Commentaria in Summam contra Gentiles, Liber IV

Having set down the determination of the truth concerning original sin, St. Thomas wishes next to eliminate certain objections ¹. Concerning this, however, he does two things: first, he sets forth the objections themselves; second, he responds to them in the following chapter.

The first argument, therefore, is that the sin of one person is not imputed to others as fault: as is clear from Ezek. 18, The son etc.

The second: that if it be said that one's own sin is imputed to each in this matter, and not that of another, because all sinned in Adam when he sinned, as the Apostle seems to say—this is not valid. Because those who were born from Adam were not yet in him in act, but only in power.

The third is that if it be said that we sinned in Adam because sin derives originally from him into us together with nature—this seems impossible. Because an accident cannot be transmitted unless its subject is transmitted. But the rational soul, which is the subject of sin, is not transmitted into us from the first parent, but is created individually in each one by God.

The fourth is that it would follow that even Christ was subject to original sin, since he too derived his origin from the first parent.

The fifth is that what follows something according to its natural origin is natural. But what is natural to someone is not a sin in him.

The sixth: that if it be said that sin is derived through origin, not inasmuch as it is natural, but inasmuch as it is vitiated—this cannot stand. Because a defect in the work of nature does not happen except on account of the defect of some natural principle. But one cannot observe the corruption of any natural principle in human semen.

The seventh is that sins which come about in the works of nature through the corruption of some principle do not happen always or for the most part.

The eighth is that human origin, since it is an act of the generative power, which in no way participates in reason, cannot have in itself a defect that belongs to the genus of fault. And consequently neither can the defect coming about in the offspring through a vitiated origin have the character of fault, since effects are conformable to their causes.

The ninth is that, since according to Dionysius the good of nature is not taken away by sin, and generation is an act of nature, the origin of human generation could not have been vitiated through the sin of the first man.

The tenth is that in those things which do not belong to the character of the species, a son need not be assimilated to his parents. But sin cannot belong to the character of the species, since it is the corruption of the natural order.

The eleventh is that children are more assimilated to proximate parents than to remote ones. But it happens that proximate parents are without sin, and that in the act of generation no sin is committed.

The twelfth is that it follows that Adam's justice and satisfaction also passed through him to others, since good is of greater power in acting than evil.

The last is that, by parity of reasoning, the sins of other parents also descend to their posterity; and thus later generations are always more burdened with sins.