Lecture 1 — The intellect in general

As to the part of the soul by which it knows and judges (whether being separable according to magnitude or not separable according to magnitude but only in account), we must consider how it differs and, further, how understanding itself arises.

For if understanding is like sensing, it will be some kind of being acted upon by the intelligible object or some thing of that sort. It must, then, be impassible and yet receptive of a species, and in potency for such, but not this; and as the sense power stands to the sense-object, so will the intellect to the intelligible.

It is also necessary, since it understands all things, that it be unmixed, as Anaxagoras says, “so that it may command,” i.e., that it may know. For what appears inwardly would prevent and impede what was without. Hence it has no nature and is not one, except in being potential. What, then, is called the intellect of the soul (I mean that intellect by which the soul understands and forms opinions) is, in act, none of the things that exist before it understands.

Hence, it is a reasonable inference that it is not mixed with the body. Were it so, it surely would also receive some quality, either hot or cold, if there were some organ for it, like for a sensitive power; but there is in fact none such.

And now, they spoke well who said that the soul was the place of species—yet not the whole soul, but the intellectual part; nor actually, but only potentially, is it any species.

That the impassibility of the sensitive power is not like that of the intellectual power is evident from the organs and from sensation itself.

For the sense cannot sense too strong a sense-object, e.g., a sound from very great sounds, while on account of some odors and colors being very powerful, one does not smell or see them.

But when the intellect understands something highly intelligible, it does not understand lower things less, but more. For whereas the sensitive power is not without the body, the intellect is separate.

671. As to the part of the soul (429a10). Having treated of the sensitive part of the soul, and shown that to sense and to understand are quite distinct activities, the Philosopher now turns to the intellectual part of the soul. His treatment falls into two main divisions.

First, he comes to certain conclusions on the intellectual part in general.

Second, from what has been concluded about sense and intellect, he deduces, at now recapitulating (431b20; [787]), some necessary consequences with regard to the soul as a whole.

The former division falls into two sections.

In the first, he makes determinations about the intellect as such.

In the second, at and it appears that the sense-object (431a4; [765]), he compares the intellect with the senses.

The first divides into two parts.

In the first, the intellect is treated in itself.

In the second, at the intellectual grasping of indivisible things (430a26; [746]), the intellect is treated according to its activity.

The former part then subdivides again into three parts.

First, he determines about the potential intellect; (Throughout this translation, we have translated intellectus possibilis as “potential intellect” rather than as “possible intellect” or “passive intellect.” While “possible intellect” is a common and more direct transliteration of the Latin, the term in English might confusingly suggest the opposite of impossibility rather than the intellect’s potency to the intelligible; as for the term “passive intellect,” we have reserved its use for the intellectus passivus (see below, at lect. 4, n. 745).)

second, about the agent intellect, at now, since in all nature (430a10; [728]);

third, about the intellect in act, at but knowledge in act (430a19; [740]).

Concerning the first, he does three things.

First, he determines the potential intellect;

second, he determines its object, at now, as magnitude is one thing (429b10);

and third, he adduces an objection, at one might well inquire (429b22).

The determination of the potential intellect is in two parts.

First, he explains the nature of the potential intellect.

Second, he explains the way it is reduced to act, at but when it becomes particular objects (429b5; [700]).

And as to its nature, he does two things:

first, he states the problems he is attempting to solve;

second, at for if understanding is like sensing (429a13), he shows what he proposes.

672. So he says that, having dealt with the sensitive part of the soul, and having shown that judgment and understanding differ from sensation, it is now time to consider that part of the soul by which it knows (429a10), that is, understands, and judges. We have already distinguished between rational judgment and understanding: for to judge rationally pertains to the judgment of the intellect, but to understand pertains to its apprehension. (Bk. 2, lect. 28, n. 629.)

673. At this point, an old problem emerges (which Aristotle for the time being sets aside), namely, whether this part of the soul is separable as a subject from the other parts of the soul, or is not separable as a subject but only in its account. He understands separability in subject when he speaks of its being separable according to magnitude, because Plato, asserting that the soul’s parts are separate from each other in subject, associated them with different organs of the body. This problem Aristotle sets aside.

674. And he keeps two ends in view. One is to examine how this part of the soul differs from the others, if it can be separated from them in account. And, as the property of a power is known from the quality of its act, his second aim is to examine how understanding itself arises, that is, how intellectual activity is completed.

