Cosmology

On the Possible Diurnal Rotation of the Earth

Introduction by Edward Grant

5. Nicole Oresme: The Compatibility of the Earth’s Diurnal Rotation With Astronomical Phenomena and Terrestrial Physics

Translated by Albert D. Menut³¹

Annotated by Edward Grant

T. There are others who hold that the earth is at the center of the world and that it revolves and moves in a circuit around the pole established for this purpose, as is written in Plato’s book called Timaeus.³²

G. This was the opinion of a philosopher named Heraclides Ponticus,³³ who maintained that the earth moves circularly and that the heavens remain at rest. Here Aristotle does not refute these theories, possibly because they seemed to him of slight probability and were, moreover, sufficiently criticized in philosophical and astrological writings.

However, subject, of course, to correction, it seems to me that it is possible to embrace the argument and consider with favor the conclusions set forth in the above opinion that the earth rather than the heavens has a diurnal or daily rotation. At the outset, I wish to state that it is impossible to demonstrate from any experience at all that the contrary is true; second, that no argument is conclusive; and third, I shall demonstrate why this is so. As to the first point, let us examine one experience: we can see with our eyes the rising and setting of the sun, the moon, and several stars, while other stars turn around the arctic pole. Such a thing is due only to the motion of the heavens, as was shown in Chapter Sixteen, and, therefore, the heavens move with daily motion. Another experience is this one: if the earth is so moved, it makes its complete course in a natural day with the result that we and the trees and the houses are moved very fast toward the east; thus, it should seem to us that the air and wind are always coming very strong from the east and that it should make a noise such as it makes against the arrow shot from a crossbow or an even louder one, but the contrary is evident from experience.³⁴ The third argument is Ptolemy’s—namely, that, if someone were in a boat moving rapidly toward the east and shot an arrow straight upward, it would not fall in the boat but far behind it toward the west. Likewise, if the earth moves so very fast turning from west to east and if someone threw a stone straight upward, it would not fall back to the place from which it was thrown, but far to the west; and the contrary appears to be the case.³⁵ It seems to me that what I shall say below about these experiences could apply to all other theories which might be brought forward in this connection. Therefore, I state, in the first place, that the whole corporeal machine or the entire mass of all the bodies in the universe is divided into two parts: one is the heavens with the sphere of fire and the higher region of the air; all this part, according to Aristotle in Book I of Meteors,³⁶ moves in a circle or revolves each day. The other part of the universe is all the rest—that is, the middle and lower regions of the air, the water, the earth, and the mixed bodies—and, according to Aristotle, all this part is immobile and has no daily motion. Now, I take as a fact that local motion can be perceived only if we can see that one body assumes a different position relative to another body. For example, if a man is in a boat a, which is moving very smoothly either at rapid or slow speed, and if this man sees nothing except another boat b, which moves precisely like boat a, the one in which he is standing, I maintain that to this man it will appear that neither boat is moving,³⁷ If a rests while b moves, he will be aware that b is moving; if a moves and b rests, it will seem to the man in a that a is resting and b is moving, just as before,³⁸ Thus, if a rested an hour and b moved, and during the next hour it happened conversely that a moved and b rested, this man would not be able to sense this change or variation; it would seem to him that all this time b was moving. This fact is evident from experience, and the reason is that the two bodies a and b have a continual relationship to each other so that, when a moves, b rests and, conversely, when b moves, a rests. It is stated in Book Four of The Perspective by Witelo that we do not perceive motion unless we notice that one body is in the process of assuming a different position relative to another.³⁹ I say, therefore, that, if the higher of the two parts of the world mentioned above were moved today in daily motion—as it is—and the lower part remained motionless and if tomorrow the contrary were to happen so that the lower part moved in daily motion and the higher—that is, the heavens, etc.—remained at rest, we should not be able to sense or perceive this change, and everything would appear exactly the same both today and tomorrow with respect to this mutation. We should keep right on assuming that the part where we are was at rest while the other part was moving continually, exactly as it seems to a man in a moving boat that the trees on shore move. In the same way, if a man in the heavens, moved and carried along by their daily motion, could see the earth distinctly and its mountains, valleys, rivers, cities, and castles, it would appear to him that the earth was moving in daily motion, just as to us on earth it seems as though the heavens are moving. Likewise, if the earth moved with daily motion and the heavens were motionless, it would seem to us that the earth was immobile and that the heavens appeared to move; and this can be easily imagined by anyone with clear understanding. This obviously answers the first experience, for we could say that the sun and stars appear to rise and set as they do and that the heavens seem to revolve on account of the motion of the earth in which we live together with the elements. To the second experience, the reply seems to be that, according to this opinion, not only the earth moves, but also with it the water and the air, as we stated above, although the water and air here below may be moved in addition by the winds or other forces.⁴⁰ In a similar manner, if the air were closed in on a moving boat, it would seem to a person in that air that it was not moving. Concerning the third experience, which seems more complicated and which deals with the case of an arrow or stone thrown up into the air, etc., one might say that the arrow shot upward is moved toward the east very rapidly with the air through which it passes, along with all the lower portion of the world which we have already defined and which moves with daily motion; for this reason the arrow falls back to the place from which it was shot into the air. Such a thing could be possible in this way, for, if a man were in a ship moving rapidly eastward without his being aware of the movement and if he drew his hand in a straight line down along the ship’s mast, it would seem to him that his hand were moving with a rectilinear motion; so, according to this theory it seems to us that the same thing happens with the arrow which is shot straight down or straight up.⁴¹ Inside the boat moved rapidly eastward, there can be all kinds of move-ments—horizontal, criss-cross, upward, downward, in all directions—and they seem to be exactly the same as those when the ship is at rest.⁴² Thus, if a man in this boat walked toward the west less rapidly than the boat was moving toward the east, it would seem to the man that he was approaching the west when actually he was going east; and similarly as in the preceding case, all the motions here below would seem to be the same as though the earth rested. Now, in order to explain the reply to the third experience in which this artificial illustration was used, I should like to present an example taken from nature, which, according to Aristotle, is true. He supposes that there is a portion of purefire called a in the higher region of the air; this fire, being very light, rises as high as

