A Naturalistic Defense of Realism by Michael Devitt The basic idea of this paper is that arguments against realism depend on a couple of different kinds of mistakes. The first mistake is in assuming that realism is inherently bound up with the correspondence theory of truth, or with a reference theory of meaning. Devitt thinks that this is a very widespread error, and attempts to correct it. The second mistake is in taking a priori arguments more seriously than the results of empirical science. In other words, the second mistake is in not adopting a thoroughgoing naturalism. Devitt’s definition of Realism Realism: Tokens of most common sense, and scientific, physical types objectively exist independently of the mental. This definition is not in any way idiosyncratic. It captures the basic idea behind realism, viz., that the world exists independently of human experience, and that the concepts we use to refer to the things in the world, both common sense and scientific, really exist. (Note: familiarize yourself with the typetoken distinction. A token is simply a particular instance of a type. Brenda is a token of the type “woman”, Everest is a token of the type “mountain”, etc.) Since we have just finished reading Sellars, you may be surprised to see that Devitt is not involved in choosing between the objects of the manifest and the theoretical objects of science: he explicitly accepts them both. What he specifically rejects is captured as follows (p.2): In insisting on the objectivity of the world, Realists are not saying that it is unknowable. They are saying that it is not constituted by our knowledge, by our epistemic values, by our capacity to refer to it, by the synthesizing power of the mind, by our imposition of concepts, theories, or languages; it is not limited by what we can believe or discover. He then goes on to identify many philosophers who explicitly do not qualify as realists by this definition: Berkeley, Kant, Dummet, Goodman, Kuhn, Putnam. Some, like van Frassen are common sense realists, but not scientific realists. Others, like Sellars (who gets no mention here) are scientific realists, but not common sense realists. One of the most important things to understand about Devitt’s definition is that it makes no use at all of the concept of truth. This is important. We can, if we want to, identify a perfectly acceptable definition of realism that does use the word true. For example: Most common sense, and scientific, physical existence statements are objectively and mind-independently true. The problem in doing this is that it makes people think that realism is inherently tied up with some conception of truth, viz., the correspondence theory of truth. This is wrong, and Devitt goes to some length to demonstrate its wrongness. The easiest way to understand his point is to observe that the second definition really adds nothing to the first. To see this, just look at two simpler sentences like: Cats meow. “Cats meow” is true. We learn nothing from the second sentence that we did not already get from the first. The simple use of the word “true” does not add any information. It is just a way of conveying the original information by talking about sentence, rather than the world. Note that neither of the above sentences is equivalent to this sentence: “Cats meow” is true in virtue of corresponding to the fact that cats meow. This statement invokes the correspondence notion of truth, and it purports to tell us what is actually involved in a particular statement being true. Devitt points out that this statement is entirely consistent with realism, but it does not imply realism, nor does realism imply it, and in fact the correspondence theory of truth is actually compatible with any metaphysics at all. o What does he mean by this? Well, for example, if you are an idealist you could still assert that truth of a statement consists in a correspondence relation between that statement and the fact that the statement represents. It is just that you understand the fact in ideational, rather than, say, physical terms. Devitt offers a kind of hand-waving explanation for why so many very smart people have been confused about such an apparently simple point. He thinks that philosophers’ metaphysical intuitions got really messed up by the “linguistic turn” in philosophy: too much talk about language, too little talk about reality. It is important to see that Devitt is not dismissing talk about truth, or even the correspondence theory of truth (to which he apparently subscribes). Rather, he thinks that people just don’t really understand what theories of truth are really for. So he tells us (p. 6) Correspondence truth is a semantic doctrine about the pretensions of one small part of the world [i.e. language] to represent the rest. This doctrine is the subject of lively debate in the philosophy of language, philosophy of mind, and cognitive science. Do we need to ascribe truth conditions to sentences and thoughts to account for their roles in the explanation of behavior and as guides to reality. Do we need reference to explain truth conditions. Should we prefer a conceptual role semantics? Or should we, perhaps.. eliminate meaning altogether. These are interesting questions… but they have no immediate bearing on scientific realism. Why Be a Common-Sense Realist? In this section Devitt summarizes the history of philosophy insofar as it gives us reasons to be doubtful about realism. Essentially this all boils down to the ‘gap’ between the external world and