This is mostly a dry, technical chapter. But as you read it your curiosity will be piqued. The kicker comes in the penultimate argument.
1 Now, it is not possible for there to be natural malice in the intelligent substances with whose help the arts of magic work.
2 A thing does not tend accidentally, but essentially, to the objective to which it inclines by its nature, as, for instance, a heavy body tends downward. But, if intellectual substances of this kind are evil in their nature, they tend to evil naturally. Therefore, they do not tend accidentally, but essentially, to evil. But this is impossible, for we showed above that all things essentially tend to the good, and that nothing tends to evil, except accidentally. Therefore, these intellectual substances are not evil in their nature.
3 Again, whatever is present in things must be either a cause or a thing caused; otherwise, it would have no relation to other things. So, these substances are either causes only or they are also caused. Now, if they are causes, and if evil cannot be the cause of anything, except accidentally, as we showed above, but if everything that is accidental must be traced back to what is essential, then there must be something in them prior to their malice, something by which they may be causes. Now, first in each thing is its nature and essence. Therefore, substances of this kind are not evil in their nature.
4 Moreover, the same thing follows, if they are caused. For no agent acts unless it intends the good. So, evil cannot be the effect of any cause, except accidentally. Now, that which is only caused accidentally cannot be according to nature, since every nature has a definite way of coming into being. Therefore, it is impossible for substances of this kind to be evil in their nature.
5 Furthermore, each thing has its proper act of being in accord with the mode of its nature. Now, to be, as such, is good: the mark of this is that all things desire to be. Therefore, if substances of this kind were evil in their nature, they would have no act of being.
6 Again, we showed above that nothing can be unless it gets its act of being from the first being, and that the first being is the highest good. Now, since every agent, as such, produces something like itself, the things that come from the first being must be good. Therefore, the aforesaid substances, in so far as they exist and have a nature, cannot be evil.
7 Besides, it is impossible for anything to be which is wholly deprived of participation in the good. For, since the desirable and the good are the same thing, if something were utterly devoid of goodness it would have nothing desirable in it; but to each thing its own being is desirable.
Therefore, it is necessary that, if anything is called evil in its nature, then this is not evil in the absolute sense, but evil in relation to a particular thing or in some particular way. Thus, poison is not an unqualified evil, but only to this individual for whom it is harmful. Hence, “what is one man’s poison is another man’s meat.”
Now, this happens because the particular good that is proper to this individual is contrary to the particular good that is proper to another individual. Thus, heat, which is good for fire, is the contrary to and is destructive of cold, which is good for water. Now, something which is by its nature ordered to the good that is not particular, but absolute, cannot be called evil naturally, even in this sense. But every intellect is such, for its good is found in its proper operation, which is concerned with universals and with things that exist without qualification. So, it is impossible for any intellect to be evil in its own nature, either absolutely or relatively so.
8 Moreover, in each thing that possesses understanding the intellect moves the appetite according to the natural order, for the proper object of the will is the good that is understood. But the good of the will consists in the fact that it follows the understanding; in our case, for instance, the good is what is in accord with reason, but what is apart from reason is evil. So, in the natural order, an intellectual substance wills the good. It is impossible, then, for these intellectual substances, whose help the arts of magic use, to be naturally evil.
9 Furthermore, since the will tends naturally toward the good that is understood as to its proper object and end, it is impossible for an intellectual substance to have a will evil in its nature unless its intellect naturally errs in regard to the judgment of the good. But no intellect can be like that, for false judgments in the area of intellectual operations are like monsters among natural things; they are not in accord with nature, but apart from nature. In fact, the good of the intellect, and its natural end, is the knowledge of truth. Therefore, it is impossible for any intellect to exist which is naturally deceived in its judgment of the true. And so, neither is it possible for there to be an intellectual substance naturally possessing a bad will.
10 Again, no cognitive potency fails in the knowing of its object unless because of some defect or corruption in itself, since it is ordered according to its own rational character to the knowledge of this object. Thus, sight does not fail in the knowing of color unless there be some corruption present in sight itself. But all defect and corruption are apart from nature, because nature intends the being and perfection of the thing. So, it is impossible that there be any cognitive power which naturally falls short of the right judgment of its object. But the proper object of the intellect is the true. It is impossible, then, for there to be an intellect naturally tending to err in regard to the knowledge of the true. Therefore, neither can any will naturally fall short of the good.
11 This is also solidly supported by the text of Scripture. Indeed, it is said in 1 Timothy (4:4): “Every creature of God is good”; and in Genesis (1:31): “God saw all things that He had made, and they were very good.”
12 By this, then, we refute the error of the Manicheans, who asserted that intellectual substances of this kind, whom we call by the customary name of demons or devils, are naturally evil.
NOTES The consequences of this deduction are many and complex, which we shall see in time.
13 Also disposed of is the view which Porphyry reports, in his Letter to Anebontes, where he says: “Some people are of the opinion that there is a kind of spirits whose function is to hear the requests of the magicians, spirits who are false by nature, having every form, taking on the appearance of gods and demons and the souls of the dead. And this is the kind that produces all these apparitions, whether good or bad. Moreover, as regards the things that are truly good, no help is given by them; or, better, they do not even know them. Instead, they advise evil things, and blame and frequently binder zealous followers of virtue; and they are full of boldness and pride; they take pleasure in frothy exhalations and are overcome by false praises.”
Indeed, these words of Porphyry quite plainly express the evil character of the demons whose help the magic arts employ. The only point in which his words are objectionable is his statement that this evil is naturally present in them.