophysiological states will typically cause certain kinds of phenom enal states to occur. But the two kinds of states would still be distinct in their essential natures, despite the contingent causal relations between them . Accordingly, a reductive identification of the one with the other remains out of the question. This position will rightly remind the reader of epiphenomenalism as discussed earlier (pp. 17-18). But Chalmers ' argu m ent here, against the identity theory, is new, and he prefers the more encompassing term "naturalistic dualism" as descrip tive of his own positive position. But let me push these broader matters aside. W hat should we make of his argument, and of its antireductive conclusion? Some will resist his claim that the zombie scenario is clearly conceivable, but I am prepared to go along with Chalmers on this point, at least as we currently conceive of our phenom enal states. W hat is more central here is Chalmers' presumption that our current conception of those phenom enal states is a reliable guide to their essential natures. Let us agree that we currently think of our phenom enal states as qualitative sim ples, as structureless unities, and (at the very least) as belonging to an ontologically distinct domain. No doubt most of us do. But nothing guarantees that these (almost) universal convictions are ' orrect. Perhaps our com m on convictions on these matters reflect, not so much our positive knowledge, but our massive ignorance of the ultimate nature of those phenom enal states—of their so-far hidden structure, of the systematic ground of their qualitative diversity, and of their comfortable
60
Chapter 2
but so-far unappreciated place w ithin the ontology of the physi cal brain. The idea that we can reliably determine the essential nature of any phenom enon simply by examining, from the com fort of the armchair, our current conception of that phe nom enon is an idea that is dubious in the extreme. It assigns to our current conceptions an authority that they may not deserve. Perhaps, to put it bluntly, we currently misconceive the real nature of our qualitative phenom enal states. Perhaps they need to be reconceived w ithin the more comprehensive fram e work of a completed science of the brain. Historical precedents for this sort of situation are numerous and highly instructive. For example, until the late modern period, our common-sense conception of ' ight portrayed it as som ething simple and utterly distinct from anything physical, som ething whose 'essential nature' was precisely to make physi cal objects visible. (This is parochial and ridiculous, of course.) Light displayed a complex range of qualitatively distinct colors, to be sure, but these were evidently qualitative simples also, unanalyzable into any underlying physical structure. Against this widespread conceptual background, the suggestion, by the English m athem atician Jam es Clerk Maxwell, that light was identical with his newly postulated electromagnetic waves was widely regarded as incomprehensible, at least initially. After all, the arcane theory of the utterly invisible force-fields that moved compass-needles and charged bits of chaff around had nothing obvious to do with the 'essential' features of light. Those fam il iar features evidently lay outside of or beyond the arcane and quite different features of electricity and magnetism. Or so it was initially, and quite wrongly, thought. But in the end, we slowly learned to reconceive light in terms of electromagnetic waves (and m uch to the illum ination of the former).
The Ontological Problem
61
Although I am unaware that anyone in Maxwell's era actually voiced an analogue to Chalmers' zombie scenario, constructing one to 'illustrate' the 'uniquely special' status of light is plainly possible. Consider the following (outrageously invalid) argument. "I can clearly imagine a universe that is physically identical to our own, down to the last atom, and with electric and magnetic fields bouncing around all over the place, but w hich is neverthe less pitch dark throughout, because it is devoid of light. The essential feature of light is lum inance, w hich feature lies outside of or beyond the domain of invisible forces such as electric and m agnetic fields. Light must therefore be som ething distinct from physical phenom ena such as electromagnetic waves." Here we have an entire 'zombie universe' whose conceivability is proposed as a refutation of the proposed identification of light with electromagnetic waves. Such a thought experiment, I suggest, is unlikely to undo your modern conviction that light is indeed identical with electromagnetic waves. Neither should Chalmers' scenario undo your well-founded anticipation that conscious phenom enal qualia m ight be identical with some appropriate type of brain states. In fact, in chapter 7, we will see that our beloved phenom enal qualia have already revealed a surprisingly com plex family of similarity and difference relations to one another, a family whose internal structure is positively explained on the assumption that qualia are n ot ontological 'simples' at all, but rather diverse configurations of neural activ ity in brain areas that science already understands. So far, the identity theory has proved to be very resilient in the face of these predominantly antimaterialist objections. But further objections, rooted this time in com peting forms of
62
Chapter 2
m aterialism , constitute a rather more serious threat, as the fol lowing sections will show. Suggested Readings
On the Identity Theory Place, U. T. "Is Consciousness a Brain Process?" British Journal o f Psychol
ogy 47 (1956). Reprinted in The Philosophy o f Mind, ed. V. C. Chappell (Englewood Cliffs, NJ: Prentice-Hall, 1962). Smart, J. J. C. "Sensations and Brain Processes." Philosophical Review 48 (1959). Reprinted in The Philosophy o f Mind, ed. V. C. Chappell (Engle wood Cliffs, NJ: Prentice-Hall, 1962). Lewis, David. "An Argument for the Identity Theory." Journal o f Philoso
phy 63, no. 1 (1966). Nagel, Thomas. "W hat Is It Like to Be a Bat?" Philosophical Review 83 (1974). Reprinted in Readings in Philosophy o f Psychology, vol. I, ed. N. Block (Cambridge, MA: Harvard University Press, 1980). Jackson, Frank. "Epiphenom enal Qualia." Philosophical Quarterly 32 (127) (April 1982). Chalmers, David. The Conscious Mind. Cambridge: Cambridge University Press, 1996. Churchland, Paul. "Reduction, Qualia, and the Direct Introspection of Brain States." Journal o f Philosophy 82 (1) (1985).
On Intertheoretic Reduction Nagel, Ernst. The Structure o f Science, chap. 11. New York: Harcourt, Brace & World, 1961. Feyerabend, Paul. "Explanation, Reduction, and Empiricism' " In Min
nesota Studies in the Philosophy o f Science, vol. III, ed. H. Feigl and G. Maxwell. M inneapolis: University o f M innesota Press, 1962.
The Ontological Problem
63
Churchland, Paul. Scientific Realism and the Plasticity o f Mind, chap. 3 . Cambridge: Cambridge University Press, 1979.
4
Functionalism
According to f unctionalism, the essential or defining feature of any type of m ental state is the set of causal relations it bears to (1) environm ental effects on the body, (2) other types of mental states, and (3) bodily behavior. Pain, for example, characteristi cally results from some bodily damage or trauma; it causes dis tress, annoyance, and practical reasoning aimed at relief; and it causes wincing, blanching, verbal outbursts, and nursing of the traumatized area. Any state that plays exactly that functional role is a pain, according to functionalism . Similarly, other types of m ental states (sensations, fears, beliefs, and so on) are also defined by their unique causal roles in a complex econom y of internal states mediating sensory inputs and behavioral outputs. This view may remind the reader of behaviorism, and indeed it is an heir to behaviorism, but there is one fundam ental dif ference between the two theories. Where the behaviorist hoped to define each type of m ental state solely in terms of environ m ental inputs and behavioral outputs, the functionalist denies that this is possible. As he sees it, the adequate characterization of almost any m ental state involves an inelim inable reference to a variety of other mental states with which it is causally con nected, and so a ' definition' solely in terms of publicly observ able inputs and outputs is quite impossible. Functionalism is therefore im mune to one of the main objections against philo sophical behaviorism. Thus the difference between functionalism and behaviorism. The difference between functionalism and the identity theory
64
Chapter 2
will emerge from the following (novel) argument against the identity theory. Imagine a being from another planet, says the functionalist, a being with an alien physiological constitution, a constitution based on the chemical elem ent silicon, for example, instead of on the element carbon, as ours is. His chemistry and physical details would have to be systematically different from ours. But even so, that chem ically alien brain could well sustain a func tional econom y of internal states whose mutual relations parallel perfectly the mutual causal relations that characterize our own m ental states. For example, the alien may have an internal state that meets all of the conditions for being a pain state, as out lined above. That state, considered from a purely physical point of view, would have a very different physical makeup from a hum an pain state, but it could nevertheless be identical to a hum an pain state from a purely functional point of view. And so for all of his functional states. If the alien's functional econom y of internal states were indeed functionally isomorphic with our own internal econom y— if those alien states were causally connected to inputs, to one another, and to behavior in ways that parallel our own causal connections—then the alien would have pains, and desires, and hopes, and fears just as fully as we do, despite dif ferences in the physical system that sustains or ' realizes' those functional states. W hat is im portant for mentality, argues the functionalist, is the n ot the matter of w hich the creature is made, but the causal structure of the internal activities which that matter sustains. If we can think of one alien constitution, we can think of many, and the point just made can also be made with respect to an artificial system. Were we to create an electronic system— a
The Ontological Problem
65
copper and silicon computer of some kind—whose internal econom y were functionally isomorphic with our own in all of the relevant ways, then it too would be the subject of m ental states. W hat this illustrates is that there are almost certainly m any more ways than one for nature, and perhaps even for ourselves, to put together a thinking, feeling, perceiving creature. And this raises a problem for the identity theory, for it seems that there is no single type of physical state to which a given type of m ental state must always correspond. Ironically perhaps, there are too m any different kinds of physical systems that can realize or instantiate the functional econom y characteristic of con scious intelligence. If we consider the universe at large, there fore, and the future as well as the present, it seems quite unlikely that the identity theorist is going to find the unique one-to-one match-ups between the concepts of our com m on-sense m ental taxonom y and the concepts of an overarching theory that encompasses all of the relevant, but quite various, physical systems. The prospects for universal, type/type identities, between types of brain states, and types of physical states, are therefore slim, concludes the functionalist. If the functionalists reject the traditional 'mental-type = physical-type' identity theory, virtually all of them remain com m itted to a weaker 'm ental-token = physical-token' identity theory, for they still m aintain that each instance of a given type of mental state is num erically identical with som e specific physical state in som e physical system or other. It is only the universal (type/type) identities that are rejected. Even so, this rejection is im portant because it is typically taken to support the claim that the science of psychology is or should be m ethodologically autonomous from the various physical sciences such physics, biology, and even
66
Chapter 2
neurophysiology. Psychology, it is claimed, has its own universal laws and its own abstract subject matter. As this book is written, functionalism is probably the most widely held theory of m ind among philosophers, cognitive psy chologists, and artificial intelligence researchers. Some of the reasons are apparent from the preceding discussion, and there are further reasons as well. In characterizing mental states as essentially functional states, functionalism places the concerns of psychology at a level that abstracts from the teem ing detail of a brain' s neurophysiological (or crystallographic, or m icro electronic) structure. The science of psychology, it is occasion ally said, is m ethodologically autonomous from those other sciences (biology, neuroscience, circuit theory) whose concerns are with what am ount to engineering details. This provides a rationale for a great deal of work in cognitive psychology and artificial intelligence, where researchers postulate a system of abstract functional states and then test the postulated system, often by way of its computer simulation, against hum an behav ior in similar circumstances. The aim of such work is to discover in detail the functional organization that makes us what we are. (Partly in order to evaluate the prospects for the functionalist philosophy of mind, we shall examine some of the research in artificial intelligence in chapter 6.) Arguments against Functionalism
Currently popularity aside, functionalism also faces difficulties. The m ost com m only posed objection cites an old friend: sensory qualia. Functionalism may escape one of behaviorism's fatal flaws (i.e., ignoring the m any causal relations am ong one's inter nal states), it is said, but it still falls prey to the other. By attem pt
The Ontological Problem
67
ing to make its m any relational properties the definitive feature of any given type of m ental state, functionalism ignores the 'inner' or qualitative aspect of our m ental states. But that qualita tive nature is the essential feature of a great m any types of m ental state (pain, sensations of color, of temperature, of pitch, and so on), runs the objection, and functionalism must there fore be false. The standard illustration of this apparent failing is called the "inverted spectrum thought experim ent." It is entirely conceivable, runs the story, that the range of color sensations that I enjoy upon viewing standard objects is simply inverted relative to the color sensations that you enjoy. W hen viewing a ripe tom ato, I may have what is really a sensation-of-green where you have the normal sensation-of-red; when viewing a ripe banana, I may have what is really a sensation-of-blue where you have the normal sensation-of-yellow; and so forth. But since we have no way of comparing our inner qualia, and since I shall make all of the same observational discriminations among objects that you will, there is no way to tell whether my inner spectrum is inverted relative to yours. The problem for functionalism arises as follows. Even if my spectrum is inverted relative to yours, we remain functionally isomorphic with one another. My visual sensation upon viewing a tom ato is functionally identical with your visual sensation upon viewing the same tom ato. According to functionalism , therefore, they are the very same type of sensation, and it does not even make sense to suppose that my sensation is 'really' a sensation-of-green. If it meets the functional conditions for being a sensation-of-red, then by definition it is a sensation-ofred. According to functionalism , apparently, a spectrum inver sion of the kind described is ruled out by definition. But such
68
Chapter 2
inversions are entirely conceivable, concludes the objection, and if functionalism entails that they are not conceivable, then functionalism is false. Another qualia-related worry for functionalism is the so-called absent qualia problem. The functional organization characteris tic of conscious intelligence can be instantiated (i.e., realized or instanced) in a considerable variety of physical systems, some of them radically different from a normal hum an. For example, a giant electronic computer m ight instantiate it, and there are more radical possibilities still. The philosopher Ned Block asks us to imagine the people of China— all 109 of them — organized into an intricate game of mutual interactions, guided by indi vidual instruction cards distributed to each citizen, so that col lectively they constitute a giant 'brain' w hich exchanges inputs and outputs with a single robot body. No individual Chinese citizen, of course, will have any idea of the system's overall cog nitive activities, any m ore than one of your own neurons grasps the larger picture of which it is but a tiny part. Still, that system of the robot-plus-10' -unit-'brain' could presumably instantiate the same functional organization that you do (though no doubt it would be rather slower in its activities than a hum an or a computer), and would therefore be the subject of genuine mental states, according to functionalism . But surely, it is urged, the com plex states that there play the functional roles of pain, plea sure, and sensations-of-color would n ot have any intrinsic qualia as ours do, and would therefore 'ail to be genuine conscious m ental states. Once again, functionalism seems at best an incom plete account of the nature of mental states. It has recently been argued that both the inverted-qualia and the absent-qualia objections can be met, without violence to functionalism , and without significant violence to our
The Ontological Problem
69
common-sense intuitions about qualia. Consider the inversion problem first. Perhaps the functionalist is right to insist that the type-identity of our visual sensations be reckoned strictly accord ing to their functional role. But the objector is also right in insisting that a relative inversion of two people's qualia, without functional inversion, is entirely conceivable. The apparent inconsistency between these two claims can be dissolved by insisting that (1) our functional states (or rather, their physical realizations) do indeed have an intrinsic nature on w hich our introspective identification of those states depends; while also insisting that (2) such intrinsic qualitative characters are never theless not essential to the type-identity of a given m ental state, and may indeed vary from instance to instance of the same type of functional state. W hat this means is that the qualitative character of your sensation-of-red m ight be different from the qualitative character of my sensation-of-red, slightly or substantially, and a third per son's sensation-of-red m ight be different yet again. But so long as all three states are caused by red objects and standardly cause all three of us to believe that some object is red, then all three states are sensations-of-red, whatever their intrinsic qualitative characters. Such intrinsic qualia, though quite real, merely serve as salient features that permit the quick introspective identifica tion of sensations, in the same way that black-on-orange stripes serve as a salient feature for the quick visual identification of tigers. But specific qualia are not essential to the type-identity of m ental states, any more than black-on-orange stripes are essen tial to the type-identity of tigers (think, for one example, of the uniformly white Himalayan tigers). Plainly, this solution requires the functionalist to admit the reality of qualia, and we may wonder how there can be room for
70
Chapter 2
qualia in his materialist world-picture. Perhaps they can be fit in as follows: identify them with the incidental physical properties of whatever physical states instantiate the m ental (functional) states that display them. For example, identify the qualitative nature of your sensations-of-red with that physical feature (of the brain that instantiates it) to w hich your m echanism s of intro spective discrim ination are in fact responding to, when you normally judge that you have a sensation-of-red. If materialism is true, then there must be some internal physical feature or other to w hich your introspective discrim ination of sensations-of-red is keyed: that is the quale of your sensations-of-red. If the pitch of a sound can turn out to be the frequency of an oscillation in air pressure, there is no reason why the quale of a sensation cannot turn out to be, say, the spiking frequency in a certain neural pathway. ('Spikes' are the tiny electrochem ical pulses by which our brain cells com m unicate with each other.) I leave it to the reader to judge the adequacy of these responses. If they are adequate, then, given its other virtues, functionalism must be conceded a very strong position among the competing theories of mind. It is interesting, however, that the defense just offered in the last paragraph found it necessary to take a leaf from the identity theorist's book (i.e., types of quale are reduced to or identified with types of physical state), since the final objection we shall consider also tends to blur the dis tinction between functionalism and reductive materialism. Consider the property of 'emperature, begins the objection. Here we have a paradigm of a physical property, one that has also been cited as paradigm of a successfully reduced property, as expressed in the intertheoretic identity "temperature of x = mean kinetic energy of x's m olecules."
