Authors/Thomas Aquinas/physics/L7/lect1

Lecture 1 It is necessary that whatever is moved, be moved by another

Latin	English
	Lecture 1 It is necessary that whatever is moved, be moved by another.
lib. 7 l. 1 n. 1 Postquam philosophus in praecedentibus libris determinavit de motu secundum se, et de consequentibus ad ipsum, et de partibus eius, hic incipit determinare de motu per comparationem ad motores et mobilia. Et dividitur in partes duas. In prima ostendit esse primum motum et primum motorem. In secunda inquirit qualis sit motus primus et primus motor; et hoc in octavo libro, ibi: utrum autem factus sit aliquando et cetera. Prima autem pars dividitur in partes duas. In prima parte ostendit esse primum motum et primum motorem. Et quia ea quae sunt unius ordinis, habent aliquam comparationem ad invicem, ideo in secunda parte determinat de comparatione motuum ad invicem, ibi: dubitabit autem utique et cetera. Circa primum tria facit: primo praemittit quoddam quo indiget ad propositum ostendendum; secundo ostendit propositum, ibi: quoniam autem omne quod movetur etc.; tertio manifestat quoddam quod supposuerat, ibi: primum autem movens et cetera.	884. After discussing motion in itself, and the concomitants of motion, and the division of motion into parts, in the preceding books, the Philosopher now begins to treat of motion in its relationship to movers and things moved, i.e., the mobiles. The treatment falls into two parts; In the first he shows that there is a first motion and a first mover; In the second he investigates the properties of the first motion and of the first mover, in Book VIII. The first part is divided into two sections: In the first he shows that there is a first motion and a first mover. And because things that belong to one order are mutually related, therefore in the second part he compares the various types of motion (L-7). About the first he does three things: First he mentions the pre-notes needed for proving the proposition; Secondly, he proves the proposition (L. 2). Thirdly, he proves something he took for granted (L. 3)
lib. 7 l. 1 n. 2 Proponit ergo primo quod necesse est omne quod movetur, ab aliquo alio moveri. Quod quidem in aliquibus est manifestum. Sunt enim quaedam quae non habent in seipsis principium sui motus, sed principium motus ipsorum est ab extrinseco, sicut in his quae per violentiam moventur. Si ergo aliquid sit quod non habeat in seipso principium sui motus, sed principium sui motus est ab extrinseco, manifestum est quod ab alio movetur. Si vero sit aliquod mobile quod habeat in seipso principium sui motus, circa hoc potest esse dubium an ab alio moveatur. Et ideo circa hoc instat, ad ostendendum quod ab alio movetur. Si ergo aliquid tale ponatur non moveri ab alio, accipiatur mobile ab, cui quidem moveri conveniat secundum se et primo, non autem ex eo quod aliqua pars eius movetur. Sic enim non moveretur secundum se, sed secundum partem; oportet autem, si aliquid movet seipsum non motum ab altero, quod sit primo et per se motum; sicut si aliquid est calidum non ab alio, oportet quod sit primo et per se calidum. Hoc ergo dato, procedit ad propositum ostendendum dupliciter: primo quidem excludendo illud, unde maxime videri posset quod aliquid non ab alio moveatur; secundo directe ostendendo quod nihil potest a seipso moveri, ibi: amplius quod a seipso movetur et cetera. Id autem ex quo maxime videtur quod aliquid non moveatur ab alio, est quia non movetur ab aliquo exteriori, sed ab interiori principio. Dicit ergo primo, quod opinari quod ab moveatur a seipso propter hoc quod totum movetur, et non movetur ab aliquo exteriori, simile est ac si aliquis diceret quod mobile, cuius una pars movetur et alia movet, moveat seipsum, propter hoc quod non discernitur quae pars sit movens, et quae sit mota; sicut si huiusmodi mobilis quod est dez, pars quae est de, moveat partem quae est ez, et non videatur quae pars earum sit movens et quae sit mota. Vult autem per primum mobile ab, quod totum movetur et a principio interiori movente, intelligi aliquod corpus animatum, quod totum movetur ab anima: per mobile autem dez vult intelligi corpus aliquod quod non totum movetur, sed una pars eius corporalis est movens, et alia mota; in quo quidem mobili manifestum est quod id quod movetur, ab alio movetur. Et ex hoc vult simile ostendere de corpore animato, quod videtur movere seipsum. Hoc enim ei convenit inquantum una pars aliam movet, scilicet anima corpus, ut in octavo plenius ostendetur.	885. He proposes therefore first (676 241 b24) that everything that is being moved is necessarily being moved by some other. In some cases this is indeed evident, for there are some things which do not possess in themselves the principle of their motion; rather the principle of their motion is from without, as in things which are being moved by compulsion. Therefore, if there is anything that does not have in itself the principle of its own motion but its principle of motion is from without, it is clear that it is being moved by some other. However, if there is a mobile which does have in itself the principle of its own motion, there could be doubt whether it too is being moved by some other. Accordingly, he devotes himself to showing that this type of mobile is being moved by some other. Therefore, if it is supposed that such a mobile is not being moved by some other, let AB be a mobile capable of being moved primarily and according to itself and not in the sense that some part of it is being moved; for then it would not be being moved according to itself, but according to a part. Now it is necessary that if