I am quite interested in winning new friends for the views that this book defends – as many new friends as possible. Accordingly, I have written for a group that is somewhat more inclusive than the community of professional philosophers. I hope the book will find readers among undergraduate philosophy students and also among computer scientists, neuroscientists, and psychologists. (Some readers may find that the second half of Chapter 2 and the middle of Chapter 3 are a bit taxing. I hope they will persevere. A partial understanding of this material is entirely sufficient for an adequate grasp of the main themes of the book.)

My main debts are to Ivan Fox and Sydney Shoemaker, each of whom has been extremely generous with his time and wisdom. They have saved me from many errors, and pointed the way toward many ideas that would otherwise have eluded me. Although it is somewhat paradoxical, since they both disagree with many of my main contentions, it is nonetheless true that such value as the book may have is largely due to them.

I have received encouragement and valuable help of other kinds from Anthony L. Brueckner, Anil Gupta, Richard Lee, William G. Lycan, R.J. Nelson, Hilary Putnam, Vola Shulkin, Lynne Spellman, and Chris Swoyer. Each has played an important role at several stages. I am also indebted to Clyde L. Hardin and Brian McLaughlin, who commented on the penultimate draft.