The Ontological Problem
71
Strictly speaking, however, this identity is true only for the tem perature of a gas, where the molecules are free to move about in a ballistic fashion. In a solid, temperature is realized slightly dif ferently, since the tightly interconnected molecules are confined to a variety of vibratory m otions. In a p la sm a, temperature is som ething else again, since a plasma has no constituent m ole cules; they, and their constituent atoms, have so m uch energy that they have been ripped to pieces. They display ballistic m otions once more, but it is ions and electrons and other sub atomic particles that do the moving. And even a vacuum has a so-called blackbody temperature—in the peculiar distribution of electromagnetic waves coursing through it. Here, temperature has nothing to do with the kinetic energy of particles. It is plain that the physical property of temperature enjoys 'multiple instantiations' no less than do psychological proper ties. Does this mean that thermodynamics (the theory of heat and temperature) is an ' autonomous science ' , separable from the rest of physics, with its own irreducible laws and its own abstract subject matter? Presumably not. W hat it means, concludes the objection to functionalism , is that reductions are dom ain-specific: temperature-in-a-gas = the mean kinetic energy of the gas's molecules, whereas temperature-in-a-vacuum = the blackbody distribution of the vacuum's transient radiation. Similarly, perhaps joy-in-a-human = resonances in the human' s nucleus accumbens, whereas
72
Chapter 2
joy-in-a-martian = som ething else entirely. This means that we may expect some type/type reductions of hum an m ental states to hum an physical states after all, though such reductions will be species-specific. Furthermore, it means that functionalist claims about the radical autonom y of the science of psychology cannot be sustained. And last, it suggests that functionalism was not so profoundly different from the identity theory as was first made out. As with the defense of functionalism outlined earlier, I leave the evaluation of this criticism of functionalism to the reader. We shall have occasion for further discussion of functionalism in later chapters. At this point, let us turn to the final materialist theory of mind, for functionalism is n ot the only major reaction against the identity theory. Suggested Readings Putnam, Hilary. "M inds and M achines." In Dimensions o f Mind, ed. Sidney Hook. New York: NYU Press, 1960. Putnam, Hilary. "Robots: M achines or Artificially Created Life?" Journal
o f Philosophy 61 (21) (1964). Putnam, Hilary. "The Nature o f M ental States ' " In Materialism and the Mind-Body Problem, ed. David Rosenthal. Englewood Cliffs, NJ: PrenticeHall, 1971. Fodor, Jerry. Psychological Explanation. New York: Random House, 1968. Dennett, Daniel. Brainstorms. Montgomery, VT: Bradford, 1978.
Concerning Difficulties w ith Functionalism Block, Ned. "Troubles with Functionalism ." In Minnesota Studies in the
Philosophy o f Science, vol. IX, ed. C. W. Savage. M inneapolis: University
The Ontological Problem
73
o f M innesota Press, 1978. Reprinted in Readings in Philosophy o f Psychol ogy, ed. N. Block (Cambridge, MA: Harvard University Press, 1980). Churchland, Paul, and Patricia Churchland. "Functionalism , Qualia, and Intentionality' " Philosophical Topics 12, no. 1 (1981). Reprinted in
A Neurocomputational Perspective (Cambridge, MA: MIT Press, 1989). Shoemaker, Sidney. "The Inverted Spectrum' " Journal o f Philosophy 79 (7) (1982). Enc, Berent. "In Defense o f the Identity Theory' " Journal o f Philosophy 80 (5) (1983). Churchland, Paul. "Functionalism at Forty: A Critical Retrospective . "
Journal o f Philosophy 102 (1) (2005).
5
Eliminative Materialism
The identity theory was called into doubt not because the pros pects for a materialist account of our m ental capacities were thought to be poor, but because it seemed unlikely that the arrival of an adequate theory would bring the nice one-to-one match-ups, between the concepts of folk psychology on the one hand, and the concepts of theoretical neuroscience on the other, that intertheoretic reduction requires. The reason for that doubt was the great variety of quite different physical systems that could instantiate the required functional organization. Eliminative m aterialism also doubts that the correct neuroscien tific account of hum an cognitive capacities will produce a neat reduction of our common-sense framework of concepts, but here the doubts arise from a quite different source. As the eliminative materialists see it, the required one-to-one match-ups will n ot be found, and our common-sense psychologi cal framework will n ot enjoy an intertheoretic reduction, because that fram ew ork is a false and radically m isleading conception o f the
74
Chapter 2
causes o f human behavior and the nature o f our cognitive activity. On this view, folk psychology is not just an incom plete (because high-level) representation of our inner states and activities; it is an outright m isrepresentation of those inner states and activities. Consequently, we cannot expect a truly adequate neuroscientific account of our inner lives to provide theoretical categories that m atch up nicely with the existing categories of our com m onsense framework. Accordingly, we must expect that the older framework will simply be eliminated, rather than be reduced, by a matured neuroscience. We will thus end up using the theoreti cal vocabulary of that matured neuroscience to conduct our interpersonal affairs and even our private introspections. Historical Parallels
Just as the identity theorist can point to historical cases of suc cessful intertheoretic reduction, so the eliminative materialist can point to historical cases of the outright elim ination of the ontology of an older theory in favor of the ontology of a new and superior theory. For most of the eighteenth and nineteenth centuries, learned people believed that heat was subtle fluid held in bodies, m uch in the way water is held in a sponge. A fair body of moderately successful theory described the way this fluid substance— called "caloric fluid"—flowed within a body, or from one body to another, and how it produced therm al expan sion, boiling, melting, and so forth. But by the end of the eigh teenth century it had becom e abundantly clear that heat was not a kind of substance at all, but just the energy of m otion of the trillions of jostling molecules that make up the heated body itself. The new theory—the "m olecular/kinetic theory of matter and heat"—was much more successful than the old in explain ing and predicting the thermally-related behavior of bodies.
The Ontological Problem
75
And since we were unable to 'dentify caloric fluid with kinetic energy (according to the old theory, caloric is a kind of sub stance; according to the new theory, kinetic energy is a form of m otion), it was finally agreed that there is no such thing as caloric fluid. Caloric was simply eliminated from our accepted ontology of real things. A second example. It used to be thought that when a piece of wood burns, or a piece of metal rusts, a spiritlike substance called "phlogiston" was being released: briskly, in the former case, very slowly in the latter. Once gone, that 'noble' substance left only a base pile of ash or rust. It later came to be appreci ated, thanks to the French chemist Lavoisier, that both processes involve, n ot the loss of something, but the gaining of a substance drawn from the atmosphere, namely oxygen. Phlogiston chem istry emerged, n ot as an incom plete description of these familiar processes, but as a radical misdescription. Phlogiston was there fore not suitable for reduction to or identification with some thing within the new "oxygen chemistry," and it was simply eliminated from science. Admittedly, both of these illustrative examples concern the elim ination of som ething nonobservable, but our intellectual history also includes the elim ination of certain widely accepted 'observables'. Before Copernicus' views became available, any normal hum an who ventured out on a clear night could look up at the starry sphere o f the heavens, and if he stayed for a little while he could also see that the entire sphere turned, around an axis through the pole star, Polaris. W hat that gigantic sphere was made of (crystal?) and what made it turn (the gods?) were theoretical questions that exercised us for over two millennia. But hardly anyone doubted the existence of what everyone could observe with their own eyes. In the end, however, we
76
Chapter 2
learned to reinterpret our visual experience of the night sky w ithin a very different conceptual framework—that of Coperni cus and Newton— and the 'turning sphere' evaporated. Witches provide another example. Psychosis is a fairly com m on affliction among humans, and in earlier centuries its victims were standardly seen as cases of demonic possession, as instances of Satan' s spirit itself, glaring m alevolently out at us from behind the victim's eyes. That witches exist was n ot a matter of any controversy. One would occasionally see them , in any city or hamlet, engaged in incoherent, paranoid, or even murderous behavior. But observable or not, we eventually decided that witches simply do n ot exist. We concluded that the concept of a witch is an elem ent in a conceptual framework that misrepresents so badly the phenom ena to which it was standardly applied that literal application of the notion should be perm anently withdrawn. Modern theories of m ental illness led to the elim ination of witches from our serious ontology. The concepts of folk psychology—belief, desire, pain, joy, and so on— await a similar fate, according to the view at issue. And when neuroscience has matured to the point where the poverty of our current conceptions is apparent to everyone, and the superiority of the new framework is established, then we shall be able to set about reconceiving our internal states and activities, w ithin a truly adequate conceptual framework at last. Our explanations of one another' s behavior will appeal to such things as our neuropharmacological states, our high-dim en sional prototype representations, and the activation-patterns across specialized brain areas, and they may be profoundly enhanced by reason of the more accurate and dynamically pen etrating framework we will have to work with— just as the astronomer's perception of the night sky is enhanced by the
The Ontological Problem
77
detailed knowledge of modern astronomical theory that he or she possesses. The magnitude of the conceptual revolution here suggested should not be minimized: it would be enormous. And the b en efits to hum anity m ight be equally great. If each of us possessed an accurate and automatic neuroscientific understanding of (what we now dimly conceive as) the varieties and causes of m ental illness, the factors involved in learning, the neural basis of emotions, intelligence, and socialization, then the sum total of hum an misery m ight be m uch reduced. The simple increase in mutual understanding that the new framework makes pos sible could contribute substantially toward a more peaceful and hum ane society. Of course, there would be dangers as well: increased knowledge means increased power, and power can always be misused. Arguments fo r Eliminative Materialism
The arguments for eliminative materialism are diffuse and less than decisive, but they are stronger than is widely supposed. The distinguishing feature of this position is its denial that a sm ooth intertheoretic reduction is to be expected— even a species-specific reduction— of the framework of folk psychology to the framework of a matured neuroscience. The reason for this denial is the eliminative materialist' s conviction that folk psy chology is a hopelessly primitive and deeply confused concep tion of our internal states and activities. But why this low opinion of our com m on-sense conceptions? There are at least three reasons. First, the eliminative m ateri alist will point to the widespread explanatory, predictive, and manipulative failures of folk psychology. So much of what is central and familiar to us remains a complete mystery from
78
Chapter 2
w ithin folk psychology. We do n ot know what sleep is, or why we have to have it, despite spending a full third of our lives in that condition. (The answer, "For rest," is mistaken. Even if people are allowed to rest continuously, their need for sleep is undiminished. Apparently, sleep serves some deeper functions, but we do not yet know what they are.) We do n ot understand how learning transforms each of us from a gaping infant into a cunning adult, or how differences in intelligence are grounded. We have almost no idea how m em ory works, or how we manage to retrieve relevant bits of inform ation instantly from the awesome mass we have stored. We do not know what mental illness is, nor how to cure it. In sum, the most central things about us remain almost entirely mysterious from within folk psychology. And the defects noted cannot be blamed on inadequate time allowed for their correction, for folk psychology has enjoyed no significant changes or advances in well over 2,000 years, despite its m ani fest failures. We still use the same conceptual framework, in the marketplace and at the dinner table, as did the ancient Greeks. Truly successful theories may be expected to find successful reductions, but chronically unsuccessful theories m erit no such expectation. This argument from explanatory poverty has a further aspect. So long as one sticks to normal brains, the poverty of folk psychology is perhaps not strikingly evident. But as soon as one examines the perplexing behavior or cognitive deficits suffered by people with dam aged brains, one' s descriptive and explanatory resources start to claw the air (see, e.g., chapter 7.3, pp. 2 23-225). As with other humble theories asked to operate successfully in unexplored extensions of their original domain (for example, Newtonian m echanics in the domain of
The Ontological Problem
79
near-light velocities, or the classical gas law in the domain of very high pressures or temperatures), the descriptive and explanatory inadequacies of folk psychology becom e starkly, and frustratingly, evident. The second argument in support of the eliminativist tries to draw an inductive lesson from our deep conceptual history. Our early folk theories of the structure and activities of the heavens were wildly off the mark, and survive only as historical lessons of how wrong we can be. Our folk theories of the nature of fire, and the nature of life, were similarly cockeyed. And one could go on, since the vast m ajority of our past folk conceptions have been similarly exploded. All except folk psychology, which sur vives to this day and has only recently begun to feel critical pressure. But the phenom enon of conscious intelligence is surely a more com plex and difficult phenom enon than any of those just listed. So far as accurate understanding is concerned, it would be a m iracle if we had got that one right the very first time, when we fell down so badly on all the others. Folk psy chology has survived for so very long, presumably, n ot because it is basically correct in its portrayal of hum an cognition, but because the phenom ena addressed are so surpassingly difficult that any useful handle on them , no matter how feeble, is unlikely to be displaced in a hurry. A third argument focuses— skeptically— on the central family of representational states ascribed to us by folk psychology— namely, the 'propositional attitudes' such as believes that P, thinks that P, suspects that P, perceives that P, hopes that P, fears that P, doubts that P, desires that P, and so on. In all of these states, what substitutes for the variable "P," so as to identify the specific cognitive state being ascribed, is a declarative sen tence, a grammatically well-formed l inguistic item. That is, folk
80
Chapter 2
psychology portrays our cognitive econom y as an internal dance of sentence-like states, a dance that respects the various infer ential relations holding among the sentences used to specify the various Ps. This way of specifying internal cognitive states may be fine for creatures that com m and a language and understand its sen tences. But what of creatures that have no com m and of lan guage at all? That is, what of every creature on the p lan et except us humans? Is their cognition also an internal dance of sentence like states? Presumably not, since nonhum an animals display no capacity whatever for learning the com plex com binatorial struc tures involved in any language, or for manipulating cognitive representations in accordance with those com binatorial rules. Admittedly, we ascribe propositional attitudes, rightly or wrongly, to the broad range of nonhum an animals, and we do so because their cognition, in its underlying power and sophistication, is often comparable to, and in some dimensions even greater than, our own. The idea that only hum ans engage in com plex cogni tion is an idea that won 't stand a m om ent 's scrutiny. But the idea that animal cognition consists in a dance of sentence-like states is just as dubious. It is also dubious for prelinguistic hum an children, who manage to do w ithout the skills of language-manipulation for roughly the first two years of their lives. But during that period they have urgent practical impulses, they perceive the world around them in great detail, and they learn like the dickens. And among the things they learn, of course, is language! W hich suggests, again of course, that they possess a prior cognitive system that makes such learning possible. W hat is that prior and sublinguistic system?
