Gabriel Segal, A Slim Book About Narrow Content (MIT Press, 2000), 177 pp.

The Mind-Body problem is the problem of saying how a person’s mental states and events relate to his bodily ones. How does Oscar’s believing that water is cold relate to the states of his body? Is it itself a bodily state, perhaps a state of his brain or nervous system? If not, does it nonetheless depend on such states? Or is his believing that water is cold independent of his bodily states? And, crucially, what are the notions of dependence and independence at issue here? An influential resource for approaching these questions was introduced by Hilary Putnam. His so-called ‘‘Twin Earth Thought Experiment’’ involves imagining identical bodies in different environments, and considering whether they share mental states. Putnam claimed to have shown that the meanings of a person’s natural kind words are not fixed by that person’s intrinsic bodily states, but depend on his physical environment. Tyler Burge extended this conclusion in two ways. First, he argued that the thought experiment also shows that a person’s mental states are not fixed by his intrinsic bodily states and, second, that the dependence extends to a person’s social environment. It is fair to say that these ‘‘Externalist’’ conclusions constitute current orthodoxy in the philosophy of mind. But the heterodox persist. Gabriel Segal is now among the leading voices of ‘Internalism’. In a powerful, elegant and often ingenious work, Segal argues that a person’s mental states are fixed by his intrinsic bodily ones.