Correspondence Truth and Scientific Realism

Synthese DOI 10.1007/s11229-006-9064-6 O R I G I NA L PA P E R

Correspondence truth and scientific realism Stephen Leeds

Received: 18 February 2005 / Accepted: 12 June 2006 © Springer Science+Business Media B.V. 2006

Abstract I argue that one good reason for Scientific Realists to be interested in correspondence theories is the hope they offer us of being able to state and defend realistic theses in the face of well-known difficulties about modern physics: such theses as, that our theories are approximately true, or that they will tend to approach the truth. I go on to claim that this hope is unlikely to be fulfilled. I suggest that Realism can still survive in the face of these difficulties, as a claim about the kind of theories we want to aim for. I relate this conception of Realism to various contemporary discussions, both by realists and antirealists. Keywords Truth · Realism · Correspondence · Fine · Boyd · Kitcher A theme in recent discussions of Scientific Realism has been the claim that a scientific realist is committed to a correspondence notion of truth. There is a sense of course in which most of us, scientific realists or not, would allow that truth is a correspondence relation between sentences and the world: as Tarski and then Davidson argued long ago, there is a pretty clear sense in which satisfaction is a correspondence relation between well-formed formulas and n-tuples of objects, and truth is just the degenerate case n = 0. But such writers as Kitcher (2001) and Psillos (2002) have something more in mind. To call truth a correspondence notion in the Tarskian sense is consistent with thinking, as Tarski himself did, that satisfaction is definable only disquotationally, and therefore only for (fragments of) one’s own language, or other languages translatable into one’s own language. For Kitcher and the rest, a real correspondence notion must be something more substantial: at the very least, it must be a notion that allows us to speak of truth for languages in general, and not relatively to a choice of how to translate them into our own language. And this view is shared even by writers, such

S. Leeds (B) Department of Philosophy, University of Wisconsin, P.O. Box 413, Milwaukee, WI 53201, USA e-mail: [email protected]

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as Leplin, who for the most part steer clear of the word ‘correspondence’ : open their writings, and you will sooner or later find them making use of, or defending, some version of the causal theory of reference—which is the paradigm of a correspondence theory in the present sense. Sometimes changes in our thinking happen so gradually that we need to be reminded to realize that a change has taken place. Scientific realists have always claimed that our best scientific theories were true, but I think one would be hard pressed to find, even as late as JJC Smart in the 1960’s, any defender of scientific realism whose conception of truth was explicitly a correspondence view in Kitcher’s sense. When a pre-1970’s scientific realist claimed truth on behalf of scientific theories, it was generally pretty clear which theories he had in mind, and the claim that, e.g. electron-theory was true could in his arguments be replaced without loss by claims about the existence and behavior of electrons; the lack of interest in a theory of truth that would apply, say, to future theories in languages not translatable into our own was reflected in the conviction, unchallenged before Hartry Field, that Tarski had settled the problem of truth. Why the change? There are no doubt many ways of telling the story; for example, one might see the scientific realists as taking over a point of view on truth whose motivation sprang completely from problems in philosophy of language. I think that we can learn something more by seeing the use of correspondence-truth as a reaction to difficulties specifically within philosophy of science. These are difficulties that arise within the pre-1970’s version of scientific realism—the version that claimed no more than disquotational truth for our best theories—and it is to the credit of Putnam, Boyd, and the other founding fathers of the causal theory of reference that they—at least some of the time—saw these problems more clearly than their predecessors. I say ‘at least some of the time’ because they, like their present-day descendents, also invoked the correspondence theory in places where scientific realism does not need such help. In what follows I will be sorting all this out: the places where there is no need for a correspondence theory from those in which it is a plausible response to some real problems. I will also argue that it finally does not help with these, and that it seems likely that nothing can. The conclusion I draw is that, instead of trying to fix what cannot be fixed, a realist should change his conception of what realism is. Doing this has the effect of reframing the debates between realist and antirealist in a radical, and I think interesting way, and I will end by saying something about that.1

I Let us begin with an official statement of scientific realism without correspondence2 — what I will call Moderate Scientific Realism (MSR). MSR is the claim that we have good reason to believe true each of the main tenets, and many of the subsidiary claims, of our current theories, or at least to assign a high degree of probability (in the sense of personal probability) to their truth. Truth here is Tarskian, disquotational 1 The larger topic of what becomes of the realist-antirealist debate absent the correspondence theory is barely touched on at the end of this paper; a much more extended discussion can be found in Leeds (2006). 2 I will use the term ‘correspondence truth’ for the kind of theory Kitcher and the rest have in mind; though I think this unfair to us deflationists.

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truth;3 what makes this moderate realism is that, since it is innocent of any notion of correspondence truth, it makes no claims about scientific theories in general, past and future, for example that they tend to be true. It is also moderate, maybe more moderate than it needs to be, in that it does not claim that we assign high probability to any conjunction of claims of current theory, only to each of them individually. I shall nonetheless speak of our having good reasons to believe our current theories, and will take the reader to understand that I am speaking distributively not collectively. The obvious way to argue for MSR is simply to give in detail our reasons for believing our current theories, and then claim that these are good reasons; it then follows from the disquotational account of truth that we also have good reasons for believing them true. The second step in the argument being well-nigh unassailable, challenges to MSR have tended to focus on the first step. The main lines of attack have been: to claim, on empiricist grounds, that some important kinds of scientific reasons are not good reasons for belief, and to claim (via the pessimistic induction) that our reasons in favor of our best theories, although good reasons, are outweighed by better reasons to doubt them. One place where Realists have tried to put the correspondence theory to work is in resisting these arguments. They have tried to show, for example, using arguments acceptable to empiricists, that those features of the scientific method which empiricists regard with suspicion, or an important subset of these, tend to produce true theories; similarly, they have attempted to establish the tendency of our methodology to produce true theories as a direct counter to the pessimistic induction. The ‘true theories’ which, according to these arguments, our methods tend to produce include past and future theories in vocabularies other than our own; for this reason, the notion of truth required here can only be correspondence truth. I think all these arguments are at best unnecessary—there are no problems here that MSR cannot handle. Let us see why. To claim that scientific reasons are not good reasons for belief one might deny the legitimacy of such forms of abductive reasoning as inference to the best explanation (IBE), no matter what context we use it in; more weakly, one might reject IBE only when the conclusion of the argument involves unobservables. (van Fraassen is often read as endorsing only the second, less sweeping rejection of IBE, but in fact, as he makes clear in (Ladyman et al., 1997), he takes the stronger position). I cannot hope here to say in any detail why I think none of this need trouble MSR; luckily, my reasons will not be unfamiliar—indeed, as I explain in footnote 4, I think they represent an emerging consensus about these issues. They are as follows. First, I take it that to ask whether we are justified in using a particular rule of reasoning, or in counting a particular instance as conforming to the rule, is to ask whether the rule, or the particular use of it, is in agreement with our general practice—where to say that a rule of reasoning is ‘in agreement with our general practice’ is to say, roughly, that we knowingly follow it, and justify our reasoning by more or less explicitly citing it, and second, that we don’t accept other rules that conflict with it, or that require it to be validated (and we can’t produce the validation).4 Next, with respect to our 3 So my MSRist is a minimalist or deflationist or disquotationalist. I want however to distinguish his view from that of Horwich’s, in which truth is not definable in terms of satisfaction. My MSRist does define truth in terms of satisfaction: the disquotationalism shows up in the “dog” refers to dogs—style definition of satisfaction. 4 This is not entirely uncontroversial: it goes against the ‘externalist’ view of justification according to which no pattern of reasoning counts as justified unless it is truth-tracking. It does seem to me that recent discussion has pretty much defeated this view: with the most telling objection to it being that

