Chapter 10 — That the cause of evil is a good

We may conclude from the foregoing that evil is not caused except by a good.

For were some evil caused by an evil, since evil does not act save by virtue of a good, as proved above, (Ch. 9.) it follows that good itself is the primary cause of evil.

Again. That which is not, is not the cause of anything. Therefore, every cause must be some being. Now evil is not a being, as shown above. (Ch. 7.) Therefore, evil cannot be the cause of anything. Hence if evil be caused by something, this must be a good.

Again. Whatever is properly and by itself the cause of something intends its proper effect. Hence, if evil by itself be the cause of something, it would intend its proper effect, namely, evil. But this is false, for it has been shown (Ch. 3.) that every agent intends a good. Therefore, evil is not the cause of anything by itself, but only accidentally. Now every accidental cause is reduced to an essential cause. But good alone can be an essential cause, and evil cannot be an essential cause. Therefore, evil is caused by good.

Further. Every cause is either matter, or form, or agent, or end. But evil cannot be either matter or form: for it has been shown above (Ch. 7.) that being, whether actual or potential, is a good. Neither can it be an agent, since a thing acts insofar as it is actual and has a form. Nor again can it be an end, since it is beside the intention, as we have shown. (Ch. 4.) Therefore, evil cannot be the cause of a thing, and if anything be the cause of an evil, that evil must be caused by a good.

Since, however, evil and good are opposite to each other, and one opposite cannot be the cause of the other except accidentally (thus a cold thing causes heat, as stated in Physics), (Physics 8 [1].) it follows that good cannot be the effective cause of evil except accidentally.

In the physical order, this accident may be on the part of the agent, or on the part of the effect. On the part of the agent, as when the agent’s power is defective, the result being that the action is defective, and the effect deficient. Thus when the power of the digestive organ is defective, the result is imperfect digestion of the food and an undigested humor, which are physical evils. Now it is accidental to the agent as such that its power be defective, it acts not as having a defective power, but as having some power; if it lacked power altogether, it would not act at all. Accordingly, evil is caused accidentally on the part of the agent, insofar as the agent’s power is defective. Hence it is said that evil has not an efficient, but a deficient, cause: evil does not follow from an active cause except insofar as this cause is defective in power, and in this respect it is not effective. And it comes to the same if defect in the action and effect results from a defect in the instrument, or in any thing else required for the agent’s action—as when the motive power causes a limp on account of crookedness in the tibia—for the agent acts by both its power and its instrument.

On the part of the effect, evil is caused by good accidentally, either on the part of the matter of the effect, or on the part of its force. For if the matter be indisposed to receive the impression of the agent, the effect must be defective: thus a deformed offspring results from an indisposition of matter. Nor is it put down to defect in the agent if it fails to transform an indisposed matter to perfect act, since to each natural agent there is appointed a power in proportion to its nature. If it does not go beyond that power, it will not on that account fall short of its power, but only when it falls short of the measure of power due to it by nature.

On the part of the effect’s form, evil occurs accidentally insofar as one form necessarily involves the privation of another; hence the generating of one thing is necessarily followed by the corruption of another. But this evil is not an evil of the effect intended by the agent, as was made clear above, (Ch. 6.) but of the other thing.

Accordingly, it is evident that evil is caused only accidentally by a good. And the same applies to things produced by art. For art imitates nature in its work, (Physics 2, [2].) and faults occur in both in the same way.

In morals, however, the case would seem to be different. For moral fault does not seem to follow from a defective power, since weakness of power either wholly excludes, or at least diminishes, moral fault; for weakness does not deserve punishment, which is due to guilt, but rather mercy and pardon, seeing that moral fault must be voluntary and not necessary. But if we consider the matter carefully, we shall find that there is a likeness in one respect, and unlikeness in another. There is unlikeness in that moral fault is considered in the action alone, and not in some effect produced, for moral virtues are directed not to making but to doing. But the arts are directed to making, for which reason it has been stated that faults occur in them in the same way as in nature. Therefore, moral evil is considered as resulting not from the matter or form of the effect, but only from the agent.

