Lecture 26 — Sensing sensation

Since, however, we do sense that we see and hear, we must sense that we see either by sight or by another sense.

And if by another sense, then either we see by this or by a different one. But if it is the same, one sense will bear on both sight and the subject of color.

Hence, either there will be two senses for one object or one sense must be its own object.

Further, if the sense of sight itself is other, either there is a process to infinity, or there must be some sense that is judge of its very self; hence it is better to admit this in the first instance.

Here is a problem: if to sense by sight is to see, and color, or what possesses it, is what is seen, then if someone is seeing that he is seeing, the first thing seeing will have a color.

It is clear, then, that to sense by sight has not only one meaning. For even when we are not seeing, it is by sight that we distinguish between light and dark, though not in the same way.

Moreover, that which sees is, in a way, colored; for each sensitive power is receptive of the sense-object without matter. Hence, in the absence of the sense-objects, there remain sensations and phantasms in the sense-powers by which we sense. The act of the sense-object and the sensation are one and the same; but these—I mean, for instance, sound in act or hearing in act—are not identical in their being. For it happens that what has hearing does not hear all the time, and what has sound is not always sounding. But when that which is able to hear is active, and that which is able to sound sounds, both hearing in act and sound in act arise simultaneously (of which two, one might call one hearing, the other sounding).

If, then, movement and action and passion are in that which is acted upon, it follows that sound and hearing in act reside in that which is these potentially. For the act of what moves or causes comes to be in what is acted upon; hence it is not necessary that what moves it be itself in motion. The act of the sound-producing or the sound is therefore the sounding, and the act of the hearing power or hearing is audition. For hearing and sounding are both twofold.

And the same reasoning applies to the other senses and their objects. For as the action and the passion are in the recipient, not in the agent, so the act of the sense-object and of the sense power are in the sensitive power. However, whereas both are named in some cases (as sounding and hearing), in others, one or the other is nameless. Vision is the act of sight, but the act of color has no name; and tasting is the act of the tasting power, but the act of flavor has no name.

Since the act of the sense-object and of the sense power is one and the same (though they are different in being), it is necessary that they pass away or remain simultaneously, as in the above-mentioned case of hearing and sounding; and, therefore, of taste and flavor and the rest. It is not, however, necessary to hold this of the potency.

But on this point the earlier natural philosophers did not speak well, holding that there was no black or white without sight, no flavor without taste. In one way, what they said was right; in another, wrong. Inasmuch as both the sense-object and the sense power exist in two ways, one in potency, the other in act, what they alleged applies to the latter, but not to the former. But they spoke simply about matters that are not simple.

Now, if voice is a harmony of some sort, and voice and the hearing of it are somehow one and also, somehow, not one and the same, and if harmony is a proportion, then the hearing must be a kind of ratio. For this reason anything excessively shrill or deep destroys the hearing; and the same in flavors destroys the taste; and in colors, the sight, whether the excessively brilliant or the dark; and in smell, a strong odor, whether sweet or bitter; as if the sense were a certain ratio.

Hence, too, those flavors become delectable which, from having been pure and unmixed (e.g., the sour or sweet or saline) are brought into a ratio. Then indeed they give pleasure.

And in general, what is compounded is more of a harmony than the sharp or low sounds alone; or in the case of touch, what can be both heated and chilled. Sense is a ratio which is hurt or destroyed by extremes.

584. Since, however, we do sense that we see and hear (425b12). Having shown that there are no more than five proper senses, the Philosopher next proceeds to ask whether there is some sensitive power common to these five senses. He is led to ask this by observing two activities that do not seem to belong to some proper sense but seem to require some common sensitive power; there are two actions of this sort.

One activity is that according to which we perceive the acts of the proper senses, for example, we sense our own seeing and hearing;

the other is that according to which we distinguish between the objects of the different senses, for instance, that sweet is other than white.

So he first inquires into the source of the former activity;

and second, at each of the senses, then (426b8; [599]), he inquires into the source of the latter.

The former inquiry divides into three parts.

First, he states the problem, saying that the fact that we do sense our own seeing and hearing and so forth implies either that sight (for example) is able to see its very seeing or that some other power has this ability; and so also with the other senses.

585. Second, at and if (425b13), he brings objections against both these alternatives.

But first, he proposes two arguments to show that it is sight that sees its own seeing.

First, if a man senses his seeing not by sight but by another sense, then either this will be because a man sees color by that other sense, or by a totally different sense he sees color and senses the sight of color. But if by the same sense whereby one senses color he senses the sight of color, then the act of one and the same sense will be of sight in act, that is, of seeing, and of the subject of color.

