Lecture 22 — The problem about the earth's rest

353 The difficulty must have occurred to every one. It would indeed be a complacent mind that felt no surprise that, while a little bit of earth, let loose in mid-air moves and will not stay still, and more there is of it the faster it moves, the whole earth, free in midair, should show no movement at all. Yet here is this great weight of earth, and it is at rest. And again, from beneath one of these moving fragments of earth, before it falls, take away the earth, and it will continue its downward movement with nothing to stop it. The difficulty then, has naturally passed into a common place of philosophy;

354 and one may well wonder that the solutions offered are not seen to involve greater absurdities than the problem itself.

355 By these considerations some have been led to assert that the earth below us is infinite, saying, with Xenophanes of Colophon, that it has 'pushed its roots to infinity',—in order to save the trouble of seeking for the cause.

356 Hence the sharp rebuke of Empedocles, in the words 'if the deeps of the earth are endless and endless the ample ether—such is the vain tale told by many a tongue, poured from the mouths of those who have seen but little of the whole.

357 Others say the earth rests upon water. This, indeed, is the oldest theory that has been preserved, and is attributed to Thales of Miletus. It was supposed to stay still because it floated like wood and other similar substances, which are so constituted as to rest upon but not upon air.

358 As if the same account had not to be given of the water which carries the earth as of the earth itself! It is not the nature of water, any more than of earth, to stay in mid-air: it must have something to rest upon.

359 Again, as air is lighter than water, so is water than earth: how then can they think that the naturally lighter substance lies below the heavier?

360 Again, if the earth as a whole is capable of floating upon water, that must obviously be the case with any part of it. But observation shows that this is not the case. Any piece of earth goes to the bottom, the quicker the larger it is.

361 These thinkers seem to push their inquiries some way into the problem, but not so far as they might. It is what we are all inclined to do, to direct our inquiry not by the matter itself, but by the views of our opponents: and even when interrogating oneself one pushes the inquiry only to the point at which one can no longer offer any opposition. Hence a good inquirer will be one who is ready in bringing forward the objections proper to the genus, and that he will be when he has gained an understanding of all the differences.

494. After rejecting the opinions of those who held false theories about the earth, the Philosopher here pursues the opinions of those who, while holding a true theory about the earth, namely, that it is at rest, assigned unsuitable explanations for the earth's rest.

First he poses the problem;

secondly, he points out where the solutions which others proposed are insufficient, at and one may well wonder that the solutions (294a20; [496]);

thirdly, he examines these solutions, each in turn, at by these considerations (294a21; [497]).

495. He says therefore first (294a11) that it seems necessary that a certain problem about the earth should occur to everyone. For if someone did not wonder about this, he would seem to have an irrational mind, as though not being able to perceive the difficulty, namely, as to how it is that, if some small particle of earth be raised against its nature and then released, it is borne downward and does not wish to remain, i.e., has no natural tendency to rest, and the larger the particle of earth is, so much the faster does it move downward. Yet it seems that if the whole earth could be raised by someone on high out of its place, and then let loose, it would not move down. This seems so from what presently happens in regard to the whole earth. For, while it does have great heaviness, it does not move downward but remains at rest in its place. Hence, it seems that no matter where in the world the earth might be set, it would rest there, for the same reason that it now rests in this place. This, indeed, is in keeping with the opinion of those who suppose that any place at random is suitable for just any body.

But someone could say that the particles of earth, when lifted and then released, move down no farther than the place where earth now is. Therefore, in order to augment the difficulty, he adds that if someone were to raise some particles of earth, and it should happen that, before the falling particles returned to earth, someone should remove the earth from their place, then those clods would move downward, i.e., farther downward than the place from which they were picked up, since nothing would now be there to stop them. Now we can guess about the whole from the part—for if someone should throw a stone upward and then, before it fell, dig a ditch in the earth, that stone would fall until it encountered an obstacle; and thus it seems strange that, since the earth as a whole has no resistance from anything impeding its descent, it does not move downward.

He concludes therefore that the stupor, i.e., the great wonder, evoked by this made it a philosophema, i.e., a consideration of philosophy or occasion for philosophizing for all philosophers—just as in the beginning of the Metaphysics it is said that it is from wonder that men began to philosophize.

496. Then, at and one may well wonder that the solutions (294a20) he presents the inadequacy of the solutions proposed on this point by the philosophers. And he says that one can wonder, not only at the way things happen thus with regard to the earth, but also why philosophers trying to solve this problem have not seen that their solutions given to this problem are more at odds than the problem itself. For they have given forth theories more improbable than the situation which gives rise to the problem—hence those solutions only increase the problem.

497. Then, at by these considerations (294a21) he presents five solutions of the aforesaid problem:

the second one begins at others say the earth rests upon water (294a28; [499]);

the third at Anaximenes (L. 23; 294b13);

the fourth at they then seek a reason (L. 24; 295a14);

the fifth at they then seek a reason (L. 25; 295b10).

