Philosophically, the most interesting objection to the reliance on advance directives to guide treatment decisions for formerly competent patients is the argument from the loss of personal identity. Starting with a psychological continuity theory of personal identity, the argument concludes that the very conditions that bring an advance directive into play may destroy the conditions necessary for personal identity, and so undercut the authority of the directive. In this article, I concede that if the purpose of a theory of personal (...) identity is to provide an answer to the question What is it for a person to persist over time?, then reflection on personal identity poses a potentially serious threat to the moral authority of advance directives. However, as Marya Schechtman observes, questions about how a single person persists through change are not what most of us are interested in when we think about who a person is. Rather, we are interested in what it means to say that a particular set of actions, experiences, and characteristics is that of a given person rather than someone else. (shrink)