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prima facie commitment to IBE—our willingness to use it, not only in cases involving observables, but also in cases in which we don’t yet know whether the inferred entities or properties, if they exist, are observable or not, and finally in cases where they are known to be unobservable—I know of no reason to think that any of this needs to be validated, or that any of it is in conflict with any other rules of ours. In particular, we do not have a rule that each of our rules needs to be validated by a proof that it tends to the truth before we are allowed to use it (else no one would ever have legitimately given any inductive argument); as for rules that might be held to conflict with IBE, such proposals as ‘always accept the weaker of two theories that fit the known facts’ seem pretty clear non-starters.5 Footnote 4 continued it is hard to see how such a notion of justification might play into any of the uses we want a notion of justification for—the central one being the role it plays in our deciding what to believe. A paper that trenchantly makes this point is Mark Kaplan’s (1991). 5 For more on this ‘rule,’ see Kukla’s (1998), passim, but especially essay. One piece of evidence that the position is becoming a consensus is how close van Fraassen’s current position is to it. A recent paper by him and others (Ladyman et al. 1997) gives as complete an account of his recent views as I have seen, and it is noteworthy how little the central positions in that paper disagree with the position I sketched. There is no disagreement between my position and van Fraassen’s claim that one is not rationally compelled to accept arguments about unobservables, if all he means by the latter is that a rational being might adopt abductive rules other than ours—this is no doubt true, just as it is true that a rational being might adopt grue-like inductive rules. There is disagreement only if we read van Fraassen as saying that our abductive practice does not so compel us—i.e. as saying that you might deny the existence, e.g. of atoms but still be conforming to our usual practice—but I see little reason to think this the intended reading. (I should mention that Ladyman et al do give one argument that can be read this way but it is hard to believe it is intended seriously: namely, that our ‘common sense’ abductive practice is consistent with the supposition that we infer only to the empirical adequacy of our theories, since ‘common sense’ deals only with theories about observables, and for these empirical adequacy and truth coincide. But, putting aside the curious idea that we can’t tell what practice people are following by asking them, there is no particular epistemological privilege enjoyed by the inferences we make in the grocery store, as opposed to in the lab, or reading the science columns in the newspaper. Surely there is no question that nearly everyone believes in viruses—the people who don’t generally believe in other unobservables like souls—and that they will say something that sounds a lot like an IBE if you push them on it.) Rather than claim that our practice fails to justify IBE in the sense of the position sketched in the text, van Fraassen’s tendency lately has been to argue that even if this is our practice, we ought to revise it. This position is opposed to MSR—at least in the sense that although someone might agree with van Fraassen but still play the game and argue for MSR, it would be a kind of bad faith—but the arguments I have seen, with one exception, do not really speak to this issue. It is not relevant to claim that science has no interest in unobservables, or that we can interpret the aims of science in a way that disclaims any such interest. MSR is not a claim about the aims or practice of science; it is a claim about a matter of interest to you and me, namely whether our science is true — whether there are atoms and electrons. Elsewhere (Churchland & Hooker, 1985) van Fraassen accuses the Realist of a kind of moral turpitude: to use IBE to conclude that there are atoms and electrons is to engage in a hypocritical display of ‘courage under fire’—pretending to take risks when one is in no danger at all. But this really begs the point at issue, since if we are interested in knowing the truth about unobservables, then we are in genuine danger of not having our desire satisfied. (Even if it could be argued that in the case of unobservables we will never know that our desire has been satisfied, one can surely have one’s desires fulfilled or frustrated without one’s knowledge, as is amply attested by such practices as the making of wills.) One argument that does speak to the issue is the practical argument that pursuing our interest in unobservables leads to ‘inflationary metaphysics’—which Ladyman et al. gloss as ‘laws, causes, kinds, and so on.’ But (putting aside the possibility that this is one more claim about what science should be doing, as opposed to whether you and I should believe in viruses) consider that either there is a persuasive argument that leads from the existence of unobservables to there being some correct ‘inflationary metaphysics’ or there is not. If not then it is hard to see why pursuing our

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Let us turn now to the idea that our reasons to believe our best theories are outweighed by reasons on the other side. One argument of this form is sometimes advanced in favor of constructive empiricism: that even if one accepts IBE as a legitimate style of inference, it cannot be used to establish MSR, since constructive empiricism is always a better explanation of the success of our scientific theories.6 This argument is powerful against anyone who proposes to defend realism by arguing that it is the best explanation of our theories’ success. But the MSRist does not argue directly from the success of our theories to their truth; he begins by arguing, not that it is true that there are electrons, but simply that there are electrons; the inference to truth comes later. Where the MSRist does make use of inference to the best explanation is in ‘ground-level’ explanations—i.e. explanations, not of the success of his theories, but of the phenomena themselves: there are electrons because their existence would explain e.g. cathode-ray tube phenomena. Here, however, constructive empiricism does not offer a competing explanation; instead, it changes the subject. The MSRist explains why your TV works in terms of the effects of magnetic fields on beams of electrons; the constructive empiricist offers at best an explanation of why it is predictive to speak as if there were magnetic fields and beams of electrons, but proposes to get along without an explanation of why your TV works. But the standards of inference to the best explanation surely advise us to prefer a plausible explanation of so striking a phenomenon over none whatever. The most prevalent form of the claim that our reasons in favor of our theories are outweighed by reasons against is the pessimistic (meta)induction: the fact that our theories have so often been false7 gives reason to believe them false that outweighs the scientific reasoning in favor of the theories themselves. I want to say where I think this argument goes wrong, both because I think that there is no general consensus about this, and also because what goes wrong here bears a close resemblance to what I will later be claiming goes wrong with the most popular argument to save Realism from certain objections. Consider a typical use of the pessimistic induction. Suppose we, as scientists, have made a particular application of a particular scientific method, and the antiRealist wants to challenge our use of the method on the basis of its past history. We have been using a certain test, or making a particular assumption, or drawing a particular sort of inference, and as we look back, we see that test or assumption or inference has had a poor track record. Now I want to claim that there are two importantly different Footnote 5 continued interest in unobservables should commit us to inflationary metaphysics. If there is such an argument, then one can reject inflationary metaphysics only by saying either that there are no unobservables, or that some inflationary metaphysics is correct but even so having to think about metaphysics is too high a price to pay for finding out about the parts of the world we can’t observe. The first line seems to me bizarre, and I doubt if van Fraassen would subscribe to any such thing. The second is so clearly a matter of one’s guess about how awful the metaphysics is going to turn out to be that it seems hard to imagine supporting it with any general arguments. I pass over the Dutch book argument against having any non-Bayesian inductive policy. This would worry me if I were forced to bet with the devil; otherwise I cannot see that it proves anything at all. 6 The source of the argument is a passage in Fine’s (1996a); I am not sure, however, whether he directs it against MSR, to which I am about to say it is irrelevant, or against something much closer to the scientific realism of our correspondence theorists. 7 Since we are discussing the bearing of this argument on MSR, the relevant notion of truth or falsity is deflationist. So, for the purposes of the argument, let us assume that we have used the standard translation of ancient Greek or 17th century English science into our current language to allow us to speak of claims in past theories as true or false.

