Social justice and happiness in the Republic: Plato's two principles

In the Republic, Socrates says that social justice is ‘doing one's own’, i.e. ‘everyone must practice one of the occupations in the city for which he is naturally best suited’. One would ordinarily suppose social justice to concern not only the allocation of duties but also the distribution of benefits. I argue that this expectation is fulfilled not by Plato's conception of social justice, but by the normative basis for it, Plato's requirement of aiming at the happiness of all the citizens. I argue that Plato treats social justice as a necessary but not sufficient means to happiness that guarantees only the production of the greatest goods; ensuring that these goods are distributed so as to maximize the happiness of the whole city requires a direct application of Plato's happiness principle, which I interpret individualistically and then use to explain women's equality in work and education.