its representation in the human mind, and the perennial question how we could ever really know that we are representing this reality correctly. The traditional failed attempts to bridge this gap have been: Cartesian foundationalism, which attempts to close the gap by building all of our empirical knowledge on a indubitable foundation. Lockeian empiricism, which holds that there must be a resemblance relation between the mind and reality. Berkelian idealism, which actually eliminates the gap by claiming that the real world is not mind independent at all. Kant’s a priori intuitions, according to which the common sense world is known because it is constituted by our a priori intuitions, but the real world is in principle unknowable. Machian phenomenalism, which, in a Berkelian vein, attempts to translate physical object language into language about sense data (i.e., by showing that a sentence like “The cat is purring” has the same truth conditions as a very complex statement about catty purry sense data. Contemporary constructivism, which is essentially Kantian without the universality of the a priori intuitions. All of these kinds of gap closures have failed. Devitt groups them all as having made the same basic kind of mistake, and that is to have taken what are essentially a priori speculations more seriously than empirical research. In other words: Reflecting from the comfort of armchairs [philosophers] decide what knowledge must be like, and from this infer what the world must be like. The mistake, then is that philosophers proceed as follows A priori epistemology → a priori metaphysics Instead of Empirical metaphysics → empirical epistemology. On Devitt’s view philosophy has simply failed to produce a plausible metaphysics because it begins with a priori speculation about the nature of knowledge. But if we are naturalists, then we simply begin with the ontology of successful science, and develop our epistemology on that basis. From this point on, Devitt takes some contemporary philosophers (Dummett and Kuhn) to task for developing highly implausible anti-realist views on the basis of a priori theories of meaning. Again, the problem is the direction of the inference. On a naturalistic view, theories of meaning should not precede our metaphysics. Rather, a theory of meaning should be the result of scientific inquiry, which begins with the basic ontology of science. Starting from scratch Cartesian methodology requires us to take absolutely nothing for granted. But what we learned from Descartes and others is that when you take absolutely nothing for granted, you are condemned to skepticism. The question, then, is not whether you should take anything for granted, but what to take for granted, and the naturalistic answer is that you take for granted is our best science. This, of course, does not mean that our best science is beyond doubt. Rather, it means that you have to be given a reason to doubt it. And, the fact that it is not beyond doubt is not such a reason. Why be a scientific realist? There are two basic arguments for scientific realism, i.e., realism about the postulated entities of science, both of which Devitt endorses. Argument 1 We ought to believe in unobservables because supposing them to exist allows us to give good explanations of the behavior and characteristics of observed entities. Argument 2 We ought to believe in unobservables, because science using observables has been successful, and the existence of the observables provides the best explanation of the success of the science that uses them. (Put differently: If unobservables don’t really exist, then why are the scientific theories that make use of them so successful? Anti-realism leaves this entirely unexplained) These arguments both lean heavily on the concept of explanation. They depend on something like the following principle: If theory T provides a good explanation of phenomenon P, then the basic entities of T should be supposed to exist. This sounds good on the surface, perhaps a little too good. The problem is that to provide a good explanation, at least on one definition, just is to reveal the underlying causal structure of the world. But on this definition, whether scientific theories give good explanations is actually the very point at issue. A more careful way of expressing the idea in both of the above arguments is to observe that scientific theories have been highly successful at achieving the predictive goals of scientific inquiry. Surely it is reasonable to ask for an explanation of this predictive success, and the best explanation we have is that the entities really exist and that they really behave as our theories say they do. Formulated as an alternative principle: For any theory T that consistently provides accurate predictions of previously unknown phenomena, the best explanation of this predictive success is that the basic entities of T exist. The problem with a claim like this is that it’s really not clear what kind of explanation it is. For Devitt, as a naturalist, it would evidently have to be a scientific explanation, i.e., subject to the same predictive criteria as any other scientific theory. This means that, among other things, it should generate testable predictions itself. But, about the only sort of explanation generate by T is that it will continue to meet with predictive success in the future. This certainly lacks the kind of precision we normally expect of scientific theories, but, given the nature of the claim, perhaps it is all we require.