Lecture 28 — Sense distinguished from intellect and imagination distinguished from opinion

Now, if the soul is defined principally by two differences, by motion according to place and by what it is to understand, to discern, and to sense, it would seem that both to understand and to judge are a kind of sense-perception—for in either case the soul judges something and knows of things that exist.

The early philosophers, indeed, said that rational judgment and sensation were the same thing, as when Empedocles says, the will is increased in man in the present, and in another place, whence it always presents them new objects of judging. To the same purport is that line of Homer: the intellect of mortals is such as the father of gods and men brings into light.

All these suppose the intellect to be something bodily, like sensation, and that both sensing and rationally judging are of like by like, as we explained at the beginning of this treatise.

But they ought at the same time to have treated of error, which is a state more proper to animals, and in which the soul spends the greater part of its time. So it must follow, either that all that seems so is true (as some maintain) or that error is a contact with what is unlike, this being the contrary of knowing like by like.

It would appear, however, that error and knowledge are the same with respect to contraries.

Therefore it should be evident that rational judgment and sensation are not the same. For the latter is in all animals, the former in but few.

Nor again is understanding. It may be correct or incorrect—correct as prudence, science, and true opinion, incorrect as the opposite of these. Nor is this the same as sensation. For sensation is always true of its own proper objects and is found in all animals, whereas intelligence is sometimes accompanied by error and is found in no species that lack reason.

But imagination is other than both sensation and understanding. Yet it cannot occur without sensation, and without it there is no opinion.

It is evident, however, that opinion and imagination are not identical. For the latter passion arises in us at will, as a picture before our eyes, like the imagery employed by those who cultivate memory training. But opinion is not within our power in this way; it must express the true or the false, of necessity.

Further, when we opine that anything is arduous or fearful, we are at once emotionally acted upon; and likewise, if there is an occasion for confidence. But in imagining, it is as though we were regarding in a picture things arduous or encouraging.

These are, besides, the various modes of making a judgment: science, opinion, and prudence, with their contraries. Let the question of their differences be discussed elsewhere.

615. Now, if the soul is defined principally (427a17). After showing that the two activities about which there was a difficulty, perceiving the acts of the proper senses and discriminating between their various objects, are not beyond the range of the sensitive principle, the Philosopher now addresses himself to the question whether rational judgment and understanding are beyond its range. And he does two things here.

First, he proves that rational judgment and understanding do not pertain to sense, which is the same as to show that sense and intellect are distinct powers.

Second, at but imagination is other (427b14; [632]), he shows that the imagination, which pertains to sense, is other than the power to form opinions, which pertains to the understanding.

The former argument subdivides into two.

First, he states the theory of the identity of sense and intellect.

Second, he refutes this theory, at but they ought at the same time (427a29; [624]).

Concerning the first, he does two things.

First, he states the opinion.

Second, he assigns the cause of this opinion, at all these suppose the intellect (427a26; [622]).

Concerning the first, he does two things.

First, he states the opinion in common;

second, he brings in some remarks of certain philosophers that seemed relevant, at the early philosophers, indeed (427a21; [617]).

616. First, then, he says that as the early philosophers defined the soul (427a17) in terms of motion according to place and knowledge—which includes intellectual discernment and sensation—it would seem to have been their view that to understand and to judge rationally were the same sort of activity as sense-perception; for in both the soul judges and knows.

617. Next, where he says, the early philosophers (427a21), he shows that this is more than a mere inference from their general teaching and that they explicitly taught that sensation and rational judgment through understanding were identically the same.

But in order to understand the words which he quotes here of these philosophers, and their relevance to the present argument, we have to consider that no body can act directly upon what is purely incorporeal. Now, the sense powers are in some way bodily, because they are powers in bodily organs. Therefore they are subject to the influence of the heavenly bodies, though only accidentally, for neither the soul itself nor any of its powers is moved by a body’s being moved except accidentally. Consequently, the imagination and sense-appetite are modified in various ways by the influence of the heavenly bodies. Brute animals, which are led by appetite alone in their own motions, for the most part follow the impressions of the heavenly bodies. Hence to suppose that heavenly bodies act directly upon the intellect and will is to posit that these powers are bodily. And this is what some of the early philosophers seem to have said.

618. Empedocles, for instance, said that in man, no less than in other animals, the will is increased, that is, prompted to act, in the present, that is, according to the disposition of the present hour, which itself depends on the disposition of the heavenly bodies. It is the present moment that always presents them, that is, presents to men and the other animals, new objects of judging; for all the animals, men included, judge things differently at different times.

