A Skeptical Look at Justification

Cladistics Cladistics 21 (2005) 203–207 www.blackwell-synergy.com

Letter to the editor

A skeptical look at justification Accepted 3 February 2005

To the Editor: ‘‘Parsimonious reasoning is a rule of logic and it is fundamental to the scientific method’’—Kluge (1977, p. 2). ‘‘Parsimony is a methodological principle dictating a bias towards simplicity in theory construction …’’—‘‘The Oxford Companion to Philosophy’’ (Honderich, 1995).

1. Professor Kluge is a ‘‘skeptical realist’’ (Kluge, 2002, and below). He writes (Kluge, 2001, p. 200): ‘‘Empirical scientists claim their research leads to increased knowledge, through explanation … It seems equally fair to say, however, that few researchers actually … justify their inferential methods and results … Hume (1739) [2000] long ago recognized the importance of justification, arguing that knowledge must be distinguished from belief and concluding that knowledge is belief based on rational justification (Sober, 1988, p. 42).’’ 2. Hume concluded that the belief that the future will resemble the past (the belief that underlies inductive inference) cannot be rationally1 justified (Hume’s skepticism: Sober, 1988, p. 43). The ultimate answer to the question ‘‘Is justified true belief knowledge?’’ is ‘‘no’’. One can have justified beliefs, one can have true beliefs, but one still may have no knowledge. 3. Describing the world means to apply language to the world of things. Explaining the world means to apply theories to observable states of affairs. Tautological statements are not statements about the world. Statements about the world may be either right, or wrong. 4. Science makes statements about what there is in the world. Science explains what it describes, and describes what it explains. Scientific theories are theories about what there is in the world. For science, what there is in the world is what there is in its theories. 5. The theory of ‘‘descent, with modification’’ has troubled many minds. Buffon thought that there exist organic molecules; Darwin thought that there exist 1

‘‘Rationally’’ meaning ‘‘logically’’, i.e., deductively (compare Kluge, 2003a; versus Sober, 1988).
The Willi Hennig Society 2005

organic molecules. Mendel thought that there are genes; Dawkins thinks that there are genes. We have exons and introns, upstream and downstream. 6. Scientists communicate about what there is in the world through language. The world appears structured, language appears structured. To the description of regularities in the world must correspond regularities of language. 7. Rules govern the meaning of words. Rules govern the meaning of words that are used to interpret the rules that govern the meaning of words. When no more rules are left, the understanding of a word is a leap in the dark. 8. Does Robinson Crusoe need to know whether he correctly follows the rules that govern the meaning of words? He needs to know whether Friday understands him or not. 9. Friday’s interlocutor is not Monday’s. The meaning of words changes. Democritus’ atom is not Niels Bohr’s. Owen’s homology is not Kluge’s. Kluge’s justification is not Hume’s. No finite number of times a word has been used fully determines the meaning of a word.2 The meaning of a word is underdetermined. Scientific theories are underdetermined. 10. The brush that science uses to paint a picture of what there is in the world is more or less coarse. What there is in the picture of the world drawn by science will be more or less blurred. 11. Robinson Crusoe finds lightning and thunder to precede rain. He paints a picture of his world that shows him seeking shelter after he saw lightning, heard thunder. His picture is blurred. Sometimes rain hits him without warning. Sometimes there is lightning, or rumbling, without rain. But he keeps seeking shelter after having seen lighting and having heard thunder, knowing his expectation of rain may be wrong. It’s pragmatic for him to do so.

2 For singular terms consider ‘‘The Grateful Dead’’ (the example is Lycan’s 2000), or ‘‘Laura believes that her neighbor’s dog Nero dug a hole in her flower-bed.’’ See also Quine (1964), Kirk (2004).