675. Next, at for if understanding (429a13), he presents what he proposes in three stages:

first, he suggests a similarity between intellect and sense;

second, he argues, at it is also necessary (429a18; [677]), to a conclusion touching the nature of the potential intellect;

third, he in turn deduces a difference between intellect and sense, at that the impassibility (429a29; [587]).

First of all, then, to show what was proposed, he starts on the supposition that understanding and sensing are similar; he manifests this likeness by noting that just as sensing is a certain knowing, and we of course sometimes sense in potency and sometimes in act, so too, understanding is a certain knowing, and sometimes we understand in potency and sometimes in act. Whence it follows that, as sensing is a certain being acted upon by a sensible object (or is something like a passion), so understanding is either some kind of being acted upon by the intelligible object or something of that sort, that is, like a passion.

676. Of these alternatives, the second is the more true. For even sensing, as we have seen in Book II, is not properly speaking a being acted upon—for being acted upon, properly speaking, involves something coming from its contrary. (Bk. 2, lect. 10, nn. 350–51; lect. 13, n. 393.) Yet sensing resembles a passion inasmuch as the sense is potential with respect to its sensible object, and it is receptive of sensibles. Then, if understanding resembles sensing, the intellectual part too must be impassible (taking “passion” properly), yet it must have some likeness to passibility, for it must be receptive to an intelligible species; and it must be in potency for such a species, but not this in act*. And* thus it must be the case that as the sense power stands to the sense-object, so will the intellect to the intelligible, each being potential with respect to its own object and able to receive that object.

677. Then, at it is also necessary (429a18), he proceeds to deduce the nature of the potential intellect. And about this he does two things.

First, he shows that the potential intellect is not a bodily thing nor compounded of bodily things;

second, at hence it is a reasonable (429a24; [684]), he shows that it has no bodily organ.

As to the first point, we should note that there used to be two opinions about the intellect. Some—and this, as we have seen, was the view of Empedocles—thought that intellect was a composition of the principles of all things so that it could know all things. (Bk. 1, lect. 4, n. 45.) On the other hand, Anaxagoras thought it was simple and unmixed and had nothing in common with any bodily realities. And therefore, precisely because the intellect, as he has just said, is not actually the intelligible objects, but only potentially, he concludes that it is necessary that the intellect, on account of the fact that it understands all things, cannot be composed of bodily things, as Empedocles thought, but must be unmixed, as Anaxagoras thought.

678. But the reason why Anaxagoras thought this was that he regarded intellect as the principle of the whole of motion, one by which all things are moved according to its command, but if it were mixed of the bodily natures or had any of them in a determinate way, it could not move all things by its command; for it would be determined to one thing. Hence Aristotle’s observation that, in Anaxagoras’s view, the intellect was unmixed so that it may command, that is, so that it might move all things by its own command.

679. But since we are not concerned at present with the intellect that moves all things, but with an intellect that understands all things, this middle term is not relevant to showing that the intellect is unmixed with bodily things; rather, one needs to take a middle term for showing this based on the intellect’s knowing all things. That is why Aristotle adds, that it may know, as if to say: “as Anaxagoras maintained that intellect was unmixed so that it may command, so we assert that it is unmixed so that it might know.”

680. The following argument makes this point clear. Anything that is in potency with respect to an object and able to receive it lacks that object; thus, the pupil of the eye, being potential to colors and able to receive them, is itself colorless. But our intellect understands intelligible objects in such a way that it is in potency with respect to them and capable of receiving them (just as sense is of sensible objects). Therefore it lacks all those things that it is naturally apt to understand. Since, then, our intellect is naturally apt to understand all sensible and bodily things, it must lack every bodily nature, just as the sense of sight, because it is able to know color, lacks color. For if sight had any color, this color would prevent it from seeing other colors; just as the tongue of a feverish man, being coated with a bitter fluid, cannot perceive a sweet flavor, so too, if the intellect possessed any determinate nature, this connatural nature would prevent it from knowing other natures.

This is why he says, what appears inwardly would prevent and impede its knowledge of what is without, that is, it would get in the way of the intellect, and in a way veil it and impair its inspection of other things. He names that which “appears inwardly” anything internal that is connatural to the intellect, that which, so long as it appeared therein, would always impede the understanding of other things, as we might say that the bitter fluid is what appears inwardly to the fevered tongue.

