Functionalism and Zombies

David Chalmers's brief for metaphysical dualism (in The Conscious Mind) is sporting (like Berkeley is sporting), and I appreciate that. It does not turn out to be field-transforming, however (Wittgenstein, Putnam, Fodor: field-transforming, for better or for worse). Too much of the work is done by Chalmers's claim that we can conceive of zombies: humans who behave (function) exactly like other persons, but who have no phenomenal experience (who are quale-free). Chalmers takes this counterfactual to be, by itself, an argument for mind-body dualism. For myself, I doubt that one can conceive of a zombie. There are several possible lines of argument here. Today I am thinking of Wittgenstein's claim that the semantics of psychological descriptions (like the semantics of all descriptions) must be public, as language is essentially (necessarily) intersubjective. All phenomenal terms, then ("pain," "taste," "sensation"), have double lives: their nominal referents are qualia, but their conditions of use (W. would say their "grammars") are public. My view is that the mind-body problem is a complex problem, specifically that we need one theory to deal with intentional properties and another to deal with phenomenal properties. Functionalism is the kind of theory that deals with intentional properties, which I take to be some sort of formal, relational, "public" properties. For phenomenal properties we need reductive materialism. That is, phenomenal properties are not multiply realizable. When we say that David Chalmers, Flipper the Dolphin, My Favorite Martian, and Commander Data all like chocolate, we are referring to something that instantiates a particular functional role. It is not required (it does not follow) that they all have the same qualitative experience. If this is right, then the (alleged) conceivability of zombies does not constitute a proof of mind-body dualism, only of the inadequacy of functionalism.