Advance directives are instructions given by patients specifying what actions ought to be taken for their health in the event that they are no longer capable to make decisions due to illness or incapacity. This book takes as its point of departure one of the most commonly discussed medical-ethical argument against granting advance directives moral authority: the Objection from Personal Identity. The adherers of this objection basically asserts that when there is lack of psychological continuity between the person who formulated the advance directive and the later patient to whom it supposedly applies, this seriously threatens the directive's moral authority. Whereas most philosophers in the advance directives debate argue that the Objection from Personal Identity fails, the arguments in this book suggest that it is an argument we should take seriously. Lack of psychological continuity between the author and the later patient, it is concluded, does threaten the moral authority of an advance directive.