MATERIALISM AND QUALIA: THE EXPLANATORY GAP

J n “Naming and Necessity”1 and “Identity and Necessity,”2 Kripke presents a version of the Cartesian argument against mate­ rialism. His argument involves two central claims: first, that all identity state­ ments using rigid designators on both sides of the identity sign are, if true at all, true in all possible worlds where the terms refer; second, that psycho-physical identity statements are conceivably false, and therefore, by the first claim, actually false. My purpose in this paper is to transform Kripke’s argument from a metaphysical one into an epistemological one. My general point is this. Kripke relies upon a particular intuition regarding conscious experience to support his second claim. I find this intuition important, not least because of its stubborn resistance to philosophical dissolution. But I don’t believe this intuition supports the meta­ physical thesis Kripke defends—namely, that pyscho-physical identity statements must be false. Rather, I think it supports a closely related epistemological thesis— namely, that psycho-physical identity statements leave a significant explanatory gap, and, as a corollary, that we don’t have any way of determining exactly which psycho-physical identity statements are true.3 One cannot conclude from my version of the argument that materialism is false, which makes my version a weaker attack than Kripke’s. Nevertheless, it does, if correct, constitute a problem for materialism, and one that I think better captures the uneasiness many philos­ ophers feel regarding that doctrine. I will present this epistemological argument by starting with Kripke’s own argument and extracting the underlying intuition. For brevity’s sake, I am going to assume knowledge of Kripke’s general position concerning necessity and the theory of reference, and concentrate only on the argument against materialism. To begin with, let us assume that we are dealing with a physicalist type-identity theory. That is, our materialist is committed to statements like: (1) Pain is the firing of C-fibers. On Kripke’s general theory, if (1) is true at all it is necessarily true. The same of course, is the case with the following statement: (2) Heat is the motion of molecules. That is, if (2) is true at all it is necessarily true. So far so good.