At the center of the debate about personal identity since the 1970s has been the work of Derek Parfit, whose ideas, first published in his article "Personal Identity" (1971) and then extended and elaborated in his monumental Reasons and Persons (1984, part 3), revitalized and to some extent transformed the topic. The following discussion explains how this has come about and relates Parfit's ideas to those of other influential writers on personal identity from the 1960s on, in particular Bernard Arthur Owen Williams (1973), Sydney Shoemaker (1970, 1985, 1999), Robert Nozick (1981), Roderick M. Chisholm (1976), David Wiggins (1967, 1980, 1996), and Richard G. Swinburne (1973–1974). Since the 1990s the debate about personal identity has come to be focused on the correctness of the animalist view, the view that we are animals and that our identity conditions are entirely biological. This view is defended by a number of authors including Paul F. Snowdon (1991), Peter van Inwagen (1990), and...