Fig. 1

possible to a place called b near the concave surface of the heavens [see Fig. 1]. I maintain that, just as with the arrow above, the motion of a in this case also must be compounded of rectilinear and, in part, of circular motion, because the region of the air and the sphere of fire through which a passed have, in Aristotle’s opinion, circular motion. If they were not thus moved, a would go straight upward along the line ab; but because b is meanwhile drawn toward c by circular and daily motion, it appears that a describes the line ac as it ascends and that, therefore, the movement of a is compounded of rectilinear and of circular motion, and the movement of the arrow would be of this kind of mixed or compound motion⁴³ that we spoke of in Chapter Three of Book I. I conclude, then, that it is impossible to demonstrate by any experience that the heavens have daily motion and that the earth does not have the same.

With regard to the second point, if it could be demonstrated by rational arguments, in my opinion they would be the following, to which I shall reply in a manner that could be employed to refute all other pertinent argument. First, every simple body has a single simple motion, and the earth is a simple element which has, according to its various parts, natural rectilinear movement downward. So, it can have no other motion, a fact fully explained in Chapter Four of Book I. Circular motion is not natural to the earth for it has another motion, as already noted; if circular motion is violent to it, the earth could not be perpetual, as appears in several passages of Book I. All local motion is relative to some body at rest, as Averroes states in Chapter Eight,⁴⁴ from which he concludes that the earth must be at rest in the center of the heavens. Now, all motion is produced by some motive power or force, as shown in Books Seven and Eight of the Physics,⁴⁵ and the earth cannot move circularly because of its weight; if it is so moved by an external force, this movement would be violent and not perpetual. If, in reality, the heavens did not have diurnal motion, all astronomy would be false as well as a large part of natural philosophy throughout which such motion is taken for granted. It would, moreover, contradict Holy Scripture which states: The sun riseth and goeth down and returneth to his place; and there rising again, maketh his round by the south and turneth again to the north; the spirit goeth forward surveying all places round about and returneth to his circuits.⁴⁶ And it is also written of the earth that God made it motionless: Etenim firmavit orbem terre, qui non commovebitur.⁴⁷ The Scripture states that the sun stopped its course in Joshua’s time and returned in King Hezekiah’s;⁴⁸ if, as is posited in this theory, it is the earth that moves and the heavens that remain motionless, then this stopping would have been a turning backward, which would have been more than a stoppage. And this is contrary to the statement in the Scriptures. As for the first argument where it is stated that every simple body has a single simple motion, I say that the earth, which as a whole is a simple body, has no movement, according to Aristotle in Chapter Twenty-two. Against the interpretation of anyone who maintained that Aristotle means that this body has a single simple motion not proper to itself as a whole, but applying only to its parts when they are out of their proper place, we can cite the case of air which moves downward when it is in the region of fire and upward when it is in the region of water, both being simple move-merits. Therefore, we can say with an ever greater show of reason that each simple body or element of the universe, with the possible exception of the sovereign heaven, moves in its proper place with circular motion. If any part of such a body is out of its place or outside the main body, it returns to it as directly as it can, once the hindrance is removed; this would surely happen if some part of the heavens were to get outside. It is not necessary that a simple body have its own simple motion in its proper place and another motion in its parts when they return to their proper place, and, according to Aristotle, we shall have to grant this assumption, as I shall do a little later. To the second argument, I say the motion is natural to the earth as a whole and in its place; however, its parts have a different natural motion, rectilinear upward and downward, when they are out of their natural place. According to Aristotle, we must admit the same with respect to fire, parts of which move naturally upward when out of their proper place, and besides, also