Commentaria in Primam Partem Summae Theologiae

In the title, "to corrupt" is taken formally. But "the whole good" is taken for the whole integral, or quasi-integral, good, about which evil is posited. So that the sense is: Whether evil posited in something formally takes away whatever goodness is found in it.

II. In the body there is a single principal conclusion, directly responsive to the question in the negative: Evil cannot totally consume the good. – This conclusion, however, is made manifest by one threefold distinction, with special conclusions annexed to each member.

III. The distinction is: Good is threefold, namely form, subject, and the subject's aptitude for the form. - The first conclusion is: Good as form is entirely removed by evil. It is proved: because it is opposed to it. And it is made clear: just as light is removed by darkness, and sight by blindness. - The second conclusion is: Good as subject is neither removed nor diminished by evil. And it is made clear in the case of air and darkness. - The third is: Good as the subject's aptitude for act is diminished by evil, and not entirely removed. And this conclusion is explained, first as regards the diminution¹; second, there: If therefore contrary dispositions, as regards the non-total removal².

IV. Intending, therefore, to declare of what sort and how great such a diminution is, he indicates that a twofold mode of diminution is found to exist, namely by subtraction and by remission: the first is quantitative, the second is qualitative. And again, diminution by remission, or qualitative diminution, occurs in two ways: first, through the remission of the quality itself; and second, through contrary dispositions of the subject toward such an act. — In the case at hand, the diminution is to be understood as taking place by remission, not in any manner whatsoever, but by the addition of contrary dispositions.

And this is proved as follows. Habituality is intensified by the dispositions that prepare matter for act; therefore it is diminished by the dispositions that impede the potency with respect to act. — The antecedent is made evident: because the more the dispositions of matter are multiplied, the more apt it is for act. The consequence, however, is proved: because diminution is taken from the contrary of intensification.

V. Then, intending to show how the good of aptitude is never entirely removed³, he distinguishes two ways in which remission through contrary dispositions can be found: first, finitely; second, infinitely. And by neither way does he show that the subject's aptitude for act is entirely taken away.

For that the remission of aptitude is at some point finite is proved from the fact that the multiplication of contrary dispositions is finite; as is evident in the multiplication of the qualities of the elements, by which the aptitude of matter for form—fire, for example—is diminished. – That, however, in such remission the aptitude is not wholly taken away is evident from this: since the apposition of contraries and their remission are finite in existence, there is no need for the aptitude of the remaining subject to be eradicated.

That the remission is sometimes infinite is made manifest from the infinite multiplication of opaque bodies between the sun and the air; and proportionally, from the infinite multiplication of sins between the Sun of justice and the soul. – That, however, by such infinite remission the aptitude is not entirely taken away is proved by reason: because there always remains in its root what is the substance of the subject. And it is made manifest in the examples adduced, in natural things and in moral matters: namely, in the diaphanous with respect to light, and in the soul with respect to grace.

And so the principal conclusion is clear⁴, namely that evil never wholly takes away good: for it leaves behind the subject, and something of aptitude for act.

VI. In response to the third, note that so great is the difference between being diminished per se and per accidens—that is, by reason of itself or of another—that although it is impossible for a finite thing not to be consumed by an infinite and equal subtraction per se, it is nevertheless possible, as the text says, that from a finite thing there be subtracted equally even to infinity, and yet that thing not be consumed, when the diminution is per accidens, that is, through another, as in the case at hand; for the aptitude is diminished on account of the impediment applied to it, and not in itself.