619. To the same purport Homer says that the intellect of mortals is such as the father of gods and men (that is, the sun) brings into light. He calls the sun the father of men because it is a certain cause of human generation; for a man is born from a man and the sun. And the sun he calls the father of gods, either following the old view that made gods of the other heavenly bodies which, the astronomers tell us, are governed somehow by the sun, or following the view that certain men are divine because generated by the power of the sun. And the sun’s power is, of course, strongest in the daytime while it is visible and is moving across the upper hemisphere; hence the name of “day planet” given it by astronomers. So what Homer is saying is that the sun is the cause of understanding in men and that their knowledge of things varies with the movement, situation, and appearance of the sun.

620. In point of fact, Aristotle quotes only the beginning of Homer’s line; neither the Greek text nor the Arabic gives us more than the intellect of mortals is such. Aristotle relies on his readers remembering the whole of it from a part, as when one quotes the first words of a well-known verse of any author. But Boethius cites the whole of the line from Homer, for the sake of his Latin readers who were not familiar with that poet.

621. What has been said, then, makes it quite clear that if the heavenly bodies do have a direct influence on the intellect and will, then there is no difference between the intellect and the senses. There is no difficulty, however, about admitting an indirect influence of the heavenly bodies upon intellect and will, insofar as these powers are joined in their activity with the sense powers. Thus any injury to the organ of the imagination will impede the intellect’s own activity; and the will is inclined towards choosing or refusing something by the sensitive appetite. But since the will is never drawn of necessity by the sensitive appetite, but remains free to follow or not the inclination of the appetite, human actions are never completely determined by the influences of the celestial bodies.

622. Next, he states the reason why this opinion arose, at all these suppose the intellect (427a26). If you take away that by which things differ, they are left the same; for example, if rationality is removed from man, he is left as one of the irrational animals. Now, the difference between intellectual and sensitive cognition is that the latter is something bodily. For sensation cannot occur without a bodily organ, whereas understanding, as we shall prove later, is not bodily, since the intellect’s activity does not take place through a bodily organ. (Bk. 3, lect. 1, n. 684.) But to the early philosophers intellect seemed to be something bodily, like sensation; hence they supposed that intellect and sense were the same.

623. And how they thought of both activities as bodily he next explains, saying that they maintained that the acts of judging rationally by intellect and sensing arose from the power of a likeness, as it was said in book 1; and they thought this likeness was bodily in its being, so that earth was known by earth and water by water, and so on with other objects. (Bk. 1, lect. 4, nn. 43–44.) And consequently, sensing and understanding both followed upon our bodily nature and in the same way, and therefore it follows that sensing and understanding are the same thing.

624. He goes on now, at but they ought (427a29), to criticize this opinion:

first, with regard to the premise on which it depends;

and second, at therefore it should be evident (427b6; [629]), directly in itself.

So he remarks, first, that the philosophers who explained knowledge by the likeness of the knower and the thing known should have also given some explanation of error; for error seems to be even more proper to animals than knowledge, according to the condition of their own nature. For we see that people can easily deceive themselves and commit errors, while to know the truth they need to be taught by others. Again, the soul is involved in error for a longer time than it spends in knowing the truth, for to acquire knowledge of the truth even a long course of study hardly suffices. Now, this argument is indeed valid against those early philosophers who regarded knowledge to be in the soul by its own nature, as though the soul was constituted of the first principles of things, not merely in potency to things that can be known, but actually knowing them.

625. One could answer this in two ways. One might say that since the early thinkers did not admit the existence of error (their view being, as we have seen, that all that seemed to be was true), they did not need to explain error. (Bk. 1, lect. 3, n. 39; bk. 2, lect. 26, nn. 595–96.)

626. Second, it might be answered that to explain knowledge as a contact of the soul with what is like itself is implicitly to explain error as the soul’s contact with what is unlike itself. Hence, from the fact that the early thinkers did not explicitly render an account of error, he infers that either it must follow, either that all that seems so is true, as some have said, or that the contact whereby the soul touches something unlike itself is the cause of deception; since to touch the unlike seems to be the contrary of knowing like by like.

627. The first alternative is refuted in Metaphysics 4. (Aristotle, Metaphysics 4.4–7, 1005b35–1011b22; cf. Aquinas, Commentary on Metaphysics, bk. 4, lect. 6–15, nn. 606–719.)

628. So he proceeds to examine the second alternative, at it would appear (427b5). The like and the unlike are obviously contraries. But man holds the knowledge and deception about contraries in the same way, for if you know one, you know the other; if you err about one, you err about the other. Hence he says that it would appear that error and knowledge are the same with respect to contraries. It follows that it is not possible that touching a like thing is the cause of true knowledge and touching an unlike thing a cause of error; for in that case one would know one of a pair of opposites and be mistaken about the other.

