 This approach to the virtues by way of moral psychology, in fact, proves to be remarkably durable in ancient moral theory. In one way or another, the various schools attempt to explain the virtues in terms of the soul, although there are, of course, variations in the accounts. Indeed, we can treat the theory of the Republic as one such variation. While the account in Republic IV has affinities with that of Aristotle in Nicomachean Ethics, for instance, further developments in Republic V–VII make Plato’s overall account altogether unique. It is in these books that the theory of forms makes its appearance.