Chapter 27 [XXIV.]--Through Lust Original Sin is Transmitted; Venial Sins in Married Persons; Concupiscence of the Flesh, the Daughter and Mother of Sin.
Wherefore the devil holds infants guilty who are born, not of the good by which marriage is good, but of the evil of concupiscence, which, indeed, marriage uses aright, but at which even marriage has occasion to feel shame. Marriage is itself "honourable in all" [2151] the goods which properly appertain to it; but even when it has its "bed undefiled" (not only by fornication and adultery, which are damnable disgraces, but also by any of those excesses of cohabitation such as do not arise from any prevailing desire of children, but from an overbearing lust of pleasure, which are venial sins in man and wife), yet, whenever it comes to the actual process of generation, the very embrace which is lawful and honourable cannot be effected without the ardour of lust, so as to be able to accomplish that which appertains to the use of reason and not of lust. Now, this ardour, whether following or preceding the will, does somehow, by a power of its own, move the members which cannot be moved simply by the will, and in this manner it shows itself not to be the servant of a will which commands it, but rather to be the punishment of a will which disobeys it. It shows, moreover, that it must be excited, not by a free choice, but by a certain seductive stimulus, and that on this very account it produces shame. This is the carnal concupiscence, which, while it is no longer accounted sin in the regenerate, yet in no case happens to nature except from sin. It is the daughter of sin, as it were; and whenever it yields assent to the commission of shameful deeds, it becomes also the mother of many sins. Now from this concupiscence whatever comes into being by natural birth is bound by original sin, unless, indeed, it be born again in Him whom the Virgin conceived without this concupiscence. Wherefore, when He vouchsafed to be born in the flesh, He alone was born without sin.
[2151] Heb. xiii. 4.
Chapter 28 [XXV.]--Concupiscence Remains After Baptism, Just as Languor Does After Recovery from Disease; Concupiscence is Diminished in Persons of Advancing Years, and Increased in the Incontinent.
If the question arises, how this concupiscence of the flesh remains in the regenerate, in whose case has been effected a remission of all sins whatever; seeing that human semination takes place by its means, even when the carnal offspring of even a baptized parent is born: or, at all events, if it may be in the case of a baptized parent concupiscence and not be sin, why should this same concupiscence be sin in the offspring?--the answer to be given is this: Carnal concupiscence is remitted, indeed, in baptism; not so that it is put out of existence, but so that it is not to be imputed for sin. Although its guilt is now taken away, it still remains until our entire infirmity be healed by the advancing renewal of our inner man, day by day, when at last our outward man shall be clothed with incorruption. [2152] It does not remain, however, substantially, as a body, or a spirit; but it is nothing more than a certain affection of an evil quality, such as languor, for instance. There is not, to be sure, anything remaining which may be remitted whenever, as the Scripture says, "the Lord forgiveth all our iniquities." [2153] But until that happens which immediately follows in the same passage, "Who healeth all thine infirmities, who redeemeth thy life from corruption," [2154] there remains this concupiscence of the flesh in the body of this death. Now we are admonished not to obey its sinful desires to do evil: "Let not sin reign in your mortal body." [2155] Still this concupiscence is daily lessened in persons of continence and increasing years, and most of all when old age makes a near approach. The man, however, who yields to it a wicked service, receives such great energies that, even when all his members are now failing through age, and those especial parts of his body are unable to be applied to their proper function, he does not ever cease to revel in a still increasing rage of disgraceful and shameless desire.
[2152] 1 Cor. xv. 53.
[2153] Ps. ciii. 3.
[2154] Ps. ciii. 4.
[2155] Rom. vi. 12.