something moves itself without having been moved by some other, that it be moved primarily and per se; for example, if something is hot not from some other source, it must be primarily and per se hot. With this in mind, he proceeds to prove his proposition in two ways: First by excluding the most evident case in which it would appear that something is not being moved by some other; Secondly, by proving directly that nothing can be moved by itself, at 886. The most evident reason why it seems that something is not being moved by some other is that it is not being moved by something outside itself but by an intrinsic principle. He says therefore first (676 bis 241 b27) that to believe that AB is being moved by itself because the whole is being moved, and this without being moved by anything outside of it, is like saying that, when one part of a whole is being moved and another part causes it to be moved, it is moving itself, because it is not evident which part is the mover and which is being moved. Such would be the case if a mobile DEZ is such that one part DE moves the part EZ and it is not seen which part moves the other, and which is being moved. When he speaks of the first mobile AB as being moved as a whole by an intrinsic principle of motion, he means a living body which is, as a whole, being moved by the soul; but when he speaks of the mobile DEZ he means some body that is not being moved as a whole but one bodily part of it is the mover and another the moved. In this latter case, it is evident that what is being moved is being moved by some other. From this latter case he wants to prove of a living body that seems to move itself that it too is being moved by some other. For it seems to move itself inasmuch as one part moves another, i.e., as the soul moves the body, as will be more fully explained in Book VIII.
lib. 7 l. 1 n. 3 Deinde cum dicit: amplius quod etc., ostendit directe quod omne quod movetur ab alio movetur, tali ratione. Omne quod movetur a seipso, non quiescit a suo motu per quietem cuiuscumque alterius mobilis. Et hoc accipit quasi per se notum. Ex hoc autem ulterius concludit, quod si aliquod mobile quiescit ad quietem alterius, quod hoc movetur ab altero. Hoc autem supposito, concludit quod necesse est omne quod movetur ab aliquo alio moveri. Et quod hoc sequatur ex praemissis, sic probat. Illud mobile quod supposuimus a seipso moveri, scilicet ab, oportet divisibile esse, quia omne quod movetur est divisibile, ut supra probatum est. Quia ergo divisibile est, nullum inconveniens sequitur si dividatur. Dividatur ergo in puncto c, ita quod una pars eius sit bc, et alia ac. Si ergo bc est pars eius quod est ab, necesse est quod quiescente bc parte, quiescat totum ab. Si ergo non quiescat totum, quiescente parte, accipiatur quod totum moveatur, et una pars quiescat: sed quia una pars ponitur quiescere, non poterit poni totum moveri, nisi ratione alterius partis. Sic ergo bc quiescente, quod est una pars, movetur ac, quod est alia pars. Sed nullum totum cuius una sola pars movetur, movetur primo et per se. Non ergo movebitur ab primo et per se, quod erat suppositum. Ergo oportet quod bc quiescente, quiescat totum ab. Et sic illud quod movetur pausabit, idest desinet moveri, ad quietem alterius. Sed supra habitum est, quod si aliquid quiescit et desinit moveri ad quietem alterius, hoc ab altero movetur. Ergo ab ab altero movetur. Et eadem ratio est de quolibet alio mobili: quia omne quod movetur est divisibile, et eadem ratione oportet quod quiescente parte, quiescat totum. Manifestum est ergo quod omne quod movetur, ab aliquo alio movetur.	886. Then at (677 241 b34) he proves directly that whatever is being moved is being moved by some other. This is his argument: Nothing that is being moved by itself rests from its motion on account of some other mobile’s resting. (He takes this as per se evident). From this he further concludes that if a mobile rests on account of the rest of another, then the mobile is moved by another. On this ground he concludes that. necessarily whatever is being moved is being moved by some other. And that this follows from the premises, he now proves. That mobile which we have supposed as being moved by itself, i.e., ABI must be divisible, for whatever is being moved is divisible, as was proved above. Hence, because it is divisible, nothing prevents it from being divided. Therefore, let it be divided at the point C so that one part of it is PC and the other part AC. Now, if PC is part, of AB, then when the part BC rests, the entire AB must rest. But if upon the part resting, the whole does not rest, let us grant that the whole is being moved and one part is at rest. But because we have assumed that one part is resting, the whole could not be granted as being moved except by reason of the other part. Therefore, when BC (which is one part) is at rest, the other part AC is being moved. But no whole of which one part only is being moved is being moved primarily and se. Therefore AB is not being moved primarily and per se, as we originally assumed. Therefore while BC is at rest, the entire AB must be at rest. Thus, what is being moved ceases to be moved upon the occasion of something else resting. But above we held that if something rests and ceases to be moved on the occasion of another’s resting, it is being moved by that other. Therefore, AB is being moved by some other. The same argument applies to any other mobile, for whatever is being moved is divisible and, for the same reason, if the part rests the whole rests. Therefore, it is clear that whatever is moved is moved by some other.
