Book I. ¹

Wherein He expounds the peculiar and natural blessings of marriage. He shows that among these blessings must not be reckoned fleshly concupiscence; insomuch as this is wholly evil, such as does not proceed from the very nature of marriage, but is an accident thereof arising from original sin. This evil, notwithstanding, is rightly employed by marriage for the procreation of children. But, as the result of this concupiscence, it comes to pass that, even from the lawful marriage of the children of God, men are not born children of God, but of the world, and are bound with the chain of sin, although their parents have been liberated therefrom by grace; and are led captive by the devil, if they be not in like manner rescued by the self-same grace of Christ. He explains how it is that concupiscence remains in the baptized in act though not in guilt. He teaches, that by the sanctity of baptism, not merely this original guilt, but all other sins of men whatever, are taken away. He lastly quotes the authority of Ambrose to show that the evil of concupiscence must be distinguished from the good of marriage.

on marriage and concupiscence.