Commentary Aristotle Physics
Lecture 4
In alteration and in increase and decrease, the mover and the moved are together
Neither is there an intermediary between the altered and the alterer. This is clear from induction. For in all cases the ultimate alterer and the first thing which is altered are together.
Quality is altered by that which is sensible. There are sensible things by which bodies differ from each other: as heaviness and lightness, hardness and softness, sound and no sound, whiteness and blackness, sweetness and bitterness, wetness and dryness, density and rarity, and their intermediaries. Likewise there are other things that are under the senses. These include hot and cold, smoothness and roughness. For these are passions of the subject of quality. In these the sensibilities of bodies differ insofar as one of these is more and less and is undergoing one of these: becoming hot or becoming cold, or becoming sweet or becoming bitter, or in respect to some other of the things mentioned. The same applies to both animate and inanimate bodies. And certain parts of animate bodies are inanimate. And the senses themselves are altered because they suffer. Their action is motion through the body, the sense suffering something. Animate bodies are altered in respect to all the things by which inanimate bodies are altered. But inanimate bodies are not altered in respect to the things by which animate bodies are altered. For they are not altered in respect to sense, and when inanimate bodies are altered, it is concealed from them.
Moreover, nothing prevents animate bodies also from being unaware when they are altered. For alteration not in respect to sense occurs to them. Therefore, if there are sensible passions, every alteration occurs through them. From this, therefore, it is clear that the passion and the patient are together, and there is no intermediary between them.
Moreover, air is continuous with this, and the body is contained by the air. And the surface is terminated at light, and light at sight. Hearing and smelling are similarly related to that which first moves them. In the same way, taste and flavor are together. And it is the same in both inanimate and insensible things.
And that which is increased and the increaser are together. For increase is a certain addition. For this reason, that which is increased and the increaser are together. And decrease: the cause of decrease is a certain subtraction.
It is clear, therefore, that there is no intermediary between the ultimate mover and the first thing moved.
909. After showing that the mover and moved are together in local motion, he shows the same for alteration, namely, that there is nothing between the thing altered and the cause of the alteration.
This he proves first by induction (244a25). For in all things that are altered, it is clear that the last thing altering and the first thing altered, are together. However, this seems to suggest a difficulty in certain alterations, such as when the sun heats the air without heating the intermediate orbs of the planets, or when a certain kind of fish held in a net shocks the hand of the one holding the net without shocking the net.
To this, it must be said that things that are passive undergo the action of things that are active in their own proper ways, and therefore the intermediate between the first cause of an alteration and the last thing altered undergo something from the first cause, but perhaps not in the same way as the last thing affected. For the net undergoes something from the fish that causes the shock, but not a shock, because it is not capable of being shocked. And the intermediate orbs of the planets receive something from the sun, its light, but not its heat.
910. Second, at “quality is altered” (244a27), he proves the same thing by an argument, which is this. Every alteration is similar to an alteration that affects a sense. But, in an alteration that affects a sense, the cause of the alteration and the thing altered are together. Therefore, the same is true in every alteration.
To prove the major premise, he says that every alteration takes place according to a sensible quality, which is the third species of quality. For bodies are apt to be altered in respect of those qualities by which bodies are primarily distinguished one from the other, in sensible qualities such as heaviness, lightness, hardness, and softness—which are perceived by touch—and sound and non-sound, which are perceived by hearing.
(However, if sound is considered in act, it is a quality of the air resulting from a local motion; consequently, it does not seem that there can be a primary and per se alteration according to a quality of this sort. But, if sound is taken in an aptitudinal sense, then it is through some alteration that something becomes soundable or non-soundable.)
There are also blackness and whiteness, which pertain to sight; sweetness and bitterness, which pertain to taste; and dryness, wetness, density, and rarity, which pertain to touch. The same goes for the contraries of these and for the intermediates. Likewise, there are others that are perceptible by sense, such as cold and heat and smoothness and roughness, which are apprehended by touch.
