Sed si nihil ut contingit neque a casu evenit in sempiternis esse, caelum autem sempiternum et circulatio; propter quam quidem causam ad alteram fertur sed non ad alteram? 275 But nothing which concerns the eternal can be a matter of chance or spontaneity, and the heaven and its circular motion are eternal. We must therefore ask why this motion takes one direction and not the other. Necesse enim et hoc aut principium esse, aut esse ipsius principium. 276 Either this is itself an ultimate fact or there is an ultimate fact behind it. Forte quidem igitur de quibusdam enuntiare aliquid tentare, et de omnibus, et praetermittere nihil, forsitan utique videbitur esse signum aut multae stultitiae aut multae promptitudinis. Non tamen iustum quidem omnes similiter increpare, sed videre oportet causam dicendi quae est; adhuc autem qualiter habens in credendo prius, humano modo aut firmius. Certiores quidem igitur necessitates quando quis attingit, tunc gratiam habere oportet invenientibus. 277 It may seem evidence of excessive folly or excessive zeal to try to provide an explanation of some things, or of everything, admitting no exception. The criticism, however, is not always just: one should first consider what reason there is for speaking, and also what kind of certainty is looked for, whether human merely or of a more cogent kind. When any one shall succeed in finding proofs of greater precision, gratitude will be due to him for the discovery, but at present we must be content with a probable solution. Nunc autem quod videtur dicendum est. Si enim natura semper facit contingentium quod optimum, est autem quemadmodum earum quae in rectum lationum, quae ad superiorem locum honorabilior (divinior enim locus qui sursum eo qui deorsum); eodem modo et qui ad anterius ea quae ad posterius se habet, siquidem et ad dextrum et ad sinistrum, quemadmodum dictum est prius. Et testificatur etiam dicta dubitatio quoniam habet prius et posterius: haec enim causa solvit dubitationem. Si enim habet ut contingit optime, haec utique erit causa dicti: optimum enim moveri simplicem motum et incessabilem, et hunc ad honorabilius. 278 If nature always follows the best course possible, and, just as upward movement is the superior form of rectilinear movement, since the upper region is more divine than the lower, so forward movement is superior to backward, then front and back exhibits, like right and left, as we said before and as the difficulty just stated itself suggests, the distinction of prior and posterior, which provides a reason and so solves our difficulty. Supposing that nature is ordered in the best way possible, this may stand as the reason of the fact mentioned. For it is best to move with a movement simple and unceasing, and, further, in the superior of two possible directions. 361. Postquam philosophus determinavit de partibus caeli et de figura ipsius, hic determinat de motu eius. 361. After determining as to the parts of the heaven and its shape, the Philosopher here decides the question of its motion. Et primo determinat de modo motus; First he discusses the manner of its motion; secundo determinat de uniformitate motus caelestis, ibi: de motu autem ipsius et cetera. secondly, the uniformity of its motion, at we have next to show that the movement (L. 8). Circa primum tria facit: Regarding the first he does three things: primo ponit quaestionem; first he raises the question; secundo ostendit difficultatem quaestionis, ibi: forte quidem igitur etc.; secondly, he shows the difficulty of the question, at it may seem evidence 364; tertio proponit solutionem, ibi: nunc autem quod videtur et cetera. thirdly, he proposes a solution, at if nature always follows 365. Circa primum tria facit. About the first he does three things: Primo proponit quaedam ex quibus oritur dubitatio. Quorum unum est, quod dupliciter contingit per aliquem circulum aliquid moveri. Signetur enim punctum a in aliquo circulo, et ab eo ducatur diameter, et in superiori semicirculo signetur punctum b, in inferiori autem signetur punctum g. Dupliciter ergo potest aliquid moveri per hunc circulum: uno modo quod moveatur ab a versus b, alio modo quod moveatur ab a versus g. Aliud autem quod proponit est, quod isti duo motus non sunt contrarii: ostensum est enim in primo quod duo motus circulares non sunt contrarii. Si enim isti motus essent contrarii, oporteret quod competerent naturis contrariorum mobilium, ita quod unus eorum attribueretur uni mobili, et alius contrario: quia sicut supra dictum est, si unum contrariorum est in natura, necesse est alterum esse. first he mentions certain things that give rise to the question. One of these is that there are two ways in which a thing could be moved through a circle. For if we let A be a point on a circle and draw a diameter from A, and let B be a point on the upper semicircle, and G a point on the lower, there will then be two possible ways for something to move over this circle: in one way, something could go from A to B; in another, from A to G. Another thing he mentions is that those two motions are not contrary, for it has been shown in Book I that two circular motions are not contrary. For if they were contrary, they would have to belong to the natures of contrary mobile things, so that one motion would be attributed to one mobile and the other to the contrary mobile — because, as has been said, if one of two contraries exists in nature, so must the other. 