Lecture 27 — The common sense

Each of the senses, then, is of a sensible subject and in a sense organ precisely as such, and it discerns the differences within its subject—for example, for sight: black and white; for taste: sweet and bitter; and likewise with the other senses.

Since by something we distinguish, however, between white and sweet, and any other of the sense-objects, and we sense that they differ, there must be some sense for this too; for these objects are sensible. Hence it is also clear that flesh is not the ultimate sense organ; for, in that case, this discrimination would have to be effected by touching.

Nor could it be by divided powers that the sweet is discerned as other than the white; but both must be presented to some one power. For otherwise it would be like my perceiving one thing and you, another: it would then certainly be evident that the two were different, but some one single power must say that they differ—i.e., sweet from white. Therefore it is one single power that asserts this; and as it asserts, so it understands and senses. It is patent, then, that it is not possible to distinguish separate objects by powers themselves separate.

And the same holds with regard to separate points of time, as the following considerations show.

For just as the same power says that the good and bad differ, so too is the instant the same in which it says that they differ, and being different and being different at that time are not accidental to when the statement is said—I mean, as in now saying that they are different, but not that there is now a difference—whereas this power both says this now and that the difference is now.

Therefore this happens simultaneously; an undifferentiated principle distinguishes the two in an indivisible time.

But it is impossible for one and the same indivisible thing to move in different directions in one and the same indivisible moment of time. For if the object is sweet, it so affects the sense or the intellect, but if bitter, contrariwise, and if white, in another way.

Therefore what judges simultaneously is numerically indivisible and inseparable, yet distinct in being. For it is in one way capable of multiplicity because it perceives things divided off from one another: but in another way, it is indivisible. Thus in its being indeed it is divisible, but it is indivisible locally and numerically.

Or this is not possible; for one and the same indivisible thing can be in contrary states potentially, but not in its very being. It can be divisible in its activities indeed, but it cannot be black and white at the same time; and therefore neither can it receive the species of both—if this is how sensation and understanding occur.

But it is just as some speak of a point as one or as two, and in this sense as divisible. As indivisible, it is one thing making the discernment, and simultaneously. But as divisible, it uses the same point twice. Therefore, insofar as it uses the terminus as two, it judges two things, and they have been separated, and as by what is separate. Yet insofar as it is one, it does this by one thing and simultaneously.

So much then by way of explaining the principle by which we call any animal sensitive.

599. Each of the senses, then (426b8). So far, Aristotle’s approach to an examination of the common sense has been by way of the act whereby we sense our own seeing and hearing. But his scrutiny of this sensing has so far only led him to the conclusion that seeing is itself sensed by the power of sight, though not in the same way as exterior objects are sensed. He has not yet determined that there is any one common power that makes a judgment about the acts of the senses. But now he takes his inquiry a step further by pointing to another activity of the soul as evidence of the existence of a power with, in a way, a common relationship to all the five senses: the activity of discriminating between various sense-objects. And here he does two things:

first, he shows how far the proper senses can so discriminate;

second, he investigates that discrimination of sensible objects which exceeds the power of any proper sense, at since by something we distinguish (426b12; [601]).

600. He observes then, first, that we have seen that each of the senses knows its own sensible subject, the species of which comes to be within its own particular organ as such; for the organ of each sense is, through itself and not accidentally, impressed by the proper object of that sense. (Lect. 13.) And each sense discerns the differences of that proper sensible, as sight, for example, discerns white and black; taste, sweet and bitter; and likewise with the other senses.

601. Then, at since by something we distinguish (426b12), he shows to what one should attribute that discrimination that exceeds the proper senses, that is, the discrimination between the objects of the different senses. And here he does two things:

first, he demonstrates his conclusion;

second, he poses and solves an objection, at but it is impossible (426b29; [606]).

The demonstration has three parts:

first, he shows that there is a sense that discriminates between white and sweet;

second, that this sense is one power, not two, at nor could it be divided (426b17; [603]);

third, that it simultaneously perceives both objects between which it discriminates, at and the same holds (426b23; [605]).

First, then, he observes that whereas we are able to distinguish not only between black and white, or sweet and bitter, but also between white and sweet, and indeed between any one sense-object and another, it must be through a sense that we do this, for to know sense-objects as such is a sense activity. For we know the difference between white and sweet not only as far as what each of these are, which pertains to the intellect, but even as far as different modifications of the senses, and this can pertain only to some sense power.

602. If this occurs through a sense, the most likely sense power would seem to be touch, the first of the senses, the root and foundation, as it were, of all the senses, the one which entitles an animal to be called “sensitive.” But it is clear that, if this discrimination were to come from touch, then flesh is not the ultimate organ of the sense of touch; for if this discrimination were to occur through the sense of touch, it would have to be that in the very contact of flesh and the tangible this discrimination of the tangible from the other senses would occur. But this discrimination is attributed to touch not insofar as touch is a proper sense, but only as the foundation of all the senses and as standing closer to the fundamental root of them all, namely, the common sense itself.

603. Then, at nor could (426b17), he shows that it is by one and the same sense that we distinguish white from sweet. For one might have supposed that we did it by different powers, such that we know the sweet by taste and the white by sight. But he excludes this, saying, it could not happen that by divided, that is, distinct, powers the sweet is discerned as other than the white. But both must appear to some one power if they are to be distinguished. For if this were so, if we were to sense the sweet and the white by diverse powers, it would be like they were sensed by two different men, one perceiving sweet and the other white; for example, my perceiving one thing and you, another. In this case, it will be manifest that sweet and white are different, because I am acted upon by the sweet otherwise than are you by the white.