629. Then, at therefore it should be evident (427b6), he attacks the theory in question, and shows that neither rational judgment nor understanding is the same as sensing; but these two belong to intellectual knowledge. For the intellect has a power to judge, which here is called “rational judgment” (sapere), and to apprehend, which here is called “understanding” (intelligere).

First, therefore, he shows that judgment and sensation are not the same, arguing thus: sensation belongs to all animals, but rational judgment is found in but few; therefore they differ. And he says that rational judgment is found in few animals, and not that it is in man alone, because even certain brute animals participate in something of prudence and of a certain wisdom, in that they form correct judgments on what they need to do through their natural estimation.

630. Second, at nor again (427b8), he shows the difference between understanding and sensation; and this in two ways.

The first is as follows. Understanding may be correct or incorrect. Correct understanding happens in reference to science, which is about speculative and necessary truths; or in reference to prudence, which is right reasoning about contingent things that can be done; or in reference to true opinion, which is open to both alternatives, but without a determination to either of the opposites (as happens in science and prudence), but orients to one along with an anxiety about the other. Incorrect understanding is in each case the opposite of these, that is, in reference to a false science, or imprudence, or false opinion. Sensation, on the other hand, cannot happen incorrectly, for it is always true about the proper sensible objects. Therefore, sensation and understanding are not the same thing.

631. And since it might be objected that correct understanding, at least, is the same as sensation, to exclude this he adds that sensation is found in all animals, whereas intelligence is not, but only in those wherein reason is present, that is, in men. For man reaches an apprehension of intelligible truth by way of rational inquiry; whereas the separated substances, which are in a higher degree intellectual, understand the truth immediately without any inquiry. Therefore, not even correct understanding is the same as sensation.

632. Next, when he says, but imagination (427b14), he shows the difference between opinion, which follows intellect, and imagining, which follows sensation. And here he does two things.

First, he shows that imagining is not opinion.

Second, he asks what imagining is, at concerning understanding (427b27; [637]).

The former subdivides into three parts.

First, he states his aim, saying that another way to grasp the difference between sense and understanding is to consider that imagination is other than both sensation and understanding, yet it cannot occur without sensation because it follows it, as will be shown later, and without imagination there is no opinion. (Lect. 30, nn. 655–59.) For it seems that, as imagining is to the senses, so is opinion to the understanding. When we sense any sensible object, we affirm that it is such and such; but when something is seen according to imagination, we make no such affirmation: we merely state that such and such seems or appears to us. (For the word “imagining” is taken from seeing or appearing.) (Lect. 30, n. 668; the noun phantasia (“imagination”) could also be translated as “appearing” or the “appearing power,” as it derives from the verb phainesthai (“to appear”).) Similarly, with regard to intelligible things: when we understand something, we affirm that it is such and such; but when we form opinions, we say that such and such seems or appears to us. Therefore, as understanding requires sensing, so opinion requires imagining.

633. In the second place, at it is evident (427b16), he proves by two arguments the difference between opinion and imagination.

The first argument is this. Imagination’s passion arises in us at will, for it is in our power to form something as though appearing before our eyes—golden mountains, for instance, or anything else we please, as people do when they reminisce and form for themselves icons of things that appear to them at will. But opinion is not within our power, since of necessity one who has an opinion has a reason on which it is based, whether true or false. Therefore opinion is not the same as imagination.

634. The second argument, at further, when (427b21), is this. Opinion has an immediate effect on the passions in our appetite; so when we opine that anything is grave or fearful, we are at once emotionally acted upon, either with grief or fear. Likewise if anything is an occasion of confidence, that is, it is something about which one should be confident or hopeful, we at once feel hopeful or glad. But a passion in the appetite does not follow upon imagining; for so long as anything appears to us merely in imagining, it is as though we were regarding in a picture frightening or encouraging objects. Therefore, opinion differs from imagining.

635. Now, the cause of this difference is that our appetite is not acted upon or moved by the simple apprehension of the sort of thing that imagination brings forth; rather, it is necessary that it be apprehended under the account of the good or evil, useful or harmful; and, in man, opinion brings this about by its composing or dividing, when we opine this thing is fearful or evil and that thing is hopeful or good; but imagination does not compose or divide. Nonetheless, in brute animals the appetite is acted upon by their natural estimation, which plays the same part in them as opinion in man.

636. Third, at there are, besides (427b24), he remarks that because many things pertain to the intellectual judgment, such as science, prudence, and opinion, with their contraries, he does not intend to treat their differences here. They are dealt with elsewhere, in Ethics 6. (Aristotle, Ethics 6.3–4, 1139b14–1140b30; cf. Aquinas, Commentary on Ethics, bk. 6, lect. 3.)