362. Secundo ibi: sed si nihil etc., movet dubitationem. Manifestum est enim ex praemissis quod in sempiternis nihil accidit contingenter aut casualiter: quia ea quae sunt a casu, non sunt semper, neque etiam ut frequenter. Dictum est autem supra quod caelum est sempiternum, et etiam circularis motus eius. Unde rationabiliter quaeritur propter quam causam caelum movetur versus unam partem et non versus aliam, puta ab oriente versus superius hemisphaerium, et non versus inferius. 362. Secondly, at but nothing [275] he raises the question. For it is plain from the foregoing that in things that are eternal nothing happens contingently or fortuitously, because happenings due to chance do not occur always or even nearly always.. But it has been said above that the heaven is eternal and also its circular motion. Hence it is reasonable to ask why it is that the heaven is moved in one direction rather than in the other; for example, from the east in the direction of the upper hemisphere and not of the lower. 363. Tertio ibi: necesse enim etc., ostendit qualiter sit huiusmodi causa assignanda. In praecedentibus enim dupliciter assignavit causam caelestium accidentium. 363. Thirdly, at either this is itself an ultimate fact [276] he shows how such a cause must be assigned. For in the previous accounts he assigned a cause of celestial events in two ways. Primo enim ostendit quod oportet esse diversos motus in caelo, ad hoc quod sit principium generationis et corruptionis: secundo ostendit quod oportet figuram caeli esse rotundam, ex aliquo principio priori supposito, quia scilicet corpori primo debetur figura prima; et sic primitas corporis est principium primae figurae. Et ideo hic dicit quod, si debeat assignari ratio quare caelum sic moveatur et non aliter, necesse est huiusmodi rationem assignari, aut secundum hoc quod talis modus motionis sit principium alicuius effectus, aut potius quod iste modus motionis dependeat ex aliquo priori principio. First, he showed that there have to be various motions in the heaven in order that generation and corruption be possible; secondly, he showed that the figure of the heaven has to be round by assuming a prior principle, namely, that the first shape is appropriate to the first body. Thus the primacy of the body is the reason why it has the first shape. And therefore he says here that if we must assign the reason why the heaven is moved as it is and not in some other way, that reason must be assigned either on the ground that such a type of motion is the principle of some effect, or rather that this type of motion depends on some prior principle. Potest autem et aliter intelligi. Dixerat enim quod sempiterna non possunt esse a casu: nec tamen omnia sempiterna habent causam, sed aliquod sempiternum est quod causam non habet, sed ipsum est prima causa aliorum. Quia igitur ex sempiternitate caeli et motus eius concluserat quaestionem, qua quaeritur propter quam causam motus caeli est versus unam partem et non versus aliam; ne videatur quaestio irrationabilis seu inutilis, subiungit quod necesse est hoc ipsum quod est caelum sic moveri, aut esse primum principium omnium (quod est impossibile, cum omnis motus habeat causam moventem); aut oportet dicere quod eius sit quoddam aliud principium. Et sic rationabiliter quaesitum est de causa quare movetur ad hanc partem et non ad aliam. This can also be understood in another way. For he had said that eternal things cannot be due to chance. Yet not all eternal things have a cause, for there is an eternal thing which has no cause but is itself the first cause of other things. Since, therefore, on the grounds of the eternity of the heaven and of its motion, he had arrived at the question concerning the cause why the motion of the heaven is in one direction rather than another, lest the question appear foolish or useless, he adds that it is necessary that the manner of the heaven's movement be either the first principle of all motions (which is impossible, because all motion has a movent cause) or else there must be said to be some other principle of its motion. Consequently it is reasonable to ask why it is that the heaven is moved in this direction rather than some other. 364. Deinde cum dicit: forte quidem igitur etc., ostendit difficultatem huius quaestionis. Et dicit quod hoc quod aliquis de quibusdam difficilibus et occultis velit attente enuntiare, assignando causam eorum, et quod de omnibus velit inquirere et nihil praetermittere, forte videbitur esse signum vel multae stultitiae, ex qua provenit quod nescit discernere inter facilia et difficilia; aut est signum multae promptitudinis, idest magnae praesumptionis, ex qua contingit quod homo non cognoscit mensuram suae facultatis circa inquisitionem veritatis. Et quamvis quidam super hoc sint increpandi, non tamen iustum est quod omnes similiter reprehendantur, sed ad duo oportet attendere. 