FOR 2,500 years the family has been a theme of tragedy and occasionally of comedy. Plato first made it a concern of political philosophers. In the Republic, Socrates was asked to prove that justice is good in itself-that is, that living justly under a just regime is the necessary and sufficient condition of happiness. Socrates and his interlocutors set about designing a polity to which anyone could freely be devoted because it is just, and therefore good.  The men agree that children of exceptional or inferior ability must be taken from their parents and appropriately placed in a hierarchy of merit, not birth. With much reluctance, they then deny the ruling class private property and families altogether.  Female as well as male guardians are taught to make war, and both are to make love only (and as much) as eugenics dictates.  Children are to be reared in common as brothers and sisters; every parent will be a parent of every child in a given generation, and every child the child of every parent. The city as a whole must be one big happy family so that, unlike Antigone, no one will have private ties in whose name to oppose public authority.  These arrangements, we are told, will work only when philosophers rule as kings and queens. They can rule only after having persuaded the inhabitants of some city to go into voluntary exile, leaving behind them their children under the age of ten, to be molded as citizens of the new order. Socrates’s scheme seems ridiculously impossible because it requires some men and women to abandon the families they have, and all others to agree not to make new families. Even were it possible, this justice would be, on balance, undesirable. The “irrational,” “unjust,” and very strong desire that human beings have for families of their own is an indication that the public good and private happiness can be quite distinct from one another.