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situations in which this can happen, and that the pessimistic induction has seemed more persuasive than it should be by running these together. The first situation is one in which the issue of the correctness of the method can be reformulated as a ‘normal’ scientific hypothesis—that is, one which we would expect journal referees or sceptical fellow scientists to ask us to consider: a hypothesis about the probability of a false positive or negative under the test, or the validity of the assumption, or the frequency of (disquotational) truth of the conditional associated with the inference. And in such cases, it might turn out that the poor track record of the method is decisive—that we cannot explain away the past failures or show that the failure rate is high only in a class which is not the most relevant one. But it would be a very naïve antiRealist indeed who would expect to find many instances of this kind. Within the range of hypotheses of the kind scientists take themselves to be committed to considering, there isn’t much they miss—surely not enough to allow a serious attack on the inferences on which the more central and successful parts of our sciences are based. Of course one might object to the specific reasoning by which we do explain away the past failures of our method; but our antiRealist is supposed to be one who accepts scientific reasoning. An antiRealist should thus not expect to argue that chemists have failed to notice the failure rate of e.g. spectographic analysis; if he expects to get much done using the pessimistic induction he needs to aim it at scientific methods the issue of whose correctness cannot be reformulated as normal scientific hypotheses—this is the second of the two situations mentioned above. The obvious way to do this is to give a very broad characterization of whatever specific reasoning he wants to challenge—to see it not as a use of the flame test, but as an instance of IBE, or of the choice of the simplest hypothesis (this ‘method’ is no doubt hedged with a great number of provisos), or even of the ‘scientific method’ itself. What makes it difficult to formulate the issue of the correctness of these methods as garden-variety scientific hypotheses is that there is no obvious way to parse out the notions, absent elsewhere in our scientific theories (as opposed to our epistemological talk about these theories), as best explanation, and simplicity. We have as yet no good characterization of what makes for a good explanation, or what the notion of a ‘simplest’ hypothesis really amounts to. So an antiRealist may fairly claim that the scientists have not squarely faced the question whether IBE tends to lead to correct results. It is however no accident that scientists are unused to considering hypotheses about explanation or simplicity in general: on the face of it our criteria for best explanations or simplest theories are a pretty heterogenous assortment. The fact that the central notions of the pessimistic induction are not particularly unified or natural has been widely noticed; one often sees it claimed that for this reason the induction cannot be well supported. This may be right, but there is another, more significant consequence to be drawn. Our interest is after all not so much in the pessimistic induction, as in the particular bit of reasoning, the IBE, say, that is under challenge. And here, even if we were certain that most IBEs fail, it is by no means clear that this undercuts the acceptability of the particular one that interests us. Suppose, for example, the reasoning is the multi-pronged IBE that supports our belief in the existence of atoms. Suppose we know that most IBEs lead to false conclusions; this tells us that there is a particular class to which this reasoning belongs, most of whose members are false. It goes without saying that there exists some such class, indeed no end of them; what is crucial is what these classes are. It is here where it makes a difference, both that our criteria for IBE’s and simplest theories are many and various, and—perhaps even more—that we have a well-founded suspicion that the success rate of any abductive method depends greatly on the circumstances

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in which we use it:—IBE, for example, is much more successful in daily life, biology, and engineering than in figuring out the ultimate constituents of the universe. The situation is a bit like the competition between reference classes in ‘direct inference’ in statistics—should we assign Jones a (credal) probability of dying based on the fact that he is a man, or based on the fact that he is a smoker? Here the fact that our IBE belongs to a ‘reference class’ most of whose members are false competes, not with our knowledge of some another reference class to which our IBE belongs, but rather with the IBE itself, which has great plausibility according to our normal criteria for judging IBE’s, and independently of any class we know it to belong to. As with direct inferences, it is difficult to give exact rules for adjudicating the competition, but a few examples will remind the reader of our usual procedure when a persuasive IBE competes with a heterogenous reference class. We do not allow the inference that neutron stars are extremely dense to be undercut by the observation that most things are not all that dense—we expect the composition of an object to make a great deal of difference to its density. We do not allow the fact that virtually all languages spoken in Southern Europe are Indo-European to undermine the reasoning that shows that Basque is an exception.8 The antiRealist has a reply to this last. He can propose that the rate of failure among so many IBEs itself cries out for explanation, and that the best explanation is that the various uses of IBE do share some common feature, and in fact one which rather badly mismatches the way the world is: the tendency of IBE to fail is present whatever the circumstances in which we put it to use. The trouble with this argument—beyond the fact that it is somewhat overstated (as I remarked above, IBE surely doesn’t fail most of the time in our daily lives)—is that we really ought to consider it, not in isolation, but as part of an explanatory package. The competition is really between two entire explanatory pictures: one in which we have an explanation of all the facts that atomic theory explains, but no systematic account of our past failures, and one in which we have—well, not quite an explanation but the hope of one, for our past failures, but no explanation of, say, Boyle’s Law.9 And here three considerations seem to me decisively to favor the first picture: First, that no one has shown that truth is a natural—‘causal-explanatory’—property; the only definition we have of satisfaction is a pretty artificial-looking list. Until we can show that truth is more ‘natural’ a property than that, it is not a high priority to explain regularities involving truth. Second, there are after all reasonable explanatory stories about why we failed at various times in the past—namely, the detailed accounts in the history books. These accounts are somewhat piecemeal, though not entirely: we can explain a whole set of failures in terms of lack of the appropriate mathematics, another set in terms of people’s inability or unwillingness to do the experiments, and of course it hardly requires explanation 8 It may seem relevant that in the IBE case it is the actual reasoning employed which turns out to belong to a reference class most of whose members are false, whereas in the neutron star case this is not so: the competing reference class—the set of all things—rather than casting doubt on the method of reasoning, casts doubt only on the conclusion of that reasoning (that there are some things that are very dense). I think this is a distinction without a difference: the fact that most things are not very dense also shows that the reference class of arguments that lead to the conclusion that something is dense are for the most part mistaken. Against this, one might wish to protest that seeing an argument as an IBE characterizes it in a much more natural way than seeing it as an argument for the conclusion that something is dense; maybe so, but the issue is whether this characterization is natural enough to outweigh the plausibility of the IBE taken by itself. 9 A third picture is one in which we usually fail, but not this time around. We need not consider this, since if it wins the competition, MSR is supported anyway.

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that no one so much as thought of quantum physics or relativistic spacetime until other more obvious accounts had run into trouble. Finally, the explanatory account hoped for by the pessimistic induction is after all pretty speculative: it would require not only uniformity in how we approach the various questions in the various sciences, but (what seems a good deal harder to argue for) a hidden uniformity in all the questions themselves—a general tendency of Nature to violate our sense of what is plausible. Even if the account were less speculative than it is, it is hard to see how it could compete with atomic theory: one could multiply examples in the sciences in which a theory that explains much is preferred over a theory that explains little, even if the preferred theory offers a less unified explanation of one particular explanandum (think for example of cases in which we finally dismiss observations that were well explained by the rejected theory as due to some unexplained problem with the measuring instruments).

II We have been discussing the supposed difficulties with MSR that are not really difficulties and therefore do not require the correspondence theory for their solution. I now turn to a real difficulty, which does provide a strong motivation for turning to the correspondence theory. MSR is a schematic point of view, one that gets its content from the particular ‘best theories’ that we feed into it. Now it is true of me, and I am almost certain it is true of you too, that when I feed in our best fundamental physical theories, then the standard MSR argument seems not to get off the ground. What goes wrong is the very first step in the argument: the step in which we cite as a premiss the conjunction of claims which is supposed to constitute the core of, say Quantum Field Theory or General Relativity. And the trouble is that although there are perhaps some claims within each theory that I might fairly claim to believe (or to assign a high degree of belief to), these are far from the core of these theories: they do not add up to anything I can identify as QFT or GTR. The reasons for this are familiar. In the case of QFT, the problem is to say what the core claims of the theory are, in view of the fact that any one physicist’s candidates are likely to be rejected by others—not merely as not central, but as outright false. Are Feynman diagrams an intrinsic part of QFT, or are they just a way of thinking about the perturbation expansion—itself a crutch while we await exact solutions? and if they are part of the theory, does this mean the theory is committed to virtual particles? In fact, is the theory committed in any sense to particles, in view of Rindler particles, or in view of the fact that the theory permits states of the universe which are not eigenstates of any particle number operator? Or is the Copenhagen-type presupposition of my last sentence not part of the theory? and if not, if the theory hasn’t made up its mind about the eigenstate–eigenvalue link, what does it say about the existence of particles? Is the theory committed to fields? Certainly it talks about an operator field, but that doesn’t seem like a physical entity. And so on. QFT is of course notorious for its interpretive problems; our other fundamental theory, GTR, has arguably no such difficulties. More precisely, it has no such difficulties considered on its own. The trouble is, as is well known, we cannot consider it on its own: in a quantum world, we find nothing like the continuous and single-valued stress-energy tensor of GTR; and any attempt to remedy this immediately calls into question whether we can speak with any confidence of a single well-defined Einstein

