But it is true that, in the interchange of services, this is the rule of justice that holds society together, viz. requital⁠—but proportionate requital, and not simple repayment of equals for equals. For the very existence of a state depends upon proportionate return. If men have suffered evil, they seek to return it; if not, if they cannot requite an injury, we count their condition slavish. And again, if men have received good, they seek to repay it: for otherwise there is no exchange of services; but it is by this exchange that we are bound together in society.

This is the reason why we set up a temple of the graces [charities, χάριτες ] in sight of all men, to remind them to repay that which they receive; for this is the special characteristic of charity or grace. We ought to return the good offices of those who have been gracious to us, and then again to take the lead in good offices towards them.

But proportionate interchange is brought about by “cross conjunction.”