according to him, the entire element of fire in its sphere and in its place moves perpetually with diurnal motion, which could not be a true statement if its movement were violent. Now, in the theory we are discussing, it is not the element of fire, but the earth that moves in this manner. I say no to the third argument which states that all motion requires some body to be at rest, unless the motion must be perceptible to the senses; to make such motion apparent, it would suffice that the first body be moved in a different manner. But it is not required that there be a second body in order that this motion should exist, as was explained in Chapter Eight. Assuming that the heavens have diurnal movement and that the earth is moving in the opposite direction or imagining even that the earth were annihilated, we would note that the heavens had not stopped moving on this account; nor would they move faster or more slowly because neither the intelligence which moves the heavens nor the moving body of the heavens as a whole would be disposed to do otherwise. Besides, if it is assumed that circular motion did require another body at rest, such a body would not be situated in the middle of the one moving; in the middle of a millstone of a flour mill or of any similar moving body, nothing is at rest save a single mathematical point which is not a body, and the same is true at the center of the movement of the polar star. Thus, it could be said that the sovereign heaven rests or moves differently from the motion of the other bodies because its movement requires the existence of the other motions or requires that they be perceptible to the senses. To the fourth argument, we can say that the force causing this lower region of the world to move in a circle is its nature or form; and this same force—similar in nature to that which draws iron to the magnet—moves the earth to its proper place when it gets outside. Besides, I ask Aristotle what force it is that moves fire in the diurnal movement of its sphere, for we cannot say that the heavens pull it thus or seize it violently not only because this motion is perpetual, but also because the concave surface of the heavens is so highly polished, as noted in Chapter Eleven, that it passes over the sphere of fire without rubbing, pulling, or pushing, as stated in Chapter Eighteen. So, we must say that fire is moved circularly by its own nature and form or by some intelligence or celestial influence, Exactly the same could be said by one who maintains that the earth has diurnal rotation and that the sphere of fire remains at rest. I say to the fifth argument, where it is held that, if the heavens did not make a rotation frown day to day, the whole of astronomy would be false, that such a statement is not true, because all heavenly aspects, conjunctions, oppositions, constellations, figures, and influences would be exactly as they are in every respect, as is apparent from what was stated in reply to the first experience; and the astronomical tables of the heavenly motions and all other books would remain as true as they are at present, save that, with respect to diurnal motion, one would say that it is apparently in the heavens, but actually in the earth; no other effect would follow or result from one theory more than from the other. Aristotle’s statement in Chapter Sixteen is pertinent in this connection, namely, that the sun seems to us to turn and twist and the stars to flicker and twinkle and that whether the thing we see moves or whether our vision moves makes no difference; and in the present case one could say that our vision is affected by diurnal movement. One could answer the sixth argument, which concerns the reference in Holy Scripture about the sun’s turning, etc., by saying that this passage conforms to the customary usage of popular speech just as it does in many other places, for instance, in those where it is written that God repented, and He became angry and became pacified, and other such expressions which are not to be taken literally.⁴⁹ And more pertinent to our present subject, we read that God covers the heavens with clouds: Qui operit celum nubibus,⁵⁰ while the fact is that the heavens cover the clouds. Thus, we could say that the heavens, rather than the earth, appear to move with diurnal motion, while the truth is the exact opposite. And we could say that, in reality, the earth does not move from its place, nor apparently within its place, but it does actually move within its place. To the seventh argument, we could reply in much the same manner that in the time of Joshua the sun stopped and that in the time of

