Lecture 17 — Simultaneous sensation continued

Moreover, if movements of contraries are contrary; and contraries cannot simultaneously be in the same atomon; and there are contraries, for instance, sweet and bitter, under one sense power—then one cannot sense them simultaneously.

But likewise, clearly, neither can one simultaneously sense objects that are not contraries. For some belong to white and some to black. And likewise in other cases: for instance, some flavors belong to sweet and some to bitter.

Nor can one simultaneously sense mixtures, for the proportions belong to opposites, for instance the octave and the fifth; unless they are perceived as one, but thus one proportion is made of the extremes, but otherwise not.

For there will be simultaneously many to few, or odd to even, or few to many, or even to odd.

If, then, the so-called “corresponding elements,” which are in different genera, stand apart and differ from one another still more than do objects in the same genus (I call sweet and white, for instance, corresponding elements in different genera, and sweet differs specifically from black much more than white does); then one can sense these simultaneously still less than those in one genus. So if not the former, then neither the latter.

Some of those who discuss symphoniae say that sounds do not arrive simultaneously, but they seem to, and it escapes notice, since the time is insensible. Is it correct to say this or not? Perhaps someone will say that it is also because of this that one thinks that he simultaneously sees and hears, namely because the intervening lengths of time escape notice.

Or perhaps it is not true that any length of time can be insensible or escape notice: rather, absolutely all of them can be perceived.

For if, when one senses oneself or something else in a continuous length of time, it cannot escape his notice that it is existing; and something is existing in a continuous length of time; and it is so brief as to be completely insensible; it is clear that it will then escape his notice whether he himself is existing, and that he is seeing, and that he is sensing, and whether he is sensing.

Moreover, there will be no length of time (and no thing that one senses) during which it is not the case that it is being sensed in some part of it (or that one sees some part of the thing)—if indeed there is some magnitude of time and of a thing that is insensible because of smallness.

For if one is seeing and sensing the whole during the same continuous length of time not because one does so in some part of it—then let GB, in which it was not being sensed, be subtracted. Accordingly, one does not sense “during a part of it,” or “a part of it,” in the way that one sees the whole earth because one sees a part of it, and one walks during a year because one does so during this part of it.

Rather, one senses nothing in GB. Therefore, it is because one senses it in a part, namely AG, that one is said to sense the whole of AB, and the whole thing. But the same account also applies to AG: it is always a case of “during a part of it,” and “a part of it,” and it is impossible to sense the whole of AGB.

All things, then, are sensible, but do not appear to be everything that they are: the size of the sun appears from far away to be four cubits. A thing does not appear to be everything that it is: rather, sometimes it is indivisible, but one sees what is not indivisible. The cause of this has been stated in the foregoing.

Therefore, it is clear from these remarks that no length of time is insensible.

265. Moreover, if movements of contraries (448a1). Having presented two arguments to show that it is impossible for two senses to sense simultaneously, here he presents a third argument for the same conclusion based on the contrariety of sensible objects.

He says that alterations caused by contraries are contrary, for instance heating and cooling. But contraries cannot simultaneously be in the same “atomon”—that is, the same indivisible part (contraries can simultaneously be in the same divisible part with respect to different parts of it). But it is clear that objects under one sense power are contraries, for instance sweet and bitter. Therefore they cannot be sensed simultaneously.

266. The argument is similar in the case of objects that are not contraries, that is, intermediate objects, some of which more closely approach one extreme, and some the other. For instance, as was said above about colors and flavors, some intermediate colors pertain to white and some to black, and likewise some intermediate flavors pertain to sweet and some to bitter. (Cf. ch. 6, nn. 97–100; ch. 10, nn. 148–61.)

And the argument is the same in the case of all mixtures, for different mixtures have a contrariety between themselves because they are made in different proportions, and different proportions have an opposition to one another. This is clear in harmonies: one is called the octave, which consists in the double proportion, that of two to one; another is called the fifth, which consists in the sesquialteral proportion, that of three to two. Such things, I say, thus mixed together in different proportions, cannot be simultaneously sensed, because of the opposition between proportions—unless, perhaps, two are perceived as one, because thus one proportion will be made out of two extremes.