The Ontological Problem
81
Presumably, it is roughly the same cognitive system deployed by all of the other animals on the planet, a cognitive system that gets by without any language-like states at all. This guess is strongly supported by the systematic similarity of structure that unites all mammalian brains, and even reptilian brains. We are all subtle variations on a robustly com m on theme. Gross brain anatomy locates all of our brains on a rough continuum of visible configurations, and exam ination of the brain' s m icro structure reveals the same basic com putational organization across the entire morphological spectrum. Throughout that spectrum, the basic forms of representation and computation are manifestly not linguaformal. (We shall examine what form they do have in chapter 7.) Apparently, our ascriptions of propositional attitudes to nonlinguistic animals is a massive case of anthropomorphism, a case of projecting parochial and human-focused conceptions onto creatures that do not, indeed, cannot, realize or instantiate them . But if none of the millions of other cognitive creatures on the planet are literally the subjects of propositional attitudes, what are we to say about the internal cognitive activities of hum ans? The same thing, argues the eliminativist. Plainly, early humans modeled their conception of hum an cognitive activity on the only systematic medium of representation and computation available to them at the time: hum an language. And a good thing, too, for it gave us at least som e predictive and explanatory advan tages, for the behavior of humans, and also for animals. But ultimately, he says, that linguaformal conception of our cogni tion is no more accurate for us than it is for any of the other creatures. Our brains work in essentially the same ways as all of
82
Chapter 2
our evolutionary brothers and sisters, and 'propositional atti tudes' have little or nothing to do with our mostly shared cogni tive activities. If we want to really understand hum an cognition, he concludes, we need to get rid of our linguaformal self-delu sion, and learn to discuss, and even to introspect, our cognition from w ithin the conceptual framework of a theory (cognitive neurobiology) that is adequate to all of the Earth's creatures. Our current conception is useful, no doubt, but at bottom it must misrepresent our true cognitive economy. Arguments against Eliminative Materialism
The initial plausibility of this rather radical view is rather low for almost everyone, since it denies some of our m ost deeply entrenched assumptions. That is at best a question-begging complaint, of course, since those assumptions are precisely what is at issue. But the following line of thought does attempt to m ount a real argument. Eliminative materialism is false, runs the com plaint, because one's introspection reveals directly the existence of beliefs, desires, fears, and so forth. Their existence is as obvious as any thing could be. The eliminative materialist will reply that his argument makes the same mistake that an ancient or medieval person would be making if he insisted that he could just see with his own eyes that the heavens form a rigidly organized turning sphere, or that witches exist. The fact is, all observation (introspection included) occurs w ithin some system of concepts, and our observation judgments are only as good as the conceptual framework in which they are expressed. In all three cases—the starry sphere, witches, and the familiar m ental states—precisely what is chal lenged is the integrity of the background conceptual frameworks
The Ontological Problem
83
in w hich the relevant observation judgments are expressed. To insist on the validity of one 's experience, as traditionally inter preted, is therefore to beg the very question at issue. (That is, it covertly assumes precisely what it is trying to prove.) For in all three cases, the question is whether we should reconceive the underlying nature of some familiar observational domain. A second criticism attempts to find an incoherence in the eliminative materialist' s position. The bald statem ent of elim i native materialism is that the familiar m ental states do not really exist. But that very statem ent is meaningful, runs the argument, only if it is the expression of a certain belief, and an intention to communicate, and a knowledge of the language in which it is expressed. But if the statem ent is true, then no such m ental states exist, and the 'statem ent' is therefore a m eaning less string of marks or noises, and thus cannot be true. Evidently, the assumption that eliminative materialism is true entails that it cannot be true! The hole in this judo-flip argument concerns the conditions supposedly necessary for a statem ent to be meaningful. Once again, it begs the question. If eliminative materialism is true, then meaningfulness must have some different source than the familiar one appealed to. To insist on the 'old' source is to insist on the validity of the very framework at issue. Again, an histori cal parallel may be helpful here. Consider the widespread m edi eval theory that being biologically alive is a matter of being ensouled by an im material vital spirit. And consider the follow ing response to someone who has just claimed that this theory, called vitalism , is false. My learned friend has stated that there is no such thing as vital spirit. But this statem ent is incoherent. For if it is true, then my friend does n ot have vital spirit, and must therefore be dead. But
84
Chapter 2
if he is dead, his 'statem ent' is just a string of noises, devoid of meaning or truth. Evidently, the assumption that antivitalism is true entails that it cannot be true! This second argument is now a joke, but the first argument begs the question in exactly the same way. A final criticism draws a much weaker conclusion against eliminative materialism, but makes a rather stronger case. Elimi native materialism, it has been said, is making m ountains out of molehills. It exaggerates the defects of folk psychology, and underplays its real successes. Perhaps the arrival of a matured neuroscience will require the elim ination of the occasional folkpsychological concept, continues the criticism, and some minor adjustments in certain folk-psychological principles may have to be endured. But the large-scale elim ination forecast by the eliminative materialist is just an alarmist worry or a romantic enthusiasm. Perhaps this com plaint is correct. And perhaps it is merely complacent. Whichever, it does bring out the im portant point that we do not confront two simple and mutually exclusive possibilities here: pure reduction versus blanket elim ination. Rather, these are the extremal points of a sm ooth spectrum of possible outcomes, between which there are mixed cases of partial elim ination
and partial reduction.
Only empirical
research (see chapter 7) can tell us where on that spectrum our own case will fall. Perhaps we should speak here, more cau tiously, of revisionary materialism, instead of concentrating on the more radical possibility of an across-the-board elim ination. Perhaps we should. But it has been my aim in this section to make it at least intelligible to you that our collective conceptual destiny lies substantially toward the revolutionary end of the spectrum.
The Ontological Problem
85
Suggested Readings Feyerabend, Paul. "Com m ent: 'M ental Events and the Brain.' " Journal
o f Philosophy 60 (1963). Reprinted in The Mind/Brain Identity Theory, ed. C. V. Borst (London: Macmillan, 1970). Feyerabend, Paul. "M aterialism and the M ind-Body Problem ." Review o f Metaphysics 17 (1963). Reprinted in The Mind/Brain Identity Theory, ed. C. V. Borst (London: Macmillan, 1970). Rorty, Richard. "M ind-Body Identity, Privacy, and Categories . " Review
o f Metaphysics 19 (1965). Reprinted in Materialism and the Mind-Body Problem, ed. D. M. Rosenthal (Englewood Cliffs, NJ: Prentice-Hall, 1971). Rorty, Richard. "In Defense o f Eliminative M aterialism ." Review o f Meta physics 24 (1970). Reprinted in Materialism and the Mind-Body Problem, ed. D. M. Rosenthal (Englewood Cliffs, NJ: Prentice-Hall, 1971). Churchland, Paul. "Elim inative Materialism and the Propositional Atti tudes." Journal o f Philosophy 78, no. 2 (1981). Reprinted in A Neurocom-
putational Perspective, Paul Churchland (Cambridge, MA: MIT Press, 1989). Dennett, Daniel. "W hy You Can ' t Make a Com puter That Feels Pain ' " In Brainstorms. Montgomery, VT: Bradford, 1978. Churchland, Paul. "The Evolving Fortunes of Eliminative M aterialism." In Contemporary Readings in the Philosophy o f Mind, ed. J. Cohen. Oxford: Blackwell, 2011.
3 The Semantical Problem
Where do the terms of our common-sense psychological vocab ulary get their meanings? This apparently innocent question is im portant for at least three reasons. First, psychological terms form a crucial test case for theories of m eaning in general. Second, the semantical problem is closely bound up with the ontological problem, as we saw in the first chapter. And last, it is even more closely bound up with the epistemological problem, as we shall see in the next chapter. In this chapter, we shall explore the arguments for and against each of the three main theories at issue. The first says that the m eaning of any common-sense psychological term (or m ost of them , anyway) derives from an act of inner ostension. A second claims that their m eaning derives from operational defini tions. And a third claims that the m eaning of any such term derives from its unique place in a network o f laws that collec tively constitute our 'folk' psychology. W ithout further ado, let us address the first theory. 1
Definition by Inner Ostension
One way to introduce a term to someone's vocabulary— "horse," or "fire engine," for example— is just to show that person an
88
Chapter 3
item of the relevant type, and say som ething like, "That is a horse," or "This is a fire engine." These are instances of what is called ostensive definition. One expects the hearer to notice the relevant features in the situation presented, and to be able to reapply the term correctly when a new situation displays the same features. Of course, both of the expressions cited could have been introduced in another way. One could have just said to the hearer, "A horse is a large, hoofed animal used for riding." Here one gives the m eaning of the term by connecting it in specific ways with other terms already in the hearer 's vocabulary. Such term introductions range from the explicit and the complete ("An isosceles triangle is a three-sided closed plane figure with at least two equal sides") to the partial and incom plete ("Energy is what makes our cars run and keeps our lights burning"). But not all terms get their m eaning in this way, it is often said. Some terms, it is claimed, can get their m eaning only in the first way, by direct ostension. Terms like "red," "sw eet," and "warm," for example. Their m eaning is not a matter of the relations they bear to other terms; it is a matter of their being directly associated with a specific quality displayed by perceiv able objects. Thus speak orthodox sem antic theory and com m on sense alike. What, then, of the terms in our common-sense psychological vocabulary? W hen one thinks of terms like "pain," "itch ," and "sensation of red," ostension seems the obvious source of meaning. How could one possibly know the m eaning of any of these terms unless one had actually had a pain, or an itch, or a sensation of red? Prima facie, it seems one could not. Call this "the standard view." W hile the standard view m ight be correct for a significant class of psychological terms, it is clearly not correct for all such
The Semantical Problem
89
terms, or even for the majority. Many im portant types of mental states have no qualitative character at all, or none that is rele vant to their type-identity. Consider the variety of different beliefs, for example: the belief that P, the belief that Q, the belief that R, and so on. We have here a potential infinity of im por tantly different states. One could n ot possibly master the meaning of each such expression by learning, one by one, a qualitative character peculiar to each state. Nor does each have a distinct quale anyhow. And the same goes for the potential infinity of distinct thoughts that P, and desires that P, and fears that P, and for all of the other 'propositional attitudes ' as well. These are perhaps the most central expressions in our com m onsense framework, and they are distinguished, one from another, by a role-playing element, the proposition or sentence P, not by some introspectible quale (= 'phenom enological quality'). Their meaning must derive from some other source. Clearly the standard view cannot be the whole story about the m eaning of psychological predicates. Further, the standard view is suspect even in its m ost plausible cases. Among those m ental states that are associated with qu alia, n ot all types have uniform quale. In fact, very few do, if any. Consider the term "pain," and think of the wide variety of substantially different sensations included under that term (think of a headache, a burn, a piercing noise, a blow to the kneecap, and so on). Granted, all of these qualia are similar in causing a reaction of dislike in the victim, but this is a causal/relational property com m on to all pains, not a shared quale. Even sensations-of-red show a wide variation through m any shades and hues, border ing on brown, orange, pink, purple, or black at their several extremes. Granted, intrinsic similarities do som ething to unify this diffuse class, but it seems clear that the class of sensationsof-red is equally delimited by the fact that such sensations
90
Chapter 3
typically result from viewing such standard examples as lips, strawberries, apples, and fire engines. That is, they are united by their shared causal/relational features. The idea of meaning being exhausted by a single, unambiguous quale seems to be a myth. Indeed, are we certain that knowing the quale is even neces sary to knowing the meaning? It has been argued that someone who has never been in pain (because of some defect in his nervous system) could still know the m eaning of the word "pain" and use it in conversation, explanation, and prediction, just as we use it in describing others. Granted, he would not know what pain feels like, but he could still learn all of its causal/ relational properties, and hence would know as well as we do what role the state of pain plays in all normal people. There would remain something he would not know, but it is n ot clear that the som ething is the m eaning of the word "pain." Finally, if the m eaning of terms like "pain" and "sensationof-red" really were exhausted by their association with an inner quale, then we would hard pressed to avoid a sem antic solipsism . (Solipsism is the thesis that all knowledge is impossible save for knowledge of one 's immediate conscious self.) Since each one of us can experience only one' s own states of consciousness, it would then be impossible for anyone to tell whether or not one's own m eaning for "pain" is the same as anyone else's. And surely it is an odd theory of m eaning that entails that no one ever understands what anyone else means by their shared vocabulary. These doubts about the standard 'inner ostension' theory of m eaning have prompted philosophers to explore other approaches. The first serious attempt to articulate and defend an alternative theory was provided by the philosophical behav-
The Semantical Problem
91
iorists, whom we met in the preceding chapter. These thinkers advanced a further argument against the standard view, which we shall now examine. 2
Philosophical Behaviorism
According to the behaviorists, the m eaning of any m ental term is fixed by the m any relations it bears to certain other terms: terms for publicly observable circumstances and behaviors. In its clearest formulations, behaviorism pointed to purely dispo sitional terms like "soluble" and "brittle" as semantical ana logues for m ental terms, and it pointed to operational definitions as the structures whereby the meanings of m ental terms could be made explicit. The details of this view were outlined in chapter 2.2, so I shall not repeat them here. A m ajor problem for behaviorism was the insignificant role it assigned to the qualia of our m ental states. But we have just seen some good reasons for reestimating (downward) the im por tance standardly assigned to qualia. And one of the m ost influ ential
philosophers
in
the
behaviorist
tradition,
Ludwig
W ittgenstein, had a further argument against the standard view: the private language argument. Despite the consequence of sem antic solipsism, m any defend ers of the standard view were prepared to live with the idea that one's vocabulary for sensations was an inescapably private lan guage. W ittgenstein attempted to show that such a necessarily 'private' language was completely impossible. His argument ran as follows. Suppose you attempt to give m eaning to a term "W " solely by associating it with a certain sensation you feel at the time. At a later time, upon feeling a sensation, you may say, "There is another W." But how can you
92
Chapter 3
determine whether you have used the term correctly on this occasion? Perhaps you misremember the first sensation, or care lessly see a close similarity between the second and the first when in fact there is only a faint and distant resemblance. If the term "W " enjoys no m eaning connections whatsoever with other phenom ena, such as certain standard causes and/or effects of the kind of sensation at issue, then there will be absolutely no way to distinguish between a correct use of "W " and an incorrect use of "W ." But a term whose proper application is forever and always beyond determ ination is a meaningless term. A necessarily private language is therefore impossible. This argument gave behaviorists m uch encouragement in their attempts to define our com m on terms for mental states in terms of their connections with publicly observable cir cumstances and behaviors. Despite the encouragement, those attempts never really succeeded (as we saw in chapter 2.2), and frustration gathered quickly. Perhaps this should have been expected, because W ittgenstein's private language argument draws a stronger conclusion than its premises justify. If a check on correct application is what is required for m eaning fulness,
then
all that one's understanding of "W "
need
include is some connections between the occurrence of the W-sensation and the occurrence of other phenom ena. Those other phenom ena need not be publicly observable phenomena: they can be other m ental states, for example, with causal con nections to W-sensations, and still serve as checks on the correct application of "W ." W hat W ittgenstein's argument should have concluded, therefore, is just that no term can be meaningful in the absence of systematic connections with other terms. Meaning, it appears, is som ething a term can enjoy only in the context of other
The Semantical Problem
93
terms, terms connected to one another by means of general statements that contain them . If W ittgenstein and the behaviorists had drawn this slightly weaker conclusion, then perhaps philosophers might have arrived at the semantic theory of the following section more swiftly than they did. Suggested Readings M alcolm, Norman. "W ittgenstein's Philosophical Investigations." Philo sophical Review 63 (1954). Reprinted in The Philosophy o f Mind, ed. V. C. Chappell (Englewood Cliffs, NJ: Prentice-Hall, 1962). Strawson, Sir Peter. "Persons." In Minnesota Studies in the Philosophy o f Science, vol. II, ed. H. Feigl and M. Scriven. M inneapolis: University of M innesota Press, 1958. Reprinted in The Philosophy o f Mind, ed. V. C. Chappell (Englewood Cliffs, NJ: Prentice-Hall, 1962). Hesse, Mary. "Is There an Independent Observation Language?" In The Nature and Function o f Scientific Theories, ed. R. Colodny. Pittsburgh: Pittsburgh University Press, 1970. See especially pp. 4 4 -4 5 .