Hezekiah it returned, but only apparently so; for, in fact, it was the earth which stopped moving in Joshua’s time and which later in Hezekiah’s time advanced or speeded up its movement; whichever occurrence we prefer to believe, the effect would be the same.⁵¹ The latter opinion seems more reasonable than the former, as we shall make clear later.

Regarding the third point of this discussion, I want to present several opinions or reasons favorable to the theory that the earth moves as we have stated. In the first place, everything that requires another thing for its natural existence must aim at receiving the good it derives from the other through the motion or action natural to it. In this way we can see that each element moves to its natural place where it is conserved and that it goes to its place rather than its place coming to it. Thus the earth and the elements here below which require the heat and influence of the heavens round about them must needs be disposed by their movements to receive these benefits in due degree, just as, to speak familiarly, the meat being roasted before the fire receives around it the heat of the fire by being turned and not by the turning of the fire around the meat. If neither experience nor reason indicates the contrary, it is much more reasonable, as stated above, that all the principal movements of the simple bodies in the world should go or proceed in one direction or manner. Now, according to the philosophers and astronomers, it cannot be that all bodies move from east to west; but, if the earth moves as we have indicated, then all proceed alike from west to east—that is, the earth by rotating once around the poles from west to east in one natural day and the heavenly bodies around the zodiacal poles: the moon in one month, the sun in one year, Mars in approximately two years, and so on with the other bodies.⁵² It is unnecessary to posit in the heavens other primary poles or two kinds of motion, one from the east to the west and the other on different poles in the opposite direction, but such an assumption is definitely necessary if the heavens move with diurnal motion. . . . Although Averroes says in Chapter Twenty-two that motion is nobler than rest,⁵³ the contrary seems true, because, again on Aristotle’s authority in Chapter Twenty-two, the noblest thing possible achieves its perfection without movement, and this is God Himself. Rest is the end purpose of motion, and so Aristotle holds that the bodies here below move to their natural places in order to rest there.⁵⁴ A further sign that rest is best is that we pray for the dead that God may give them rest: Requiem eternam, etc. Therefore, to rest or to be moved less is a better and nobler condition than to be moved or to be moved farther and farther from rest.⁵⁵ From this, it seems that the position we have taken above is very reasonable, for it could be said that the earth, the vilest element, along with the other elements here below make their rotation very fast, that the sovereign air and fire move less fast—as can be observed in the case of the comets—and that the moon and lunar sphere move still more slowly, for it moves in a month only the distance the earth travels in a natural day. Proceeding in this manner, the higher heavens make their revolution more slowly yet, although there is some variation, and this process continues up to the heaven of the fixed stars, which is motionless or makes its revolution very slowly, according to some in thirty-six thousand years or one degree in one hundred years.⁵⁶ In this way and no other can we solve the question proposed by Aristotle in Chapter Twenty-one, with only slight additions. It is not necessary to assume so many degrees of things nor such obscure difficulties as Aristotle introduces in his reply in Chapter Twenty-two. It is indeed very reasonable that the bodies that are larger or farther from the center should make their circuit or revolution in longer time than those nearer the center, because, if they made their circuit in the same or equal time, their movements would have to be excessively fast. So we could say that nature compensates by ordaining that the rotations of the bodies farther from the center shall be accomplished in much longer time. Accordingly, because of its great size, the sovereign or primary heaven takes a very long time to make its circuit or rotation although it moves very fast. But the earth, which has a very small circuit, can cover the distance in one diurnal movement, while the other bodies intermediate between the highest and lowest heavens accomplish their circuits in time periods midway between the extremes, although these periods are not proportionate. In this way, a constellation near the north, i.e., the Great Bear which we call the Chariot, does not move backward, the chariot in front of the oxen, as it would if moved with diurnal motion; but it actually goes forward in the right direction. All philosophers say that an action accomplished by several or by large-scale operations which can be accomplished by fewer or smaller operations is done for naught.