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12. Professor Russell feeds his turkey every day at precisely 9 a.m. Having experienced this 729 times, the turkey paints a picture of himself in a world that shows Professor Russell approaching his enclosure every day at 9 a.m. True to this picture, Professor Russell approaches the turkey’s enclosure the next day at 9 a.m. The turkey watches him approach, looking forward to being fed. Is the turkey justified in expecting to be fed? 13. This next day is Christmas day, and Professor Russell cuts off the turkey’s head at precisely 9 a.m. The picture the turkey had painted represented nothing but the memory of the turkey. The picture seemed to say something about the future, but if it did, it was wrong. The turkey did not live to find out that it was wrong. The turkey’s knowledge expressed in the picture the turkey had painted represented nothing but an historical account of what the turkey had lived through. Professor Goodman concluded that the turkey was not justified to expect being fed. 14. The turkey might argue that he was justified in expecting to be fed, because Professor Russell was a good-hearted man such that there was every reason to believe that he would never kill a bird for Christmas. How could the turkey have knowledge that justified him to expect being fed? The turkey, it seems, would have to justify the knowledge that justified him in expecting to be fed. When no justifications are left, the turkey’s trust in Professor Russell’s good-heartedness is a leap in the dark. 15. Professor Sober experienced the sunrise every morning for as long as he had lived, and he trusts that all other humans who ever lived had had the same experience. He therefore expects the sun to rise again the following morning. Is his expectation justified? 16. Professor Sober knows the laws of interplanetary motion that Newton was talking about, and that explain why the sun had always risen in the past. After all, he shares a common language with Newton. To the extent that Newton’s laws are true, Professor Sober is justified in assuming that the sun will rise again tomorrow. 17. Professor Sober concludes that inductive inference from past experience to predictive hypothesis is justified if it is mediated by background theories about the world. The rational justification of his belief that the sun will rise again tomorrow will be as strong as is the background theory on which it rests. 18. But what if Newton made a mistake? What if the laws Newton was talking about would stop governing interplanetary motions the day after tomorrow, or in 1001 years? To answer Professor Kripke’s question (Professor Kripke might claim that this is Wittgenstein’s question) Professor Sober would have to justify his belief that Newton’s talk about laws would be true tomorrow, and the day after. But then he would have

to justify his justification of his belief that … When no justifications are left, Professor Sober’s belief in the truth of Newton’s talk about laws is a leap in the dark. 19. Science paints a picture of the world in which the sun rises every day. The picture is not entirely sharp, but very remarkably so. The picture is based on universal laws3 that provide an explanation for the observation that the sun rises every morning. These universal laws cannot be known to be truly true; what can be known is that until now, the sun has risen every morning. Tomorrow at sunset, Professor Sober may look back on the day, finding his belief in Newton’s talk of laws once again justified. 20. Professor Popper was happy with the fact that in science, the unknown explains the known. But he was not happy with the fact that inductive inference requires justification on positive grounds. David Hume had asked: ‘‘If I ask you why you believe in any particular matter of fact …, you must tell me some reason …’’. Professor Popper answered: ‘‘I do not believe in belief: I am not interested in a philosophy of belief, and I do not believe that beliefs and their justification … are the subject matter of the theory of knowledge’’ (Popper, 1996, p. 21). 21. Professor Popper firmly believed in the rules of deductive logic.4 Like a law in science, ‘‘all ravens are black’’ is a universal proposition, and Professor Popper accordingly transformed this proposition to: ‘‘There is no one thing that is not black and is a raven.’’ This statement he transformed into: ‘‘There is no white raven here now.’’ 22. Logical relations exist between statements, not between physical objects, nor between words and physical objects, nor between propositions and observable states of affairs. Deduction is a matter of logic, not an observational experience. 23. The statement ‘‘all unicorns have a horn on their forehead’’ does not predict ‘‘there is a unicorn here now’’, because whether there is a unicorn here now in our world of experience is a matter of observation; its existence cannot be deduced from ‘‘all unicorns have a horn on their forehead.’’

3

The old notion of ‘‘universal law’’, used inter alia by Hume and Popper, is discredited today. Scope restriction aligns the notion of ‘‘natural law’’ more closely with the modern understanding of the causal structure of the world, but can be exercised to a degree that renders causal laws uninteresting (Kitcher, 1993; see discussion in Rieppel, 2005). 4 Popper (1973), like Quine (Gibson, 1982), adopted an evolutionary epistemology. On that account, the capacity to think in terms of laws of logic is an evolutionary adaptation. Laws of logic become historically contingent (Feyerabend, 1981), or in Quine’s terms, laws of logic are empirical and might ultimately be found to be in need of revision.

