Autonomy and the Moral Authority of Advance Directives

Although advance directives are widely believed to be a key way to safeguard the autonomy of incompetent medical patients, significant questions exist about their moral authority. The main philosophical concern involves cases in which an incompetent patient no longer possesses the desires on which her advance directive was based (e.g., in cases of severe dementia). The question is, does that entail that prior expressions of medical choices are no longer morally binding? I believe that the answer is "yes." I argue that a patient's autonomy is not respected by honoring the desires she used to have but no longer does. I also consider and reject the view that honoring an advance directive that reflects the patient's previous values must be in that patient's best interests. If that is correct, then advance directives in the kind of case at issue are not morally binding.