lib. 7 l. 1 n. 4 Contra istam autem Aristotelis probationem multipliciter obiicitur. Obiicit enim Galenus contra hoc quod dicit Aristoteles, quod si una tantum pars eius mobilis moveatur et reliqua quiescat, quod totum non per se movetur: dicens hoc esse falsum; quia ea quae moventur secundum partem, per se moventur. Sed deceptus est Galenus ex aequivocatione eius quod est per se. Per se enim quandoque sumitur secundum quod opponitur ei tantum quod est per accidens; et sic quod movetur secundum partem, movetur per se, ut Galenus intellexit. Quandoque vero sumitur secundum quod opponitur simul ei quod est per accidens, et ei quod est secundum partem; et hoc dicitur non solum per se, sed etiam primo. Et sic accipit per se Aristoteles hic: quod patet quia, cum conclusisset non ergo movetur per se ab, subiungit: sed concessum est per seipsum moveri primum.	887. Many objections are leveled against this argument of Aristotle. For Galen objects against the statement that if just one part of a mobile is being moved and the others are at rest, then the whole is not being moved per se. Galen says this is false, because things that are being moved according to a part are moved per se. But Galen was deceived by playing on the phrase “per se”. For sometimes it is taken in opposition to per accidens, and then it is true that what is being moved according to a part is being moved per se, as Galen said. But sometimes per se is taken in opposition both to per accidens and to what is according to a part: and in this sense something is said to be not only per se, but also primarily so. And this is the sense in which it was being used by Aristotle in his proof. That he does so is clear, because after concluding, “therefore AB is not being moved per se,” he adds, “whereas it had been assumed that it was being moved primarily and per se.”
lib. 7 l. 1 n. 5 Sed magis urget obiectio Avicennae, qui obiicit contra hanc rationem, dicens eam procedere ex suppositione impossibili, ex quo sequitur impossibile, et non ex eo quod ponitur aliquid a seipso moveri. Si enim ponamus aliquod mobile a seipso moveri primo et per se, naturale est ei quod moveatur et secundum totum et secundum partes. Si ergo ponatur quod aliqua pars eius quiescat, erit positio impossibilis. Et ex hac positione sequitur impossibile ad quod Aristoteles inducit, scilicet quod totum moveatur non primo et per se, ut positum est. Huic autem obiectioni posset aliquis obviare dicendo, quod licet impossibile sit partem quiescere secundum determinatam naturam, inquantum est corpus talis speciei, ut puta caelum vel ignis, non est tamen impossibile, si ratio communis corporis consideretur: quia corpus, inquantum corpus, non prohibetur quiescere vel moveri. Sed hanc responsionem excludit Avicenna dupliciter. Primo quidem quia pari ratione posset dici de toto corpore, quod non prohibetur quiescere ex hoc quod corpus est, sicut dicitur de parte; et ita superfluum fuit assumere ad probationem propositi divisionem mobilis et quietem partis. Secundo quia aliqua propositio simpliciter redditur impossibilis, si praedicatum repugnet subiecto ratione differentiae specificae, quamvis non repugnet ei ratione generis. Est enim impossibile quod homo sit irrationalis, quamvis non impediatur irrationalis esse ex hoc quod est animal. Sic igitur simpliciter impossibile est quod pars corporis moventis seipsum quiescat, quia hoc est contra rationem talis corporis, licet non sit contra rationem communem corporis.	888. But a more serious objection is that of Avicenna who says against the argument that it proceeds from an impossible assumption, from which the impossible follows, and not from the assumption that something is being moved by itself. For if we assume that a mobile is being moved first and per se, it is natural that it be moved both according to the whole and according to the parts. Therefore, if it is then assumed that a part is at rest, that is the same as assuming what is impossible. And it is from this added assumption that there follows the impossibility which Aristotle deduces, namely, that the whole is not being moved first and per se, as was assumed. One might obviate this objection by countering that although it is impossible for a part to rest if you confine yourself to a body of a definite kind, for example, the heaven or fire, yet it is not impossible, if you consider the general definition of body, for body as body is not prevented from being at rest or in motion. However, Avicenna forestalled such a response. First, because for the same reason it could be said of a whole body that it is not being prevented from resting just because it is a body, just as it is said of the part. Thus it was superfluous to assume, in order to prove the proposition, the division of the mobile and the rest of a part. Secondly, because some propositions are rendered impossible absolutely, if the predicate is repugnant to the subject by reason of its specific difference even though it be not repugnant to it by reason of its genus. For it is impossible for man to be non-rational, although he is not prevented from being non-rational from the fact of his being animal. Thus, therefore, it is impossible absolutely that a part of a body moving itself be at rest, for this is against the nature of any particular body, even though it be not against the common notion of body.
