Is morality a system of rules to live by? Many philosopher think so and regard ethics as the discipline that formulates, systematizes, and justifies such rules. Yet this approach to ethics can make living a decent, upstanding life seem a matter of living according to formulae. The culprit is almost always an excessive rationalism, which takes morality to be an abstract system of principles whose truth no fully rational soul who gave them a complete and impartial hearing could deny. On the most ambitious of these rationalist views, the relation of the system to the customary morality of this or that earthly society is understood to be like the relation of a Platonic form to each of its exemplifications in the world. Just as each exemplification resembles imperfectly the form, so the customary morality of each earthly society resembles imperfectly the system. And just as according to Plato's theory of education one arrives at knowledge of the forms by stages that begin with acquaintance with their ex-emplifications, so according to a well-respected rationalist theory of moral education one arrives at moral knowledge, knowledge of the abstract system of principles, by stages that begin with the inculcation of the mores of one's society.