Commentary Aristotle Physics
Lecture 7. What things are in place simply
If, then, a body has another body outside it and containing it, it is in place, and if not [thus contained], [then] not.
That is why, even if there were to be water that had not a container, the parts of it, on the one hand, will be moved (for one part is contained in another), while, on the other hand, the whole will be moved in one sense but not in another.
For as a whole, it does not simultaneously change its place, though it will be moved in a circle. For this place is the place of its parts. (Some things are moved not up and down, but in a circle; others up and down—namely, such things as admit of condensation and rarefaction.)
As was explained, some things are potentially in place, others actually. So, when you have a homogeneous substance that is continuous, the parts are potentially in place; when the parts are separated but in contact, like a heap, they are actually in place.
Again, some things are in place per se—every body that is movable either by way of locomotion or by way of increase is per se somewhere—but the heavens, as has been said, are not anywhere as a whole, nor in any place, if at least, as we must suppose, no body contains it. On the line on which it is moved, its parts have place: for each is contiguous to the next.
But other things are in place indirectly, through something conjoined with them, as the soul and the heavens. The latter is, in a way, in place, for all its parts are; for on the orb, one part contains another.
That is why the upper part is moved in a circle, while the all is not anywhere. For what is somewhere is itself something, and there must be alongside it some other thing wherein it is and that contains it. But, alongside the all or the whole, there is nothing outside the all, and for this reason, all things are in the heavens; for the heavens, we may probably say, are the all.
Yet their place is not the same as the heavens. It is part of it, the innermost part of it, that is in contact with the movable body, and for this reason, the earth is in water, and this in the air, and the air in the ether, and the ether in heaven—but we cannot go on and say that the heavens are in anything else.
472. After defining place, the Philosopher now shows how something exists in place.
About this, he does two things:
first, he shows how something is absolutely in place and how not;
second, he shows how a thing not absolutely in place is in place in a certain respect, at “that is why” (212a32; [481]).
473. Therefore, he first (212a31) concludes from the foregoing that, since place is the boundary of the container, whenever a body has another body outside it and containing it, it is in place absolutely and per se. But, if such a body does not have an external body containing it, it is not in place at all. The only body in the universe that exemplifies this second case is the outermost sphere, whatever it may be. Hence, according to this definition, it follows that the outermost orb is not in place.
474. But this seems to be impossible, because the outermost sphere is in motion in place, and nothing is moved in place unless it is in place.
Now this difficulty does not arise for those who hold the opinion that space is place. For they are not forced to say that, in order to be in place, the outermost sphere must have a body containing it. Rather, the space penetrating the entire universe and all its parts is the place of the entire universe and of each of its parts, according to these philosophers. But this position is impossible, for one must admit either that place is not distinct from the thing in place or that space has dimensions existing per se but yet penetrating the dimensions of sensible bodies—both of which positions are impossible.
475. Therefore, Alexander said that the outermost orb is not in place at all, for it is not necessary for every body to be in place, since place is not in the definition of body. For this reason, he held that the outermost sphere is not in motion in place, neither as a whole nor as to its parts.
But, since every motion must fit into one of the genera of motion, Avicenna, following him, said that the motion of the outermost sphere is not motion in place, but motion in position. This is against Aristotle, who says in book 5 that motion is present only in three genera: quality, quantity, and place.
Avicenna’s position is untenable because it is impossible that motion strictly speaking be in a genus the account of whose species consists in an indivisible. For the reason why there is not motion in the genus “substance” is that the account of every species of substance consists in an indivisible, due to the fact that the species of substances do not admit of more or less.
On this account, since motion is successive, a substantial form is not made existent by motion, but by generation, which is the terminus of motion. The case is different with whiteness and like things, which can be participated according to more or less. But every species of position has an account that consists in an indivisible, such that, if anything be added or taken away, the original species does not remain. Hence, it is impossible for motion to exist in the genus of position.
Besides, the same difficulty remains. For position taken as a predicament implies the order of parts in place, but if it be taken as a difference in the genus of quantity, it implies merely an order of parts in a whole. Therefore, whatever is moved according to position must be moved according to place.
476. Others, such as Avempace, said that place should be assigned in one way to a body moving in a circle and in another way to a body moving in a straight line. For since a straight line is imperfect, since it can be added to, a body moving in a straight line requires a place externally containing it, but because a circular line is perfect within itself, a body moving in a circle does not require an external place to contain it, but merely a place about which it may revolve; hence it is that circular motion is said to be motion about a center. So, therefore, they say that the convex surface of the sphere contained is the place of the first sphere. But this is against the common suppositions about place already laid down—namely, that place is a container, and that it is equal to the thing in place.
477. And therefore Averroes said that the outermost sphere is in place per accidens. To understand this, one should consider that everything that has fixity by means of something else is said to be in place per accidens, due to the fact that that by means of which it is fixed is in place, as is evident in the cases of a nail fixed in a ship and of a man at rest in a ship. Now, it is clear that bodies moving rotationally are fixed, because their center is immobile; hence, the outermost sphere is said to be in place per accidens insofar as the center about which it is revolving has existence in place. The fact that the lower spheres have a per se place in which they are contained is accidental and not essential to a body moving rotationally.
But, against this, it is objected that, if the outermost sphere is in place per accidens, then it is in motion in place per accidens, and so per accidens motion is prior to per se motion. To this, the answer is given that, for rotational motion it is not necessary for a body moving per se rotationally to be in place per se, although it is necessary for straight line motion.
But this seems to be against Aristotle’s definition, given above, of what is in place per accidens. For he said that some things exist or are moved in place per accidens because that in which they exist is in motion. But nothing is said to be in place per accidens because something entirely outside it is in place. Now, since the center is completely extrinsic to the outermost sphere, it seems ridiculous to say that the outermost sphere is in place per accidens because the center is in place.
478. And, therefore, I favor more the opinion of Themistius, who said that the outermost sphere is in place by means of its parts. To understand this, it must be recalled that Aristotle said above that there would be no discussion about place except for the act of motion, which reveals the existence of place from the fact that bodies succeed one another in the same place. Hence, although place is not of the essence of body, yet it is necessary for a body moved according to place. In the case of a body moving locally, the reason it is necessary to assign a place is that, in that motion, a succession of diverse bodies in the same place is considered. Therefore, in the case of bodies moving in a straight line, it is clear that one body succeeds another in the same place according to their totality, for one whole body leaves one whole place, which is then occupied by another whole body. Hence, a body that is in motion in a straight line must be in place in its entirety.