Now, in moral actions four active principles are to be found in due order. The first of these is the executive power, namely, the motive force by which the members are moved to execute the will’s command. Hence this power is moved by the will, which is a second principle. And the will is moved by the judgment of the apprehensive power, which judges that a particular thing is good or evil (which are objects of the will, the one moving to pursuit, the other to flight). Again, the apprehensive power is moved by the thing apprehended. Hence the first active principle in moral actions is the thing apprehended; the second is the apprehensive power; the third is the will; and the fourth is the motive force, which carries out the command of reason.

Now the act of the executive power already presupposes moral good or evil. For these external acts do not belong to morals except insofar as they are voluntary. Therefore, if the act of the will be good, the external act will also be good, and evil, if it be evil. And there would be nothing savoring of moral evil if the defect in a defective external act has nothing to do with the will, for limping is not a moral but a physical evil. Therefore, a defect in this executive power either wholly excuses or diminishes moral fault. Again, the act whereby the object moves the apprehensive power is devoid of moral fault: for the visible object moves the sight according to the natural order of things, and so too does every object move a passive power. Again, the act of the apprehensive power, considered in itself, is devoid of moral fault, since a defect in it either excuses or diminishes moral fault in the same way as a defect in the executive power: for weakness and ignorance equally excuse or diminish sin. It follows, then, that moral fault is found first and chiefly in the sole act of the will: an act is logically called moral precisely because it is voluntary. Therefore, the root and origin of moral fault is to be sought in the act of the will.

But there seems to be a difficulty attendant upon this inquiry. For, since a defective act results from a defect in the active principle, we must presuppose a defect in the will to precede the moral fault. And if this defect be natural, it will always adhere to the will, so that the will must be guilty of moral fault whenever it acts—but acts of virtue prove this to be false. But if the defect be voluntary, it is already a moral fault, the cause of which will still remain to be sought: thus the reason will carry on indefinitely. Accordingly, we must say that the defect already existing in the will is not natural, lest it follow that the will sins in every act. Further, neither is it casual or fortuitous, for then there would be no moral fault in us, since casual things are unforeseen and outside the domain of reason. Therefore, it is voluntary. Yet it is not a moral fault, lest we be forced to proceed indefinitely. How this may be remains to be considered.

The perfection of every active principle depends on a higher active principle, for the second agent acts by virtue of the first. Therefore, while the second agent remains subordinate to the first, it acts unfailingly; it fails in acting if it should happen to stray from the order of the first agent, as in the case of an instrument that falls short of the first agent’s movement. Now it has been said that, in the order of moral actions, two principles precede the will, namely, the apprehensive power and the apprehended object (which is the end). And since for each movable there is a corresponding proper motive power, every apprehensive power is not the motive force due to every appetitive power, but this one belongs to this, and another to that. Accordingly, just as the proper motive force of the sensitive appetite is the apprehensive power of the senses, so the proper motive force of the will is the reason.

Again, since the reason is able to apprehend many goods and many ends, and each one has its proper end, the will also must have as its end and first motive force not any good, but a definite good. Hence when the will tends to its act through being moved by the apprehension of reason that presents to it its proper good, a right action follows. But when the will breaks away at the apprehension of the sensitive power, or even of the reason which presents some good other than its proper good, there follows in the will’s act a moral fault.

Consequently, the sin of action in the will is preceded by lack of order to reason and to its proper end. To reason, as when the will, on the sudden apprehension of a sense, tends to a good that is pleasurable to sense. To its due end, as when by deliberating the reason arrives at some good which is not good now, or in some particular way, and yet the will tends to that good as though it were its proper good. Now this lack of order is voluntary, for it is in the will’s power to will or not to will. Again, it is in the will’s power that the reason actually consider the matter, or cease from considering it, or that it consider this or that matter. Nor is this lack of order a moral evil: for if the reason were to consider nothing, or to consider any good whatever, as yet there is no sin until the will tends to an undue end. And this itself is an act of the will.

Accordingly, both in the physical and in the moral order, it is clear that evil is not caused by good except accidentally.