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tensor, and thus of the spacetime metric itself. So we end up in a position with GTR which resembles the situation with QFT: we would like to say there is something right about the theory, but there is not one core piece of it, not even its overall structure in any unambiguous sense of ‘structure,’ that we can point to as the part we actually believe. Still, what exactly is a problem for Realists here? Why not say that MSR works when it does, and that’s all a Realist needs? There are two reasons (at least) why a Realist might hesitate before making this response. The first is that it is questionable whether our problems with fundamental physics will ever go away; the response makes Realism sound likely to turn out a mere historical curiosity. The other reason is the enormous temptation to say that in some sense, these theories are well-confirmed—QTR marvelously so. A Realist will want, no doubt, to reserve the term ‘confirmation’ only for a relation between theories and knowers that increases the knower’s degree of belief in the individual statements or the core statements of the theory, but our temptation to speak of QFT as well-confirmed might easily suggest that the notion of confirmation he is working with may not be the one we should care about: perhaps the only kind of confirmation we need or want for our theories is the kind that QFT has right now—and if confirming a theory in this way doesn’t justify belief in its truth, well, then, so much the worse for Realism. Enter the correspondence theory. Our correspondence theorists don’t often represent themselves as trying to address the challenges posed by modern physics—a pity this, since their Instrumentalist opponents certainly do argue from the peculiarities of modern physics; and strange too, given that the challenges of modern physics to realism have been on the table, or in the Science section of your newspaper, ever since the 20’s, if not earlier. But their arguments for realism must implicitly bear on these issues, and it is useful to ask how. I suggest that the correspondence theory is one way to acknowledge the force of the suggestion that our theories are in some (non-standard sense) well-confirmed; and that it does so by giving us the terminology we need to say that it is something else that really is well-confirmed, that we have good reason to believe—namely the claim that our theories are approximately true. Showing that we have reason to believe our theories approximately true is a project that requires a correspondence theory; a deflationist cannot so much as formulate the goal in a way that doesn’t immediately make us despair of success. The reason is that there are an uncounted number of ways in which GTR might be approximately true: perhaps spacetime is granular, perhaps there’s a superposition of the values of the metric, perhaps there’s a cosmological constant, 14 dimensions. . . To say that our theory is approximately true, we are forced to generalize: we must say ‘There is some true theory which GTR approximates.’ For a deflationist, the trouble with this is that, for him, a ‘true theory’ must mean a true theory formulable in his language: a deflationist can believe his theory approximately true only if he believes that some theory formulable in his language is strictly true. But none of us believes that, or should. With a correspondence theory of truth we escape at least part of this problem: we now can make sense of the idea that a theory of ours resembles some true theory in some unspecified language. We might wonder how easy it is to define the relevant sort of resemblance, but, once the correspondence theory has gotten us over the first big hurdle, the rest may seem only a technical problem. This of course leaves the problem of arguing that our theories are approximately true. This cannot be done, it hardly needs saying, by repeating the arguments for MSR, only inserting the word ‘approximately’ in front of ‘true’: for one thing, we no longer have a disquotational argument

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whose conclusion is ‘S is approximately true’—what would its premises be?10 —and in any case we don’t want such an argument: the only sense in which our theories might be approximately true allows any individual central claim in the theory to be deeply, irretrievably false. The argument for the approximate truth of our theories must use something other than the piece-by-piece confirmation of the parts: it must be an argument that directly addresses the approximate truth of the whole theory. And indeed there is an argument that seems to hold promise here—I think it is essentially the only one, though it takes superficially different forms. This is the argument that the best explanation of our past successes is the approximate truth of our theories in the past, so there is reason to think that a successful theory like QFT is likewise approximately true. I follow most of the literature in formulating this argument (let’s call it The Realist Argument or TRA) as an IBE rather than as the straight inductive argument that past successful theories have been approximately true, so probably QFT is too. There is reason for doing this: whatever you think about the view, first I think defended by Harman, that all inductions are IBE’s, the fact that the pessimistic metainduction has been put forward and taken seriously shows that there is more than one way to project our past history of successes and failures into the future: it seems hard to defend the idea that it is the property of approximate truth rather than approximate falsehood which deserves to be projected unless one can argue that it is approximate truth which explains the past successes. As it turns out, the problems with the IBE version will apply to any purely inductive version of TRA as well, so there is no harm done by following the literature here. TRA should be distinguished from the claim that the inference from success to truth is simply part of our standard justificatory practice, and as such requires no separate argument. When we argue from the phenomena to, say, the existence of electrons, we always have the option of summarizing our arguments using semantic ascent: instead of saying that we conclude that there are electrons because their existence would make all sorts of effects fall into place, we say that we have inferred the truth of electron-theory from its success. If this is what one means by saying that we accept a rule of inference from success to truth, then it cuts no ice here: we are assuming that the ground-level arguments are by themselves insufficient to persuade us to believe QFT, and restating these arguments using semantic ascent cannot change matters. The success-to-truth inference can be of use to us only if it adds something new: only if, for example, after giving all the ground-level arguments for a theory, we were in the habit of awarding it extra points because it was successful. But we do not do this. The predictive successes of a theory already enter into the ground-level arguments; I see no reason to think we are in the habit of counting them twice.11 Returning to TRA, there has been a considerable amount of discussion over the years about its first step: that the best explanation of our past successes (or, sometimes, 10 It can’t be, for example ‘Approximately there are virtual particles?’—what would that mean? 11 It might be claimed that, although the success-to-truth inference adds nothing when we know the

arguments for a theory, there is at least a pattern of inference of this type that we employ when we don’t know anything about a theory other than that it is successful. I don’t know how one would establish the existence of such a pattern of inference. No doubt you and I sometimes believe a theory true without knowing the arguments (we might read about it in the newspaper) but then our reason for believing the theory true is that we have divided our labors with the scientists: we assume that we would approve of their reasoning if we knew it. Are we ever presented with a theory about which all we know is that it was successful: we don’t even know that it struck someone as plausible enough to write down?