681. From this, he concludes that it is not possible that there be a nature of the intellect, nor that it be one, that is, it has no determinate nature, except that its nature is to be potential to all things. And this is the case for intellect because it is capable of knowing, not merely one genus of sensible objects (like sight and hearing), nor even all qualities and sensible accidents, whether these be common or proper sense-objects, but universally the whole of sensible nature. Therefore, just as sight lacks a certain genus of sensible objects, so must the intellect lack the whole of sensible nature.

682. He concludes further that what we call the intellect of the soul is, in act, none of the things that exist before it understands. This is contrary to the early philosophers’ assertion that intellect must be compounded of all things so that it can know all things. But if it knew all things because it has them all in itself, the intellect would always be in act and never in potency, in the same way he has remarked already of the senses, that if they were composed of the sensible objects, they would not require any exterior sensible objects in order to sense. (Bk. 2, lect. 10, nn. 352–55.)

683. And lest anyone should suppose this to be true of every intellect, that it is in potency to its objects before it knows them, he adds that he is speaking here of the intellect by which the soul understands and forms opinions. Thus he excludes from this context the intellect of God, which is not in potency, but rather is in a certain way the act of all things—of which intellect Anaxagoras said that it is unmixed so that it might command.

684. Next, at hence it is a reasonable (429a24), he shows that the intellect has no bodily organ.

First, he shows what he proposed.

Second, at and now, they spoke well (429a27), he approves a saying of the early philosophers.

First, then, he concludes from what has been said that if our intellect, to know all things, must not have any determinate nature from among the natures of bodily realities, which it knows, for the same reason, it is a reasonable inference that the intellect is not mixed with the body, that is, that it has no bodily organ, as the sensitive part of the soul has. For if there were some organ for the intellect as there is for the sensitive part, it would follow that it would have some determinate nature from among the natures of sensible realities. Therefore, he says, it follows that it will be some quality, meaning that it has some sensible quality, such as either hot or cold. For it is obvious that the power of the soul that is the act of any organ must conform to that organ as act to what receives it.

685. It makes no difference to the act of the power whether it is the power itself that has a determinate sensible quality or the organ, since an act is not of the power alone but of the power and bodily organ together. For the seeing of colors would be impeded in the same way if it were the visual power or the pupil that has the determinate color. So he says that it comes to the same thing to maintain that intellect has no bodily organ and that it has no determinate bodily nature. And he concludes that the intellectual part of the soul, unlike the sensitive, has no bodily organ.

686. Next, where he says, and now, they spoke well (429a27), he relates his view to an opinion of the early philosophers, saying that, granted the intellectual part’s lack of an organ the way the sensitive part has one, we can now see why some have said that the soul is the place of species, meaning that through a likeness it is said that it is receptive of species. Now, this saying would be false if every part of the soul had an organ, for then the species would not be received into the soul alone, but into the composite. For it is not only sight that receives species but the eye. It follows that the soul as a whole is not the place of species, but only that part of it which lacks a bodily organ, that is, the intellectual part; nor is it the place of the species in such a way that it has species actually, but potentially only.

687. Then, at that the impassibility (429a29), he shows how the intellect and the senses differ with respect to impassibility. He has already observed that just as sensing is not a “being acted upon” (pati), taking “passion” (passione) properly, so neither is understanding; whence he had inferred earlier that the intellect was impassible. But so that no one might think that the senses and the intellect stand in the same grade of impassibility, he adds here that the impassibility of the sensitive power is not like that of the intellectual power. For though a sense in itself is not acted upon by its object (taking “passion” properly), still it is acted upon accidentally, inasmuch as the proportion of the organ is corrupted by an excessively sensible object. But this does not happen to the intellect, since it has no organ; it is therefore neither in itself nor accidentally passible.

688. This is what he means when he proceeds to say that the dissimilarity between sense and intellect in point of passibility is manifest from the organs and from sensation. For too strong a sense-object can take away the power of sense. For example, one cannot sense a sound because of the motion caused by very great sounds, nor can sight see or smell smell if these senses have been moved first by powerful colors and smells corrupting the organ. But since the intellect has no bodily organ that could be corrupted by an excess of its proper object, when the intellect understands something highly intelligible, it does not understand lower things less, but more afterward; and the same would happen to the senses, if they did not have bodily organs. All the same, an injury to an organ of the body may indirectly weaken the intellect, insofar as the latter’s activity requires the activity of the sense that has the organ. The cause, then, of the difference is that sensitive power is not without the body, but the intellect is separate.

