As in the past two weeks, we’re in territory which is no longer in live dispute. There are still some nuggets useful for us, however; only these will be highlighted. Next week are two more Chapters in which we will—finally!—wrap up this historical diversion. Then, in two weeks time, the juicy stuff starts. Proof of the immortality of the soul!
1 From the foregoing it can be inferred that neither is there one agent intellect in all, as maintained by Alexander and by Avicenna, who do not hold there is one possible intellect for all.
2 For, since agent and recipient are proportionate to one another, to every passive principle there must correspond a proper active one. Now, the possible intellect is compared to the agent intellect as its proper patient or recipient, because the agent intellect is related to it as art to its matter; So that if the possible intellect is part of the human soul and is multiplied according to the number of individuals, as was shown, then the agent intellect also will be part of the soul and multiplied in like manner, and not one for all…
4 Just as prime matter is perfected by natural forms, which are outside the soul, so the possible intellect is perfected by forms actually understood. Natural forms, however, are received into prime matter, not by the action of some separate substance alone, but by the action of a form of the same kind, namely, a form existing in matter; thus, this particular flesh is begotten through a form in this flesh and these bones, as Aristotle proves in Metaphysics VII. If the possible intellect is a part of the soul and not a separate substance, as we have shown, then the agent intellect, by whose action the intelligible species are made present in the possible intellect, will not be a separate substance but an active power of the soul…
6 Then, too, if the agent intellect is a separate substance, its action must be continuous and not interrupted; or at least it is not continued or interrupted at our will—this in any case must be said. Now, the function of the agent intellect is to make phantasms actually intelligible. Therefore, either it will do this always or not always. If not always, this, however, will not be by our choosing. Yet we understand actually when the phantasms are made actually intelligible. Hence it follows that either we always understand or that it is not in our power to understand actually.
7 A separate substance, furthermore, has one and the same relationship to all the phantasms present in any men whatever, just as the sun stands in the same relation to all colors. Persons possessed of knowledge perceive sensible things, but so also do the ignorant. Hence, the same phantasms are in both, and these phantasms will in like manner be made actually intelligible by the agent intellect. Therefore, both will understand m similar fashion.
Notes Yet not all will understand all things, as is also obvious and as the next paragraph shows.
8 Even so, it can be said that the agent intellect is, in itself, always acting, but that the phantasms are not always made actually intelligible, but only when they are disposed to this end. Now, they are so disposed by the act of the cogitative power, the use of which is in our power. Hence, to understand actually is in our power. And this is the reason why not all men understand the things whose phantasms they have, since not all are possessed of the requisite act of the cogitative power, but only those who are instructed and habituated…
15 And again, present in the nature of every mover is a principle sufficient for its natural operation. If this operation consists in an action, then the nature contains an active principle; for instance, the powers of the nutritive soul of plants.
But, if this operation is a passion, the nature contains a passive principle, as appears in the sensitive powers of animals.
Now, man is the most perfect of all lower movers, and his proper and natural operation is understanding, which is not accomplished without a certain passivity, in that the intellect is passive to the intelligible; nor again, without action, in that the intellect makes things that are potentially intelligible to be actually so.
Therefore, the proper principles of both these operations must be in man’s nature, nor must either of them have being in separation from his soul. And these principles are the agent and the possible intellects…
17 Furthermore, no thing operates except by virtue of a power formally in it. Hence, Aristotle in De anima II  shows that the thing whereby we live and sense is a form and an act. Now, both actions—of the agent intellect and of the possible intellect as well—are proper to man, since man abstracts from phantasms, and receives in his mind things actually intelligible. For, indeed, we should not have become aware of these actions had we not experienced them in ourselves. It follows that the principles to which we ascribe these actions, namely, the possible and agent intellects, must be powers formally existing in us…
19 Again, a thing that cannot initiate its proper operation without being moved by an external principle is moved to operate rather than moves itself. Thus, irrational animals are moved to operate rather than move themselves, because every one of their operations depends on an extrinsic principle which moves them.
For the sense, moved by an external sensible object, places an impress upon the imagination, thus giving rise to an orderly process in all the powers, down to the motive ones.
Now, man’s proper operation is understanding, and of this the primary principle is the agent intellect, which makes species intelligible, to which species the possible intellect in a certain manner is passive; and the possible intellect, having been actualized, moves the will.
Therefore, if the agent intellect is a substance outside man, all man’s operation depends on an extrinsic principle. Man, then, will not act autonomously, but will be activated by another. So, he will not be master of his own operations, nor will he merit either praise or blame. All moral science and social intercourse thus will perish; which is unfitting. Therefore, the agent intellect is not a substance separate from man.
Notes Unfitting indeed. We are not puppets.