Bioethicists are widely agreed that patients have a right of self-determination over how they are treated. Our duty to respect this is said to be based on the principle of respect for autonomy. In end-of-life care the patient may be incompetent and unable to exercise that right. One solution is to exercise it in advance. Advance directives, which include living wills and powers of attorney for health care, enable people to decide what medical treatment they will receive later, when they (...) become incompetent. Advance directives have been criticized in two general ways. First, many critics contend that advance directives fail on a practical level to effect a patient's autonomous choices because, for example, people cannot foresee their futures well enough to make informed decisions in advance. Second, many critics contend that, practical problems aside, there is no moral authority for exercising control over one's incompetent future self. (shrink)