 Because the division of functions paves the way for the definition of justice as ‘doing your own thing’ in Book IV (432d–433b), it is necessary to briefly review the kind of social order Plato has in mind, the psychological principles he assumes, and the political institutions by which that order is to be attained. For this explains not only the establishment of a three-class society and the corresponding structure of the soul, but also Plato’s theory of education and its metaphysical underpinnings. That economic needs are the basis of the political structure does not, of course, mean that they are the only human needs Plato recognizes. It indicates, however, that the emphasis here is on the unity and self-sufficiency of a well-structured city, not on the well-being of the individual (423c–e; 425c). This focus should be kept in mind when assessing the ‘totalitarianism’ and rigorous cultural conservatism of Plato’s political philosophy.