We proceed to the fourth article thus:
1. It seems that original sin is not in all men equally. It was said in the preceding article that original sin is inordinate desire. But all men are not equally subject to desire. It follows that original sin is not in all men equally.
2. Again, original sin is the disordered disposition of the soul, as sickness is the disordered disposition of the body. Now sickness admits of more or less. Therefore original sin also admits of more and less.
3. Again, Augustine says: "lust transmits original sin to posterity." (1 De Nup. et Concup.23-24.) But the lust in generation may be greater in one than in another. Original sin may therefore be greater in one than in another.
On the other hand: it was said in the preceding article that original sin is the sin of nature. But nature is in all men equally. Original sin is therefore also in all men equally.
I answer: there are two things in original sin. One is the lack of original justice. The other is the relation of this lack to the sin of our first parent, from whom it is inherited through our corrupt origin. Now original sin cannot be greater or less in respect of the lack of original justice, since the whole gift of original justice has been taken away. Privations do not admit of more and less when they deprive us of something altogether, as we said of death and darkness in Q.73, Art.2. Nor can original sin be greater or less in respect of its relation to its origin. Everyone bears the same relation to the first beginning of the corrupt origin from which sin derives its guilt, and relations do not admit of greater and less. It is plain, then, that original sin cannot be greater in one man than in another.
On the first point: since man has lost the control of original justice which once kept all the powers of his soul in order, each power tends to follow its own natural movement, and to follow it more vehemently the stronger it is. Now some powers of the soul may be stronger in one man than in another, because bodily characteristics vary. That one man should be more subject to desire than another is not therefore the consequence of original sin, since all are equally deprived of the control of original justice, and the lower parts of the soul are equally left to themselves in all men. It is due to the different dispositions of their powers, as we have said.
On the second point: sickness of the body does not have an equal cause in all cases, even if it is of the same kind. For example, fever which results from putrefaction of the bile may be due to a greater or lesser putrefaction, or to one which is more or less removed from a vital principle. But the cause of original sin is equal in respect of everyone. There is therefore no comparison.
On the third point: it is not actual lust that transmits original sin to posterity, for one would still transmit original sin even if it were divinely granted that one should feel no lust in generation. We must understand it to be habitual lust, on account of which the sensitive appetite is not subject to reason, now that the control of original justice is lost. Lust of this kind is equally in all.