The Diachronic Mind makes an original contribution to current philosophical debates on the nature of personal identity and the reducibility of the mind. It traces traditional problems facing psychological continuity theories of personal identity to the ease with which theorists of personal identity adopt and apply a sometimes naive physicalism about the mind. This novel diagnosis opens that way to new solutions to traditional problems in the debate on the psychological criterion of personal identity. Through these solutions, an unorthodox version of nonreductive physicalism about the mind-brain relation is developed that avoids the recurrent epiphenomenalism objection to such positions. The book is written in a crisp style that presupposes no more than an elementary knowledge of philosophy. It is intended for students and professional philosophers alike.