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the present success of the part of our current theory that doesn’t have the problems of foundational physics) is that our theories have been approximately true. It is often assumed, I think, that establishing the first step shows that truth is a ‘causal-explanatory’ notion, and that once we have done this, the second step in the argument— projecting the truth of current and future successful theories as the best explanation of their success—will be smooth sailing. And so antirealists have joined forces with deflationists—who, although often scientific realists, have an interest in blocking any attempt to see the notion of truth as projectible—in arguing against the first step in TRA, often by trying to show how to eliminate the notion of truth from all explanations across the board. Speaking as a deflationist who once participated in this project, I think (and have argued in (Leeds, 1995)) that it was misguided, for two reasons: first, because to deny that past theories succeeded because they were true is to fly in the face of the obvious, and second because conceding the first step in TRA is very far from conceding the whole argument. Any of us who, like you and me, believes a huge proportion of what the scientists and historians tell us, believes also that there is a referential map under which our beliefs are largely true. That there is any referential map under which beliefs as detailed as our own give so largely correct a picture of the world is a wonderful fact about us—perhaps it is the wonderful fact about us—and one can always hope that we can find an explanation of how it came to be—or, rather, an explanation more systematic than simply telling the history of science, or of mankind. But even if we can offer no more unified explanation of our coming to have accurate representations of the world than we can offer for the evolution of Sonata form or baseball, everyone should agree that we have come to have such representations, in which case there is no reason why this remarkable fact should not in turn be used to explain other facts, such as our successes in dealing with the world. Kitcher, whose (Kitcher, 2002) is a good representative of the correspondence theorist’s side of the discussion, goes carefully through the attempts by various deflationists to explain our successes without appealing to truth; he has no trouble arguing that their alternative explanations leave out the fact that our map of the world, being a largely correct one, is endlessly and systematically versatile. But I do not see why a deflationist should need to eliminate all use of ‘true’ in explanations, any more than someone who thinks there is no general, systematic account of how people come to have good maps of Venice needs to show how we can replace every explanation of the form ‘I looked on the map, and saw that if I followed this street I would land in a canal’ with one that doesn’t make implicit reference to the particular projection under which the map resembles Venice. So I think that every realist, deflationist or not, can agree that the success of our current theories (the unproblematic ones) is explained by their being true. In fact a deflationist can extend this to past theories (and so agree with the whole of the first step in TRA) by using the standard translations of past scientific vocabularies into ours to specify exactly what he means by the approximate truth of past theories. But this still leaves the second step to be argued for. Let us suppose (what a deflationist need not concede) that the first step of TRA has established that truth is a notion suitable for use in broadly inductive reasoning (so we are supposing that we understand ‘correspondence truth’ well enough to formulate hypotheses about the truth or approximate truth of future theories—although again a deflationist need not concede this); nonetheless, it should go without saying that every case of projecting a ‘best explanation’ into the future needs to be judged on its own merits. In the case

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at hand, we will presumably want to argue that the process by which we think up and test theories is such as to make it unlikely that we will hold (or long hold) successful theories that are very far from the truth, either because our methods are able to test theories in ways that prevent the really false ones from being successful, or because our hunches about what is plausible tend to favor the more-or-less true theories.12 But I want to stress that one needs to argue this. The ‘unlikely’ in the statement above is an ‘objective’ probability—it talks about a tendency of our methods to track the truth. But such a tendency doesn’t come out of nowhere—it supervenes on what our methods are, and what the world is like, and I suggest that before concluding that there is such a tendency we need some rough inkling of how this might happen. Well, do our methods track the truth? Sure. We discard any theory that claims that 2 + 3 = 6, any theory that tells us that roses are blue; we constrain our theories in all sorts of ways that have the effect of ruling out false theories. The issue, however, is whether our methods track the truth in ways that will be helpful in the situation that TRA is addressing: a situation in which the ground-level arguments in support of a theory have left us in doubt whether the theory is true, and we are hoping for an argument to shore up our confidence in at least its approximate truth. Now if you get down to the details of any particular feature of our inductive methodology, you will generally be able to find some general claim about the world which will hold if and only if that feature tracks the truth. It is truth-tracking to assume that no roses are blue if and only if they aren’t blue; one tracks the truth by preferring geometrically formulated theories over others iff the world is geometrical, and so on. In such cases, we may be able to argue for the general claim about the world: perhaps we have inductive reason for thinking that the world is in the appropriate sense geometrical and of course we have excellent reason to think that roses aren’t blue. But if we can give such arguments, and they are relevant to our assessment of QFT, then we have already used them (and found them insufficient) long before the correspondence theorist appeared on the scene: if it’s a point in QFT’s favor that we used geometrical ideas (e.g. representations of the Poincare group) in creating it, then that point is made no stronger when we reformulate the claim ‘The world has a geometry’ as ‘Our method is truth-tracking in assuming the world has a geometry.’ Here is a possible response for the defender of TRA: Admittedly, any claim that a particular feature of our methods tracks the truth can always be replaced by a ‘ground-level’ claim about the world, which can then play its role in our ordinary scientific reasoning without any need for talk about us and our methods. However, we can eliminate reference to our methods in this way only when we know what these methods are. There’s much we don’t know about how we reason—for example, how exactly we order hypotheses by simplicity. As soon as logicians came up with a correct characterization of deductive reasoning, they were able to argue that it tracked the truth; mightn’t it be that were we to come up with an accurate description of our inductive methodology we would also be able to give a ‘ground-level’ argument that the universe is such as to allow this methodology to be truth-tracking? And if we now have reason to think this would be the case, shouldn’t we take the fact that we have come up with, and in some sense accept, a particular theory as an additional reason in favor of that theory’s approximate truth? 12 In fact, if one wants to claim that we approach the truth, we need to ask for even more. But I don’t think we can get even this much, so I won’t bother to formulate a more extensive claim on behalf of the correspondence theorist.

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The answer to this suggestion is that even if we aren’t able to characterize our methodology in detail, we know it well enough to know that understanding it better than we do would lead us to no new ‘ground-level’ claims about the world that we would have any reason to believe. Suppose we were to learn that we tend to rate theories more highly if they obey a particular interesting syntactic condition; suppose (what is more likely) that we can give a deeper characterization than we have so far of what it is that makes us value a theory as giving an intelligible picture of the world. It might be useful to know these things—it would allow us to do consciously what we already do by instinct, or even to think of ways to revise or extend our methods—but isn’t it clear that we wouldn’t know where to begin trying to show that the syntactic condition, or our sense of what makes a theory intelligible, is truth-tracking—except of course by arguing directly that the particular theories they favor are true?13 Against this, I can imagine a defender of TRA saying that it’s irrelevant whether we can argue for the ground-level uniformities that make our methodology succeed: his hypothesis is that there are such uniformities, not that we would be able to establish their existence. That would be a mistaken response, however. We are trying to decide whether the past successes of our science give us reason to think that there are undiscovered features of our reasoning that allow it to track the truth, and it is quite relevant if we are sure that no particular feature that anyone might suggest would be such that we would find reason to think that it was truth-tracking. The situation would be different if we had a general argument to show that there must be such features, e.g. if one could argue that otherwise the story of our past successes would be an inexplicable mystery: such an argument might override our scepticism about any particular feature one might offer as a candidate. But no one has given such an argument.

III So I think the correspondence theory offers little promise of allowing us to believe in the approximate truth of theories that we would otherwise find problematic. To say this isn’t automatically to say that every use to which philosophers try to put the correspondence theory (or the hope that there is one) is doomed to failure. But as it turns out, these projects tend to have enough in common with the one we’ve been discussing so that in fact our discussion applies with few changes to them too. Take for example, Boyd’s (1973), a paper that as much as any other initiated the current interest in invoking correspondence theories to defend scientific realism. Most of us think of Boyd’s target as an empiricist like van Fraassen who rejects using IBE to infer to unobservables, in which case the central questions to ask about Boyd’s argument are whether it is, and whether it can legitimately be, itself an instance of IBE. In fact, although later writings of Boyd are explicitly directed against van Fraassen, (Boyd, 1973) antedates The Scientific Image; the only challenge to realism mentioned in (Boyd, 1973) is the conventionalist challenge to GTR. Now no doubt 13 In which case arguing that our methods track the truth would not provide them any additional confirmation. My argument against TRA has depended on two assumptions: that any claim that one of our methods tracks the truth can be ‘factored’ into a statement about what that method is and a ‘groundlevel’ claim about the nature of the world, and that the best strategy for showing that the method is truth-tracking is by supporting the ground-level claim. I do not say this is the only strategy: Descartes’ Meditations, for example, gives a completely different argument to show a certain method truth-tracking. It is the only plausible strategy I have been able to think of.