604. But, nevertheless, this diversity would not be manifest; rather, there must be one who says that the sweet is other than the white, for this distinction is some one truth, that the sweet is other than the white. Thus there must be one thing by which it is said, but speech is expression of an inward apprehension, so just as it is one thing it asserts, so too, there must be one thing that understands and senses that sweet and white are different.

He says, understands and senses, either because he has not yet shown the distinction between sense and intellect or perhaps because both these powers know the difference in question. As, then, the man who says that white is other than sweet must be one man aware of both objects, so he must do this by means of one power whereby he knows each; for a man does not know except through some power. Hence, Aristotle’s conclusion: that it is clearly not possible to distinguish separate objects, that is, that two things are distinct, by separate, that is, by distinct, means. There must be one single power aware of both things.

605. Next, at and the same (426b23), he proves that this awareness is of both things simultaneously, not at *separate (*that is, distinct) points of time. This will appear, he says, from what follows; for just as he who judges that certain things are different says some one thing, as for example, that the good and bad differ, so too is the instant the same in which he says they differ. For he says that they are different at that time when he is judging. And this now is not accidental, such as when the time refers to the speaker, as now saying that they are different (and not that there is now a difference)—for this now would be merely accidental to the object—whereas the judgment of difference is in the present in the sense that there is difference at present, which necessarily implies a simultaneous apprehension of the two different objects; they are both known in the same instant as they are known to be different. Obviously, then, they are known at once and together. Hence, just as one undivided power perceives each of the things among which it judges the difference, so too in an indivisible time both are apprehended.

606. However, he now poses an objection to himself; concerning which he does four things.

First, he states the objection, as follows. But it is impossible for one and the same indivisible thing to move in different directions in one and the same indivisible moment of time (426b29). But the intellect and the senses are moved by the sensible and the intelligible insofar as they are sensing and understanding; now, distinct and mutually exclusive sense-objects move by distinct and mutually exclusive movements; therefore one and the same sensitive or intellectual power cannot know distinct and mutually exclusive objects at the same time.

607. Second, at therefore what (427a2), he suggests the following solution. That which judges the difference between contrary and diverse things simultaneously is numerically indivisible and inseparable, that is, it is one in subject; but in being, and therefore in its account, it is distinct. Therefore, it is in one way capable of multiplicity because it perceives things divided, that is, as diverse, but in another way the indivisible senses distinct objects; for in its being, that is, in its account, it is diverse, but it is indivisible locally and numerically, that is, it is one in subject. He says, locally, referring to the fact that different powers are found in different parts of an organic body.

608. Third, at or this is not possible (427a5), he rejects this solution by saying that this position cannot stand. For if a thing really is one and the same indivisible in subject, but not in its very being or account, it can indeed hold contrary states, in potency, but that it hold contraries in its activities, that is, in act, it must be divisible. One and the same indivisible thing cannot be white and black at the same time in the same respect; nor, for the same reason, can it receive the species of both, white and black objects. And the same is true of understanding and sensing, if this is how understanding and sensing occur, that is, by a certain being acted upon.

609. Fourth, at but it is just as (427a9), he gives the true solution, using the likeness of a point.

For any point between two parts of a line can be regarded either as one or two. It is one as continuing the parts of the line that lie on either side of it, as a common terminus. It is two inasmuch as we use the point twice, that is, as the beginning of one line and as the end of the other.

In this way one should understand that the power of sensing flows to the organs of all the five senses from one common root, from which goes forth the capacity of sensing in all the organs and to which all the modifications of the individual organs are terminated. Therefore this can be regarded from two points of view: either as the one principle and terminus of all sensible modifications, or as the principle and terminus of this and that sense.

And so he says that just as a point is as one or as two, and in this sense it is divisible, so too with the common sensitive principle. It is divisible insofar as it uses the same point twice, that is, the sensitive principle as the principle and terminus of sight and hearing.

610. Insofar as this single principle uses the terminus as two, insofar as it judges two things and they have been separated, which things are taken as separate, that is, divisible, they are known by the principle; yet insofar as it is one in itself, that is, by one principle, it knows their differences simultaneously. Therefore this common sensitive principle has the power to know several objects simultaneously inasmuch as it is taken twice, as the term of two sensible modifications. But inasmuch as it is one, it is able to judge the difference between one and the other.

611. Now, because the sensitive part has no activity without an organ, this common sensitive principle must have its organ; and since the organ of touch is all over the body, it seems necessary that, wherever the primary root of the organ of touch may be, there also is the organ of the common sensitive principle. It was with this in mind that Aristotle has said that if flesh were the fundamental organ of touch, we should discriminate between various sense-objects by merely touching things with our flesh.

612. We may note also that though this common principle is modified by the proper senses because the modifications of all the proper senses reach all the way to the common sense as to their common terminus, nonetheless the proper sense is not nobler than the common sense, even though a mover is nobler than what is moved, and an agent than what it acts upon. Nor is the exterior sensible object nobler than the proper sense moved by it, though it does move it; for it is nobler in a certain respect, that is, insofar as it is actually white or sweet whereas the sense is so potentially. But simply speaking, the proper sense is nobler on account of the sensitive power; this is also why it receives in a nobler way (that is, without matter), for every receiver receives something according to its own mode. And in this way too the common sense receives its object in a still nobler way than does the proper sense, because the sensitive power is considered to be in the common sense as in its root, and as less divided.

Yet we must not suppose that the species are received in the organ through some action of the common sense; for all powers of the sensitive part are passive, and no power can be both active and passive.

613. Observe too that each proper sense is able to discriminate between contrary sense-objects in virtue of its share in the power of the common sense; for each is one of the terminal points for the various modifications that reach us from mutually exclusive exterior sense-objects through a medium. But the final judgment and discrimination belong to the common sense.

614. Concluding, he says that he has now discussed the principle by which we call any animal (427a15) sensitive, or able to sense.