3
The Theoretical N etw ork Thesis and Folk Psychology
The view to be explored in this section can be stated as follows. Our common-sense terms for m ental states are the theoretical terms of a theoretical fram ew ork (namely, 'folk psychology') embed ded in our com m on-sense understanding, and the m eaning of those terms is fixed by the set of laws/principles/generalizations in w hich they figure. In order to explain this view, let me back up a few steps and talk about theories for a few moments. The Semantics of Theoretical Terms
Consider large-scale theories, such as those found in the physi cal sciences: chemical theory, electromagnetic theory, atomic
94
C hapter 3
theory, thermodynamics, and so on. Typically, such a theory consists of a set of sentences—usually general sentences or pre sumptive taws o f nature. These laws express the relations that hold between the various properties/values/states/entities whose existence is postulated by the theory. Such states and entities are expressed or denoted by the set of theoretical terms peculiar to the theory in question. Electromagnetic theory, for example, postulates the existence of electric charges, electric force fields, and magnetic force fields; and the laws of electromagnetic theory state how these things are related to one another and to various observable phenom ena. To fully understand the expression "electric field" is to be familiar with the network of theoretical principles or laws in which that expression appears. Collectively, they tell us what an electric field is and what it does. This case is typical. Theoretical terms do not, in general, get their meanings from single, explicit definitions stating the conditions necessary and sufficient for their correct application. Rather, they are implicitly defined by the entire network of principles or laws that embed them . Such casual ' definitions' as one does find given (for example, "The electron is the funda m ental unit of electricity") usually give only a small part of the term's significance, and are always subject to falsification in any case. (For example, it now appears that the quark is the basic unit of electricity, with a charge one-third that of the electron.) Call this 'framework-focused' account the network theory o f m eaning. The Deductive-Nomological M odel of Explanation
The collected laws of any theory do more, however, than just give sense to the theoretical terms they contain. They also serve
The Semantical Problem
95
a predictive and explanatory function, and this is their main purpose and value. W hich raises the question: W hat is it to give an explanation of an event or state of affairs, and how do theories make this possible? We may introduce the conventional wisdom on this point with the following story. In my laboratory there is an apparatus consisting of a long metal bar with two facing mirrors, one attached to each end. The point of the bar is to keep the mirrors a precise distance apart. One morning, while measuring that distance just prior to performing some experiment, m y assistant notices that the bar is now longer than it was originally, by about one millimeter. "Hey," he announces, "this bar has expanded. W hy is that?" "Because I heated it," I explain. "Y-e-s?" he queries, "what's that got to do with anything?" "Well, the bar is made of copper," I explain further. "Y-e-s?" he persists, "and what 's that got to do with it?" "Well, all copper expands when heated," I reply, suppressing my exasperation. "A-h-h, I see," he says, as the light finally dawns. If, after m y final remark, my assistant had still failed to under stand, then I should have to fire him, because the explanation of why the bar expanded is now complete, and even a child should get it. We can see why, and in what sense, it is complete by looking at the assembled inform ation m y explana tion contained. 1. All copper expands when heated. 2. This bar is copper. 3. This bar is heated. Thus, 4. This bar is expanded.
96
C hapter 3
The reader will notice that, collectively, the first three proposi tions deductively entail the fourth proposition, the statem ent of the event or state of affairs to be explained. The bar' s expansion is an inevitable consequence of the conditions described in the first three propositions. We are looking here at a valid deductive argument. An expla nation, it seems (when all of its elements are made explicit), has the form of an argument, an argument whose premises (the so-called explanans) contain the explanatory inform ation, and whose conclusion (the so-called explanandum ) describes the puz zling fact-to-be-explained. Most important, the premises include at least one nomological statem ent— a law of nature, a general statement expressing the general patterns to w hich nature adheres. The other premises express what are com m only called "initial conditions," and it is these that connect the law to the specific fact in need of explanation. In sum, to explain an event or state-of-affairs is to deduce its description from a law of nature. (Hence the name, "the deductive-nomological model of explanation.") The connection between comprehensive theories and explanatory power is now easy to see. The prediction of events and states of affairs, we should note, follows essentially the same pattern. The difference is that the conclusions of the relevant arguments are in the future tense, rather than in the past or present tense. Notice also a further point. W hen voicing an explanation in ordinary life, one hardly ever states every premise of the relevant argument. (See m y first response to my assistant.) There is generally no point, since one can assume that one' s hearers already possess m ost of the rele vant inform ation. W hat one typically gives them is just the specific piece of inform ation one presumes they are missing (for example, "I heated it"). Most explanations, as voiced, are only
The Semantical Problem
97
explanation ' sketches.' The hearer is left to fill in what is left unsaid. Last, it should also be pointed out that the 'laws' that lie behind our common-sense explanations are usually on the rough-and-ready side, expressing only a rough approximation to, or an incom plete grasp of, the true regularities involved. This is thus one further dimension in which our explanations are generally explanation-sketches. Folk Psychology
Consider now the considerable capacity that norm al humans have for explaining and predicting the behavior of their fellow humans. We can even explain and predict the psychological states of other humans, the states that are hidden from our external perceptions. We explain their behavior in terms of their beliefs and desires, and their pains, hopes, and fears. We explain their sadness in terms of their disappointment, their intentions in terms of their desires, and their beliefs in terms of their per ceptions and their inferences. How is it we are able to do all this? If the account of explanation in the preceding section is correct, then each of us must possess a knowledge or a comm and of a rather substantial set of laws or general statements con necting the various m ental states with (1) other m ental states, with (2) external circumstances, and with (3) overt behaviors. Do we? We can find out by 'pressing' some common-sense explana tions, as the explanation was pressed in the sample conversation earlier, to see what other elements are com m only left unsaid. W hen we do, argue the proponents of this view, we uncover literally hundreds and hundreds of common-sense generaliza tions concerning m ental states, such as the following.
98
Chapter 3
Persons tend to feel pain at points of recent bodily damage. Persons denied fluids for some time tend to feel thirst. Persons in pain tend to want to relieve that pain. Persons who feel thirst tend to desire drinkable fluids. Persons who are angry tend to be im patient. Persons who feel a sudden sharp pain tend to wince. Persons who want that P, and believe that Q would be sufficient to bring about P, and have no conflicting wants or preferred strategies, will try to bring it about that Q. These familiar platitudes, and hundreds of others like them in which other m ental terms are embedded, are what constitute our understanding of how we work. These rough-and-ready general statements or laws support explanations and predictions in the normal fashion. Collectively, they constitute a theory, a theory that postulates a range of internal states whose diverse causal relations are described by the theory's laws. All of us learn that framework (at m other' s knee, as we learn our language), and in so doing we acquire the common-sense conception of what conscious intelligence is . We may call that theoretical framework "folk psychology." It embodies the accumulated wisdom of thousands of generations' attempts to understand how we hum ans work. To illustrate, briefly, the role that such laws play in ordinary explanations, consider the following exchange. "W hy did M ichael wince slightly when he first sat down to the meeting?" "Because he felt a sudden sharp pain." "I see. And why did he feel a pain?" "Because he sat on the tack I placed on his chair."
The Semantical Problem
99
Here we have two explanations, one on the heels of the other. If each is pressed, in the m anner of our initial example, the sixth and first laws of the preceding list will emerge from the presumptive background, and two deductive arguments will becom e apparent, showing the same pattern as in the explana tion of the expended metal bar. If folk psychology is literally a theory—albeit a very old theory, deeply entrenched in hum an language and culture— then the meanings of our psychological terms should indeed be fixed as the thesis of this section says they are: by the set of folk-psychological laws in which they figure. This view has a certain straightforward plausibility. After all, who will say that someone understands the m eaning of the term "pain" if he has no idea that pain is caused by bodily damage, that people hate it, or that it causes distress, wincing, moaning, and avoidance behavior? Qualia Again
But what of the qualia of our various psychological states? Can we really believe, as the network theory of meaning seems to require, that qualia play no role in determining the meanings of our psychological terms? The intuition that they do is extremely strong. There are at least two ways in w hich a defender of the network theory m ight try to handle this peren nial question. The first is just to admit that qualia do play som e role in the meaning of som e terms, though only a secondary role at best. This concession would go a long way toward soothing our intu itions, and it is tem pting to just adopt it and declare the issue closed. But it does leave certain problems unsolved. Since the
100
Chapter 3
qualia of your sensations are apparent only to you, and m ine only to me, then a part of the m eaning of our sensation-terms will remain private, and it will still be a stubbornly open ques tion whether any of us means the same thing by those terms. The second compromise concedes to qualia a significant role in the spontaneous application of sensation-terms, but still attempts to deny that their role enjoys any sem antic significance. The idea is that your introspective discrim ination of a pain from a tickle, or a sensation-of-red from a sensation-of-green, is of course keyed to the qualitative character, in you, of the relevant states. Each of us learns to exploit such qualia as our internal states display, in order to make spontaneous observation judg m ents as to which states we are in. But what is strictly and pub licly m eant by "pain," for example, does n ot include any com m itm ent to any specific qualia. The qualitative character of pains varies substantially even within a given individual; it may well vary even more widely across different individuals; and it almost certainly varies substantially across distinct biological species. Qualia, therefore, can be conceded an epistemological significance, but without conceding them a sem antic signifi cance for terms in an intersubjective language. (This is the same dodge briefly explored concerning functionalism on p. 69.) Thus two com peting addenda to the network theory of meaning. W hich one should be adopted, if either, I leave to the reader to decide. In either case, the background lesson appears plain: the dominant, and perhaps the only, source of meaning for our psychological terms is the common-sense theoretical network in which they are embedded. As with theoretical terms generally, one comes to understand them only as one learns to use the predictive and explanatory generalizations in which they figure.
The Semantical Problem
101
General Significance
The significance of this network theory of meaning—for the m ind-body problem— is as follows. The network theory is strictly consistent with all three of the current materialist posi tions, and it is also consistent with dualism. It does n ot by itself entail or rule out any of these positions. W hat it does do is tell us som ething about the nature of the conflict between them all, and about the ways in which the conflict will eventually be resolved, one way or the other. The lesson is as follows. If our com m on-sense conceptual framework for psychologi cal states is literally a theory (albeit an old one), then the ques tion of the relation between mental states and brain states becomes a question of how an old theory (folk psychology) is going to be related to a new theory (matured neuroscience) which threatens in some way to displace it. The four major positions on the m ind-body issue emerge as four different antic ipations of how that theoretical conflict is going to be resolved. The identity theorist expects that the older theory will be sm oothly reduced, in the benign explanatory way discussed above, by a matured neuroscience. The dualist m aintains that the old theory will not be reduced by a matured neuroscience, because folk psychology describes a nonphysical econom y of nonphysical cognitive states. The functionalist also expects that the old theory will not be reduced, but because (ironically) too m any different kinds of physical systems can produce exactly the causal organization specified by the old theory. And the eliminative materialist also expects, once again, that the old theory will fail to find a successful neuroscientific reduction, on the yet different grounds that the old theory is simply too con fused and inaccurate to win survival through intertheoretic reduction.
102
Chapter 3
W hat is at issue here is the fate of a theory, the fate of a speculative and at least partly successful explanatory frame work, namely, our own beloved folk psychology. And it is appar ent that the issue between these four possible fates is basically an empirical issue, to be settled decisively only by continuing research in the neurosciences, cognitive psychology, and artifi cial intelligence. Some of the available research results have already been marshaled in chapter 2. More will be explored in the final three chapters. The conclusion of this chapter—that our familiar self-conception is and always has been a theoretical conception in its own right— places all of those results in a deeper perspective. As we shall see, the network theory of m eaning also has m ajor consequences for the vexing epistemological problems explored in the next chapter. We shall turn to those problems after exam ining one final issue concerning meaning: the socalled intentionality of m any of our mental states. Suggested Readings Sellars, Wilfrid. "Em piricism and the Philosophy of M ind." In Minnesota
Studies in the Philosophy o f Science, vol. I, eds. H. Feigl and M. Scriven. M inneapolis: University o f M innesota Press, 1956. Reprinted in Wilfrid Sellars, Science, Perception, and Reality (New York: Routledge & Kegan Paul, 1963); see especially sections 4 5 -6 3 . Fodor, Jerry, and C. Chihara. "Operationalism and Ordinary Language: A Critique o f W ittgenstein." American Philosophical Quarterly 2, no. 5 (1965). Churchland, Paul. Scientific Realism and the Plasticity o f Mind. Cambridge: Cambridge University Press, 1979. Hempel, Carl, and Paul Oppenheim . "Studies in the Logic o f Explana tion ." Philosophy o f Science. 15 (1948), part I. Reprinted in Aspects o f
The Semantical Problem
103
Scientific Explanation, ed. Carl Hempel (New York: Collier-Macmillan, 1965). Churchland, Paul. "The Logical Character of Action-Explanations."
Philosophical Review 79 (2) (1970).