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24. The statement ‘‘all ravens are black’’ allows the deduction ‘‘there is no white raven here now.’’ If the negation of that statement can be applied to an observable state of affairs, it contradicts the universal proposition ‘‘all ravens are black’’ in logical space. Falsification occurs. Does it? 25. In order to apply the negation of ‘‘there is no white raven here now’’ to an observable state of affairs, the gap between the world of words and the world of things needs to be bridged. Science needs to paint a picture with a white raven in it. But what if the picture is blurred to the extent that some no longer recognize the raven as being a raven, or white as being white? What if some say that this bird is not a raven precisely because it is white, or that this bird is not white but rather is ‘‘blite’’, or a shade of gray that might still pass as black? 26. Unless the meaning of words can be fixed, there is no unequivocal falsification to be had. But no finite use of a word unequivocally fixes its meaning. When no rules are left to interpret the rules that govern the rules that rule the meaning of words, falsification is a leap in the dark. 27. Professor Popper conceded that falsification requires agreement to fix the meaning of words. But at least he could dispense with the justification. As the unknown explains the known, a belief (such as: all ravens are black) amenable to falsification requires no justification, because the aim is not to believe the belief to be truly true. The sum of all the black ravens Professor Popper had ever seen, and which corroborate his belief that all ravens are black, for him merely constitutes a historical account, and he was ready to meet his first white raven tomorrow, or the day after. In fact, he would make an effort to find one! 28. Systematics is the science that paints a picture of the phylogenetic relationships of species (or taxa). Phylogenetic systematics, or cladistics, tries to paint that picture as sharply as possible. The backbone of the picture is the logical concept of an inclusive hierarchy. 29. The tool used by cladists to sort out where each species (or taxon) is to be pictured in that hierarchy is parsimony. Parsimony is a way of finding regularity among statements describing characters, which in turn specify where species will be pictured on the cladogram. 30. Professor Kluge appeals to the theory of ‘‘descent, with modification’’ as a means of justifying the use of parsimony (Kluge, 2001). Parsimony is not a knowledge claim, it is a methodological principle. A theory justifies a method insofar as the method must produce results to which the theory is applicable, for which the results are relevant. 31. The meaning of ‘‘descent, with modification’’ is underdetermined. It could be mother and child, father and son, cells dividing and differentiating, species transforming into other species, or the origin of two (or more) new species from one. The meaning of

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‘‘species’’ is underdetermined. Let ‘‘descent, with modification’’ be the origin of two new species from one. ‘‘Descent, with modification’’ is then a theory about species. Its concern is evolutionary events that affect species. Parsimony is a methodological principle. Its concern is statements describing characters. 32. Professor Boyd has confidence in airplanes. They don’t crash, or very rarely so. His trust is justified by laws of aerodynamics. Airplanes are built according to methods that take into account the laws of aerodynamics. The fact that airplanes are very reliable is taken by Professor Boyd to justify the knowledge claim that the laws of aerodynamics are relevantly approximately true. 33. Professor Kluge has confidence in cladograms. They are chosen using the method of parsimony, which he believes to be justified by ‘‘descent, with modification.’’ The principle of parsimony justifies the choice of the hypothesis of relationships that is most consistent with the characters available for analysis (Kluge and Farris, 1969). Professor Kluge shifts gears again: ‘‘consistency with characters’’ becomes ‘‘maximum explanatory power’’ (Kluge, 1999, 2002; this follows Farris, 1983). 34. Professor Kluge’s appeal to maximal explanatory power is remarkable, for it fails to explain what the maximized explanatory power is supposed to explain. To merely minimize ad hoc auxiliary hypotheses of homoplasy does not yet explain by common ancestry the maximal congruence of shared derived characters that obtains on hypothesis A. 35. Professor Kluge remains skeptical, for truly true beliefs cannot be had. So he contends that whereas maximal congruence obtained on hypothesis A shows all hypotheses of not-A to be false, it does not show hypothesis A to be true. But if it is impossible to know any hypothesis to be truly, or approximately, true—it is also impossible to know any hypothesis to be truly, or approximately, false. 36. Professor Kluge justifies ‘‘phylogenetic parsimony’’ with ‘‘descent, with modification’’, but concludes that it must remain silent on hypothesis A. For not all the shared derived characters that obtain on the maximally congruent hypothesis A may be due to common ancestry, some might be due to parallelisms (Farris, 1983; Kluge, 1999, 2002, 2003b; see discussion in Rieppel, 2004, 2005). 37. The paradoxical situation obtains where the absence of knowledge generates knowledge. The absence of knowledge that A creates the presence of knowledge that not-A. Professor Moore once raised his hands exclaiming: ‘‘Here is one hand’’, and ‘‘here is another one’’, therefore ‘‘there are hands’’. Professor Kluge’s skeptic is one who raises his hands in front of a mirror, concluding that although he cannot know whether he has two hands, he can know that the hands he sees in the mirror do not exist.

