All men agree that a just distribution must be according to merit in some sense; they do not all specify the same sort of merit, but democrats identify it with freemen, supporters of oligarchy with wealth (or noble birth), and supporters of aristocracy with excellence.
If we are to keep our flock at the highest pitch of excellence, there should be as many unions of the best of both sexes, and as few of the inferior as possible, and that only the offspring of the better unions should be kept.