364. Then, at it may seem evidence [277], he shows the difficulty of this question. And he says that the very desire to attentively set forth difficult and occult things and give their cause, and to inquire into all the aspects, without omitting anything, will perhaps be seen as a sign either of a deep-rooted stupidity, causing one to be unable to distinguish between what is easy and what is difficult, or else as a sign of great promptitude, i.e., of great presumption, causing one not to know the measure of his ability with respect to the search for truth. And although some deserve rebuke on this point, it is not a just thing to condemn all investigators indiscriminately. Rather we should first have regard to two things. Primo quidem ad causam quae movet hominem ad loquendum de talibus: utrum scilicet hoc faciat ex amore veritatis, an ad ostentationem sapientiae. First, we must look for the motive which induces a man to speak of such things: Is he doing it out of love for the truth or in order to show off his wisdom? Secundo oportet considerare quomodo se habeat aliquis in credendo ea quae asserit: utrum scilicet habeat de eis debilem certitudinem, secundum communem hominum modum, aut etiam firmius ea cognoscat, scilicet supra communem modum hominum. Quando igitur aliquis potest attingere ad hoc quod cognoscat necessarias causas certius quam secundum communem hominum modum, tunc oportet reddere gratias his qui tales necessitates inveniunt, magis quam eos increpare. Secondly, we must consider how one is in assenting to the things he asserts: does he have a weak certitude about them like the common run of mankind, or does he know them more firmly, i.e., above the general run? When, therefore, a person can attain to a knowledge of necessary causes with greater certitude than the general run of man, he who finds such necessary reasons deserves our thanks rather than a rebuke. 365. Deinde cum dicit: nunc autem quod videtur etc., solvit praemissam quaestionem. Et dicit quod, si gratiae sint agendae his qui certiores necessitates inveniunt, nunc autem in hac quaestione sufficit dicere illud quod nobis videtur, etsi non sit adeo certum. Dicit ergo quod inter ea quae contingit fieri, natura semper facit id quod est optimum, tanquam mota et directa a primo principio, quod est ipsa essentia bonitatis. Videmus autem quod tanto aliquis motus localis est dignior, quanto versus digniorem partem procedit; motus enim accipit speciem a termino; sicut in motibus localibus rectis, motus localis qui est ad superiorem locum, est honorabilior et nobilioris corporis quam motus localis qui est ad inferiorem locum, eo quod locus qui est sursum est dignior loco qui est deorsum. Et hoc quidem manifestum est in homine: nam caput, quod est sursum, est nobilius pedibus, qui sunt deorsum. Et similiter pars anterior dignior est posteriori, sicut etiam et dextrum est dignius quam sinistrum, sicut supra dictum est, et sicut patet in animalibus. Dicta ergo dubitatio quam nunc movimus, testificatur quod in caelo sit prius et posterius, idest ante et retro, de quibus supra nullam mentionem fecit. Haec enim causa, scilicet distinctio anterioris et posterioris in caelo, solvit praedictam dubitationem. Si enim motus caeli se habet optime quantum contingit, sicut dictum est, haec erit causa dictae dubitationis: quia optimum est quod caelum moveatur motu simplici, idest semper versus eandem partem, et incessabili, idest sine interpolatione quietis, quam necesse esset intervenire, si quandoque moveretur versus unam partem, quandoque versus aliam; et ulterius optimum est quod moveatur versus honorabiliorem partem, est autem anterior pars nobilior. Et ideo caelum movetur ab oriente versus suum anterius, idest versus superius hemisphaerium; non autem versus inferius, quod est caeli posterius. 365. Then, at if nature always follows [278], he solves the question he raised. And he says that if thanks should be rendered to those who discover more certain necessary things, as to the present question it is enough to say how the matter seems to us, even though it is not so certain. He says, therefore, that among things that come to be produced, nature always does what is best, as moved and directed by the first principle, which is the essence of goodness, Now, we observe that a local motion is more noble to the extent that it tends toward a nobler direction—for the species of a motion is determined by its terminus. Thus with regard to straight local motions, a local motion toward a higher place is more honorable and more noble than one to a nether place, since the place which is above is of more worth than one which is down. This fact is also plain with regard to