Hence follows one of two consequences. For if this sense that senses sight and color is a different sense than sight, then there are two senses with the same subject, namely, color; or if the sense whereby we sense sight and color is the same as sight, it must be its own object, that is, sight is the sense of its very self, which was denied from the beginning. Now, to say that that other sense whereby one senses his seeing does not sense color is altogether unreasonable; for if it should not know color, it would not be able to know what seeing is; for seeing is nothing other than sensing color.

586. The second argument begins at further (425b15). If the sense of sight (that is, of seeing, whereby we sense that we see) is other than sight, then one must ask whether that sense also senses its own sensing; and if it does not, then there must be a third sense that senses that sensing. And either there is a process to infinity—which is impossible, both because no action could ever be completed which depended on an infinity of actions, and because no single reality can possess an infinite number of powers—or we have to come to some sense that is judge of its very self, that is, it perceives its own sensation. Therefore, by the same reasoning, it will happen in the first sense, that is, such that sight would sense its seeing; therefore there is no other sense that perceives color and that perceives the sight of color.

587. Then, at here is a problem (425b17), he puts an objection from the other side in the form of a difficulty; and because the first arguments in a way reach the truth, this argument he proposes in the manner of a doubt and then solves it.

The objection runs thus. If by sight we sense our seeing, but to sense by sight is nothing other than seeing, then we see our seeing. But nothing is seen except color or what possesses color; if, then, one is seeing about himself that he is seeing, it follows that the first seeing (that which is subsequently seen) has a color; and that would seem incongruous, for it was said above that sight, since it receives color, is colorless. (Lect. 15, n. 427.)

588. Next, at it is clear, then (425b20), he answers this difficulty in two ways.

In the first place, it is clear from what has been said that to sense by sight can mean different things—for it was shown above that we sense by sight that we are seeing, and again, it was shown that we sense by sight only color; and this gives two distinct senses of “to sense by sight”:

in one way, according to which we sense by sight that we see, and in another way when we see color by sight. And because “to sense by sight” is said in different ways, from this it is clear that we sometimes say that we sense by sight when, at the present moment, the sight is actually being impressed by the visible object, namely, color, but we can also sometimes mean that it is by sight that we distinguish between light and dark, even when we are not seeing through an impression from an exterior sensible object.

But “to sense by sight” does not mean the same thing in both cases. So what this solution comes to is this: that the act of sight can be regarded either as the modification of the sense organ by an exterior sensible object, and in this sense, only color is seen (so by this action sight does not see its seeing); or, as the act of sight insofar as, after the modification of the organ, it makes a judgment about the very perception of the organ coming from the sensible object even in the absence of the sensible object (and in this way, not only color is sensed, but so is the sight of color).

589. Then, with moreover, that which sees (425b22), he proposes his second answer to the difficulty. This answer is required by the fact that color has two modes of being: a natural mode in the sensible thing, and a spiritual mode in the sense. The former solution proceeded according to the first being of color; this one proceeds in reference to the second being of color. And here he does three things:

First, he sets out the solution;

second, at if, then, movement (426a2; [592]), he proves what the solution assumes;

third, at since the act (426a15; [594]), he applies it to the solution of certain other problems.

590. First, then, he says that while one solution of the difficulty was found by maintaining that the subject seeing color was not colored, moreover, it might be argued on the assumption that that which sees color is, in a way, colored because a likeness of color is in the one who sees, so the thing seeing is like the colored object. This is why the power by which one sees one’s own seeing is not outside the genus of the power of sight. That the one who sees is, in a sense, colored, he then proves from what was said above, that is, that organ of the sensitive power is receptive of the species of the sense-object without matter; this is why, in the absence of the sense-objects, there arise within us sensations and phantasms, that is, images, in reference to which animals in a way sense things. (Lect. 15, n. 427; lect. 24, nn. 551–54.) So it is clear that the one who sees is, as it were, colored insofar as he holds the likeness of a color; and not only is sight, as it were, colored and like what is colored, but also the act of any sensation is one and the same as the act of the sensible object as such, but they are not one in account.