4
Intentionality and the Propositional Attitudes
We have so far been exploring the language we use to talk about our m ental states, and exploring theories as to the source of its meaning. Let us now direct our attention to certain of those m ental states themselves—to thoughts, and beliefs, and fears, for example—for each such state also has a 'm eaning', a specific propositional 'content'. One has the thought that [children are marvelous], the b elie f that [humans have great potential], and the fear that [civilization will suffer another Dark Age]. Such states are called propositional attitudes, because each expresses a distinct ' attitude' toward a distinct proposition. In the technical vocabulary of philosophers, such states are said to display intentionality, in that they 'intend' som ething or 'point to' som ething beyond themselves: they ' intend' or ' point to' , children, humans, and civilization. (A caution: this use of the term "intentionality" has nothing to do with the term "in ten tional" as m eaning "done deliberately.") Propositional attitudes are not rare. They dominate our folkpsychological vocabulary. Recall that one can suspect that P, hope that P, desire that P, hear that P, introspect that P, infer that P, suppose that P, guess that P, prefer that P to that Q, be disgusted that P, delighted that P, amazed that P, alarmed that P, and so on and so forth. Collectively, these states constitute
104
Chapter 3
the essence of conscious intelligence, as folk psychology con ceives it. The intentionality of these propositional attitudes has occa sionally been cited as the crucial feature that distinguishes the m ental from the merely physical, as som ething that no purely physical state can display. Part of this claim may be quite correct, in that the rational m anipulation of propositional attitudes may indeed be the distinctive feature of conscious intelligence. But though intentionality has often been cited as 'the mark of the m ental', it need not constitute a presumption in favor of some form of dualism. We have already seen, in chapter 2.3, how purely physical states such as brain states m ight possess propositional contents, and hence display intentionality. Having content or meaning, it seems, is just a matter of playing a spe cific role in a com plex inferential/com putational economy. And there is no reason why the internal states of a brain, or even of a computer, could not play such roles. If certain states of our brains do play such a role, and if our m ental states are in some sense identical with those brain states (as the identity theory and functionalism both claim), then we have here not a refutation of materialism, but rather a plausible explanation of how it is that our propositional attitudes have propositional content in the first place. And if they have a dis tinct m eaning or propositional content, then of course they will have a reference (or attempted reference) as well: they will have the 'pointing beyond' themselves that originally characterized intentionality. There is a historical irony in the fact that the propositional attitudes have occasionally been cited by philosophers as that which marks off the m ental as utterly different from the physi cal. The irony is that when we examine the evident logical
The Semantical Problem
105
structure of our folk conceptions here, we find n ot differences, but rather some very deep and systematic similarities between the structure of folk psychology and the structure of paradigm atically physical theories. Let begin by comparing the ele m ents of the following two lists.
Propositional attitudes
Numerical attitudes
... believes that P
... has a lengthm o f n
... desires that P
... has a velocitym/s o f n
... fears that P
... has a temperatureF o f n
... sees th at P
... has a chargec o f n
... suspects that P
... has a kinetic energy: ° f n
and so on.
and so on.
The reader will note that where folk psychology displays propositional 'attitudes', m athem atical physics displays numerical 'attitudes'. Any expression on the first list is properly completed by putting a term for a specific proposition in place of "P," whereas any expression from the second list is properly com pleted by putting a term for a specific number in place of " n." Only then does a determinate predicate result. This structural parallel yields further parallels. Just as the arithm etic relations between numbers (for example, being twice as large as n) can also characterize the objective relations between numerical atti tudes (for example, my weight may be twice your weight), so do the logical relations between propositions (for example, logical inconsistency, entailm ent) also characterize the relations between propositional attitudes (for example, my belief that P is inconsistent with your belief that not-P). The respective kinds
106
Chapter 3
of attitudes ' inherit' the abstract relations had by their respec tive kinds of abstract objects. These parallels underlie the most im portant parallel of all. Where the relation between certain kinds of propositional attitudes, or between certain kinds of numerical attitudes, holds universally, we can state law s, laws that exploit the abstract relations holding between the ' atti tudes' that they relate. Many of the explanatory laws of folk psychology display precisely this pattern. Observe: • I f x fears that P, then x desires that not-P. • I f x hopes that P, and discovers that P, then x is pleased that P. • If x believes that P, and x believes that (if P then Q), then, barring confusion, distraction, and so on, x will believe that Q. • If x desires that P, and believes that (if Q then P), and x is able to bring it about that Q, then, barring conflicting desires or preferred strategies, x will bring it about that Q.1 The laws of m athem atical physics display a precisely parallel structure, only in their case it is numerical relations that are being exploited to state the relevant regularities, rather than logical relations. • If a gas x exerts a pressure of P, and x has a volume of V , and x has a mass of p, then, barring very high pressure or density, x has a temperature of (PV/pR). • ' f x has a mass of M, and x suffers a net force of F, then x has an acceleration of (F/M). Examples like this can be multiplied into the thousands, in both the psychological and the physical domains. As well, m any of 1. Strictly, these sentences should all be universally quantified over the variables x , P, and Q. But since this introductory textbook presupposes no form al logic, I shall simply ignore these subtleties.
The Semantical Problem
107
the expressions in the physical sciences contain a term for a vector rather than a number, and the laws comprehending such 'vectorial attitudes' characteristically display or exploit the algebraic/trigonometric relations that hold between the vectors denoted by those terms. For a simple example, • If x has a m om entum of P x and y has a m om entum of P y, and x and y are the only interacting bodies in an isolated system, then the vector sum of P x and P y is a constant over time. W hat is taking place in such examples is the same in all cases. The abstract relations holding in the domain of certain abstract objects—numbers, or vectors, or propositions— are drawn upon to help us state the empirical regularities that hold between real states and properties, such as between temperatures and pres sures, or forces and accelerations, or interacting m omenta, . . . or between various types of m ental states. The conceptual framework of folk psychology is exploiting an intellectual strat egy that is standard in m any of our intellectual endeavors. And just as a theory is neither essentially physical, nor essentially nonphysical, for exploiting numbers or vectors, neither is a theory essentially physical, nor essentially nonphysical, for exploiting propositions.
It remains an empirical question
whether the propositional attitudes are ultim ately physical in nature. The mere fact that they are propositional attitudes (and hence display intentionality) entails nothing one way or the other. There are two apparent lessons to be drawn from this brief discussion. The first is the idea that since m eaning arises from an item's place in a network of assumptions, and from the resulting conceptual role that the item plays in the system' s ongoing inferential economy, our m ental states can therefore
108
Chapter 3
have the propositional contents they do have precisely because of their intricate relational features. This would mean that there is no problem in assuming that physical states could have propositional content, since in principle they could easily enjoy the relevant relational features. This view is now fairly widespread among researchers in the field, but it is not the universal opinion, so the reader is invited to be cautious. The second lesson concerns the systematic structural parallels that hold between the concepts and laws of folk psychology, and the concepts and laws of other theories. The emergence of these parallels coheres closely with the view, already suggested in the preceding sections, that folk psychology is literally a theory. Some further encouragement for this view will emerge in the next chapter. Suggested Readings Brentano, Franz. "The D istinction between M ental and Physical Phe nom ena." In Realism and the Background o f Phenomenology, ed. R. M. Chisholm . Glencoe, IL: Free Press, 1960. Chisholm, Roderick. "Notes on the Logic o f Believing: " Philosophy and
Phenomenological Research 24 (1963). Churchland, Paul. "Elim inative Materialism and the Propositional Atti tudes." Journal o f Philosophy 78, no. 2 (1981), section 1. Churchland, Paul. Scientific Realism and the Plasticity o f Mind. Cambridge: Cambridge University Press, 1979. Field, Hartry. "M ental Representations." Erkenntnis 13, no. 1 (1978). Reprinted in Readings in the Philosophy o f Psychology, vol. II, ed. N. Block (Cambridge, MA: Harvard University Press, 1981).
The Semantical Problem
109
Fodor, Jerry. "Propositional Attitudes." Monist 61, no. 4 (1978). Reprinted in Readings in the Philosophy o f Psychology, vol. I I, ed. N. Block (Cam bridge, MA: Harvard University Press, 1981). Stich, Steven C. From Folk Psychology to Cognitive Science: The Case against Belief . Cambridge, MA: MIT Press/Bradford Books, 1983.
Against the Inferential-Netw ork Theory o f M eaning and Intentionality Searle, Jo h n . "Minds, Brains, and Programs r" Behavioral and Brain Sci
ences 3 (3) (1980).
4
The Epistemological Problem
The epistemological problem has two halves, both of them concerned with how we come to have knowledge of the internal activities of conscious, intelligent minds. The first problem is called the problem o f other minds: How does one determine whether som ething other than oneself—an alien creature, a sophisticated robot, a socially active computer, or even another hum an—is really a thinking, feeling, conscious being, rather than, for example, an unconscious automaton whose behavior arises from som ething other than genuine m ental states? How can one tell? The second problem is called the problem o f self consciousness: How is it that any conscious being has an im m edi ate and privileged knowledge of its own sensations, emotions, beliefs, desires, and so forth? How is this possible? And just how trustworthy is that knowledge? The solutions to these two prob lems, I think it will emerge, are n ot independent of each other. Let us explore the first problem first. 1
The Problem of O ther Minds
It is of course by observing a creature 's behavior in various cir cumstances, including its verbal behavior, that we judge it to be
112
Chapter 4
a conscious, thinking creature—to be an ' other m ind ' . From bodily damage and moaning, we infer pain. From smiles and laughter, we infer joy. From the dodging of a snowball, we infer perception. From complex and appropriate manipulations of the environment, we infer desires, intentions, and beliefs. From these and other things, and above all from speech, we infer conscious intelligence in the creature at issue. This much is obvious, but these remarks serve only to intro duce our problem, n ot to solve it. The problem begins to emerge when we ask what justifies the sorts of inferences cited. To infer the (hidden) occurrence of certain kinds of m ental states from the occurrence of certain kinds of behavior is to assume that appropriate general connections hold between them, connec tions presumably of the form, "If behavior of kind B is displayed by the creature, then usually a m ental state of kind M is occur ring." Such ' psycho-behavioral generalizations ' have the form of standard empirical generalizations, such as, "If a sound like thunder occurs, then there usually is (or was) a lightning strike somewhere in the vicinity." Presumably, their justification is parallel also: such general statements are justified by our past experience of a regular connection between the phenom ena cited. Wherever and whenever we perceive lightning, we gener ally perceive (very loud) thunder also, and barring the m achin ery of war, nothing else produces exactly that sound. But how can one be justified in believing that the relevant psycho-behavioral generalizations are true of other creatures, when all one can ever observe is on e-h alf o f the alleged connection: namely, the creature's behavior? The creature 's m ental states, if he happens to have any, are directly observable only by the crea ture himself. We cannot observe them . And so we cannot pos sibly gather the sort of empirical support needed. Apparently, then, one cannot possibly be justified in believing in such psy
The Epistemological Problem
113
cho-behavioral generalizations. Accordingly, one cannot be jus tified in drawing inferences from another creature's behavior, to his possession of mental states. W hich is to say, one cannot be justified in believing that any creature other than oneself has m ental states! This skeptical conclusion is deeply implausible, but the skep tical problem is quite robust. Belief in other minds requires inferences from behavior; such inferences require generaliza tions about creatures in general; such generalizations can only be justified by experience of the relevant connections in crea tures in general; but experience of one' s own case is all one can have. This is the classical problem of other minds. The Argum ent from Analogy
There are three classical attempts at a solution to the problem of other minds, and perhaps the simplest of these is the argu m ent from analogy. One can observe both halves of the relevant psycho-behavioral connections in exactly one case, it is argued: in one 's own. And one can determine that the required gener alizations are true, at least of oneself. But other hum ans are, so far as I am able to observe, entirely similar to me. If the relevant psycho-behavioral generalizations are true of me, then it is a reasonable inference, by analogy with my own case, that they are also true of other humans. Therefore, I do have some justi fication for accepting those generalizations after all, and I am therefore justified in drawing specific inferences about the m ental states of others on the strength of them. Our impulse to resist the skeptical conclusion of the problem of other minds is sufficiently great that we are likely to grasp at any solution that promises a way around it. There are serious difficulties with the argument from analogy, however, and we should be wary of accepting it. The first problem is that it
114
Chapter 4
represents one' s knowledge of other minds as resting on an inductive generalization from exactly one case: one 's own. This is absolutely the weakest possible instance of an inductive argu ment, comparable to inferring that all bears are white on the strength of observing only a single bear (a polar bear). It may well be wondered whether our robust confidence in the existence of other minds can possibly be accounted for and exhausted by such a feeble argument. Surely, one wants to object, my belief that you are conscious is better founded than that. And there are further problems. If one' s knowledge of other minds is ultimately limited by the connections that one can observe in one's own case, then it will n ot be possible for color blind people justly to believe that other hum ans have visual sensations that are denied to them, nor possible for a deaf person to believe that others can hear, and so forth. One can reasonably ascribe to other minds, on this view, only what one finds in one' s own mind. Are one' s reasonable hypotheses about the contents of other minds really limited in these paro chial ways? A third objection aims to undercut the argument from analogy entirely, as an account of how we come to appreciate the psychobehavioral connections at issue. If I am to distinguish between and clearly recognize the m any varieties of m ental states (even in my own case), thereafter to pick up on the diverse connections they bear to my behavior, I must already possess the concepts necessary for m aking such identifying introspective judgments in the first place. That is, I must already grasp the meanings of the terms "pain," "grief," "fear," "desire," "belief," and so forth. But we have already seen from the preceding chapter that the m eaning of these terms is given, largely or entirely, by a network of general assumptions connecting them with terms for other
The Epistemological Problem
115
m ental states, external circumstances, and observable behavior. Simply to possess the relevant concepts necessary for introspec tive judgments, therefore, is already to be apprised of the general connections between mental states and behavior that the exam i nation of one's own case was supposed to provide. One's under standing of our folk-psychological concepts, therefore, must derive from som ething more than just the uninform ed exam ina tion of one's own stream of consciousness. Collectively, these difficulties with the argument from analogy have provided a strong motive for seeking a different solution to the problem of other minds— a solution that does n ot create problems of the same magnitude as the problem to be solved. Behaviorism Again
The philosophical behaviorists were quick to press a different solution, one informed by the difficulties discovered in the argu m ent from analogy. Specifically, they argued that if the gener alizations connecting m ental states with behavior cannot be suitably justified by empirical observation, then perhaps that is because those generalizations were not empirical generalizations to start with. Rather, it was suggested, those generalizations are true by sheer definition. They are operational definitions of the psychological terms they contain. As such, they stand in no need of empirical justification. And a creature that behaves, or is disposed to behave, in the appropriate ways is by definition con scious, sentient, and intelligent. (Typical behaviorists were not always this bold and forthright in their claims, but neither were they often this clear in what they claimed.) Given the pressure to solve the other-minds problem, the im potence of the argument from analogy, and the appeal of the
116
C hapter 4
idea that the m eaning of psychological terms was in some way bound up with psycho-behavioral generalizations, one can appreciate why philosophers tried so hard to make some variant of the preceding position work. But they failed. W hen we examine the generalizations of folk psychology, we find that they seldom, if ever, take the form of simple 'operational defini tions' (recall the discussion of "soluble" in 2.2). Behaviorists were unable to state the necessary and sufficient behavioral con ditions for the application of even a single psychological term. Neither do the generalizations of folk psychology appear to be true-by-definition. Rather, they seem to be rough empirical truths, both in their effect on our linguistic intuitions and (more importantly) in their systematic explanatory and predictive func tions in everyday social commerce. This fact returns us to the original problem of how to justify the various behavioral gener alizations on w hich one' s systematic knowledge of other minds seems to depend. Explanatory Hypotheses and Folk Psychology
The problem of other minds was first formulated at a time when our grasp of the nature of theoretical justification was still rather primitive. Until fairly recently, almost everybody believed that a general law could be justified only by an inductive generaliza tion from a suitable number of observed instances of the ele m ents comprehended by that law. One sees a number of crows, notices that each and every one of them is black, and one gen eralizes to "All crows are black." And so for any law. It was thought. This idea m ight have been adequate for laws connect ing observable things and properties with one another, but modern science is full of laws governing the behavior of unob servable things and properties. Think of atoms, and molecules,
The Epistemological Problem
117
and genes, and electromagnetic waves. Plainly, laws concerning unobservables must enjoy some other form of empirical justifi cation, if they are to be justified at all. This other form of justification is not far to seek. Theorists postulate unobservable entities, and specific laws governing them, because occasionally this produces a theory that allows us to construct predictions and explanations of observable phe nom ena hitherto unexplained. More specifically, if we assume certain hypotheses about unobservables, and conjoin them with inform ation about observable circumstances, we can often deduce statements concerning f urther observable phenomena, statements which, it subsequently turns out, are systematically true. To the degree that any such theory (one postulating unob servable states and processes) displays such explanatory and predictive virtues, that theory becomes a beliefworthy hypoth esis. It has what is com m only called "hypothetic-deductive" justification (or "H-D justification," for short). In sum, a theory about unobservables can be beliefworthy if it allows us to explain and predict some domain of observable phenom ena better than any com peting theory. This is in fact the standard mode of justification for scientific theories in general. Consider now the network of general principles— connecting m ental states with one another, with bodily circumstances, and with behavior—that constitutes our own folk psychology. This 'theory' allows us to explain and predict the observable behavior of hum an beings better than any other hypothesis currently available, and what better reason can there be for believing a set of general laws about unobservable states and properties? The laws of folk psychology, on this account, are beliefworthy for the same reasons that the laws of any theory are beliefwor thy, namely, their explanatory and predictive success!