With respect to the first he does two things.

First he presents the first solution (294a21). And he says that some, for the sake of this, i.e., in order to evade the problem, assert that the earth's downward direction is infinite. Now this can be understood in two ways: In one way, that the air below the earth is infinite, implying that the reason why the earth is moved no farther down is because nothing is moved to an infinite goal. In the other and truer interpretation, it is taken to mean that the earth itself is infinite on its nether side, and thus the upper part is sustained by a lower part extending to infinity. This is more quickly understood and is said to have been the theory of Xenophanes of Colophon. They put this forth, not because it seemed more plausible in itself, but in order to save the trouble of laboring to find the cause of the earth's rest.

498. Secondly, at hence the sharp rebuke of Empedocles (294a24) he tells how Empedocles derided this solution. And he says that, since the aforesaid men did not assert this as though plausible but in order to sidestep the question, Empedocles was stupefied, i.e., greatly astonished at their error, speaking as follows in the verses he composed on philosophy: are indeed the deeps of the earth endless (as though to say: Is the earth infinitely deep?) and endless too the ether? i.e., air or fire And he says that these opinions have been vainly poured out, i.e., asserted without reason, since they have been told by many a tongue (as if to say: from the mouths of many men) who understood but little of the whole, i.e., understanding but little about the nature of the universe. In these words, he gives us to understand that it is from a lack of intelligence that some said this with their mouths alone, while, as interiorly considered, it is not plausible. Now Aristotle contented himself with this rebuke by Empedocles, both on account of the improbability of what is said and because it has been previously shown in book I that there cannot be infinite weight.

499. Then, at others say the earth rests upon water (294a28), he takes up the second solution.

First he proposes it;

secondly, he refutes it, at as if the same account (294a32; [500]);

thirdly, he underscores the reason for the defects in solutions of this kind, at these thinkers seem (294b6; [503]).

He says therefore first (294a28) that just as the aforesaid philosophers posited the earth to be held up by earth ad infinitum, so others declared the earth to be set on water. This indeed is the oldest theory, proposed, they say, by Thales of Miletus, who was one of the seven called "Wise Men," and the first to interest himself in natural philosophy. It was he who posited water as the principle of all things, as is said in Metaphysics I. Hence he posited the earth to be set upon water and to rest there in the manner of flotation, as occurs with wood and other similar substances, none of which naturally remains. in air, but they do remain in water in this wise because of floating. And the same thing happens with the earth, they claimed.

500. Then, at as if the same account (294a32) he refutes what has been said with three arguments. And he says that the previous solution was proposed as though the same account had not to be given of the water which sustains the earth as of the earth itself. For we see that just as earth, if raised up, does not remain unless it is supported by something, so neither is water, when raised, apt to remain so, but it must be in something supporting it, if it is to remain at rest. Therefore, if earth were sustained by water, the same problem would remain—by what is the water supported?

501. He gives the second argument at again, as air is lighter (294b1), namely, that just as air is lighter than water, so water is lighter than earth, or less heavy. Now it is the nature of something lighter to rise above that which is heavier by nature. Therefore, it is not possible for water, which is lighter, to be placed lower than earth, which is heavier, according to nature—unless someone should say that the parts of the world are not ordered according to nature, which is unacceptable.

502. The third reason, at again, if by complete (294b3), is this: As was had in book I, natural motion, and the rest as well, of the entire earth and of a clod is the same. If, therefore, the whole earth is apt to remain in water and float on it, it plainly follows that any particle of it could remain afloat on the water. But this is not what we see happening; rather, any particle of earth placed in water sinks to the bottom, the quicker the larger it is. Therefore, much more quickly would the whole earth sink, if it were set upon water.

503. Then at these thinkers seem (294b6) he indicates the reason why these arguments are deficient. And he says that the reason why they give such defective solutions is that they seem to investigate a problem up to a certain point but not as far as it is possible to inquire. But anyone who desires to solve problems properly must push his solution to the point where no doubts remain. This is something they failed to do. He assigns the reason for this, and counts himself in with the others, to avoid being boastful, and says that it seems to be the practice of all of us when resolving problems to investigate, not in terms of the thing, but in terms of the one contradicting, i.e., not as far as the nature of the matter requires but until an adversary offers no further contradiction. A man even does this with himself—when wondering about something he interrogates himself until he can no longer find to hand anything to contradict his view. But this is not enough. When someone wants to find a true solution, he must not be content merely with answering the objections he has to hand, but must diligently seek them out. Wherefore, as he says, anyone who wishes to be a good inquirer after truth must be ready to object against himself and others, not with sophistries but with real and reasonable objections proper to, i.e., befitting the genus under investigation. This arises when a man considers all the differences of the things from whose similarities a problem is solved. For example, Thales solved the present question on the basis of wood's similarity to water, but he should have considered the difference between them as well. For wood, because it contains much air, floats on water, which is not true of earth.