⁵⁷ And Aristotle says in Chapter Eight of Book I that God and nature do nothing without some purpose.⁵⁸ Now, if it is true that the heavens move with diurnal motion, it becomes necessary to posit in the major bodies of the universe and in the heavens two contrary kinds of movement: one from east to west and the other from the opposite direction, as we have often stated. And with regard to diurnal motion, we must assume an excessively great speed; for, if we consider thoughtfully the height or distance of the heavens, their magnitude, and the immensity of their circuit, mindful that this circuit is traveled in but one day’s time, no man could imagine or conceive how marvelously swift and excessively great, how far beyond belief and estimation their speed must be.⁵⁹ Since, then, all the effects we see could be produced and all appearances saved by substituting for the diurnal movement of the heavens a smaller operation, namely, the diurnal motion of the earth, a very small body as compared with the heavens, and by so doing avoid the multiplication of operations so diverse and so outrageously great, then it follows that God and nature must have created and arranged them for naught; and this is an inadmissible conclusion, as we have often said. Assuming the entire heavens to move with daily motion and, in addition, assuming the eighth sphere to have a different motion, as the astronomers believe, then we must necessarily posit a ninth sphere moving only with diurnal motion. However, if we assume that the earth moves as stated above, then the eighth heaven moves with a single slow motion and it is consequently unnecessary to imagine a ninth natural sphere invisible and starless; for God and nature would have made this ninth sphere for naught since by another method, i.e., assuming the earth to move, everything can remain exactly as it is. Also, when God performs a miracle, we must assume and maintain that He does so without altering the common course of nature, in so far as possible. Therefore, if we can save appearances by taking for granted that God lengthened the day in Joshua’s time by stopping the movement of the earth or merely that of the region here below—which is so very small and like a mere dot compared to the heavens—and by maintaining that nothing in the whole universe—and especially the huge heavenly bodies—except this little point was put off its ordinary course and regular schedule, then this would be a much more reasonable assumption. And appearances can be saved in this way, as is evident from the reply to the seventh argument, presented against this opinion. As much could be said with regard to the return of the sun in Hezekiah’s time. Thus, it is apparent that one cannot demonstrate by any experience whatever that the heavens move with diurnal motion; whatever the fact may be, assuming that the heavens move and the earth does not or that the earth moves and the heavens do not, to an eye in the heavens which could see the earth clearly, it would appear to move; if the eye were on the earth, the heavens would appear to move. Nor would the vision of this eye be deceived, for it can sense or see nothing but the process of the movement itself. But if the motion is relative to some particular body or object, this judgment is made by the senses from within that particular body, as Witelo explains in The Perspective;⁶⁰ and the senses are often deceived in such cases, as was related above in the example of the man on the moving ship. Afterward, it was demonstrated how it cannot be proved conclusively by argument that the heavens move. In the third place, we offered arguments opposing their diurnal motion. However, everyone maintains, and I think myself, that the heavens do move and not the earth: For God hath established the world which shall not be moved, in spite of contrary reasons because they are clearly not conclusive persuasions. However, after considering all that has been said, one could then believe that the earth moves and not the heavens, for the opposite is not clearly evident. Nevertheless, at first sight, this seems as much against natural reason as, or more against natural reason than, all or many of the articles of our faith.⁶¹ What I have said by way of diversion or intellectual exercise can in this manner serve as a valuable means of refuting and checking those who would like to impugn our faith by argument.

