This applies, however, only to those who are within the specified age: after that we allow them to range at will, except that a man may not marry his daughter or his daughter's daughter, or his mother or his mother's mother; and women, on the other hand, are prohibited from marrying their sons or fathers, or son's son or father's father, and so on in either direction. And we grant all this, accompanying the permission with strict orders to prevent any embryo which may come into being from seeing the light; and if any force a way to the birth, the parents must understand that the offspring of such an union cannot be maintained, and arrange accordingly. That also, he said, is a reasonable proposition. But how will they know who are fathers and daughters, and so on? They will never know. The way will be this:--dating from the day of the hymeneal, the bridegroom who was then married will call all the male children who are born in the seventh and tenth month afterwards his sons, and the female children his daughters, and they will call him father, and he will call their children his grandchildren, and they will call the elder generation grandfathers and grandmothers. All who were begotten at the time when their fathers and mothers came together will be called their brothers and sisters, and these, as I was saying, will be forbidden to inter-marry. This, however, is not to be understood as an absolute prohibition of the marriage of brothers and sisters; if the lot favours them, and they receive the sanction of the Pythian oracle, the law will allow them. Quite right, he replied. Such is the scheme, Glaucon, according to which the guardians of our State are to have their wives and families in common. And now you would have the argument show that this community is consistent with the rest of our polity, and also that nothing can be better--would you not? Yes, certainly. Shall we try to find a common basis by asking of ourselves what ought to be the chief aim of the legislator in making laws and in the organization of a State,--what is the greatest I good, and what is the greatest evil, and then consider whether our previous description has the stamp of the good or of the evil? By all means. Can there be any greater evil than discord and distraction and plurality where unity ought to reign? or any greater good than the bond of unity? There cannot. And there is unity where there is community of pleasures and pains--where all the citizens are glad or grieved on the same occasions of joy and sorrow? No doubt. Yes; and where there is no common but only private feeling a State is disorganized--when you have one half of the world triumphing and the other plunged in grief at the same events happening to the city or the citizens? Certainly. Such differences commonly originate in a disagreement about the use of the terms 'mine' and 'not mine,' 'his' and 'not his.' Exactly so.