Chapter 115 — That it is impossible for evil to be a nature

It is impossible for evil to be a nature. Every nature is either act or potency or a composite of the two. Whatever is act is a perfection, and has the character of the good, since what is in potency has a natural appetite to be in act, and what all beings desire is the good. Therefore, too, what is composed of act and potency participates in goodness to the extent that it participates in act. Potency also possesses goodness inasmuch as it is ordained to act; an indication of this is the fact that potency is esteemed in proportion to its capacity for act and perfection. Consequently, no nature is of itself an evil.

Again, every being achieves its fulfillment according as it comes to be in act, for act is the perfection of a thing. However, neither of a pair of opposites achieves fulfillment by being mixed with the other, but is rather destroyed or weakened thereby; therefore, evil does not realize its full capacity by sharing in good. But every nature realizes its full capacity by having existence in act; and so, since existence is the good desirable to all things, a nature achieves fulfillment by participating in good. Therefore, no nature is an evil.

Moreover, any nature whatever desires the preservation of its being, and shuns destruction to the extent that it can. Consequently, since good is that which all desire, and evil, on the contrary, is that which all shun, we must conclude to be a given nature is in itself good, while not to be is evil. To be evil, however, is not good; in fact, not to be evil is included in the notion of good. Therefore, no nature is an evil.