 While moral theory does not invent morality, or even reflection on it, it does try to bring systematic thinking to bear on these activities. Ancient moral theory, however, does not attempt to be a comprehensive account of all the phenomena that fall under the heading of morality. Rather, assuming piecemeal opinions and practices, it tries to capture its underlying essence. It is the nature of such an enterprise to evaluate and criticize some of these opinions and practices but that is not its primary goal. Ancient moral theory tries to provide a reflective account of an essential human activity so one can grasp what is of fundamental importance in pursuing it. In historical order, the theories to be considered in this article are those of Socrates as presented in certain dialogues of Plato; Plato in the Republic; Aristotle; the Cynics; Cyrenaic hedonism; Epicurus; the Stoics; and Pyrrhonian skepticism.