Commentary Aristotle Physics
For some continuous body is at rest according to place when it is being altered in quality, now white or black, or now hard, while previously soft. Yet it remains one and the same in number. And, on account of this changing of forms in the subject, we say that matter is something that remains one whole when change takes place with respect to forms. Because of this, place seems to be something, for in it, as remaining, different bodies succeed each other. Nevertheless, we use different terminology when referring to these two cases:
to designate matter or the subject, we say, what is now water was previously air;
to designate unity in place, we say, where water is now, there was air previously.
465. Then, at “but the matter” (211b36), he shows that matter is not place, for as we said above, matter is not separated from the thing of which it is the matter, nor does it contain the latter, both of which characteristics belong to place. Place, therefore, is not matter.
466. Then, at “well, then, if place” (212a2), having eliminated the first three members, he argues for the fourth. And he says that, since place is not any of these three—form, matter, or some space other than the internal distances of the things in place—it must be the fourth of the above named: the boundary of the containing body. And lest anyone understand that the thing contained or in place is some middle space, he adds that the contained body is what is apt to be moved in respect to change of place.
467. Then, at “place is thought to be” (212a7), he tracks down the specific difference of place, namely, that it is immobile.
In regard to this, he does two things:
first, he shows that an error arose from improperly considering this difference;
second, he shows how we must understand the immobility of place, at “in fact, just as the vessel” (212a14; [468]).
He says, therefore, that it is a large undertaking and a difficult one to understand what place is, both because some have thought it is matter or form—both of which involve lofty speculation, as was said above—and because the change that occurs when things change place occurs in something both at rest and containing. Now, since nothing seems to be containing and immobile except space, it seems that place is a sort of middle space distinct from the magnitudes that are moved in respect to place. And the fact that air seems to be incorporeal helps to make this opinion credible, for where air is, there appears to be no body, but a certain empty space. Thus place seems to be not only the boundaries of a vessel, but something between the boundaries as a vacuum or void.
468. Then, at “in fact, just as the vessel” (212a14), in order to exclude this stated opinion, he shows how we must understand the immobility of place. And he says that a vessel and place are seen to differ in that a vessel can be transported but place cannot. Hence, just as a vessel can be called “a transportable place,” so place can be called “an immobile vessel.” Therefore, when something is being moved in a body that is in motion, as a ship in a river, we speak of that in which it is being moved as a vessel rather than of a containing place, because place wants to be immobile; that is, it is of the very nature and aptitude of place to be immobile. On this account, it is better to speak of the whole river as being the place of the ship, because the river as a whole is immobile. Thus, the whole river inasmuch as it is immobile is the common place.
However, since proper place is a part of common place, we must consider the proper place of the ship in flowing water—not the water inasmuch as it is flowing, but in its relation to the order or position that this flowing water has to the river as a whole. It is this order or position that remains constant while the water flows on. Therefore, although the water materially passes on, yet, insofar as it has the account of place—that is, insofar as it is considered as having a certain order and position with respect to the whole river—it does not change.
This also shows how we ought to consider how the boundaries of natural mobile bodies are place with respect to the entire spherical body of the heavens, which is fixed and immobile on account of the immobility of the center and of the poles. Therefore, although this part of air that contains, or this part of water, flows by and moves as this water, yet, insofar as this water has the account of place—namely, a position and order to the whole spherical body of the heavens—it always remains. This is like the same fire, remaining as to its form but, as to its matter, varying as wood is consumed and other wood added.
469. This removes an objection that could be lodged against positing place as the boundary of the container, for since the container is mobile, its boundary will also be mobile; consequently, a thing at rest will have diverse places. But this does not follow, because the boundary of the container is not place insofar as it is this surface of this particular mobile body, but by reason of the order or position it has in the immobile whole. From this, it is evident that the whole account of place in all containers is taken from the first container and locator, namely, the heavens.
470. Then, at “hence, we conclude” (212a20), he concludes from the foregoing the definition of place: place is the immobile boundary of that which contains first. He says first to designate proper place and exclude common place.
471. Then, at “this explains why” (212a21), he shows that the definition is well assigned, because the things said about place concur with this definition. And he gives three such things.
The first is that, since place is an immobile container, the middle of the heavens (namely, the center) is seen as down, and the boundary of circular change of place (that is, of the bodies moved in a circle, and the boundary as to us, namely, the surface of the sphere of the moon), is seen as up, and the middle as down. The middle or center is seen to be said most properly of all to be permanent, for the center of a sphere is always at rest. Now, in relation to us, that which is the boundary of the bodies moved in a circle, although it moves in a circle, nevertheless remains permanent insofar as it remains in the same way, that is, at the same distance from us.
Hence, since natural bodies are moved to their proper places, it follows that light bodies naturally move up and heavy bodies down—for both the middle and the containing boundary in the direction of the middle are called “down”; likewise, the boundary in the other sense, and what is in the direction of that boundary, are called “up.”
He uses this manner of speaking because it is the center that is the place of the earth, which is simply heavy, while toward the center, the place of water is found. In like manner, the place of fire, which is simply light, is the outermost, while the place of air is toward the outermost.
He gives the second reason at “for this reason, too” (212a28), saying that, because place is a boundary, place seems to be like a certain surface and like a containing vessel, but not like the space of the containing vessel.
He gives the third reason at “further, place is coincident” (212a29), when he says that, because place is a boundary, the place and the thing in place are together.
For the limits of the thing in place and the boundary of the container, which is place, are together (for the boundaries of things that touch are together). This also explains why place is equal to the thing in place: namely, because they are equated as to their boundaries.