man: for the head, which is above, is nobler than the feet, which are down. Likewise, the front of a man is nobler than the back, and the right than the left, as we have said above, and as is plain also with respect to animals. Therefore the question under discussion testifies to the fact that in the heaven there is a before and an after, i.e., a front and a back, which things he did not mention previously. Now it is this, namely, the distinction between front and back in the heaven, that solves the question at hand. For if the motion of the heaven is the best possible, as has been maintained, then the cause in the aforesaid question is this: It is best for the heaven to be moved with a simple motion, i.e., always toward the same direction and one without any interruption, i.e., without the interpolation of rest (which would have to occur if the heaven were now moving in this direction and now in that direction); furthermore, it is best that it be moved toward the nobler part of the direction, and the front part is the more noble. And that is why the heaven is moved from the east toward its front, i.e., toward the upper hemisphere and not toward the lower, which is the back of the heaven. 366. Sed videtur quod inconvenienter hanc rationem assignet. Supra enim assignavit distinctionem harum partium in caelo ex principio motus, quia scilicet motus caeli videtur incipere ab una parte et non ab alia; hic autem assignat rationem quare caelum sic moveatur et non aliter, ex distinctione partium caeli; et ita videtur processus eius esse circularis. Ad quod dicendum est quod distinctio partium caeli est causa quod motus caeli incipiat ab hac parte et non ab alia, et non e converso: sed motum incipere ab hac parte caeli et non ab alia, est signum distinctionis partium caeli. Causa autem distinctionis harum partium est virtus animae moventis caelum, vel cuiuscumque intellectualis substantiae, diversimode attributa diversis partibus caeli. Nihil autem prohibet, cum quaeritur an aliquid sit, probare illud per signum; cum tamen quaeritur de causa alicuius propter quam est, oportebit signum ad causam reducere; sicut si probemus cor moveri per motum venae pulsatilis, si tamen quaeratur quae sit causa motus venae pulsatilis, dicetur quod hoc est propter motum cordis. Et similiter Aristoteles probavit esse talem distinctionem partium in caelo, per inchoationem motus a determinata parte, sicut per signum; et tamen inchoationem motus reducit in differentiam partium caeli, sicut in causam. Distinguitur autem pars anterior et posterior in caelo, non naturaliter, scilicet secundum determinatam partem corporis caelestis, quia una et eadem pars caelestis corporis quae nunc est in superiori hemisphaerio, postea erit in hemisphaerio inferiori; sed secundum situm, sicut etiam supra dictum est de differentia dextri et sinistri. 366. But this argument does not seem appropriate. For above he had explained the distinction of these parts in the heaven from the beginning of motion, namely, from the fact that the motion of the heaven seems to begin from one direction and not from another. But here he assigns the reason why the heaven is moved the way it is and not some other way, from the distinction of the parts of the heaven. Consequently, he seems to be arguing in a circle. To this it should be answered that the distinction among the parts of the heaven is the reason why the motion of the heaven begins whence it does and not elsewhere; and not conversely. But the fact that the motion does begin whence it does and not somewhere else is a sign of the distinction of the parts of the heaven. Now the cause of the distinction of these parts is the power of the soul moving the heaven, or of some intellectual substance differently applied to the different parts of the heaven. There is nothing wrong, when asking "Whether something is," should one prove with a sign; but when one is dealing with the "reason why something is," the sign must be reduced to the cause. For example, we might prove that the heart is moved by the motion of the pulsating vein; but if we should ask what is the cause of the motion of the pulsating vein, it will be said that it is because of the heart's movement. In like manner, Aristotle, from the fact that the motion of the heaven begins at a certain part, proved, as though from a sign, that there is such-and-such a distinction of parts in the heaven. Nevertheless he reduces the beginning of the motion to the difference in the parts of the heaven, as to the cause. Now the front and rear of the heaven are distinguished, not naturally, namely, in terms of some specific part of the heavenly body (since one and the same part of the heavenly body which is now in the upper hemisphere will later be in the lower), but in terms of position, just as was stated above concerning the difference between the right and left [sides of the heaven]. Lectio 8 Lecture 8 Motum caeli esse regularem, idest semper uniformem velocitatem habere, duabus rationibus ostenditur The regularity, or uniform velocity, of the heaven's motion shown by two arguments De motu autem ipsius, quia regularis est et non irregularis, deinceps utique dictis erit pertransire. 