Commentary Aristotle Physics
Lecture 10. The meaning of “void”
As a step towards settling which view is true, we must determine the meaning of the name.
The void is thought to be a place in which nothing exists. The reason for this is that people take what exists to be body and hold that, while every body is in place, void is place in which there is no body, such that, where there is no body, there must be void. Every body, again, they suppose to be tangible; and of this nature is whatever has weight or lightness. Hence, by a syllogism, a place in which there is neither a heavy nor a light body is void. This result, then, as I have said, is reached by syllogism.
It would be absurd to suppose that the point is void, for the void must be place that has in it an interval in tangible body. But, at all events, we observe, then, that the void is described in one way as what is not full of body perceptible to touch; and what has heaviness and lightness is perceptible to touch.
So, we would raise a question: what would they say of an interval that has color or sound—is it void or not? Clearly, they would reply that, if it could receive what is tangible, it was void, and if not, not.
In another way, void is that in which there is no “this” or corporeal substance. So some say that the void is the matter of the body (they identify the place, too, with this), but in this, they speak incorrectly. For the matter is not separable from the things, but they are inquiring about the void as about something separable.
Since we have determined the nature of place, and void must, if it exists, be place deprived of body, and since we have stated both in what sense place exists and in what sense it does not, it is plain that, on this showing, void does not exist, either unseparated or separated. The void is meant to be not body, but rather an interval in body. This is why the void is thought to be something, namely, because place is.
And this is for the same reasons. For the fact of motion in respect of place comes to the aid both of those who maintain that place is something over and above the bodies that come to occupy it and of those who maintain that the void is something.
They state that the void is the cause of motion in the sense of that in which motion takes place—and this would be the kind of thing that some say place is.
But there is no necessity for there being a void if there is motion. It is not in the least needed as a condition of motion in general, for a reason that, incidentally, escaped Melissus: the full can suffer qualitative change.
But not even motion in respect of place involves a void, for bodies may simultaneously make room for one another even though there is no interval separate and apart from the bodies that are in motion. And this is plain even in the rotation of continuous things, as in that of liquids.
And things can also be compressed not into a void, but because they squeeze out what is contained in them (as, for instance, when water is compressed, the air within it is squeezed out).
And things can increase in size not only by the entrance of something but also by qualitative change, such as if water were to be transformed into air.
In general, both the argument about increase of size and that about water poured on to the ashes get in their own ways.
For either not any and every part of the body is increased, or bodies may be increased otherwise than by the addition of body, or there may be two bodies in the same place (in which case they are claiming to solve a quite general difficulty, not proving the existence of void), or the whole body must be void, if it is increased in every part and is increased by means of void. The same argument applies to the ashes.
It is evident, then, that it is easy to refute the arguments by which they prove the existence of the void.
506. The Philosopher had said above that we must start with three things. So now, having finished two of them by giving the opinions both of those who posited and of those who rejected the void, he now enters upon the third by showing the general opinions people have about the void.
Concerning this, he does three things:
first, he shows what is meant by the word “void”;
second, he shows how some thought that the void exists, at “since we have determined” (214a16; [513]);
third, he rejects the reasons given by those who posit that a void exists, at “but there is no necessity” (214a26; [515]).
As to the first, he does two things:
first, he reveals his intention;
second, he executes it, at the void is thought (213b31; [520]).
507. He says first (213b30) that, since it was pointed out that some people affirmed a void and others denied it, in order to get at the truth, we must begin by the meaning of the word “void.” For just as we must begin by agreeing what a subject is when there is question about some passion existing in it, so when there is question about the existence of something, we must begin by taking as the middle term the meaning of the word. For the question of what something is comes after the question of whether it exists.
508. Then, at “the void is thought” (213b31), he shows what is meant by the word “void.”
First, he gives the more common meaning;
second, he gives what the Platonists took it to mean, at “in another way” (214a11; [512]).
As to the first, he does three things:
first, he shows what the word “void” means;
second, he shows what should be added to that meaning, at “it would be absurd” (214a4; [510]);
third, he clears up a doubt, at “so, we would raise” (214a9; [511]).
509. He says, therefore, that, according to common opinion, the void seems to signify nothing more than a place in which there is nothing. The reason for this is that, properly, that is said to be a void in which there is not any body, and since only a body can be in place, void seems to mean nothing more than a place without anything in it. But, because people suppose that every being is a body, it follows that, according to their opinion, where there is not body, there is nothing.
And, further, they believe that every body is tangible, that it has tactile qualities. And a body of this kind is heavy or light—for in their time, it was not yet known that a heavenly body is different in nature from any of the four elements. Hence, since it is in the very account of the void to be a place in which there is not a body, it follows that the void is that in which there is neither a light nor a heavy body. However, this is not to say that it belongs to the account of the void according to the primary meaning of the word, but rather by reason of a certain syllogistic deduction that starts with the general opinion of people that every body is either heavy or light, just as the common opinion of people that every being is a body leads to the conclusion that the void is that in which there is nothing.
Consequently, this word “void” has three meanings.
One is proper: void is place in which there is no body.
The others come from the general opinion of people:
the first of these others is more common, namely, that the void is a place in which nothing exists;
the second is more restricted, namely, that the void is a place in which there is neither a heavy nor a light body.
510. Then, at “it would be absurd” (214a4), he shows what must be added to this meaning. For he says that it is not correct to say that a point is a void, even though there is no tangible body in a point. So, we must add that the void is a place in which there is not a tangible body, but in which there is space to receive a tangible body, just as a blind person is said to be one who lacks sight but is apt to have it. And, so, he concludes that, in one way, the void is called a space that is not filled by a body that is sensible by touch, that is, a body that is heavy or light.