^31. Reprinted with permission of the copyright owners, the Regents of the University of Wisconsin, from Nicole Oresme, Le Livre du ciel et du monde, edited by Albert D. Menut and Alexander J. Denomy, C.S.B. †, translated with an Introduction by Albert D. Menut (Madison, Wis.: University of Wisconsin Press, 1968), pp. 519 539.

The present selection constitutes virtually the whole of Book II, chapter 25, of Oresme’s translation from Latin into French of Aristotle’s treatise On the Heavens (De caelo), along with Oreme’s accompanying commentary (see Selection 71, n. 1). The letters T and G represent Aristotle’s text and Oresme’s commentary (or gloss), respectively.

^32. These words of Aristotle’s are found in On the Heavens II.13.293b.30–32. The chapter which follows consists of Oresme’s lengthy commentary on these few words relating to the possible diurnal axial rotation of the earth.

^33. See note 3.

^34. The same point was mentioned and refuted by Buridan (see par. 7 of section 4).

^35. Although Ptolemy mentions neither boat nor stone, these arguments reproduce faithfully the substance of his counterargument in the penultimate paragraph of Book I, chapter 7, of the Almagest (see section 1).

^36. Probably Meteorologica I.3.340b.10–12, where, however, there is some dispute as to whether Aristotle intended to subdivide it quite as Oresme presents it.

^37. This particular illustration of the relativity of motion was not given by Buridan in paragraph 2 of section 4, but was included by Copernicus near the beginning of Book I, chapter 5 of De revolutionibus (see section 6).

^38. This is virtually the same point made by Buridan in paragraph 2 of section 4.

^39.Vitellonis Thuringopoloni Opticae libri decem, Bk. IV, par. 110, p. 167, of the edition published by Friedrich Risner (Basel, 1572). This declaration of the relativity of motion was taken by Witelo from Book II, paragraph 49, of the Optics of Alhazen, which, although separately paginated, was published by Risner in the same volume that included Witelo’s Optics; Alhazen’s statement appears on p. 60.

^40. See note 6.

^41. Oresme is here proposing a very different explanation than Buridan for the phenomenon of the arrow shot vertically into the air and falling vertically down to approximately the place from which it was shot. Where Buridan invoked the impetus theory (see par. 9 of section 4) to explain the arrow’s return and inferred from it that the earth and its ambient air did not rotate, Oresme argues that the arrow might share the rotational motion of earth and air and hence would naturally fall to the same place from which it was shot.

^42. In De revolutionibus, Book I, chapter 8, Copernicus says the very same thing (see section 6), as does Galileo in the Dialogue Concerning the Two Chief World Systems(Drake, p. 142).

^43. Like Oresme, Copernicus would also argue (Bk. I, ch. 8, of De revolutionibus; see section 6) that on the assumption of the earth’s rotation, rising and falling objects would have a motion that is the resultant of two motions, rectilinear and circular.