279 We have next to show that the movement of the heaven is regular and not irregular. Dico autem hoc de primo caelo et de prima latione. In his enim quae de subtus, plures iam lationes conveniunt in unum. 280 This applies only to the first heaven and the first movement; for the lower spheres exhibit a composition of several movements into one. Si enim irregulariter movebitur, manifestum quod intensio erit et virtus et remissio: omnis enim irregularis latio et remissionem habet et intensionem et virtutem. Virtus autem est aut unde fertur, aut quo, aut circa medium: puta forte his quidem qui secundum naturam, quo feruntur; his autem qui praeter naturam, unde; proiectis autem circa medium. Circulationis autem non est neque unde, neque quo, neque medium: neque enim principium, neque finis, neque medium ipsius est simpliciter; tempore enim sempiterna, et longitudine simul ducta, et infrangibilis. Quare, si non virtus ipsius lationis, neque irregularitas erit: irregularitas enim fit propter remissionem et intensionem. 281 If the movement is uneven, clearly there will be acceleration, maximum speed, and retardation, since these appear in all irregular motions. The maximum may occur either at the starting-point or at the goal or between the two; and we expect natural motion to reach its maximum at the goal, unnatural motion at the starting-point, and missiles midway between the two. But circular movement, having no beginning or limit or middle in the direct sense of the words, has neither whence nor whither nor middle: for in time it is eternal, and in length it returns upon itself without a break. If then its movement has no maximum, it can have no irregularity, since irregularity is produced by retardation and acceleration. Adhuc, quoniam omne quod movetur ab aliquo movetur, necesse irregularitatem fieri motus aut propter movens, aut propter motum, aut propter ambo: sive enim movens non eadem virtute moveat, sive motum alteretur et non permaneat idem, sive ambo transmutentur, nihil prohibet irregulariter moveri quod movetur. Nihil autem horum circa caelum fieri possibile. Quod quidem movetur, ostensum est quia primum et simplex et ingenitum et incorruptibile et totaliter intransmutabile. Movens autem multo magis rationabile esse tale: primum enim primi, et simplex simplicis, et incorruptibile et ingenitum incorruptibilis et ingeniti motivum. Quoniam igitur quod movetur non transmutatur, corpus existens, neque utique movens transmutabitur, incorporale existens. Quare et lationem impossibile irregularem esse. 282 Further, since everything that is moved is moved by something, the cause of the irregularity of movement must lie either in the mover or in the moved or both. For if the mover moved not always with the same force, or if the moved were altered and did not remain the same, or if both were to change, the result might well be an irregular movement in the moved. But none of these possibilities can be conceived as actual in the case of the heavens. As to that which is moved, we have shown that it is primary and simple and ungenerated and indestructible and generally unchanging; and the mover has an even better right to these attributes. It is the primary that moves the primary, the simple the simple, the indestructible and ungenerated that which is indestructible and ungenerated. Since then that which is moved, being a body, is nevertheless unchanging, how should the mover, which is incorporeal, be changed? It follows then, further, that the motion cannot be irregular. 367. Postquam philosophus assignavit causam quare caelum movetur versus unam partem et non versus aliam, hic determinat de uniformitate motus caeli. 367. After assigning the reason why the heaven is moved toward one direction rather than the other, the Philosopher here discusses the uniformity of the heaven's motion. Et primo proponit quod intendit; First, he proposes what he intends; secundo probat propositum, ibi: si enim irregulariter movebitur et cetera. secondly, he proves his proposition, at if the movement is uneven 369. Circa primum duo facit. About the first he does two things: Primo proponit quod intendit: et dicit quod post praedicta consequenter est pertranseundum, idest breviter dicendum, de motu caeli, ostendendo quod est regularis, idest semper uniformem velocitatem habens, et nunquam irregularis, ut quandoque scilicet velocius quandoque tardius moveatur. Et hoc rationabiliter: nam iste motus est regula et mensura omnium aliorum motuum; unde nulla irregularitas vel inaequalitas in eo debet apparere. first, he proposes what he intends [279], and says that after the foregoing we must cover, i.e., say something briefly about, the motion of the heaven and show that it is regular, i.e., that it always has a uniform velocity, and is never irregular so as to be at one time