We ordinarily believe that the inhabitants of the world - including ourselves - persist over time. Such an idea, however, has puzzled philosophers for centuries. How can we change and still be the same? More specifically, is there any constitutive condition of our identity over time? And if so, does this condition involve mental aspects (such as memories, believes, experiences, etc.), physical aspects (such as the body, or the continuity of the organism), or something else? Or is rather personal identity primitive and unanalyzable, so that our persistence is nothing but a brute fact? This volume is a collection of new essays from leading figures in the field analyzing the persistence of persons and the criteria of personal identity over time. It presents an extensive discussion of the most relevant views on personal identity in contemporary metaphysics and provides new treatments of the constitutive conditions of personal persistence.