SUMMA THEOLOGICA. Thomas Aquinas
and this grade is to be found in existence itself; for some things there are which cannot lose their existence as incorruptible things, while some there are which can lose it, as things corruptible.
As, therefore, the perfection of the universe requires that there should be not only beings incorruptible, but also corruptible beings; so the perfection of the universe requires that there should be some which can fail in goodness, and thence it follows that sometimes they do fail. Now it is in this that evil consists, namely, in the fact that a thing fails in goodness. Hence it is clear that evil is found in things, as corruption also is found; for corruption is itself an evil.
Reply to Objection 1: Evil is distant both from simple being and from simple "not-being," because it is neither a habit nor a pure negation, but a privation.
Reply to Objection 2: As the Philosopher says (Metaph. v, text 14), being is twofold. In one way it is considered as signifying the entity of a thing, as divisible by the ten "predicaments"; and in that sense it is convertible with thing, and thus no privation is a being, and neither therefore is evil a being. In another sense being conveys the truth of a proposition which unites together subject and attribute by a copula, notified by this word "is"; and in this sense being is what answers to the question, "Does it exist?" and thus we speak of blindness as being in the eye; or of any other privation. In this way even evil can be called a being. Through ignorance of this distinction some, considering that things may be evil, or that evil is said to be in things, believed that evil was a positive thing in itself.
Reply to Objection 3: God and nature and any other agent make what is best in the whole, but not what is best in every single part, except in order to the whole, as was said above ( Question [47], Article [2]). And the whole itself, which is the universe of creatures, is all the better and more perfect if some things in it can fail in goodness, and do sometimes fail, God not preventing this. This happens, firstly, because "it belongs to Providence not to destroy, but to save nature," as Dionysius says (Div. Nom. iv); but it belongs to nature that what may fail should sometimes fail; secondly, because, as Augustine says (Enchir. 11), "God is so powerful that He can even make good out of evil." Hence many good things would be taken away if God permitted no evil to exist; for fire would not be generated if air was not corrupted, nor would the life of a lion be preserved unless the ass were killed. Neither would avenging justice nor the patience of a sufferer be praised if there were no injustice.
Whether evil is in good as in its subject?
Objection 1: It would seem that evil is not in good as its subject. For good is something that exists. But Dionysius says (Div. Nom. iv, 4) that "evil does not exist, nor is it in that which exists." Therefore, evil is not in good as its subject.
Objection 2: Further, evil is not a being; whereas good is a being. But "non-being" does not require being as its subject. Therefore, neither does evil require good as its subject.
Objection 3: Further, one contrary is not the subject of another. But good and evil are contraries. Therefore, evil is not in good as in its subject.
Objection 4: Further, the subject of whiteness is called white. Therefore also the subject of evil is evil. If, therefore, evil is in good as in its subject, it follows that good is evil, against what is said (Is. 5:20): "Woe to you who call evil good, and good evil!"
On the contrary, Augustine says (Enchiridion 14) that "evil exists only in good."
I answer that, As was said above ( Article [1]), evil imports the absence of good. But not every absence of good is evil. For absence of good can be taken in a privative and in a negative sense. Absence of good, taken negatively, is not evil; otherwise, it would follow that what does not exist is evil, and also that everything would be evil, through not having the good belonging to something else; for instance, a man would be evil who had not the swiftness of the roe, or the strength of a lion. But the absence of good, taken in a privative sense, is an evil; as, for instance, the privation of sight is called blindness.
Now, the subject of privation and of form is one and the same---viz. being in potentiality, whether it be being in absolute potentiality, as primary matter, which is the subject of the substantial form, and of privation of the opposite form; or whether it be being in relative potentiality, and absolute actuality, as in the case of a transparent body, which is the subject both of darkness and light. It is, however, manifest that the form which makes a thing actual is a perfection and a good; and thus every actual being is a good; and likewise every potential being, as such, is a good, as having a relation to good. For as it has being in potentiality, so has it goodness in potentiality. Therefore, the subject of evil is good.
Reply to Objection 1: Dionysius means that evil is not in existing things as a part, or as a natural property of any existing thing.
Reply to Objection 2: "Not-being," understood negatively, does not require a subject; but privation is negation in a subject, as the Philosopher says (Metaph. iv, text 4), and such "not-being" is an evil.
Reply to Objection 3: Evil is not in the good opposed to it as in its subject, but in some other good, for the subject of blindness is not "sight," but "animal." Yet, it appears, as Augustine says (Enchiridion 13), that the rule of dialectics here fails, where it is laid down that contraries cannot exist together. But this is to be taken as referring to good and evil in general, but not in reference to any particular good and evil. For white and black, sweet and bitter, and the like contraries, are only considered as contraries in a special sense, because they exist in some determinate genus; whereas good enters into every genus. Hence one good can coexist with the privation of another good.
Reply to Objection 4: The prophet invokes woe to those who say that good as such is evil. But this does not follow from what is said above, as is clear from the explanation given.
Whether evil corrupts the whole good?
Objection 1: It would seem that evil corrupts the whole good. For one contrary is wholly corrupted by another. But good and evil are contraries. Therefore evil corrupts the whole good.
Objection 2: Further, Augustine says (Enchiridion 12) that "evil hurts inasmuch as it takes away good." But good is all of a piece and uniform. Therefore it is wholly taken away by evil.
Objection 3: Further, evil, as long as it lasts, hurts, and takes away good. But that from which something is always being removed, is at some time consumed, unless it is infinite, which cannot be said of any created good. Therefore evil wholly consumes good.
On the contrary, Augustine says (Enchiridion 12) that "evil cannot wholly consume good."
I answer that, Evil cannot wholly consume good. To prove this we must consider that good is threefold. One kind of good is wholly destroyed by evil, and this is the good opposed to evil, as light is wholly destroyed by darkness, and sight by blindness. Another kind of good is neither wholly destroyed nor diminished by evil, and that is the good which is the subject of evil; for by darkness the substance of the air is not injured. And there is also a kind of good which is diminished by evil, but is not wholly taken away; and this good is the aptitude of a subject to some actuality.
The diminution, however, of this kind of good is not to be considered by way of subtraction, as diminution in quantity, but rather by way of remission, as diminution in qualities and forms. The remission likewise of this habitude is to be taken as contrary to its intensity. For this kind of aptitude receives its intensity by the dispositions whereby the matter is prepared for actuality; which the more they are multiplied in the subject the more is it fitted to receive its perfection and form; and, on the contrary, it receives its remission by contrary dispositions which, the more they are multiplied in the