Book excerpt: The relationship between personal identity and ethics remains on of the most intriguing yet vexing issues in philosophy. It is commonplace to hold that moral responsibility for past actions requires that the responsible agent is in some respect identical to the agent who performed the action. Is this true? On the other hand, can ethics constrain our account of personal identity? Do the practical requirements of moral theory commit us to the view that persons do remain identical over time? For example, does the moral status of abortion or stem cell research depend on whether personal identity is based on psychological or biological properties? Or is it the case that personal identity is not, in fact, relevant to ethics? Personal Identity and Ethics provides the first comprehensive examination of these issues. Topics include personal identity and prudential rationality; personal identity’s significance for moral responsibility and ethical theory; and the practical consequences of accounts of personal identity for issues such as abortion, stem cell research, cloning, advance directives, population ethics, multiple personality disorder, and the definition of death.