591. I say, “the act of sense,” meaning, for instance, hearing in act, and “the act of the sensible object,” meaning sound in act. For the two are not always in act: what has hearing does not hear all the time, and what has sound is not always sounding; but when that which is able to hear has its own activity, and that which is able to sound sounds, both hearing in act (which is called “hearing”) and sound in act (which is called “sounding”) arise simultaneously. Since, then, sight perceives the sensible object and the latter’s actuality, and the one who sees is assimilated to the object, and the act of seeing is the same as the underlying actuality of the sensible (although not in account), it follows that one and the same power sees the color and the impression that comes from the color, and the thing seen in act and our sight of it. The power, then, by which we see our seeing is not external to the power of sight, though it differs from it in account. (See ST I.78.4, ad 2.)

592. Next, where he says, if, then, movement (426a2), he proves his assumption that the act of the sensible object and the act of the one sensing are one and the same, but they differ in account, based on things shown in Physics 3, in which it is proved that movement and action and passion are in that which is acted upon, that is, in the patient and the mobile. (Aristotle, Physics 3.3, 202a13–b22; cf. Aquinas, Commentary on Physics, bk. 3, lect. 5.)

Now, hearing is obviously acted upon by sound. Therefore, sound in act, which is called “sounding,” and hearing in act, which is called “audition,” reside in that which is these potentially, in the organ of hearing; and this because the act of what moves or causes comes to be in what is acted upon, not in the agent and mover. This is why it is not necessary that every mover be itself moving (for that is moving which has the movement, so if the movement or action, which is a sort of movement, were in the mover, the mover would also be moving). And as in the Physics, it was said that action and passion are one actuality of the subject, though they differ in account insofar as action is signified as from the agent, but passion is signified as in the patient, so here he says that the act of the sensible object and that of the sentient subject are one in subject, though they differ in account. (Aristotle, Physics 3.5, 202b19–22.) Therefore the act of the sound-producing or of sound is sounding, while the act of the hearing power is audition.

593. For both hearing and sound can be regarded either as in act or as in potency; and what has been said of hearing and sound in this connection applies to the other senses and their objects. For as the action and the passion are in the recipient, not in the agent as in a subject, but only as in the principle from which the act arises, so too, the act of the sense-object, no less than the act of the sense power, is in the sensitive power as in its subject. However, a distinct word is used for each act, as when the act of the object is called sounding and that of the power is called hearing; in others only the act of the power is named. Vision is the act of sight, but the act of color has no name; and tasting is the act of the tasting power, but the act of flavor has no name in Greek.

594. Then, at since the act (426a15), he uses the foregoing solution to answer two more questions.

First, do the sense power and its object together cease and together remain in being? Answering this, he observes that, since the act of the sense-object and of the sense power is one in subject, though distinct in account (as has been said), therefore actual hearing and actual sounding must simultaneously cease to be and together persist; and so also with savor and tasting and the rest. But the same is not necessarily true of the powers and objects as in potency.

595. This leads him to reject an opinion of some early natural philosophers. The earlier natural philosophers did not speak well (426a20), he says, in supposing that there was no white or black except when it was seen, no savor except when it was tasted, and so forth. And because they thought that nothing existed except what was sensible and that the only knowing was sensation, they concluded that the whole being and truth of things was a mere appearance; and further, that contradictories could both be true at the same time, because different people opined contradictory things.

596. Now, this is in a certain way right and in a certain way wrong. For the sense and the sense-object can be taken in two ways, as in potency and as in act. From the point of view of the sense and the sensible in act, what they said applies: there would be no sense-object without sensation. But it is not true from the point of view of the sense and the sensible in potency. They spoke simply, that is, without distinguishing, about matters that call for many distinctions.

597. Then, where he says, now, if voice (426a27), he applies these principles to solve another problem: why are certain sensible objects destructive of the senses, while others delight them? And he says that since a harmony, that is, consonant and proportionate voice, is a voice, and voice is in a way one with the hearing, the fact that harmony is a certain proportion necessitates that hearing must be a certain proportion. Now, because every proportion is destroyed by excess, an excessive sense-object is therefore destructive of the sense; for example, what is excessively shrill or deep destroys the hearing; an excessively tasteable thing destroys taste; excessively brilliant or dark objects destroy the sight; strong odor destroys the sense of smell, as though the sense itself in each case were a certain proportion.

598. On the other hand, if several sensible objects are mixed in due proportion, the effect is delectable. Thus, in flavors, when something sour or sweet or salty is mixed in a due proportion, it is extremely delectable. And what is compounded is more pleasant than what is simple, as a harmony more than merely the high voice or only the low voice. So, too, in touch, with the combinations of hot and cold. For the sense power delights in proportionate things, as in its like, being itself a certain proportion. But extremes destroy the sense, or at least hurt it.