^44. Averroes, Commentary on De caelo, Book II, Comment 18, on folio 107 verso, paragraph 1, in Volume V of the edition cited in Selection 44, n. 1.

^45. That is, Aristotle’s Physics.

^46. Ecclesiastes 1:5–6.

^47. Psalms 92:1.

^48. Joshua 10:12–14. This Scriptural account was also used against the Copernican theory, as Galileo reports in the Third Day of the Dialogue Concerning the Two Chief WorM Systems (Drake, p. 357), and even long before, in his 1615 Letter to Madame Christina of Lorraine Grand Duchess of Tuscany Concerning the Use of Biblical Quotations in Matters of Science (translated into English by Stillman Drake in Discoveries and Opinions of Galileo [New York: Doubleday, 1957], pp. 211–215), where Galileo attempts to reconcile the Joshua passage with the Copernican theory (see n. 51).

^49. To illustrate Oresme’s point that Scripture is not to be taken literally when it speaks of God repenting, and so on, Menut cites Genesis 6:6, Isaiah 47:6, Psalms 59:3, I Par. 13:10, Psalms 105:40.

^50. Psalms 147:8.

^51. Oresme’s solution to the "Joshua problem" is more daring than Galileo’s, since it was more at variance with the literal sense of the text. Galileo argued that the sun controls all celestial motions, which would cease immediately if the sun’s motion ceased. "The sun, then," says Galileo, "being the font of light and the source of motion, when God willed that at Joshua’s command the whole system of the world should rest and should remain for many hours in the same state, it sufficed to make the sun stand still. Upon its stopping, all the other revolutions ceased; the earth, the moon, and the sun remained in the same arrangement as before, as did all the planets; nor in all that time did day decline towards night, for day was miraculously prolonged. And in this manner, by the stopping of the sun, without altering or in the least disturbing the other aspects and mutual positions of the stars, the day could be lengthened on earth—which agrees exquisitely with the literal sense of the sacred text"(from Galileo’s Letter to Madame Christina, pp. 213–214 of Drake’s translation).

^52. Buridan says virtually the same thing in paragraph 3 of section 4.

^53. Averroes, Commentary on De caelo, Book II, Comment 61, on folio 140 recto, paragraph A, in Vol. V of the edition cited in Selection 44, n. 1.

^54.Physics V.6.230b.25–27.

^55. Buridan offers much the same argument in favor of the immobility of the heavens and the motion of the earth (see the third persuasion in par. 4 of section 4).

^56. Ptolemy’s value for the precession of the equinoxes.

^57. This principle was expressed by Aristotle as nature doing nothing in vain (see n. 58, and compare to Ock-ham’s "razor," Selection 40, n. 13).

^58. Aristotle, De caelo I.4.271a.33; see also II.8.290a. 31.

^59. The same substantive argument was made by Buridan (par. 4 of section 4) and Copernicus (ch. 7 of section 6). See note 25.

^60. See note 39.

^61. In the final analysis, then, Oresme denies the diurnal rotation of the earth. He argues that although one might plausibly believe in the earth’s rotation—for there are no persuasive arguments to deny it conclusive-ly—it seems contrary to natural reason, even more so than do some articles of the faith. Thus Oresme acquiesces in tradition, custom, and "natural reason," to conclude in favor of the earth’s immobility. He sought to humble reason and show that physical arguments could not establish a relatively simple physical problem. If reason is impotent in the solution of a physical problem, how much more impotent would it be in coping with articles of the faith, which some men had tried to demonstrate by reason. Thus Oresme’s elaborate and brilliant arguments were designed to protect the faith from demonstrations based on applications of reason and science, both of which seem incapable of deciding straightforward physical problems. By showing that it was impossible to know which alternative is really true, Oresme, the theologian, succeeded in using reason to confound reason.