267. Next he shows that different proportions are opposed according to the two kinds of opposition found in numbers. One is according to many and few, by which the proportion of double and the proportion of half are opposed: for the proportion of double is one of many to few, but the proportion of half is one of few to many. The other kind of opposition is according to even and odd, by which the double proportion and the sesquialteral proportion are opposed: for the double proportion is one of two to one, that is, of even to odd, but the sesquialteral proportion is of three to two, that is, of odd to even.

268. Thus it is clear that objects falling under the same sense cannot be sensed simultaneously. But objects that correspond to one another as “corresponding elements” existing in different genera—for instance sweet and white—stand farther apart from one another than do objects belonging to one genus. For objects belonging to one genus, such as white and black, are specifically distinguished only because of the manner of sensing.

But objects belonging to different genera can differ specifically not only from the point of view of the sense power, but also from the point of view of the manner of sensing: for instance, sweet differs from black more than white does. Hence they are less able to be sensed simultaneously, which is, as it were, to be numerically one, as was established above. (1.7, 447b24–25; cf. ch. 16, nn. 260–64.) Therefore, if objects belonging to one genus cannot, because of their contrariety, be sensed simultaneously, much less can objects belonging to different genera be sensed simultaneously.

269. Then when he says some of those who discuss symphoniae (448a19), he eliminates a false solution of this question.

First, he relates it.

Second, he disproves it, where he says or perhaps it is not true (448a24; [270]).

Accordingly, he first says that some who treated of “symphoniae”—that is, musical harmonies—said that the harmonizing sounds do not reach the sense of hearing simultaneously, but that they seem to reach it simultaneously because the intervening time is insensible on account of its brevity. There might be doubt about this: is it correct to say this or not? If it is correct, someone who agrees with the arguments presented above will be able to say that, likewise, with respect to the question posed, it is not possible to simultaneously see and hear, although this does seem to the sense power to happen, because the intervening lengths of time between the vision and the hearing escape our notice.

270. Then when he says or perhaps it is not true (448a24), he disproves the above-mentioned solution. On this point, he does three things.

First, he eliminates something that the solution stated presupposes.

Second, he proves what he has said, where he says for if, when one senses oneself (448a26; [271]).

Third, he clarifies what is true in the solution, where he says all things, then, are sensible (448b12; [278]).

Accordingly, he first says that something that the solution stated presupposes is not true, namely that there is a length of time that is insensible, or escapes the notice of the sense power. For no length of time is like this: rather, all lengths of time can be sensed.

271. Then when he says for if, when one senses oneself (448a26), he proves what he has said by two arguments.

Concerning the first of these, we must consider that time is not sensed as a permanent thing presented to a sense power in the way that color or size is presented to sight. Rather, time is sensed because something that is in time is sensed. It follows, then, that if there is some length of time that is insensible, what is in that length of time is insensible.

Accordingly, he says that if at some point, in some continuous length of time, a human being senses that he himself is existing, it cannot escape his notice that that length of time is existing. Now it is clear that the human being, or the something else, is existing in some continuous length of time. And however brief you say the insensible length of time is, it is clear that it will escape the human being’s notice that he himself is existing during that time, and it will escape his notice that he is seeing, or sensing, during that time, which is entirely unreasonable. Therefore it is impossible for a length of time to be insensible.

272. He presents the second argument where he says moreover, there will be no length of time (448a30).

Concerning this it must first be considered that, as the Philosopher says in Physics V, a thing is said to move or be moved in three ways:

in one way accidentally, for instance, if we say that the one who is musical is walking;

in another way with respect to a part, for instance, if we say that a man is healed because his eye is healed;

and in a third way primarily and per se, that is, when a thing is moved or moves not because just one part of it is moved or moves, but because the whole is moved with respect to every one of its parts. (Aristotle, Physics 5.1, 224a21–34; cf. Aquinas, Commentary on Physics, bk. 5, lect. 1.)

Likewise, a thing can be said to be sensed in three ways:

in one way accidentally, as, for instance, what is sweet is seen;

in another way with respect to a part, for instance, if we say that a man is seen because just his head is seen;

and in a third way primarily and per se, that is, not because just some part of it is seen.

