We proceed to the second article thus:

1. It seems that the whole good of human nature can be taken away by sin. The good of human nature is finite, since human nature itself is finite. Now a finite thing is removed altogether if it is continually reduced, and the good of human nature may be continually reduced by sin. It seems that it may finally be taken away altogether.

2. Again, what is simple in nature is the same in its wholeness as it is in its parts. This is obvious in the case of air, water, flesh, or any body whose parts are similar. Now the good of nature is altogether uniform. Hence since part of it may be taken away by sin, it seems that the whole of it may be taken away by sin.

3. Again, the natural good which is diminished by sin is the capacity for virtue. Sin destroys this capacity altogether in some persons. It obviously does so in the damned, who can no more recover virtue than a blind man can recover his sight. Thus sin may entirely destroy natural good.

On the other hand: Augustine says (Enchirid.13, 14): "evil exists only in what is good." But the evil of guilt can be neither in the good of virtue nor in the good of grace, since these are contrary to it. It must therefore be in the good of nature. It cannot then totally destroy the good of nature.

I answer: we said in the preceding article that the natural good which sin diminishes is the natural inclination to virtue. Now the reason why man inclines to virtue is that he is rational. It is because he is rational that he acts in accordance with reason, and this is to act virtuously. But a man would not be able to sin without his rational nature. Sin cannot then deprive him of it altogether. It follows that his inclination to virtue cannot be entirely destroyed.

Since this natural good is found to be continually diminished by sin, some have sought to illustrate the diminution of it by the continuous reduction of a finite thing which is yet never entirely removed. As the philosopher says in 1 Physics, text 37, any finite magnitude will at length be exhausted if the same quantity is repeatedly taken from it -- if I were to subtract a handbreadth from a finite quantity, for instance. But subtraction can go on indefinitely if the same proportion is subtracted instead of the same quantity. For example, if a quantity is divided in two, and the half taken from the half of it, subtraction can go on indefinitely, so long as each subsequent reduction is less than the preceding. This illustration, however, is irrelevant, because a subsequent sin diminishes the good of nature not less than a previous sin, but much more, if it be more serious.

We must say instead that the natural inclination to virtue is to be understood as a medium between two things. It depends on rational nature as its root, and inclines to the good of virtue as its term and end. The diminution of it may accordingly be understood either as referring to its root, or as referring to its term. Its root is not diminished by sin, because sin does not diminish nature itself, as we said in the preceding article. But it is diminished in respect of its term, in so far as an obstacle is put in the way of its attaining its end. If the natural inclination to virtue were diminished in respect of its root, it would be bound to be wholly destroyed in the end, along with the complete destruction of a man's rational nature. But since it is diminished by way of an obstacle preventing the attainment of its end, it is manifest that it can be diminished indefinitely. Obstacles can be interposed indefinitely. A man can add sin to sin without end. But it cannot be entirely destroyed, since the root of inclination always remains. The same sort of thing is apparent in the case of a diaphanous body, which has the inclination to take in light because it is diaphanous, and whose inclination or capacity to do so is diminished by intervening clouds, yet always remains rooted in its nature.

On the first point: this objection argues from diminution by subtraction. But the good of nature is diminished by way of an obstacle which is interposed, and which neither destroys nor diminishes the root of inclination, as we have said.

On the second point: natural inclination is indeed wholly uniform. But it is related both to its principle and to its end, and is diminished in one way and not in another because of this diversity of relation.

On the third point: the natural inclination to virtue remains even in the damned, who would not otherwise feel the remorse of conscience. The reason why it does not issue in act is that grace is withheld in accordance with divine justice. The capacity to see similarly remains in a blind man, at the root of his nature, in so far as he is an animal naturally possessed of sight, but fails to become actual because the cause which would enable it to do so, by forming the organ which sight requires, is lacking.