118
Chapter 4
Note further that one's justification here need owe nothing at all to one's introspective exam ination of one's own case. It is folk psychology's success with respect to the behavior of people in general that matters. Conceivably one 's own case m ight even differ from that of others. But this need not affect one's theoreti cal access to their m ental states, however different they m ight be from one's own. One would simply use a different psychological theory to understand their behavior, a theory different from the one that comprehends one 's own inner life and outer behavior. Turning now from general laws to specific hypotheses about individuals, the hypothesis that a specific individual has con scious intelligence is also an explanatory hypothesis, on this view. And such ascription of conscious intelligence is beliefwor thy to the degree that the candidate individual's continuing behavior is best explained and predicted in terms of desires, beliefs, perceptions, emotions, and so on. Since that is, in fact, the best way to understand the behavior of most humans, one is therefore justified in ascribing psychological states to them, so long as such ascriptions sustain the most successful explana tions and predictions of their continuing behavior. One would be similarly justified in ascribing conscious intelligence to other animals, and even to machines, if the explanatory strategy just described were similarly successful in their case also. Thus the most recent solution to the problem of other minds. Its virtues are fairly straightforward, and it coheres nicely with our earlier solution to the semantical problem. Both problems seem to yield to the assumption that our common-sense concep tual framework for mental states has all the features of a theory. Not everyone has found this assumption plausible, however, its virtues notwithstanding. If you center your attention on your
The Epistemological Problem
119
direct consciousness of your own m ental states, the idea that they are ' theoretical entities ' may seem a very strange suggestion. W hether and how that suggestion m ight make sense will be addressed in the next section, on self-consciousness. Suggested Readings Malcolm, Norman. "Knowledge of Other Minds ' " Journal o f Philosophy 55 (1958). Reprinted in The Philosophy o f Mind, ed. V. C. Chappell (Engle wood Cliffs, NJ: Prentice-Hall, 1962). Strawson, Sir Peter' "Persons." In Minnesota Studies in the Philosophy o f Science, vol. II, ed. H. Feigl, M. Scriven, and G. Maxwell. Minneapolis: University of M innesota Press, 1958. Reprinted in The Philosophy o f Mind, ed. V. C. Chappell (Englewood Cliffs, NJ: Prentice-Hall, 1962). Sellars, Wilfrid. "Em piricism and the Philosophy of M ind." In Minnesota
Studies in the Philosophy o f Science, vol. I, ed. H. Feigl and M. Scriven, (Minneapolis: University o f M innesota Press, 1956). Reprinted in Wilfrid Sellars, Science, Perception, and Reality (London: Routledge & Kegan Paul, 1963), sections 4 5 -6 3 . Churchland, Paul. Scientific Realism and the Plasticity o f Mind. Cambridge: Cambridge University Press, 1979.
2
The Problem of Self-Consciousness
Upon first reflection, self-consciousness is likely to seem im pla cably mysterious and utterly unique. This is part of what makes it so fascinating. Upon deeper reflection, however, the veil of mystery begins to part just a little, and self-consciousness can be seen as one instance of a more general phenom enon. To be self-conscious is to have, at a minim um , knowledge of oneself. But this is not all. Self-consciousness involves knowledge not
120
Chapter 4
just of one's physical states, but knowledge of one's m ental states specifically. Additionally, self-consciousness involves the same kind of continuously updated knowledge that one enjoys in one' s continuing experience of the external world. Self-consciousness, it seems, is a kind of continuous apprehension of an inner reality, the reality of one' s m ental states and activities. Self-Consciousness: A Contem porary View
The point about apprehension is im portant: evidently it is not enough just to have m ental states. One must discriminate one kind of state from another. One must recognize them for what they are. In sum, one must apprehend them w ithin some con ceptual framework or other that catalogs the various different types of m ental states. Only then will recognitional judgment be possible ("I am angry," "I am elated," "I believe that P," and so on). This suggests that there are different degrees of self consciousness, since presumably one's ability to discriminate different types of m ental states improves with practice and increasing experience, and since the conceptual framework w ithin w hich explicit recognition is expressed grows in sophis tication and comprehensiveness as one slowly learns more and more about the intricacies of hum an nature. Accordingly, the self-awareness of a young child, though real, will be m uch nar rower or less penetrating than that of a sensitive adult. W hat is simply a dislike of someone, for a child, may factor into a mixture of jealously, fear, and moral disapproval of someone, in the case of an honest and self-perceptive adult. This suggests further that self-consciousness may vary from person to person, depending on w hich areas of conception and discrim ination have been most thoroughly mastered. A novel ist or psychologist may have a running awareness of her em o
The Epistemological Problem
121
tional states that is far more penetrating than the rest of us enjoy. A logician may have a more detailed consciousness of the continuing evolution of his beliefs. A decision-theorist may have a superior awareness of the flux of her desires, in ten tions, and practical reasonings. A painter may have a keener recognition of the structure of his visual sensations. And so forth. Self-consciousness, evidently, has a very large learned com ponent. In these respects, one's introspective consciousness of oneself appears very similar to one' s perceptual consciousness of the external world. The difference is that, in the former case, w hat ever m echanisms of discrim ination are at work are keyed to internal states instead of to external ones. The m echanism s themselves are presumably innate, but one must learn to use them : to make useful descriptions and to prompt insightful judgments. Learned perceptual skills are familiar in the case of external perception. A symphony conductor can hear the clari net' s contribution to what is a seamless orchestral sound to a child. An astronomer can recognize the planets, and nebulae, and red giant stars among what are just specks in the night sky to others. A skilled chef can taste the rosemary and shallots w ithin what is just a yummy taste to a hungry diner. And so forth. It is evident that perception, whether inner or outer, is substantially a learned skill. Most of that learning takes place in our early childhood, of course: what is perceptually obvious to us now was a subtle discrim ination at age two. But there is always room to learn more. In
summary,
self-consciousness,
on
this
contemporary
view, is just a species of perception: s elf-perception. It is not perception of one' s foot with one' s eyes, for example, but is rather the perception of one' s internal states with what we may
122
Chapter 4
call (largely in ignorance) one 's faculty of introspection. Self consciousness is thus no more (and no less) mysterious than perception generally. It is just directed internally rather than externally. Nor is it at all surprising that cognitively advanced creatures should possess self-consciousness. W hat perception requires is no more than that one 's faculty of judgment should be in sys tem atic causal contact with the domain to be perceived, in such a way that one can learn to make, on a continuing basis, spon taneous, noninferred, but appropriate judgments about that domain. Our faculty of judgment is in causal contact with the external world, through our various sensory modalities; but it is also in systematic causal contact with the rest of the internal domain—the brain and nervous system—of w hich it is a part. W ho will express surprise that one kind of brain activity enjoys rich causal connections with other kinds of brain activity? But such connections carry inform ation, and thus make 'informed' judgments possible. Self-consciousness, therefore, at some level or to some degree of penetration, is to be expected in almost any cognitively advanced creature. This view coheres with an evolutionary view. Presumably, hum anity has struggled toward self-consciousness in two dim en sions: in the neurophysiological evolution of our ability to make useful introspective discriminations, and in the social evolution of a conceptual framework to exploit that discriminative capac ity in prompting explanatorily and predictively useful judg ments. As well, each of us is the site of an evolutionary struggle toward self-apprehension during his or her lifetime, in which we learn to use and refine the innate discriminative capacities, and to master the socially entrenched conceptual framework (folk psychology) necessary to exploit them.
The Epistemological Problem
123
Self-Consciousness: The Traditional View
These remarks on self-consciousness may seem plausible enough, but a long tradition in the philosophy of m ind takes a very dif ferent view of our introspective knowledge. Introspection, it has been argued, is fundamentally different from any form of exter nal perception. Our perception of the external world is always mediated by s ensations or impressions of some kind, and the external world is thus known only indirectly and somewhat problematically. W ith introspection, however, our knowledge is immediate and direct. One does not introspect a sensation by way of a sensation o f that sensation, or apprehend an impres sion by way of an impression of that impression. As a result, one cannot be the victim of a false impression (of an impression) or a misleading sensation (of a sensation). Therefore, once one is considering the states of one's own mind, the distinction between appearance and reality disappears entirely. The mind is transparent to itself, and things in the m ind are, necessarily, exactly what they ' seem' to be. It does n ot make any sense to say, for example, "It seemed to me that I was in considerable pain, but I was m istaken." Accordingly, one 's candid introspec tive judgments about one' s own m ental states— or about one' s sensations, anyway— are incorrigible and infallible. It is logically impossible that they be mistaken. The m ind knows itself first, in a unique way, and far better than it can ever know the exter nal world. This extraordinary position must be taken seriously— at least temporarily—for several reasons. First, it is part and parcel of an old and influential theory of knowledge-in-general: orthodox empiricism. Second, the claim that one's knowledge of one's sensations is unmediated by further 'sensations 2' does seem plausible. And any attempt to deny it would presumably lead
124
Chapter 4
to an infinite regress of ' sensations3', ' sensations4', and so on. Third, the proponent of this view has a powerful rhetorical question. How could one possibly be mistaken about whether or not one is in pain? How is it even possible to be wrong about a thing like that? As the reader will note, this question is n ot easy to answer. Arguments against the Traditional View
The view that the m ind knows itself first, in a unique way, and far better than it can ever know the external world, has dom i nated Western thought for over three centuries. But if one adopts a thoroughly naturalistic and evolutionary perspective on the mind, the traditional view quickly acquires a sort of fairy-tale quality. After all, brains were selected for because brains conferred a reproductive advantage on the individuals that possessed them. And they conferred that advantage because they allowed those individuals to anticipate their environment, to distinguish food from nonfood, predators from nonpredators, safety from peril, and mates from nonmates. In sum, a brain gave them knowledge and control of the external world. Brains have been the beneficiaries of natural selection precisely because of that feature. Evidently, what they know first and best is not themselves, but the environm ent in w hich they have to survive. The capacity for self-knowledge could conceivably be selected for as the incidental concom itant of the capacity for knowledge generally, and it m ight be selected for specifically if it happened to positively enhance in some way the brain' s capacity for external knowledge. But in either case, it would be at best a secondary advantage, derivative upon the increase in one's knowledge and control of the external world. And in any case,
The Epistemological Problem
125
there is no reason to assume that self-perception, to the extent that it did evolve, would be fundam entally different in kind from external perception; and no reason at all to assume that it would be infallible. If the traditional view is basically implausible, let us examine the arguments set forth in its favor, and see whether they w ith stand scrutiny. Consider first the rhetorical question, "How could one possibly be mistaken about the identity of one' s own sensations?" As an argument for the incorrigibility of our knowl edge of our sensations, it has the form, "None of us can think of a way in w hich we could be mistaken in our judgments about our sensations; therefore there is no way in w hich we could be m istaken." But this commits an elementary fallacy: it is an argu m ent from ignorance. There may well be ways— m any of them — in w hich error is possible, despite our ignorance of them . Indeed, perhaps we are unaware of them precisely because we currently understand so little about the hidden neural m echanisms of introspection. The rhetorical question, therefore, could safely be put aside, even if we could n ot answer it. But in fact we can. W ith a little effort, we can think of a variety of ways in which errors of introspection can and often do occur, as we shall see in a moment. Consider now the argument that the distinction between appearance and reality must collapse in the case of sensations, since our apprehension of them is n ot mediated by anything that m ight misrepresent them. This argument is good only if m isrepresentation by an intermediary is the only way in w hich errors could occur. But it is not. Even if introspection is unm edi ated by second-order 'sensations2', nothing guarantees that the introspective judgment, "I am in pain," will be caused only by the occurrence of pains. Perhaps other things as well can cause
126
Chapter 4
that judgment, at least in unusual circumstances, in w hich case the judgment would be false. Consider the occurrence of some thing rather sim ilar to pain— a sudden sensation of extreme cold, for example—in a situation where one already strongly expects to feel a pain. Suppose you are a captured spy, being interrogated at length with the repeated help of a h ot iron pressed briefly to your back. If, on the tw entieth trial, an ice cube is covertly pressed against your back instead, your immediate reaction would differ little or none from your first nineteen reactions. You almost certainly would think, if only for a brief m om ent or two, that you were feeling pain. The defender of incorrigibility may try to insist that sensa tion number twenty was a pain after all, despite its benign cause, on the grounds that, if you took it to be a pain, if you thought it felt painful to you, then it really was a pain. This interpreta tion sits poorly with the fact that one can recover from the kinds of misidentification just explored. One's initial screech of horror gives way to "Wait . . . wait . . . that 's not the same feeling as before. W hat's going on back there??" If sensation number twenty really was a pain, why does one's judgment reverse itself a few seconds later? A similar case: the taste-sensation of lime sherbet is only slightly different from the taste-sensation of orange sherbet, and in blindfold tests people do surprisingly poorly at telling w hich sensation is which. But if an innocent subject is led strongly to expect that she is about to be fed a spoonful of orange sherbet (but it is really lime), she may well identify her taste-sensation as being of the kind normally produced by orange sherbet, only to retract her identification im mediately upon being given a (blind) taste of the genuinely orange article. Here one corrects one's qualitative identification, in flat contradiction to the idea
The Epistemological Problem
127
that such mistakes are impossible. Mistakes of this kind, and in the earlier case, are called expectation effects, and they are a stan dard phenom enon with perception generally. Evidently, they apply to introspective judgments as well. The reality of expecta tion effects provides us with a recipe for producing almost any m isidentification you like, whether of external things or inter nal states. Further, do we really know enough about the m echanism s of introspection to insist that absolutely nothing mediates the sensation and the judgment about it? Granted, there is no inter mediary that we are aw are of, but this means nothing, since on any view there must be much of the m ind/brain's operation that is below the level of introspective detection. Here then is another possible source of error. The distinction between appearance and reality may be hard to draw, in the case of sensations, only because we know so little about the ways in w hich things can (and evidently do) go wrong. Another way in which sensations can be misjudged emerges when we consider sensations with very short durations. Sensa tions can be artificially induced so as to have durations of arbi trary length. Not surprisingly, as the durations becom e shorter, reliable identifications (of their diverse qualitative identities) becom e harder and harder to make, and mistakes become, not just possible, but inevitable. W hich is to say, the agreement between what the subject says the sensation is, and what its mode of production indicates it should be, is near-perfect for long presentations, but falls off toward chance as the length of the presentation approaches zero. Such 'presentation effects' are also standard in perception generally. And if the subject is suit ably drugged or exhausted, the reliability of his identifications falls off even more swiftly. This too is standard.