273. Accordingly, he says that if there is some magnitude—whether of time, or of a bodily thing—that is insensible because of smallness, what will follow is this: there will be no length of time and no thing that one senses (i.e., no thing that is sensed, or that a sense power senses) during which (i.e., during which length of time) it is not the case (i.e., during which the time is not being sensed) because it is being sensed in some part of it.

In other words: there will be no length of time that is sensible “primarily,” i.e., that is not said to be sensed because some part of it is being sensed. And with reference to the bodily thing he adds or because one sees some part of the thing. In other words: there will be no bodily magnitude that is not sensed because some part of it is sensed, which means that no bodily magnitude is sensible “primarily.”

274. To prove what he has said he adds that if someone sees, or senses by any sense, during some continuous length of time not by reason of a part of the time or magnitude; and nevertheless some magnitude and length of time are held to be insensible because of smallness; then let there be a magnitude—whether of time or of a bodily thing—namely AGB, and let the part of it that is the GB be insensible because of smallness. Accordingly, it cannot be said of this part that is insensible because of smallness that it is sensed “in a part of it”—if it is an insensible length of time—or that “a part of it” is sensed—if it is an insensible body—as the whole earth is said to be seen by someone because a part of the earth is seen, and as someone is said to walk during a year because he walks during a part of the year. Therefore, because one senses nothing in GB, it remains that one is said to sense the whole of AB—whether it is a time or a body—because the whole of AB is sensed in the part of it that is left, namely AG.

275. And the account of the magnitude AG, which is held to be sensed, is the same, because a part of it will be insensible because of smallness. And so anything sensible will always be said to be sensed because it is sensed in a part of it—if it is a length of time—or because a part of it is sensed—if it is a body. But it will be possible to sense nothing whole, such as AGB.

But this seems unreasonable. Therefore there is no length of time or body that is insensible because of smallness.

276. But this argument does not seem to work. For a thing is sensed because it has power to alter a sense. Now it is proved in Physics 7 that if some whole moves something moveable in some length of time, it need not be the case that a part of the whole moves the moveable thing in any length of time. (Aristotle, Physics 7.5, 250a12–19; cf. Aquinas, Commentary on Physics, bk. 7, lect. 1.) But although no part of the whole, perhaps, could cause the movement, nevertheless, the whole that causes the movement is said to be the first mover. Likewise, it seems, one could say that a thing can be sensible “primarily” although some parts of it are insensible because of smallness.

277. In response to this it must be said that there is a difference between speaking of a part existing in a whole and a part separated from a whole. If a part of what primarily causes movement is separated, it may not be able to cause movement. But if, while existing in the whole, it did not cooperate in the power to move of the whole, but completely lacked power to move, it would follow that the whole would be the mover not “primarily,” but by reason of the part to which power to move does belong.

Likewise, too, nothing prevents a part taken separately from escaping the notice of a sense power because of smallness, as was established above, while nevertheless, the part as existing in the whole does fall under the sense power inasmuch as the sense power is brought to bear on the whole, with no part left out.

278. To address this doubt, next, when he says all things, then, are sensible (448b12), he shows what is true in the foregoing. He says that all things, whether big or small, are sensible, but do not appear to be everything that they are, that is, they do not appear as they are in every way. This is clear in the case of the sun, the size of which is far greater than that of the earth, and nevertheless, because it is far away, it appears to be four cubits in size, or even smaller. Likewise, although all things are sensible by their nature, nevertheless an object does not appear in actuality to be everything that it is.

279. Rather, sometimes it is indivisible, but one sees what is not indivisible. This can be understood in two ways.

One way is according as indivisible refers to some minimal natural body that cannot be further divided without being destroyed, and then absorbed into the surrounding body. Thus the meaning will be that an indivisible body is sensible in itself, although the sense power cannot see an indivisible object of this kind.

In the other way, indivisible can be understood as what is not divided off in actuality, for example a part of a continuum. The sense power does not see this kind of indivisible object in actuality.

What he adds fits either explanation: that the cause of this has been stated above, that is, in the determination of the first question. (Cf. ch. 14, nn. 208–23.) But the second explanation seems to be better, because by means of it the abovementioned objection is resolved, because any part whatsoever of a continuous magnitude is indeed sensed within the whole inasmuch as it is in the whole in potentiality, although it is not sensed in actuality as separate.

280. Finally he concludes that it is clear from (448b16) what has been said that no length of time is insensible.