On Marriage and Concupiscence 52The Devil the Author, Not of Nature, But Only of Sin.

Now, the man who forwarded to your Love the paper in question has introduced the contents thereof with this title: "In opposition to those persons who condemn matrimony, and ascribe its fruits to the devil." This, then, is not in opposition to us, who neither condemn matrimony, which we even commend in its order with a just commendation, nor ascribe its fruits to the devil. For the fruits of matrimony are men which are orderly engendered from it, and not the sins which accompany their birth. Human beings are not under the devil's dominion because they are human beings, in which respect they are the fruits of matrimony; but because they are sinful, in which resides the transmission of their sins. For the devil is the author of sin, not of nature.