slower and at another swifter. And this is reasonable: for this motion is the rule and measure of all other motions. Hence, no irregularity or inequality should appear in it. 368. Secundo ibi: dico autem hoc etc., exponit quod dixerat. Et dicit quod hic intendit dicere de primo caelo, idest de suprema sphaera, et de prima latione, idest de motu diurno quo totum caelum revolvitur, per motum primi mobilis, ab oriente usque in occidentem. Ideo autem de hoc motu specialiter loquitur, quia in hoc motu neque est aliqua irregularitas secundum rei veritatem, neque secundum apparentiam. Sed in his quae de subtus, idest in motu planetarum, iam plures motus conveniunt ad movendum unum corpus; vel secundum diversas sphaeras volventes et revolventes, sicut dicebant astrologi qui fuerunt tempore Aristotelis, ut patet in XII Metaphys.; vel secundum motus eccentricorum et epicyclorum, secundum modernos astrologos. Et ex hac diversitate motuum causatur irregularitas quae apparet circa planetas, secundum quam quandoque videntur directi motus, quandoque retrogradi, quandoque stationarii; quamvis secundum rei veritatem nullus motus in caelo sit irregularis. Rationes enim quas hic inducet, habent locum non solum in motu primi caeli, qui est simplex, et ex hoc nulla apparet in eo irregularitas; sed etiam in motibus planetarum, in quibus apparet irregularitas propter concursum multorum motuum. 368. Secondly, at this applies only [280] he explains what he had said. And he says that he intends here to speak of the first heaven, i.e., the outermost sphere and of the first carrying, i.e., of the diurnal motion by which the whole heaven is revolved, though the motion of the first mobile, from east to west. Now he speaks of this motion in particular because there is in it no irregularity either in fact or in appearance. But in those things below, i.e., in the motion of the planets, several motions concur to move one body, either according to different shifting and revolving spheres, as the astronomers of Aristotle's time said, as is plain in Metaphysics XII, or according to the motions of eccentrics and epicycles according to modern astronomers. From this variety of motions is caused the irregularity which appears as to the planets, according to which they seem at one time to be moved with a forward motion, at another with a retrograde, and at still another to be at rest—although in fact no motion of the heaven is irregular. Now, the arguments which he will here adduce apply not only to the motion of the first heaven which is simple and hence gives no appearance of irregularity, but also to the motions of the planets, in which there is apparent irregularity due to the concurrence of many motions. 369. Deinde cum dicit: si enim irregulariter movebitur etc., probat propositum quatuor rationibus. 369. Then, at if the movement is uneven [281], he proves his proposition with four arguments. Quarum prima sumitur ex ipsa forma motus circularis, et procedit sic. Si primum caelum irregulariter moveretur, manifeste oporteret quod in eo esset intensio, idest augmentum velocitatis, et virtus, idest summum velocitatis, et remissio, idest deminutio velocitatis. Omnis enim motus irregularis habet ista tria; non ita quod in quolibet motu irregulari vel inaequali sint ista tria, sed quia in quolibet motu sunt duo horum; idest virtus et intensio, sicut in motu naturali corporum gravium et levium est intensio et virtus, quia talis motus semper augetur in velocitate usque ad finem, in quo est velocissimus; motus autem horum corporum qui est contra naturam, habet virtutem et remissionem, quia in principio est velocissimus, et semper deminuitur velocitas, quousque tandem totus motus consumatur. Et sic ly omnis accipitur quasi collective, ut intelligatur quod in omnibus motibus irregularibus ista tria inveniuntur, non autem in unoquoque eorum. The first is taken from the very form of circular motion, and proceeds thus: If the first heaven were moved in an irregular manner there would obviously have to be intension, i.e., an increase of velocity, and power, i.e., a maximum velocity, and remission, i.e., a decrease of velocity. For every irregular motion possesses all three. This is not in the sense that these three are found in each and every irregular or unequal motion, but in the sense that in any motion two of them are found. Thus "power" [a maximum] and "intension" [an increase] are found, as they are found in the natural motion of heavy and light bodies, since such motion is always increasing in velocity up to the end, when it is at its swiftest; on the other hand, when such bodies are subjected to a motion contrary to their nature, there is "power" [a maximum] and "remission" [a decrease], because in the beginning such a motion is swiftest but its velocity is continually decreased until at last the whole motion is exhausted. Thus the word "every" is taken collectively in the sense that these three things are found in all motions that are irregular but not all in each one.