Augustine of Hippo, On Marriage and Concupiscence II.14: Concupiscence Alone, in Marriage, is Not of God

You see the terms of his question to us: what the devil can find in the sexes to call his own, by reason of which they should be in his power, who are born of parents of whatsoever kind, unless they be born again in Christ; he asks us, moreover, whether it is the difference in the sexes which we ascribe to the devil, or their union, or their very fruitfulness. We answer, then, nothing of these qualities, inasmuch as the difference of sex belongs to “the vessels” of the parents; while the union of the two pertains to the procreation of children; and their fruitfulness to the blessing pronounced on the marriage institution. But all these things are of God; yet amongst them he was unwilling to name that “lust of the flesh, which is not of the Father, but is of the world;” and “of this world” the devil is said to be “the prince.” Now, the devil found no carnal concupiscence in the Lord, because the Lord did not come as a man to men by its means. Accordingly, He says Himself: “The prince of this world cometh, and findeth nothing in me”—nothing, that is, of sin; neither that which is derived from birth, nor that which is added during life. Among all the natural goods of procreation which he mentioned, he was, I repeat, unwilling to name this particular fact of concupiscence, over which even marriage blushes, which glories in all these before-mentioned goods. For why is the especial work of parents withdrawn and hidden even from the eyes of their children, except that it is impossible for them to be occupied in laudable procreation without shameful lust? Because of this it was that even they were ashamed who first covered their nakedness. These portions of their person were not suggestive of shame before, but deserved to be commended and praised as the work of God. They put on their covering when they felt their shame, and they felt their shame when, after their own disobedience to their Maker, they felt their members disobedient to themselves. Our quoter of extracts likewise felt ashamed of this concupiscence. For he mentioned the difference of the sexes; he mentioned also their union, and he mentioned their fertility; but this last concomitant of lust he blushed to mention. And no wonder if mere talkers are ashamed of that which we see parents themselves, so interested in their function, blush to think of.