511. Then, at “so, we would raise” (214a9), he clears up the following difficulty. If there is color or sound in a certain space, should it be called a void or not? This question arises because the definition first given says that the void is that in which there is nothing. And he answers by saying that, if the space in which there is just sound or color has room for a tangible body, it is a void; if not, then it is not. The reason is that the proper definition of the void is not that in which nothing exists, but such a definition is held only by people who believe that, where no body is, nothing is.
512. Then, at “in another way” (214a11), he gives the meaning of “void” as used by the Platonists. And he says that there is another meaning of the void: that in which there is no “this something” or any corporeal substance. Now, a “this something” comes about on account of the form. Hence, some claim that the matter of a body, insofar as it is apart from its form, is the void. These are the same who claim that matter is place, as was stated above. But this is poorly said, for matter is not separable from the things of which it is the matter, but men inquire about place and the void as being separable from bodies in place.
513. Then, at “since we have determined” (214a16), he tells how some posited the existence of a void:
first, what they said the void was;
second, why they posited it, at “and this is for the same” (214a21; [514]).
He says first that, since the void is a place without a body in it, and since we have already decided how place exists and how it does not (for we have said that place is not a space, but the boundary of a container), it is clear that the void is neither a space separated from bodies nor one that is intrinsic to them, as Democritus supposed. This is so because those who suppose that space exists in either of those two ways intend the void to be not a body but the space of a body. For they thought that the void was something because place was something, and just as place seems to be space, so also the void. But, if place is not a space outside of bodies, neither can the void be a space outside of bodies. And, since it is in the very account of the void to be a bodily space existing outside of bodies, as was said above, it follows that the void does not exist.
514. Then, at “and this is for the same” (214a21), he shows why they posited a void. And he says that they admitted the existence of the void for the same reason that they admitted place, namely, on account of motion, as we said above. For it comes about that local motion is saved both for those who assert that place is something over and above the bodies that are in place and for those who claim that the void exists. But, for those who deny place and the void, there cannot be local motion. Consequently, some believed that the void is a cause of motion in the way that place is, namely, as that in which motion takes place.
515. Then, at “but there is no necessity” (214a26), he rejects the arguments of those who posit existence of the void. But he does not intend here to give a true solution to the stated arguments, but rather to bring an objection that, at a glance, shows that their arguments do not conclude with necessity.
First, therefore, he rejects the reasons given by those who posit a separated void;
second, the arguments of those who posit a void existing in bodies, at “and things can also be” (214a32; [517]).
516. He rejects the first reason in two ways.
First, even though motion exists, it does not necessarily follow that the void exists. And if we speak generally of any species of motion, it is clear that the void is not necessary at all. For nothing prevents the full from being altered, since only local motion seems to be excluded if the void is not posited. Yet Melissus did not see this, for he believed that, if there were no void, no motion of any kind could exist.
Second, he rejects the same reason on the ground that not even local motion is destroyed if there is no void. For assuming that there is no separable space over and above moving bodies, local motion can take place if bodies make room for one another by contracting; thus, they would be moving into the full rather than into the empty. This is evident in the generations of continuous bodies, especially in liquids, such as water. For if a stone is thrown into a large surface of water, circles appear around the place of entry as long as one part of the moving water agitates another part and enters it. Hence, because a small portion of water enters a larger section by a process of diffusion, the circles grow from small to large until they cease entirely.
517. Then, at “and things can also be” (214a32), he rejects the reasons given by those who posit a void in bodies.
First of all, he rejects the reason based on condensation. And he says that bodies happen to become condensed and parts of a body mutually penetrate not because the invading part is entering an empty place, but because there were certain openings full of a more subtle body that escapes under condensation, just as, when water is compressed and contracted, the air that was present is expelled. This takes place manifestly in a sponge and other like porous bodies. Therefore, this solution does not give the reason for condensation, which he will give later, but it does show that the need of a void can be also clearly eliminated in this way.
518. Second, at “and things can increase” (214b1), he rejects the argument based on growth. And he says that growth occurs not only by the addition of some body invading the growing body so as to make the void necessary but also by alteration, as the quantity of air becomes greater than the quantity of water when air comes to be from water. This too is not the true solution of their argument, but merely an objection showing that it is not necessary to posit a void. The true solution is given in De generatione, where it is shown that food does not pass into that which grows as to be a body distinct from it; rather, it is converted into its substance, as wood added to fire is converted into fire.
519. Third, at “in general” (214b3), he rejects together both the argument about increase and that about water poured on ashes and says that each of these arguments blocks the other.
This is evident as follows. There is this difficulty in respect to increase: it seems either that the whole body is not being increased or that increase does not come about by the addition of body, but by the addition of something incorporeal, or that two bodies can be in the same place. Now, it is this difficulty, which seems to be against both those who posit a void and those who do not, that they wish to solve. But they do not show that the void exists, or, if increase is due to the void, then they would have to say that the whole body is a void, since the whole body is increased.
Likewise, in regard to the ashes, if a vessel full of ashes can take as much water as the empty vessel, then one has to say that the whole container must be a void. Therefore, this is not due to empty space but to being mixed in with the water. For when water is mixed with ashes it condenses and part of it evaporates; moreover, parts of the ash are condensed on account of the moisture, and a sign of this is that not as much water can be recovered as was put in.
Finally, he concludes that it is clearly easy to solve the arguments by which they prove the existence of a void.