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someone who rejects IBE will reject GTR as well; still, Poincare and Grunbaum did not reject IBE across the board—they had special problems about its use in GTR. It is not question-begging to use an IBE against them. So we can see Boyd as using what turns out to be a version of TRA as a response to Grunbaum, by arguing that, in addition to the ordinary scientific reasons that, let us suppose, do not favor GTR over its flat-spacetime, universal-force competitors, we have additional reason to think that because GTR is the theory which in some sense our methodology has selected, it is the fundamental theoretical notions of GTR such as ‘spacetime metric’—as opposed to those of the flat-spacetime theories—which denote real entities. In the following passage, Boyd is talking about a principle P that plays an important role in our methodology (Never mind for the moment what P is). “[Part of the strategy in defense of P will be to] argue that the only plausible explanation for the reliability of P lies in the assumption that it operates with respect to background theories which themselves reflect the actual causal relations among theoretical entities in such a way as to make it likely, in turn, that newly accepted theories will also provide approximately true causal accounts at the theoretical as well as observational level.” What does ‘likely’ mean here? Does it mean ‘reasonable to believe in the light of our methodology,’ or does it mean objectively probable, in some sense of ‘probable’ related to the notion of a tendency or propensity? I think it is clear that it must mean the latter, both because otherwise it is irrelevant whether the background theories reflect the actual causal relations (good reasoning is good reasoning even when the background theories are wrong), and because only this fits in with an explanation of the reliability of P as opposed, say, to an explanation of why we accept theories favored by P. Now P turns out to be the principle of testing theories where, in the light of the background, you think they are most likely to fail. This seems a rather limited principle; but both here and in later writings, Boyd sees a defense of P as at least a partial defense of “inter-theoretic judgments of plausibility” in general. Indeed, he has to see his defense of P as bearing on more general features of our methodology, if it is to connect with the issue about GTR: whatever distinguishes GTR from competing theories offered by the conventionalist, it isn’t that GTR has been tested where it is most likely to fail, while the competing theories have not been. So Boyd is committed to an across-the-board argument that our methodology is reliable—an argument which is supposed to answer, not only empiricist challenges to IBE, but at least some of the specific worries that arise in modern physics. As for the actual argument for P, here things go astray, it seems to me. It turns out that what gets argued for is not that P is reliable because, used against a background of true theories, it is likely (objectively) to produce true theories. Rather, what is argued is that a necessary condition for P’s reliability is that the background theories are true. This result is weaker than Boyd needs: in the case of GTR, no one disputes the truth of the background theories; it is precisely the new abductive step that is controversial. I think one reason he overlooks the need for an argument that P is reliable (or that the extension of it used in choosing GTR is reliable) is what appears to be a confusion between the objective and subjective senses of ‘likely:’ he claims that our reasoning is ‘inductive’ in the sense that it moves from the premise that none of the forces we are acquainted with is a ‘universal’ force in Reichenbach’s sense to the conclusion that there are no such forces anywhere, and then goes on to argue that the truth of the background theories makes this bit of inductive reasoning ‘likely’ to be true. But although there are uncontroversial claims in this general vicinity involving

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a epistemic sense of ‘likely’—e.g. that believing a theory true I will reasonably have confidence in the conclusion of a good inductive argument whose premises are drawn from that theory—what Boyd needs, if he is to persuade Grunbaum, is to argue that the conclusion is objectively likely—has a high chance of being true.14 Boyd is not atypical in making this mistake; one way in which, often, defenders of TRA overlook how hard it is to show any of our methods reliable is by confusing this with the much easier (really, trivial) task of showing that our methods confer epistemic likelihood. Kitcher’s (2001, 2002) provide a more recent example of a project on which our discussion has some bearing, here one in which the role played by TRA is not so immediately apparent. A central section of (Kitcher, 2001) is largely concerned with answering a particular van Fraassen-style empiricist argument. Against the empiricist, Kitcher argues that we are justified in making a certain kind of inference from success to truth, one which is equally applicable when its conclusion concerns unobservables as when it is about observables. For Kitcher the success-to-truth inference takes us not to the truth of entire theories, but to the (approximate) truth of certain statements within those theories—the statements that are crucial to a ‘fine-grained’ pattern of prediction; it is these which we should accept ‘realistically’. Why is it the success-totruth inference which is singled out as the style of ampliative reasoning that survives empiricist criticism? Why not IBE, for example? The answer seems to be that Kitcher has bought into the empiricist suspicion of all ampliative methods of reasoning other than inductions:15 what makes the success-to-truth inference acceptable in a way in which your run-of-the-mill IBE is not is that we can give an inductive argument to support the former. 14 I have not read through all the subsequent papers of Boyd’s on this subject, but a sampling of them suggests that, although he is quite aware of how far most of our abductive reasoning is from narrow inductions, he never takes adequate account of this when he attempts to explain why our scientific methodology is reliable: rather, he writes as if arguing for the truth of the background theories settled the matter. It does only if you regard induction as more general a method than it is, and if you follow this by running together ‘inductively likely’ with the objective notion you need. 15 I can give no good reason for this on Kitcher’s behalf. The empiricist argument (EE) he is trying to counter is, in his presentation, surprisingly weak. Here are the first few steps: “(EEA1) The only claims we can directly justify are those about observables. (EEA2) We can only check a putative method of justification by showing that it tends to lead to correct conclusions. (EEA3) Thus, we can only check methods of justification that lead to conclusions ..[about observables] (EEA4) Therefore we have no basis for trusting putative methods of justification that lead to conclusions whose truth values cannot be directly ascertained just by investigating observables.” This argument doesn’t even get off the ground if to check a method has its usual meaning of trying the method in a few cases, and giving it a pass if it turns out successful, since this reading invalidates (EEA2). If this is what it is to check a method, then (EEA2) really should read ‘showing that it has led to a few correct conclusions’ but then (EEA3) needs to insert ‘some’ before ‘conclusions,’ and (EEA4) follows only if you insert ‘exclusively’ before ‘to conclusions.’ But (EEA4), in this form, has nothing to say against IBE. Should we take checking a method to be: showing that the method tends to lead to true conclusions? This makes EEA2 acceptable, indeed tautologous, but now how do you get to (EEA3)?—all that follows is that if a method of justification leads to conclusions about unobservables then you can’t show it tends to lead to true conclusions in one particular way: namely by looking at every prediction the method ever makes. What makes Kitcher’s taking this argument seriously a little mysterious is the way in which, after coming up with, and arguing for, his own method of inference, he deals with the objection that he has tested it only on observable cases. He simply points out that this gives no reason not to use the method when unobservables are involved. Does he show it legitimate to proceed this way, in the teeth of the EE argument? Of course not: it’s just common sense. Is Kitcher begging questions against the EE argument, or is he pointing out that it is a non sequitur? No doubt he is correctly pointing out the latter, but then you don’t need to invent a whole new method of inference to reply to EE.