128
C hapter 4
Memory effects must also be mentioned. Suppose a person who, perhaps because of some neural damage in her distant youth, has not felt pain or any other tactile or visceral sensation for fifty years, or has been color-blind for the same period. Does anyone really suppose that, if the subject 's neural deficit were suddenly repaired after such a long hiatus, she would instantly be able to discriminate and identify every one of her newly recovered sensations, and do it with infallible accuracy? The idea is n ot at all plausible. Similar effects could be produced in the short term, with a drug that temporarily clouds one' s m emory of the various types of sensations. Failures of identifica tion and outright misidentifications would then be wholly natural. And even in the normal case, are spontaneous, isolated, and unnoticed lapses of memory utterly impossible? How can the defender of the traditional view rule them out? A more familiar sort of case also merits m ention. Suppose you are dreaming that you have a splitting headache, or that you are in excruciating pain from some injury. If you are then awakened suddenly, do you not realize, with a wave of relief, that you were not really the victim of a headache, or of excruciating pain, despite the conviction that attends every dream? The incorrigibility thesis is beginning to look highly implausible. None of this should be surprising. The incorrigibility thesis m ight have been initially plausible in the case of sensations, but it is n ot remotely plausible for m ost other m ental states like beliefs, desires, and emotions. We are notoriously bad, for example, at judging whether we are jealous, or vindictive; at judging our most basic desires; and at judging our own traits of character. Granted, infallibility has seldom been claimed for anything beyond sensations. But this restriction raises problems
The Epistemological Problem
129
of its own. W hy should infallibility attend our introspection of sensations, but not em otions and desires? Knowledge of the latter seems no more 'mediated' than knowledge of the former. Intriguingly, recent research in social psychology has shown that the spontaneous explanations one offers for one's own behavior often have little or no origin in reliable introspection, despite one's sincere beliefs to that effect, but are instead confabu lated (i.e., made up) on the spot as explanatory hypotheses to fit the behavior and circumstances at issue (see the paper by Nisbett and Wilson cited in suggested readings at the end of this section). And they are often demonstrably wrong, since the 'introspective' reports given prove to be a function of wholly external features of the experimental situation, features under the control of the experimenters. On the view of these researchers, much of what passes for introspective reports is really the expression of one' s spontaneous theorizing about one's reasons, motives, and percep tions, where the hypotheses produced are based on the same external evidence available to the public at large. Consider a final, and m uch deeper, argument against the incorrigibility thesis. Our introspective judgments are, of course, framed in the concepts of folk psychology, w hich framework we have already tentatively determined (in chapters 3.3, 3.4, and 4.1) to have the structure and status of a comprehensive em piri cal theory. As with any such judgments, their individual integrity is only as good as the integrity of the empirical theory in which the relevant concepts are sem antically embedded. W hich is to say, if folk psychology should turn out to be a radically false theory, then its entire ontology would lose its claim to represent reality. And any judgment framed in its terms would then have to be deemed false by reason of presupposing a false background theory. Since folk psychology is an empirical theory (runs the
130
Chapter 4
argument), it is always strictly possible that it m ight turn out to be radically false. Accordingly, it is always strictly possible that any judgment framed in its terms be false. Therefore, our intro spective judgments are not incorrigible. Not only m ight they be wrong occasionally, and one by one; they m ight all be cockeyed! The Theory-Ladenness of All Perception
The initial strangeness of the idea that m ental states are ' th eo retical' can be reduced by the following reflections. All percep tual judgments, n ot just introspective ones, are 'theory-laden': all perception involves speculative interpretation. This, at least, is the claim of more recently developed versions of empiricism. The basic idea behind this claim can be expressed with the fol lowing very brief, but very general, argument: the network argument. 1. Any perceptual judgment involves the application of a concept (for example, a is F). 2. Any concept F is a node in a network of contrasting concepts, and its m eaning is fixed by its peculiar place w ithin that network. 3. Any network of concepts is a speculative framework or theory, minimally, as to the classes into w hich nature divides herself, and the m ajor relations that hold between them. Therefore, 4. Any perceptual judgment presupposes a theory. According to this general view, the m ind/brain is a furiously active theorizer from the word go. The perceptual world is largely an unintelligible confusion to a newborn infant, but its m ind/brain sets about im mediately to formulate a conceptual
The Epistemological Problem
131
framework with w hich to apprehend, anticipate, and to explain that world. Thus ensues a sequence of conceptual inventions, modifications, and revolutions that finally produces something approximating our adult, common-sense conception of the world. This furious conceptual evolution undergone by every child in its first few years is probably never equaled throughout the remainder of its life. The point of all this, for our purposes in this chapter, is as follows. At life' s opening, the m ind/brain finds itself as confus ing and unintelligible as it finds the external world. It must set about to learn the structure and activities of the external world. W ith time, it also learns about the structure and activities of itself, but through a process of conceptual development and learned discrim ination that parallels exactly the process by which it apprehends the world outside it. Indeed, the concep tual framework—folk psychology—that the mature adult uses to comprehend psychological phenom ena in his own case is more likely learned from his lifelong experience with people-ingeneral. It is other humans, and the psychological vocabulary that they use, that provides both the examples and the template that shape his own self-conception. The traditional view, it would seem, is simply mistaken. A Final Question about Consciousness Itself
We have been discussing our consciousness of both the external and the 'internal' worlds, and how they may or may n ot differ from each other, but what about the question of what it is to be conscious at all, as opposed to being unconscious? W hat is it to be conscious of anything at all? After all, there is a big dif ference between being wide awake, on the one hand, and being deeply asleep, on the other. W hat is that difference?
132
Chapter 4
It is the difference between being a fully functioning cogni tive creature, on the one hand, and being in a state where m any or m ost of one' s normal brain functions are temporarily shut down, on the other. Perhaps one 's peripheral senses fail to send the normal neuronal signals to the relevant sensory cortexes higher up in the information-processing hierarchy of the brain, for example. Or perhaps those neuronal signals do n ot provoke the normal interpretive activities in some or all of those 'judgm ent'-m aking areas, because those areas are themselves tem po rarily inactive. Or perhaps those assembled areas are unable to interact with one another in the normal fashion so as to produce a coherent cognitive response to what little inform ation does reach them from the sensory periphery. The result is an overall system that is no longer making systematic and real-time sense of its diverse sensory or introspective inputs. In that dimension, it is temporarily 'out of business'. W hat that waking-state information-processing business is, of course, is a large and complicated question, one that will require a systematic understanding of how the normal brain processes sensory inform ation, and how such processing is vari ously compromised by the failures displayed in various kinds and degrees of sleep. But there is nothing magical or m etaphysi cally mysterious about the question, even though it may seem that way to someone who is innocent of the unfolding research activities of the several neurosciences. This is a bluntly naturalistic, and highly provisional, answer to the question at issue, and you may wish to resist it for that very reason. If so, there is a historical parallel here that may throw some light on the nature of the issue before us. Before the modern period, the question of what made any creature
The Epistemological Problem
133
alive was an issue of similar interest, and of comparable mystery. And the m ost popular theory on this topic, both in the academy and among the public, was that a nonphysical stuff called vital spirit had taken root in every living creature, and was somehow responsible for its growth, its m etabolic activities, its capacity for healing, its capacity for reproduction, and so forth. On the face of it, there certainly seemed to be a robust metaphysical divide between living things, on the one hand, and lifeless matter, on the other, a divide that the physical sciences could never hope to bridge. But bridge it they did. The chemistry of m etabolic processes gradually uncovered the sun-driven process of photosynthesis in plants, a process that produced energy-rich molecules (sugars and starches) that could and did fuel the activity and growth of m icroscopic cells and m acroscopic trees. It also fed, indirectly, the m any denizens of the animal kingdom, who depend utterly on the plant kingdom for food. The chemistry of protein syn thesis via RNA, the coding of genetic inform ation in DNA, and the self-replication of the latter molecules during cell-division all revealed crucial elements in the thermodynam ical dance we call biological life, and explained all of the crucial elements of our prescientific conception of life, including the m any preda tions we call disease. The overall story is highly intricate, of course, and it took a longish time to piece together. The phe nom enon of life is entirely real, and extraordinarily important. But as we now know, there is nothing 'metaphysically special' about it. The phenom enon of consciousness may well be a close parallel to the phenom enon of life, so far as our growing attempts to understand it are concerned. That, at least, is the provisional lesson of the preceding chapter.
134
Chapter 4
Suggested Readings Armstrong, David. A Materialist Theory o f the Mind, chapter 6, sections IX and X; and chapter 15, section II. London: Routledge & Kegan Paul, 1968 Dennett, Daniel. "Toward a Cognitive Theory of Consciousness . " In
Minnesota Studies in the Philosophy o f Science, vol. IX, ed. C. W. Savage. M inneapolis: University o f M innesota Press, 1978. Reprinted in Daniel D ennett, Brainstorms (Montgomery, VT: Bradford, 1978). Nisbett, Richard, and Tim othy Wilson. "Telling More Than We Can Know: Verbal Reports on M ental Processes." Psychological Review 84 (3) (1977). Churchland, Patricia. "Consciousness: The Transmutation o f a Concept."
Pacific Philosophical Quarterly 64 (1983). Churchland, Paul. Scientific Realism and the Plasticity o f Mind, sections 13 and 16; on the theory-ladenness o f perception in general, see chapter 2. Cambridge: Cambridge University Press, 1979. Churchland, Paul. The Engine o f Reason, the Seat o f the Soul: A Philosophi cal Journey into the Brain, chapters 1-4, and 8, esp. 2 0 8 -2 2 4 . Cambridge, MA: MIT Press, 1995.
5
The Methodological Problem
It is plain that the familiar conceptual framework of folk psy chology gives one a nontrivial understanding of m any aspects of hum an mentality. Equally plain, however, are the m any aspects of conscious intelligence it leaves largely in the dark: learning, memory, language use, intelligence differences, sleep, m otor coordination, perception, madness, and so on. We under stand so very little of what there is to be understood, and it is the jo b of science, broadly conceived, to throw back the envel oping shadows and reveal to us the inner nature and secret workings of the mind. O n this much, all parties can agree. There is m ajor disagree m ent, however, on how any science of mind should proceed if it is to have the best chance of success. There is disagreement, that is, on the intellectual m ethods that should be employed. Here follows a brief description and discussion of the four most influential methodologies that have guided research into the m ind over the last century. 1
Idealism and Phenomenology
Here it is useful back up a few steps and provide a little history. W hile de la Mettrie (see pp. 157-158) was trying to reduce mind
136
Chapter 5
to matter, other thinkers were concerned to effect a reduction in precisely the opposite direction. Bishop George Berkeley (1685-1753) argued that material objects have no existence save as ' objects' or ' contents' of the perceptual states of conscious minds. To put the point crudely, the material world is nothing but a coherent dream. If one holds that the material world is one's own dream, then one is a subjective idealist. If one holds, as Berkeley did, that the so-called material world is God's dream, a dream in w hich we all share, then one is an objective idealist. In either case, the fundamental stuff of existence is mind, not matter. Hence the term "idealism." This is a startling and intriguing hypothesis. We are asked to think of the ' objective' world as being nothing more than the 'sensorium of God': the material world stands to God 's m ind in the same relation that your sensory experience stands to your own mind. We are all of us participants, somehow, in God' s dream: the physical universe! This hypothesis may seem to some a faintly mad dream in its own right, but we can at least imagine how serious evidence m ight support it. Suppose that we could provide detailed explanations of the behavior and con stitution of matter, or of space and time, explanations grounded in theoretical assumptions about the constitution of the mind— ours, perhaps, or God's. Idealism would then start to look genu inely plausible. In fact, no genuinely useful explanations of this sort have ever been provided, and so idealism remains comparatively implausible. Explanations in the other direction— of various m ental phenom ena in terms of physical phenom ena—have been far more substantial. We need only think of evolutionary theory, empirical psychology, artificial intelligence, and the several neurosciences to see the breadth of the advancing m ate
The M ethodological Problem
137
rialist front. (These will be examined in some detail in chapters 6-8.) There was a time, however, when such idealist explanations of the material world did seem available. Immanuel Kant (1724 1804) made a lasting impression on Western philosophy when he argued, in his Critique o f Pure Reason, that the familiar human experience of the material world is in large measure constructed by the active hum an mind. As Kant saw it, the innate forms of hum an perception and the innate categories of hum an under standing 'impose' an invariant order on the initial chaos of our raw sensory input. All hum ans share a com m on experience, therefore, of a highly specific 'material world ' . Kant tried to explain, in this way, why the laws of Euclidean geometry and Newtonian physics were necessarily true of the world-of-humanexperience. He thought they were an inescapable consequence of the m ind' s own cognitive structuring activity. Both Euclidean geometry and Newtonian physics have since turned out to be empirically false, which certainly undermines the specifics of Kant 's story. But Kant 's central idea—that the general forms and categories of our perceptual experience are imposed by an active, structuring mind—is an idea that sur vives. The material objects in our constructed experience may therefore be empirically real (= real for all possible hum an expe rience) but they need n ot be transcendentally real (= real from a possible God' s point of view). This demotion of matter, to the principal category in a world of mere appearance, is characteristic of m uch philosophy since Kant. However, Kant added a second element to his story, which changes it from a purely idealist script and marks Kant as a most atypical idealist. According to Kant, the world of inner sense, the world of sensations and thoughts and em otions, is also a
138
Chapter 5
'constructed world' . As with its access to the familiar 'external' world of physical objects in space and time, the mind's access to i tself is no less mediated by its own structural and conceptual contributions. It has access to itself only through its own self-representations. Though empirically real, therefore, the mind need n ot be transcendentally real, any more than matter need be. For Kant, the transcendental nature of mindin-itself is as opaque and impenetrable as the transcendental nature of matter-in-itself. And in general, he thought, thingsas-they-are-in-themselves (i.e., independent of hum an per ception and conceptualization) are forever unknowable by humans. Subsequent philosophers have been more optim istic than Kant about the m ind' s ultimate prospects for self-understand ing. Many suppose that, through continued scientific research, the mind can make conceptual progress: progress toward the goal of reconceiving both the material world and the mind in con ceptual terms that do correspond at last to the true nature of things-in-themselves. This is the hope of scientific realism, a philosophical view that lies behind m ost of our current psycho logical and neuroscientific research. The phenom enological tradi tion, though also optim istic about self-understanding, takes an interestingly different view. Phenomenology is the name of a philosophical tradition cen tered in continental Europe. W ith roots in Kantian philosophy, it is a tree with m any branches, but its various advocates are all agreed that a true understanding of the nature of mind can be achieved only by m ethods that are radically different from those that guide the empirical sciences generally. The reasons for this bold position derive in part from the theory of knowledge (the epistemology) embraced by phenomenologists. They are keenly
The M ethodological Problem
139
aware, as are almost all philosophers since the work of Kant, that the world-of-our-daily-experience is in large measure a con structed world. Our innate forms of perception, our innate forms of understanding, and our learned conceptual frameworks collectively structure for us the familiar, common-sense percep tual world: our Lebensw elt, or life-world. Standard scientific activity, on their view, is just a continua tion of certain of these 'constructive' activities of the mind. We construct ever more intricate and deeply interpretive concep tions of the objective world, and make them answer to the perceptual facts of our Lebensw elt by way of prediction, explana tion, and so forth. But, insist the phenomenologists, such a constructive proce dure is not the way to achieve a true understanding of the m ind, the author of all this constructive activity. Such a procedure simply takes the mind farther and farther away from the original 'pure' phenomena, and wraps it ever more tightly in intricacies of its own construction. The concepts of physical science can never be anything more than the mind's constructed interpreta tion of the ' objective' world. To understand the mind, by con trast, what we need to do is make a one-hundred-and-eighty degree turn, and adopt a strategy of analysis and disinterpretation of our experience. Such a m ethodology will retrace and reveal the m ind' s structuring activity, and thus lead us back toward the essential nature of the mind itself. It is possible for the mind to intuit its own essential nature, since, in contrast to its knowledge of the objective world, the mind has, or can aspire to have, direct and unmediated access to itself. Such a program of analytical and introspective research will produce a level of insight and understanding that is both superior to and indepen dent of any possible understanding that m ight be produced by
140
Chapter 5
the essentially constructive and interpretive procedures of the empirical sciences. Beyond sharing som ething like the preceding perspective, phenom enologists come in very different varieties. Georg Hegel (1770-1831), one of the earliest figures in the tradition, advanced a novel version of 'objective' idealism. The journey of the spirit toward ultimate self-knowledge, he thought, is a journey toward the dissolution of the distinction between the subjective self and the objective world. The historical advance of hum an con sciousness, individual and collective, is just the slow and scat tered process by w hich the still 'groggy' Absolute M ind (= God = the Universe) aspires to reach complete self-consciousness. Each individual hum an ' consciousness' is just one aspect or facet of that grander Mind, and the contrast between oneself and others, and between oneself and the objective world, will eventually collapse as the Absolute Mind finally achieves full self-recognition. In the meantim e, our Lebensw elt is better interpreted not as the Absolute Mind's peaceful dream , but rather as the unfolding content of Its struggling attempts at self-conscious awareness. Hegel is not typical of the later tradition, however, and phe nom enology has no essential com m itm ent to an idealist o n tol ogy. Edmund Husserl (1859-1938) is the central figure in the modern
tradition.