689. All this goes to show the falsity of the opinion held by some that intellect is the same as the imaginative power or a certain preparation in human nature that follows on the body’s constitution.

On the other hand, this same text has been, for some, an occasion of falling into the error of regarding the potential intellect as separated in being from the body, as one of the separated substances. This is altogether impossible.

690. For it is clear that this man understands. For if one denies this, then he himself does not understand anything, nor should he be listened to. But if he does understand, he must understand by something, formally speaking, and this is the potential intellect, to which the Philosopher refers when he says, “I mean that intellect by which the soul understands and forms opinions.” The potential intellect, then, is that by which this particular man, formally speaking, understands.

Now, that by which an agent acts, as by an active principle, may be separated in being from that which acts; for example, the bailiff acts through the king because the king moves him to his act. But it is impossible for that by which something formally acts to be separated from it in being; this is because nothing acts except insofar as it is in act; something, therefore, formally acts by something just as it comes to be in act by that thing. Now, something does not become a being in act by something else if it is separated from the latter in being. Hence it is impossible that that by which something formally acts be separated from it in being.

691. With this truth in mind, those who have maintained the opinion to which I refer tried to think out some way of so linking up and uniting that separated substance (which they call the “potential intellect”) with ourselves, so that its understanding would be our understanding. For they say that the form of the potential intellect (through which it comes to be in act) is the intelligible species; and that the subject of this species is a certain phantasm that exists in us. In this way, they said, the potential intellect is linked with us through its form.

692. But this entirely fails to prove any continuity between the intellect and ourselves. This is clear as follows. The potential intellect is united with an intelligible object only to the degree that the latter is actually understood, just as we have seen that the sense is not the same as the sensible in potency. (Bk. 2, lect. 10, nn. 355–57; lect. 12, n. 382.) Therefore, the intelligible species is not the form of the potential intellect until it is actually intelligible, and it is not actually intelligible until it has been abstracted from phantasms. Hence, in the degree that it is joined to the intellect, it is removed from phantasms. Therefore, an intellectual power could not be united with us in this way.

693. And obviously the upholder of this view was led astray by the fallacy of the accident. For his argument comes to this: phantasms are somehow one with intelligible species, and the intelligible species is one with the potential intellect; therefore, the potential intellect is united to the phantasms. But it is manifest that this is falling into the fallacy of the accident, since the intelligible species is one with the potential intellect to the degree that it is abstracted from phantasms, as was said.

694. But even granted that between the potential intellect and ourselves there existed some such union as this view supposes, it would not in fact cause us to understand, but rather, it would cause us to be understood. For that of which the species is a likeness, existing in some cognitive power, does not thereby make a knower; rather, it makes a thing known. For the species, which is in the pupil, being a likeness of the color that is in the wall does not render color something that sees, but rather, something seen. Therefore, if the intelligible species, which is in the potential intellect, is a sort of likeness of our phantasms, it does not follow that we ourselves understand anything, but rather that we—or, more precisely, our phantasms—are understood by that separated intellectual substance.

695. Many other criticisms might be made, such as I have set out in more detail elsewhere, but it is enough to note for the present that the theory in question is an implicit denial that this man here understands.

696. Furthermore, it is also clearly contrary to the teaching of Aristotle. First, because he has explicitly said at the beginning of the treatise that he is inquiring about a part of the soul; hence, it is clear that the potential intellect is a part of the soul and not any separated substance.

697. Moreover, leaving aside the question whether the intellect is separable in subject from the other parts of the soul or not, he has set out to examine the intellect; so even if the intellect is not separable in subject from the other parts of the soul, that does not affect his argument.

698. Again, Aristotle calls the intellect that by which the soul understands. All these indications show that he did not assert that the intellect was separate as are the separated substances.

699. Indeed, it is astonishing how easily some have let themselves be deceived by his calling the intellect separate; for the text itself makes it perfectly clear what he means—for he calls the intellect separate because, unlike the senses, the intellect has no organ. For the human soul, on account of its own nobility, transcends the capacity of bodily matter and cannot be entirely contained by it. Hence there remains for it a certain activity in which bodily matter has no share; and on account of this, its potency for this activity has no bodily organ, and in this sense intellect is separate.