That three of them were popularly regarded as correlated with the three ages of human life; (2) that the structure of early Greek societies, as of other primitive societies, was based on the distinction of three main age-grades, of which the three virtues are characteristic; (3) that Plato's own Ideal State has the same age basis underlying the other features peculiar to it, and is indeed transparently modelled on the Spartan constitution; (4) that it is therefore probable that Plato started with the three divisions of his State and their several virtues, and then, proceeding on the assumption that the ‘natural’ State must reflect on a large scale the constitution of the individual ‘nature,’ arranged the structure of the soul to correspond with his polity.