David Boonin presents a new account of the non-identity problem: a puzzle about our obligations to people who do not yet exist. Our actions sometimes have an effect not only on the quality of life that people will enjoy in the future, but on which particular people will exist in the future to enjoy it. In cases where this is so, the combination of certain assumptions that most people seem to accept can yield conclusions that most people seem to reject. The non-identity problem has important implications both for ethical theory and for a number of topics in applied ethics, including controversial issues in bioethics, environmental ethics and disability ethics. It has been the subject of a great deal of discussion for nearly four decades, but this is the first book-length study devoted exclusively to its examination. Boonin begins by explaining what the problem is, why the problem matters, and what criteria a solution to the problem must satisfy in order to count as a successful one. He then provides a critical survey of the solutions to the problem that have thus far been proposed in the sizeable literature that the problem has generated and concludes by developing and defending an unorthodox alternative solution, one that differs fundamentally from virtually every other available approach.