Natural minds

In Natural Minds, Thomas Polger joins a growing number of theorists who defend the mind-brain type-identity theory while casting doubt upon orthodox nonreductive varieties of functionalism in the philosophy of mind. Polger has written a fine book in a fast-paced style that covers a lot of ground. He discusses different kinds of multiple realizability and their support for functionalism (ch. 1), Kripke’s modal argument against the identity theory and Levine’s explanatory gap problem for physicalism (ch. 2), the many possible functionalist views about the mind (ch. 3), various notions of the realization relation (ch. 4), and problems for specific kinds of functional realization with respect to desiderata like objectivity, biological abstractness, and causal efficacy (ch. 5). Polger also criticizes arguments that might be used to support orthodox nonreductive functionalism that are based upon Shoemaker’s fusion of causal-role functionalism and a causal theory of properties, Lycan’s analysis of levelhood in terms of functional roles and their occupants, Putnam and Fodor’s appeal to the methodological autonomy of psychology, as well as Machamer, Darden, and Carver’s multi-level account of mechanistic explanation that entails neither reduction nor property identity (ch. 6). Polger also includes a discussion of Dennett’s challenge to philosophical intuitions about zombies, which is extraneous to his main thesis but connected to matters of mechanistic explanation (ch. 7), and he concludes with a curious concession about one alleged counterintuitive consequence of the identity theory—namely, a cell-assembly that has become dissociated from the individual would still possess sensations (ch. 8). Much of Polger’s book provides a convenient summary of the literature. For example, Polger presents several familiar strategies to defend the identity theory and settles upon Lewis and Kim’s evolving proposals about species-specific properties coupled with Kim and Adams’ observation that mere physical differences between conscious brains does not exclude neurophysical commonalities that might underwrite mind-brain property identities (ch. 1). Polger also presents the muchdiscussed family of problems regarding functionalism and the causal efficacy of mental properties (ch. 5). But he organizes the philosophical landscape in a useful way. Especially noteworthy is Polger’s taxonomy of possible functionalist positions,