Proponents of assisted suicide who base their arguments on autonomy err in ways that are little attended to. In the absence of a substantive theory of the good, in neither a descriptive nor an ascriptive sense can the concept of autonomy distinguish those acts that should be morally prohibited from those that may be permitted. And to impose a particular theory of the good, whether individual liberty or the sanctity of life, violates the autonomy of those who do not share a commitment to that theory.