I began thinking about some of the material in this book in the mid-lggos as three emerging interests and activities slowly coalesced. Some of the metaphysical issues concerning the mind, particularly what I think of as the hard-nosed physicalist challenges to nonreductionist views posed by Jaegwon Kim and David Lewis, had been passed by too quickly in my first book, Cartesian Psychology and Physical Minds. I had also started developing, slowly and through trial-and-error teaching, some background in biology and the philosophy of biology. And, finally, I was forced to think about the diversity of views within cognitive science through my role as general editor for The MIT Encyclopedia of the Cognitive Sciences. It took a few years to find a thread linking these interests and issues, and for the project of which this book is a part, The Individual in the Fragile Sciences, to be articulated.