Husserl pursued his phenom enological
research w ithin a roughly Cartesian framework, in w hich mind and matter are equally real, and his dom inant concern was to understand the i ntentionality of our m ental states (see chapter 3.4). The introspective retracing of the constructive activities of the mind, he argued, reveals the source of our m ental 'contents', and leads one to a purified and indubitable awareness of an individual transcendental self, behind the empirical or phenom
The M ethodological Problem
141
enal self. Here, he thought, one can explore the indubitable foundations of hum an experience, and of all of the objective empirical sciences. This brief sketch does not do justice to what is a very rich tradition, and no tradition of its magnitude can be refuted in a paragraph. The reader will perceive, however, that what we called, in the last chapter, "the traditional view" concerning introspection is in some form or other an im portant part of the phenom enological tradition. The idea that one can have some suprascientific knowledge of the self, some special form of knowl edge other than through the medium of constructive, objectify ing conceptualization, is com m on throughout the tradition. That view, note well, goes against Kant 's own conviction that one's introspective self-knowledge is just as inevitably an instance of objectifying 'construction' as is one 's knowledge of the exter nal world. And it goes against the modern psychological evidence that one 's introspective judgments are on all fours with percep tual judgments generally, and provide knowledge that is in no way distinguished by any special status, purity, or authority. If all knowledge is inevitably a matter of conceptual construc tion and speculative interpretation (recall the conclusion of chapter 4.2), then it would seem that the 'special access' to the 'essential nature' of the mind sought by the phenom enologists is but a dream, and that the standard methods of empirical and theoretical science constitute the only hope the mind has of ever understanding itself. This need not preclude admitting introspective judgments as legitimate data for science, and thus need not preclude 'phenom enological research', but it will deny the results of such research any unique epistemological status. Returning to ' the standard methods of empirical and th eo retical science ' does n ot produce instant unanimity, however,
142
Chapter 5
for there are several competing conceptions of what those 'stan dard methods' are or should be, as the following sections will reveal. Suggested Readings Marx, Werner. Hegel's Phenomenology o f Spirit. New York: Harper & Row, 1975. Spiegelberg, Herbert. The Phenomenological Movement, vols. I, II; see espe cially the discussion o f Edmund Husserl, vol. I, pp. 7 3 -1 6 7 . The Hague: Harper & Row, 1960. Dreyfus, Hubert L., ed. Husserl, Intentionality, and Cognitive Science. Cam bridge, MA: MIT Press/Bradford, 1982. Smith, D. W., and R. M cIntyre. Husserl and Intentionality. Boston: Reidel, 1982. Piaget, J ean. Insights and Illusions o f Philosophy, chapter 3: "The False Ideal o f a Suprascientific Knowledge." New York: World Publishing, 1971.
2
M ethodological Behaviorism
M ethodological behaviorism represents a very strong reaction against the dualistic and introspective approaches to psychol ogy that preceded it. A child of the tw entieth century, it is also a self-conscious attempt to reconstruct the science of psychol ogy along the lines of the enormously successful physical sci ences such as physics, chemistry, and biology. Over the past sixty years, behaviorism has been the single most influential school of psychology in the English-speaking world. The last three decades have forced the reappraisal and the softening of some of its doctrines, but it remains a major influence.
The M ethodological Problem
143
Central Theses and Arguments
Its central principles are not difficult to understand. According to behaviorism, the first and most im portant obligation of the science of psychology is to explain the observable behavior of whatever creature it addresses, hum ans included. By "behav ior," the behaviorists mean the publicly observable, m ea surable, recordable activity of the subjects at issue: bodily movements, noises emitted, temperature changes, chemicals released, interactions with the environment, and so forth. Of the objective reality of these phenom ena there is no doubt, it is felt, and psychology cannot go astray by taking animal behavior as its primary explanatory target. This contrasts pro foundly with earlier views, w hich took the elem ents and con tents of internal consciousness as the proper explanatory target for psychology. Of comparable importance to m ost behaviorists, however, was the way in which behavior was to be properly explained. Com m on-sense explanations that make appeal to 'm ental states' are regarded as seriously defective in various ways. Such expla nations appeal to a body of folklore that has no proper scientific basis, and that may consist largely of superstition and confu sion, as with so m any of our past conceptions. The familiar m entalistic notions are ill-defined and without objective criteria for their application, especially in the case of nonhum an animals; individual introspection does n ot provide a uniform or reliable ground for their application even in the case of hum ans; m entalistic explanations are generally constructed after-thefact, and the principles invoked display very little predictive power. Such 'inward looking' explanations hide from us the very extensive role of any organism' s external environm ent in con trolling its behavior.
144
Chapter 5
Instead of appealing to m ental states, behaviorists proposed to explain any organism's behavior in terms of its peculiar envi ronm ental circumstances. Or, in terms of the environm ent plus certain observable features of the organism. Or, failing that, also in terms of certain unobservable features of the organism— dis positions, and innate and conditioned reflexes—where those features must meet a very strict condition: they must be such that their presence or absence could always be decisively deter mined by a behavioral test, as the solubility of a sugar cube is revealed by its actually dissolving (= the behavior) when placed in water (= the environm ental circumstance). In sum, explana tions in psychology are to be based on notions that either are outright publicly observable, or are operationally defined in terms of notions that are so observable. (Review chapter 2.2 for the notion of an operational definition.) Behaviorists are (or were) willing to restrict themselves to these resources, and to urge others to observe the same restric tions, because these restrictions were thought to be the unavoid able price of making psychology into a genuine science. Putting aside the ancient apparatus of common-sense folk psychology seemed a small price to pay in pursuit of such a worthy goal. If any of those m entalistic notions really do have explanatory integrity, it was thought, then the behaviorist m ethodology will eventually lead us back to them , or to suitably defined versions of them . And if they have no explanatory integrity, then reject ing them is no real loss. Furthermore, an influential view in a related field gave in ci dental support to the behaviorists. A scientifically minded school of philosophy called "logical positivism" or "logical empiricism" held the view that the m eaning of any theoretical term, in any science, ultim ately derived from its definitional
The M ethodological Problem
145
connections, however devious, to observational notions, which derive their m eaning directly from sensory experience. Certain philosophers of science connected with this school claimed specifically that any meaningful theoretical term had to possess an operational definition in terms of observables. Behaviorism, therefore, seemed only to be following the rules that were said to govern legitimate science generally. Criticisms of Behaviorism
In adopting a frankly skeptical attitude toward the ontology of m ental states, and toward our familiar conception of the causes of hum an behavior, the behaviorists provoked a strongly nega tive reaction from a wide variety of moralists, clerics, novelists, and from other schools of philosophy and psychology. The principal com plaint was that behaviorism tended to dehum an ize hum ans by arbitrarily ruling out of court the very feature that makes us special: a conscious m ental life. To some extent, this is a question-begging complaint. W hether hum ans are 'special', and, if we are, what features make us so, are th em selves scientific questions requiring scientific answers. Perhaps we are mistaken in our com m on-sense beliefs as to whether and why we are special. (It would not be the first tim e: recall the universal conviction that hum anity is placed at the center of the physical universe.) And it is no weighty criticism of behav iorism just stubbornly to repeat our culturally entrenched convictions. Even so, it is now widely agreed that behaviorism w ent too far in its initial claims and restrictions, further than was neces sary to secure scientific status for psychology. For one thing, the logical positivist's view that any meaningful theoretical term has to admit of an operational definition in terms of
146
Chapter 5
observables was quickly seen to be a mistake. Most terms in theoretical physics, for example, do enjoy at least some distant connections with observables, but not of the simple sort that would permit operational definitions in terms of those observ ables. Try constructing such a definition for "x is a neutrino," or "x has an electron in its lowest orbital shell." Adequate con ditionals connecting such terms to observables typically turn out to require the use of m any other theoretical terms drawn from the same theory, and hence the definition is n ot purely 'operational'. If a methodological restriction in favor of opera tional definitions were to be followed, therefore, m ost of th eo retical physics would have to be dismissed as meaningless pseudoscience! Current views on m eaning tend to reverse the positivist's view entirely: the m eaning of any term, including observation terms, is fixed by its place in the network of beliefs or general izations in which it figures. (The network theory of m eaning was discussed in chapter 3.3.) Our m entalistic vocabulary, there fore, cannot be ruled out of science on sheer abstract principle alone. It will have to be rejected, if at all, on grounds of its explanatory and predictive shortcomings relative to competing theories of hum an nature. Suggested Readings Skinner, B. F. About Behaviorism. New York: Random House, 1974. D ennett, Daniel. "Skinner Skinned . " In Brainstorms. Montgomery, VT: Bradford, 1978. Chomsky, Noam. "A Review of B. F. Skinner's Verbal Behavior." Language 35, no. 1 (1959). Reprinted in Readings in the Philosophy o f Psychology, vol. I, ed. N. Block (Cambridge, MA: Harvard University Press, 1980).
The M ethodological Problem
3
147
The Cognitive/C om putational Approach
W ithin the broad framework of the functionalist conception of mind discussed in chapter 2.4, we find two closely related research programs aimed at solving the mystery of conscious intelligence: cognitive psychology and artificial intelligence. Both approaches contrast with the traditional forms of behaviorism, in that both feel free to postulate or ascribe an intricate system of internal states to intelligent creatures in order to account for their behavior. Standardly, the states postulated are, in some way or other, ' inform ation-bearing' states, and their collective interactions are a function of the specific inform ation that each bears. Hence the general characterization, "the inform ationprocessing approach," or more simply, "the com putational approach." Compare the case of a simple pocket calculator. Its various input states represent specific numbers and arithm etic opera tions, and the internal activities that follow are determined by the com putationally relevant features of those states. In the end, the output states bear systematic and rule-governed relations to those input states. The same is supposed to be true of organisms that display natural intelligence, save that their input states represent m any more things than just numbers, and the ' com putations' that they execute are concerned with far more things than mere arithm etical relations. They are also concerned with logical relations, for example, and with spatial shapes, social relations, linguistic structures, color, m otion, and so forth. (Examples will be explored in the next chapter.) The aim of cognitive psychology is to account for the various
activities
that
constitute
intelligence— perception,
memory, inference, deliberation, learning, language use, m otor
148
Chapter 5
control, and so on—by postulating a system of internal states governed by a system of com putational procedures, or an inter active set of such systems governed by a set of such procedures. The aim is to piece together an outline of the actual functional organization of the hum an nervous system, or of the nervous system of whatever creature is under study. This is a tall order, given the extraordinary complexity of intelligent creatures, and a piecemeal approach is almost always adopted. A theorist m ight concentrate attention on perception, for example, or on language use, and then try to piece together a com putational system that accounts for the specific activities of that faculty alone. Such piecemeal successes can then be col lected, as they occur, to form a general account of the organism's intelligence. In formulating and evaluating these com putational hypoth eses, three criteria are relevant. First, the com putational system proposed must succeed in accounting for the inputs and outputs of the cognitive faculty under study. If the faculty is perception, for example, then the com putational system proposed must account for the discriminations the creature actually makes, given the physical stimulation of its sense organs. If the faculty is language use, then the system must account for our discrimi nation of grammatical sentences from nonsense, and for our ability to produce grammatical sentences almost exclusively. Generally speaking, the system proposed must do what the crea ture at issue succeeds in doing, or what its selected faculty does. This first criterion is important, but it is too coarse grained to be adequate on its own. The problem is that there are many different ways to skin any given cat. For any desired rela tion between inputs and outputs, there are infinitely m any
The M ethodological Problem
149
different com putational procedures that will produce exactly that relation. The point is easily illustrated with an elementary example. Suppose you have a small calculator-like device that behaves as follows. For any number n entered on its keyboard, it subse quently displays the number equal to 2n. One way in which it may compute its answers is just to multiply the input number by 2. A second way would be to multiply the input by 6 and then divide that answer by 3. A third way would be to divide the input by 10 and then multiply that answer by 20. And so on. Any of these com putational procedures will produce the same 'output behavior', so far as the doubling of arbitrary input numbers is concerned. But the calculator is presumably using only one of them. How m ight we determine which? Here enters the second criterion for evaluating computa tional hypotheses. Procedures that produce the 'same behavior' at one level of analysis may show subtle differences at a more fine-grained level of analysis. For example, the second and third procedures just contemplated
