On the Grace of Christ, and on Original Sin

It is then manifest that that must not be laid to the account of marriage, even in the absence of which, marriage would still have existed. The good of marriage is not taken away by the evil, although the evil is by marriage turned to a good use. Such, however, is the present condition of mortal men, that the connubial intercourse and lust are at the same time in action; and on this account it happens, that as the lust is blamed, so also the nuptial commerce, however lawful and honourable, is thought to be reprehensible by those persons who either are unwilling or unable to draw the distinction between them.

They are, moreover, inattentive to that good of the nuptial state which is the glory of matrimony; I mean offspring, chastity, and the pledge. The evil, however, at which even marriage blushes for shame is not the fault of marriage, but of the lust of the flesh. Yet because without this evil it is impossible to effect the good purpose of marriage, even the procreation of children, whenever this process is approached, secrecy is sought, witnesses removed, and even the presence of the very children which happen to be born of the process is avoided as soon as they reach the age of observation.

Thus it comes to pass that marriage is permitted to effect all that is lawful in its state, only it must not forget to conceal all that is improper. Hence it follows that infants, although incapable of sinning, are yet not born without the contagion of sin—not, indeed, because of what is lawful, but on account of that which is unseemly: for from what is lawful nature is born; from what is unseemly, sin. Of the nature so born, God is the Author, who created man, and who united male and female under the nuptial law; but of the sin the author is the subtlety of the devil who deceives, and the will of the man who consents.