Chapter 11 — That the subject of evil is a good

From what we have said it can be shown that every evil is seated in some good.

For evil cannot exist by itself, since it has no essence, as was proved above. (Ch. 7.) Therefore, evil needs to be in some subject. Now every subject is a good insofar as it is a substance, as is evident from what has been said. (Ch. 7.) Therefore, every evil is in a good.

Also. Evil is a privation, as we have shown. (Ch. 9.) Now privation and the lacking form are in the same subject. But the subject of a form is a being in potency to that form, and this being is a good: for potency and act are in the same genus. Therefore, privation, which is an evil, is in some good as its subject.

Moreover. A thing is called evil because it hurts. (Augustine, Enchiridion, ch. 12.) But this it only because it hurts a good, for it is good to hurt evil, since the corruption of evil is good. Now it would not hurt a good formally, unless it were in that good: thus blindness is hurtful to a man insofar as it is in him. Therefore, evil must be in a good.

Again. Evil is not caused except by good, and then only accidentally. (Ch. 10.) Now whatever is accidental is reducible to that which is essential. Consequently, together with the evil effect that is caused accidentally by a good, there must be some good which is the essential effect of that good, so as to be the foundation of that evil. For what is accidental is founded on what is essential.

Seeing, however, that good and evil are mutually opposed, and that one of two opposites cannot be the subject of the other, but expels it, someone at a cursory glance might think it unreasonable to state that good is the subject of evil.

And yet it is not unreasonable if the truth be sought thoroughly. For good, even as being, is predicated universally, since every being as such is good, as we have shown. (Ch. 8.) Now it is not unreasonable that non-being should have being for its subject, because every privation is a non-being, and yet its subject is a substance, which is a being. But non-being is not in an opposite being as its subject, for blindness is not universal non-being, but a particular kind of non-being, namely, privation of sight. Therefore, it is not in sight as its subject, but in an animal. In like manner, evil does not have the opposite good for its subject—for it is the privation of this good—but it has some other good. Thus moral evil is in a natural good, and an evil of nature (that is, privation of a form) is in matter, which is a good as a being in potency.