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There are some aspects of Kitcher’s position that I find a little obscure. For example, given that he has no difficulties with inductions involving unobservables (his validation of the success-to-truth inference is precisely such an induction) one would expect that he would also recommend our taking realistically those statements about unobservables which we can support inductively, even when they play no particular role in fine-grained prediction. This leaves unclear the precise role the success-to-truth inference is supposed to play in sorting out the parts of our theory we should believe ‘realistically’ from those we should not. Putting this problem aside, it is apparent that Kitcher intends the success-to-truth inference somehow to make the division. And so his project, although largely aimed at answering the empiricist, turns out to have bearing on the issue I have been urging is the important one: which, if any, parts of those theories that we all (not just empiricists) regard as problematic we should accept as approximately true. Kitcher’s argument for the reliability of the success-to-truth inference is thus not dispensable, as it would be if he were proposing it, in the style of MSR, as one among many rules of inference that are acceptable because part of our common practice. What sets the success-to-truth inference apart is that we can give it an inductive justification, as follows: we know already that, in quite ordinary situations, the people who are able to fine-grained predict what’s going to happen are just the ones who hold true theories, and there is no reason not to generalize this to situations involving unobservables.16 The trouble with this argument is that even if there are some philosophers who are willing to buy into inductive arguments that don’t so much as hint why the particular property we’re inducting on should be the one that projects into the future, Kitcher cannot be one of them. After all, he is rejecting a host of inductions that would fail to give the connection he needs between truth and fine-grained predictive power: people in ordinary situations who are able to make wholly unexpected predictions usually hold true theories, people in ordinary situations who have studied a question carefully, and done what seems to them to be sufficient testing in order to eliminate plausible alternatives to their best guess about the answer, are usually right, and so on. Kitcher really needs a story about why it is fine-grained prediction in particular that should be reliable, especially since fine-grained predictive power is bound to be controversial as a criterion for what parts of our science we should take literally—e.g. doesn’t it tell us to believe literally in Feynman diagrams? But it is hard to imagine what such a story might be; indeed, it is hard to suppose that any light can be shed on our problems with Feynman diagrams by looking really carefully at how we get around in the supermarket. A final example—an exception that, so to speak, proves the rule—a correspondence theorist who makes no use of TRA. This is Leplin (Leplin, 1997), who suggests that we conclude a theory is correspondence-true when it makes predictions that are, in an appropriate and carefully worked-out sense, novel. Leplin’s defense of this rule seems to me a model for the way one ought to defend a rule telling us when we are justified in believing a theory: he argues that the rule is implicit in our current practice, 16 Earlier we discussed Kitcher’s defense of the idea that the use of truth in explanations shows it to be a meatier notion than deflationists suppose: in Kitcher’s words, reference is a ‘causal relation’ between words and things, of which it is possible to give a ‘naturalistic account’—that is, ‘semantics can be conducted as a natural science’ (Kitcher, 2002, p. 347). I assume that one reason for wanting this—one reason, in fact, for formulating everything in terms of correspondence truth rather than deflationist truth—is precisely to have truth be a projectible property which we can use in an inductive argument.

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and that it is in various ways a reasonable rule to follow. Why is he not then just an ordinary defender of MSR—or the weaker thesis that sometimes one is justified in believing a theory disquotation-true? Leplin points out that there are some parts of any physical theory that we regard as merely of instrumental value, and some parts we take Realistically: correspondence-truth is supposed to mark this distinction. I agree that this is reason to want a correspondence theory, but I think Leplin escapes needing to give an explicit argument about the tendency of our methods to lead to the truth only by ignoring this motivation when he gets around to his criterion of novelty. His criterion, being theory-wide, seems unable to sort out the Realistic parts of a theory from the rest. A version of the novelty criterion which did sort this out would presumably not be one we could read off from our standard justificatory procedures: we don’t generally judge the separate claims of a theory by asking whether they lead to novel predictions (sometimes they are just a reasonable inference from other parts of the theory). So I think the version of the novelty criterion that would do the work he wants it to do would need to be argued for on the basis of past success, and here is where TRA would enter in.

IV I have been arguing that of the two tasks the correspondence theory might be called upon to perform—to answer the empiricist, and to allow us to state credible Realistic theses weaker than the flat-out claim that our current theories are true—it is not needed for the first, and there is no reason to think it can achieve the second. In fact I think that our argument suggests a stronger conclusion. Attempts to give an explicit definition of reference for arbitrary words in arbitrary languages having so far failed, and no ideas in this line having surfaced in some time, it seems that a correspondence theorist’s best prospects for convincing us that the notion of correspondence truth is a legitimate one is to do so indirectly by pointing to some explanatory theory in which that notion does some work—this is, for example, Kitcher’s approach in (Kitcher, 2001). But in suggesting that there is no general theory about the tendency of scientific reasoning to approach the truth, our argument also suggests that there is no explanatory theory whatever in which correspondence truth has a role to play—for it is hard to see what else such a theory might be.17 I can hardly claim here to have sealed the tomb of the correspondence theory; no doubt it will walk again, perhaps in guises that our discussion has not even dreamt of. But let us suppose that we accept that the weight of argument, at least for now, is against it, and ask what the implications are for the whole set of issues we classify under the heading of Realism—pro and con. One clear implication is that the problem about our contemporary theories that motivates the correspondence theory in the first place (or which at any rate is its most defensible motivation) is one that we cannot escape except by changing our physics: there is no reason to think that when ordinary scientific argument fails to convince us of the truth of our best theories, a philosophical argument can step in to close the gap. 17 I am here relying on my previous discussion and citations therein, for the claim that the correspondence theory cannot help in explaining why the particular theories we believe are successful: when we are in a position to say that they are successful because they are true, disquotational truth will do well enough.

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There is another consequence of abandoning the correspondence theory that I want to discuss in more detail. This is that, without the correspondence theory, it is easier to notice an important aspect of our current discussions of Realism which not only resists formulation as a debate about truth, but in fact is not happily formulated as a debate over any thesis about the world (or the place of us and our theorizing in it; since we too are parts of the world I will not bother in the future to say this explicitly). Rather, the disagreement is over is what kinds of theories we ought to be pursuing, where this is understood, not as a disagreement over which strategy is likely to allow us to arrive at our agreed-upon goals (this would just reduce to a disagreement over the nature of the world), but rather as a disagreement about the goals themselves. For an example of the kind of issue that I have in mind, a good place to turn is the writings of Arthur Fine. Fine is a good example for my purposes for two reasons. First, because I think that he makes most sense as proposing something other than a claim about the world: the Natural Ontological Attitude (NOA) is an attitude we are invited to take up, rather than a thesis we are invited to believe. And second, because the tendency of his readers (and, often, of Fine himself) to try to cram his position into the mold of offering or denying some thesis about the world is a good illustration of how hard it can be to see that a debate over Realism need not be about such theses at all. Consider the suggestion, more often coming from his readers than from Fine himself, that he is offering a claim about truth: for example, that he is rejecting the correspondence theory. No doubt he is, but if this is all he is doing then he has nothing new to tell us, nor, as a raftload of commentators have pointed out, does he thereby fail to be a Realist, since one can be a Moderate Scientific Realist without allowing for any notion of correspondence truth. It would indeed be novel and exciting if Fine rejected the disquotational theory of truth, but there is hardly any theory here to reject: disquotational truth is just a notion that we define according to a familiar and unexceptional mode of definition; the only ‘theory’ connected with disquotational truth is the claim that that notion coincides with our ordinary notion of truth, and here Fine has no axe to grind either way—although his general tone seems sympathetic to the disquotationalists. Fine sometimes seems to be rejecting, not (or not only) the correspondence theory, but in addition some claim put forward by Realists about the nature of the world outside our theorizing. Here is a typical passage: “Einstein wanted to claim genuine reality for the central theoretical entities of the general theory [of relativity]. . .I believe the majority opinion among working, knowledgeable scientists is that general relativity provides a magnificent organizing tool for treating [certain problems]. But few, I believe, give credence to the kind of realist existence and nonexistence claims I have been mentioning. (Fine, 1996a, p. 123).” Unfortunately for our hopes of discovering a substantive thesis on which Fine and the Realists can be said to disagree, the existence and non-existence claims Fine has been mentioning include such claims as that there is a spacetime manifold. One might indeed dispute the existence of the spacetime manifold—spacetime relationists are in the business of doing just that—but it is plain that Fine’s interest is not in taking a stand on relationalism. His objection is not to claiming that the spacetime manifold exists, but to the claim that it has genuine Reality. It is hard to see what this contrast might amount to. And perhaps Fine would agree: a few pages later in the same essay, he can be found asserting that the Realist has no thesis at all: that all his Realism amounts to is thumping the table and shouting