All these are passions contained within the genus of quality. And they are called passions because they produce a passion in the sense (that is, the senses come to be in the state of being acted upon) or because they are caused by certain passions, as is explained in the Categories.
But they are called passions of sensible bodies because it is in respect of these that sensible bodies differ, inasmuch as one is hot and another cold, one is heavy and another light, and so on, or inasmuch as some one of them is present in two things, more so in one thing and less so in another. Fire, for example, differs from water by reason of the difference of hot and cold, and from air according to more and less hot. Again, the difference of sensible bodies is based on the ability of some of them to receive one or the other of these qualities, although it not be in them naturally; for example, we say that heated objects differ from cooled objects and sweetened things from things made bitter not because they are so by nature, but because they have been acted upon by some passion.
The capacity to be altered in respect of qualities of these kinds is common to all sensible bodies, both living and non-living. And some parts of living bodies are animate, that is, capable of sensing, such as the eye and the hand, and some parts inanimate, that is, incapable of sensing, such as the hair and bones, yet in either case, all these parts are altered by qualities of this sort, because even the senses in sensing are acted upon. For the acts of the senses, such as hearing and seeing, are motions through the body and involve the sense being acted upon. For the senses have no action independent of a bodily organ, which is a body that is apt to be moved and altered.
Hence, passion and alteration are spoken of more properly in regard to the senses than to the intellect, whose operation does not take place through a bodily organ. Thus, it is evident that, according to whatever qualities and according to whatever ways inanimate bodies are altered, animate bodies are altered according to the same qualities and in the same ways, but not vice versa. For an alteration is found in animate bodies that is not found in inanimate bodies, that is, the one according to sense.
For inanimate bodies do not perceive the alterations they undergo—something that would not be if they were altered in respect of sense. Lest anyone believe that it is impossible for something to be altered with respect to a sensible quality without a sensation of the alteration, he adds that this is true not only in inanimate things but also in the animate. For there is nothing to prevent living bodies from not perceiving that they are being affected by a quality, as when something happens in them without the sense being affected, such as when they are altered in regard to non-sensitive parts.
From this, therefore, it is evident that, if the passions of the senses are such that there is nothing intermediate between the agent and the patient, and if it is true that every alteration takes place through passions by which senses are apt to be altered, it follows that the cause of an alteration (when it is producing a passion) and the object acted upon are together, and there is nothing intermediate between them.
911. Then, at “moreover, air is continuous” (245a22), he proves a second point: in alterations of the senses, the altering cause and the sense affected are together, because the air is continuous with this, namely, the sense (for example, sight)—they are in immediate contacts just as the visible body is in contact with the air. Indeed, the visible body’s surface, which is the subject of color, is terminated at light—that is, at air that is illumined, which is terminated at the sense. And, so, it is evident that the altered air and what alters it are together, as are the altered sight and the air that alters sight. The same is true in hearing and in smelling, if you relate them to the first mover—namely, the sensible body, for these two senses are affected by an extrinsic medium. But taste and its object are together, for they are not joined by means of an extrinsic medium, and the same goes for touch. Consequently, it remains that inanimate and insensible things are related in the same way, that is, the cause of alteration and the thing altered are together.
912. Then, at “and that which is increased” (245a26), he proves the same thing for the motion of growth and decrease.
He proves it first in the motion of growth. For the cause of increase and the thing that is increased must be together, because growing is a kind of adding to a quantity being increased by adding to it another quantity. The same is true of decrease, because the cause of decrease is the taking away of some quantity.
Now this proof can be understood in two ways.
In one way, it can mean that the very quantity added or taken away is the immediate mover in these motions, for Aristotle says in De anima 2.4 that flesh increases because it is quantified. Thus, it is clear that the mover and the moved are together, for nothing can be added or taken away from something unless it be together with it.
In another way, this argument can be understood in terms of the principal agent. For adding is a type of gathering and subtracting a type of scattering. But it was proved above that, in the motions of gathering and scattering, the mover and the moved are together. Hence, what remains is that, even in the motion of growth and decrease, they are together.
In this way, then, he concludes universally that there is nothing between the last mover and the first moved.