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38. In empirical sciences, an empirically confirmed hypothesis A disconfirms a hypothesis B to the degree to which hypothesis B is inconsistent with hypothesis A. Parsimony is a methodological principle that requires us to choose that hypothesis of relationships which is maximally consistent with the characters available for analysis. ‘‘Descent, with modification’’ provides the explanation for the maximally parsimonious character distribution. Professor Sober finds ‘‘Descent, with modification’’ to be underdetermined again: it must make assumptions about character evolution if it is to justify parsimony. 39. Justification gives one a reason to believe something. One has a reason to believe something because the justifying proposition somehow must imply the proposition to be justified. Parsimony justifies the chosen cladogram, ‘‘descent, with modification’’ justifies parsimony; what justifies ‘‘descent, with modification? 40. Professor Goodman tired of justification. How to justify the justifying proposition? At the end of the day, the justifying proposition must simply be accepted as indispensable, or so it seems. Professor Kluge tired of justification. He relegates ‘‘descent, with modification’’ to Professor Popper’s safe haven: background knowledge. That way, it need no longer be questioned. Nor justified. 41. Professor Popper’s haven may not be a safe place, however, for Professor Popper had rejected the justificationist program. If Professor Kluge wants to seek shelter in Professor Popper’s haven, he cannot ask for justification; if he wants to ask for justification, he must seek shelter elsewhere. 42. We can say that fire and heat are always conjoined because fire causes heat. How do we know? How do we justify that knowledge? Can heat cause fire? We can also say that we say that fire causes heat because fire and heat are always conjoined. We infer that fire causes heat from the observation that they are always conjoined. Fire and heat are found to share a constant relation—it’s called causation. 43. Causes are connected with effects; our theories connect them. We explain the constant conjunction of fire and heat causally: if fire and heat are not conjoined, we withdraw the explanation. 44. We can say that characters are found to be conjoined because ‘‘descent, with modification’’ causes the conjunction of characters. That, indeed, requires justification, for characters could also be conjoined because of developmental constraints, functional constraints, pleiotropy… 45. But we can also say that we say that ‘‘descent, with modification’’ causes the conjunction of characters because characters are found to be conjoined. If we find that characters are not conjoined, we withdraw the explanation. We do the same if we find characters to be subject to developmental constraints, functional constraints, pleiotropy…

Acknowledgments I do not here investigate why parsimony should or should not be the preferred method under the assumption of ‘‘descent, with modification.’’ I am only concerned with justification as such. The negative answer to the question ‘‘Is justified true belief knowledge’’ was given by Gettier (2001), but of course there is an epistemology ‘‘after Gettier’’. Other inspirations for this essay came from: (Boyd, 1991), Gibson (1982), Glock (2000), Goodman (2001), Hanson (1958), Kripke (1982), Moore (1962), Pears (1988), Popper (1976, 1989, 1996), Russell (2002), Sober (1988, 1994a,b), and Wittgenstein (1922). I thank several people for input into earlier versions of this paper: Lance Grande, Maureen Kearney, Garry Nelson, Norman Platnick, Michael and Lukas Rieppel.

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Olivier Rieppel The Field Museum, Chicago, IL, USA Fax: +1 312 665 7641 E-mail address: orieppel@fieldmuseum.org