What would it take to have the foresight to send a letter to one’s future self (Fig. 1.1)? And what would it take for someone, on receiving such a letter, to feel sorrow for the sender? Because the persistence of personal identity through time is such a fundamental feature of our self-concepts, it is likely that these questions rarely enter into our dayto-day thinking. However, they are significant questions because, in a very real sense, Hobbes is correct: None of us is the same either as we were in the past or as we will be in the future. If the self in the past is indeed a different person, how is it that we assume a special attachment to that particular person? More provocatively, what gives any one of us the right to make decisions now that will affect the future circumstances of the person whom we will become? Answers to these questions require an analysis of what constitutes a notion of self spanning past, present, and future. A developmental approach to these issues attempts to answer the further question: When and how

do children acquire such a notion? The chapters in this volume attempt in various ways to address these issues.