The Republic by Plato Part 5 Page 43

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