For the clearer solution of the arguments alleged we must observe that evil may be considered either in a substance or in some action of a substance. Evil in a substance consists in its lack of something which it is naturally apt to have and ought to have. It is no evil to a man not to have wings, because he is not by nature apt to have them; nor not to have yellow hair, because, though his nature is apt to have such hair, still that colour of hair is not due to his nature. But it is an evil to him not to have hands, because he is apt by nature to have them, and ought to have them, if he is to be perfect; and yet the same is no evil to a bird. Every privation, properly and strictly speaking, is of something which one is naturally apt to have and ought to have. The essence of evil consists in privation, thus understood. Primordial matter, being in potentiality to all forms, is naturally in actuality without any one particular form that you like to mention.* But some particular form is due to each of the things that are constituted out of such matter. The privation therefore of such a form, in regard of primordial matter, is no evil to the nature of primordial matter; but in regard of the compound whereof it is the form, it is an evil to that compound thing: thus it is evil to incandescent gas (ignis) to be deprived of the form of incandescent gas. And since privations are not said to 'be' except so far as they are in a subject, a privation will be 'simply evil,' when it is evil in regard of the subject in which it is: otherwise, it will be 'evil relatively to something' (malum alicujus), but not 'simply evil.'
Arg. 1 (Chap. V). What happens beside the intention of the agent is said to be 'matter of luck and chance and rare occurrence.'* But evil is not said to be matter of luck and chance, or rare occurrence, but to happen continually, or for the most part: thus in the physical order the unmaking of one thing is always attached to the making of another; and in the moral order sin is of usual occurrence.* This does not look like evil arising contrary to intention.
Reply (Chap. VI). Not everything that is beside the intention of the doer need be the result of luck or chance. For if what is beside the intention follows upon what is intended either always or frequently, it cannot be said to happen by luck or chance. Thus in him who intends to enjoy the pleasantness of wine, if from his drinking wind drunkenness follows always or frequently, it will be no matter of bad luck or chance: but it would be by chance, if it were quite the exception. Although then the evil of one thing perishing in course of nature follows beside the intention of him who brings the other thing into being, such evil nevertheless follows invariably: for invariably to the positing of one form there is annexed the privation of another:* hence this perishing does not happen by chance, nor as the exception, though the privation is sometimes not evil simply, but only a relative evil, as has been said. But if it be such a privation as to deprive the new being produced of what is due to it, it will be matter of chance and simply evil, as is the case of monstrous births: for such a mishap does not follow of necessity upon what is intended, but is contrary to it, since the agent intends the perfection of the being that he engenders. -- Evil affecting action happens in physical agents for want of active power: hence, if the agent's power is defective, this evil happens contrary to intention, yet not by chance, because it necessarily follows upon such an agent, when such agent suffers this failure of power either always or frequently: but it will be by chance, if the failure rarely accompanies such an agent. -- Coming to voluntary agents, intention in them must be of some particular good, if action is to follow: for universal considerations of themselves do not move the will, unless there be added the consideration of the particular circumstances under which the action is to take place. If then the good that is intended has conjoined with it the privation of rational good either always or frequently, there follows moral evil, and that not by chance, as is clear in his case who wishes to cohabit with a woman for pleasure, while the inordination of adultery is annexed to that pleasure: in that case the evil of adultery does not ensue by chance: but it would be an evil happening by chance, if upon the thing intended there followed some exceptional misadventure, as when one aiming at a bird kills a man. That goods of this sort, upon which privations of rational good follow, are so generally intended, arises from the practice of most men living according to sense, which they do because sensible things are more manifest to us,* and make more effectual motives in the particular circumstances in which our action is cast; and many such goods are attended with privation of rational good.
Arg. 2. Aristotle (Eth. Nic., III, vii)expressly says that wickedness is voluntary, and proves it from the fact that men do unjust acts voluntarily: but, he adds, it is irrational to pretend that a man voluntarily acting unjustly does not wish to be unjust, or voluntarily committing rape does not wish to be incontinent; and that is why legislators punish wicked men as voluntary evil-doers. It seems then that evil is not irrespective of will or intention.
Reply. Though evil be beside the intention, it is still voluntary, not as it is in itself, but incidentally. The object of intention is the final end, willed for its own sake: but the object of volition is also that which is willed for the sake of something else, though absolutely it would not be willed,* -- as one throws cargo into the sea to save the ship, not intending the casting away of the cargo, but the safety of the vessel; and yet willing the casting away of the cargo, not simply and absolutely, but for the sake of safety. In like manner, for the gaining of some sensible good, one wills to do an inordinate action, not intending the inordinateness, nor willing it simply, but for that purpose. And therefore in this way wickedness and sin are said to be voluntary, like the casting away of cargo at sea.
Arg. 3. Every process of nature serves as an end intended by nature. But destruction is as much a natural change as production: therefore its end, which is a privation and counts as evil, is intended by nature as much as form and goodness, which are the end of production.
Reply. From what has been said it appears that what is simply evil is altogether contrary to intention in the works of nature, as are monstrous births: but what is not simply evil, but only evil in a particular relation, is not intended by nature in itself, but incidentally.
3.4 : That Evil in Things is beside the Intention of the Agent
3.7 : That Evil is not a Nature or Essence