Ante-Nicene Fathers, Vol VII:
Lactantius: Chap. XXI.—Of the system of Plato, which would lead to the overthrow of states

Chap. XXI.—Of the System of Plato, Which Would Lead to the Overthrow of States.

Let us, however, see what it was that he learned from Socrates, who, having entirely rejected natural philosophy, betook himself to inquiries about virtue and duty. And thus I do not doubt that he instructed his hearers in the precepts of justice. Therefore, under the teaching of Socrates, it did not escape the notice of Plato, that the force of justice consists in equality, since all are born in an equal condition. Therefore (he says) they must have nothing private or their own; but that they may be equal, as the method of justice requires, they must possess all things in common. This is capable of being endured, as long as it appears to be spoken of money. But how impossible and how unjust this is, I could show by many things. Let us, however, admit its possibility. For grant that all are wise, and despise money. To what, then, did that community lead him? Marriages also, be says, ought to be in common; so that many men may flock together like dogs to the same woman, and he who shall be superior in strength may succeed in obtaining her; or if they are patient as philosophers, they may await their turns, as in a brothel. Oh the wonderful equality of Plato! Where, then, is the virtue of chastity? where conjugal fidelity? And if you take away these, all justice is taken away. But he also says that states would be prosperous, if either philosophers were their kings, or their kings were philosophers. But if you were to give the sovereignty to this man of such justice and equity, who had deprived some of their own property, and given to some the property of others, he would prostitute the modesty of women; a thing which was never done, I do not say by a king, but not even by a tyrant.  

But what motive did he advance for this most degrading advice? The state will be in harmony, and bound together with the bonds of mutual love, if all shall be the husbands, and fathers, and wives, and children of all. What a confusion of the human race is this? How is it possible for affection to be preserved where there is nothing certain to be loved? What man will love a woman, or what woman a man, unless they shall always have lived together,—unless devotedness of mind, and faith mutually preserved, shall have made their love indivisible? But this virtue has no place in that promiscuous pleasure. Moreover, if all are the children of all, who will be able to love children as his own, when he is either ignorant or in doubt whether they are his own? Who will bestow honour upon any one as a father, when he does not know from whom he was born? From which it comes to pass, that he not only esteems a stranger as a father, but also a father as a stranger. Why should I say that it is possible for a wife to be common, but impossible for a son, who cannot be conceived except from one? The community, therefore, is lost to him alone, nature herself crying out against it. It remains that it is only for the sake of concord that he would have a community of wives. But there is no more vehement cause of discords, than the desire of one woman by many men. And in this Plato might have been admonished, if not by reason, yet certainly by example, both of the dumb animals, which fight most vehemently on this account, and of men, who have always carried on most severe wars with one another on account of this matter.