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‘Real!’. This however does little to explain one’s sense that Fine and the Realist have a genuine, and important disagreement. We can see more clearly what Fine is after if we recall that for him, as for most of us, the paradigm Realist is Einstein. Now there are some obiter dicta of Einstein, uncovered by Fine in a fascinating essay (Fine, 1996b) on Einstein’s Realism, which indeed suggest unhealthy tendencies in the direction of the correspondence theory; these however play a rather peripheral role, both in (Fine, 1996b), and in the essay (Fine, 1996a) on NOA from which I quoted above. What is described in (Fine, 1996b) describes, and what Fine rejects in (Fine, 1996a), are not the metaphysical views of Einstein the part-time philosopher, but the methodological views of Einstein the working scientist—and in particular the Einstein of the debates with Bohr: that is, the Einstein who judged quantum theory as being unacceptable from a Realistic point of view. Realism appears here as an attribute of theories, not as a claim about the nature of the world. And the core of Fine’s disagreement with Einstein is not over what the world is like, but whether we should be trying to pursue theories that are sufficiently Realistic. It is this last issue which, I am suggesting, can be separated from debates about the nature of the world. Or largely separated from these: I do not dispute that one argument in favor of giving up the pursuit of Realistic theories is that current physics gives us some reason to think that no Realistic theory that we can create and understand is going to be successful. This is certainly a claim about the world. I think however that it does not quite capture what Fine is saying: for that, one needs to add that not only can’t we find Realistic theories, but that it isn’t a bad thing if we can’t, since there is something else just as good we can be doing. What exactly Fine has in mind—and more generally, what defensible alternatives there are to looking for Realistic theories—is a topic that is beyond the scope of this paper, but perhaps one general remark would not be out of place. This is, that much depends on we characterize the notion of a Realistic theory. If we can only characterize it, as perhaps Einstein himself would have, as a theory according to which well-individuated objects interact locally in space and time, or spacetime, then I think the cause of Realism is lost: it is unlikely that one can give a Kantian argument that any coherent conception of the world that we can give must represent it as, for example, in spacetime, and I cannot see any other strategy for arguing that there is something wrong with a theory which does not so represent it. More hopefully for Realism, it might turn out that what the Realist wants from our theories can be characterized in quite general terms. One possibility along these lines, which I explore in the longer version of this paper, is that the Realist wants theories which, taken together, answer as many as possible of the central ontological questions that one can pose in the vocabularies of these theories—questions about what sorts of things the basic objects and processes described in our theories are and what relations hold between them. Such a characterization seems to be a reasonable way to give expression to the familiar idea that a Realistic theory is one such that we know what the world would be like if the theory were true. From this point of view, Einstein’s insistence, as against Bohr, that quantum theory be explicit about what processes were taking place in spacetime when one made a measurement can be seen as the natural way to make the demand that our theories be specific about central ontological questions, given that all parties agreed that the world consisted of particles and fields in spacetime. A conception of Realism as a general requirement on our theories, one which takes different forms given different shared backgrounds, may be more easily defensible

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than a more specific conception. The case of Einstein and Bohr in fact suggests one way in which such a defense might go. A Realist might claim that someone who believed, as Bohr presumably did, that all events unfolded within the spacetime manifold, could not legitimately dismiss a question such as, for example, at what stage (if ever) in the EPR experiment the unmeasured particle acquires a definite momentum: taking such questions seriously just follows naturally on adopting the attitude of belief towards the claim that the world consists of particles and fields in spacetime. An antirealist might concede this, but claim that there are attitudes and attitudes: one might be in some sense committed to the existence of spacetime, without yet being forced to see every question about it as having a definite answer. Such an antirealist might see Fine’s phrase about ascribing genuine Reality to spacetime, with its implied contrast with ascribing to it some other status, as a misleading description of an important contrast: that between believing18 in the existence of spacetime and adopting another, weaker but still committal attitude to its existence.19 I argue in (Leeds, 2006), following out a suggestion of Alan Musgrave (1989) that Fine’s NOA is supposed to be just such an attitude. A natural response for the realist to make is to question whether we can really make sense of such an attitude. This is the direction in which I think realist and antirealist really have something to argue about, but I will say no more about it here. To see the debate between Realist and antirealist as being over what attitudes we can take and want to take towards our theories might appear to take us far from our earlier discussion of the failure of MSR, and the attempts by correspondence theorists to improve on it. But in fact the issues about attitudes were on the table right from the beginning. Consider the fact that an antirealist like Fine has no trouble with MSR, at least as applied piecemeal to the various claims of current-day physics: so long as he is not called on to decide whether particle-talk is disguised talk about fields or conversely, he is perfectly happy to say that photons are bosons, and therefore that it is true that photons are bosons.20 It was only from the Realist’s viewpoint that MSR 18 Nothing I say here is meant to include the possibility—indeed, the likelihood—that belief comes in degrees. It would be tedious to take account of this explicitly, but it could be done: thus, a few sentences back, I should have said that when you believe a theory to some degree you (to the same degree) take questions within the theory to be questions that should be taken seriously. about what the world is like. And similarly elsewhere. 19 From this point of view, van Fraassen’s position has conceded too much to the Realist, since it agrees with the Realist that the goal of our theorizing is to find theories that we can believe. To be sure, the theory van Fraassen would have us believe is not one about the stars and atoms, but only a theory T to the effect that some other theory X about stars and atoms is observationally adequate, but his attitude towards T is the same as the Realist’s belief, and his attitude towards X is simply the Realist’s disbelief. By contrast, the antirealist position I am imagining—the one I think Fine wants to occupy—is one in which our attitude to General Relativity does not contrast unfavorably with our attitude towards some other theory. Interestingly, there is another way in which van Fraassen concedes more to the Realist than an antirealist needs to: he endorses the realist’s project of coming up with Realistic theories—theories such that we know what the world would be like if they were true. I am not sure however that this is so much a commitment of Constructive Empiricism as it is a view that the originator of that position happens to hold. (Notice, however, that van Fraassen’s characterization of observational adequacy makes essential use of the idea that our theories have well-defined models.) 20 More precisely, I do not think an NOAist has any difficulty with taking truth as defined by the Tarski schema, and thereby moving from ‘Photons are bosons’ to ‘It is true that photons are bosons.’ Fine has suggested that he has no problem either with defining truth via satisfaction as Tarski did, but this is not so clear to me. The problem is that imposing the kind of regimentation on the sentences of physics that is needed for a satisfaction definition requires one to make up one’s mind about precisely the kinds of ontological questions that I follow Musgrave in thinking an NOAist will want to duck.

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failed: for him the argument was useless because he could not believe the premisses— the various object-language claims of physics. Being unable to believe these, however, is from the Realist’s point of view already bad enough; of course it does follow that he can’t believe them true either, but there is no reason to formulate his quandry in terms of truth. Or, if we do, we should do so placing the emphasis in the right place: the Realist’s problem is not that he can’t believe the claims of modern physics are true, but that he can’t believe them to be true, i.e. to believe them. If we put things this way, the antirealist’s suggestion that there are attitudes we might aim at other than belief seems a natural one. What was harder to see—what perhaps could not be seen until we abandoned the false attractions of the correspondence theory—is that what to make of this suggestion is the issue between realist and antirealist.

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