lib. 7 l. 1 n. 6 Hac igitur responsione remota, Averroes aliter solvit: et dicit quod aliqua conditionalis potest esse vera, cuius antecedens est impossibile et consequens impossibile, sicut ista: si homo est asinus, est animal irrationale. Concedendum est ergo quod impossibile est quod, si aliquod mobile ponitur movere seipsum, quod vel totum vel pars eius quiescat; sicut impossibile est ignem non esse calidum, propter hoc quod est sibi ipsi causa caloris. Unde haec conditionalis est vera: si mobilis moventis seipsum pars quiescit, totum quiescit. Aristoteles autem, si verba eius diligenter considerentur, nunquam utitur quiete partis, nisi per locutionem habentem vim conditionalis propositionis. Non enim dicit quiescat bc, sed necesse est, bc quiescente, quiescere ab; et iterum, quiescente parte, quiescit totum: et ex hac conditionali vera, Aristoteles propositum demonstrat. Sed dicit Averroes quod ista demonstratio non est de genere demonstrationum simpliciter, sed de genere demonstrationum quae dicuntur demonstrationes signi, vel demonstrationes quia, in quibus est usus talium conditionalium. Est autem haec solutio conveniens quantum ad hoc quod dicit de veritate conditionalis: sed videtur dicendum quod non sit demonstratio quia, sed propter quid; continet enim causam quare impossibile est aliquod mobile movere seipsum. Ad cuius evidentiam sciendum est, quod aliquid movere seipsum nihil aliud est, quam esse sibi causa motus. Quod autem est sibi causa alicuius, oportet quod primo ei conveniat; quia quod est primum in quolibet genere, est causa eorum quae sunt post. Unde ignis, qui sibi et aliis est causa caloris, est primum calidum. Ostendit autem Aristoteles in sexto, quod in motu non invenitur primum, neque ex parte temporis, neque ex parte magnitudinis, neque etiam ex parte mobilis, propter horum divisibilitatem. Non ergo potest inveniri primum, cuius motus non dependeat ab aliquo priori: motus enim totius dependet a motibus partium, et dividitur in eos, ut in sexto probatum est. Sic ergo ostendit Aristoteles causam quare nullum mobile movet seipsum; quia non potest esse primum mobile, cuius motus non dependeat a partibus: sicut si ostenderem quod nullum divisibile potest esse primum ens, quia esse cuiuslibet divisibilis dependet a partibus: ut sic haec conditionalis sit vera: si pars non movetur, totum non movetur, sicut haec conditionalis est vera: si pars non est, totum non est.	889. With this possible answer rejected, Avicenna solves it in another way. He says that a conditional whose antecedent is impossible and whose consequent is impossible can be true; for example, “If man is a horse, he is a non-rational animal.” It should be conceded, therefore, that it is an impossible assumption that mobile be moving itself and yet have the whole or a part of itself at rest, just as it is impossible for fire not to be hot, for fire is its own cause of its heat. Hence this conditional is true: “If a part of a mobile moving itself is at rest, the whole is at rest.” But Aristotle, if his words are carefully studied, does not speak of the rest of the part, except in a statement that has the force of a conditional. For he does not say, “Let BC be at rest,” but “If BC is at rest, AB must rest,” and “If the part rests, the whole rests”: and from this true conditional Aristotle proves his proposition. But, says Averroes, that demonstration is not an absolute demonstration but one of the type called “demonstrating by a sign” or a demonstration “quia”, in which such conditionals are used. However, this solution is agreeable in regard to what he says about the truth of a conditional but not in regard to the statement that it is a “quia” demonstration, for it seems to be a “propter quid’, because it contains the cause why it is impossible for a mobile to move itself. To see this, recall that to move oneself is nothing more than to be the cause of one’s own motion. Whatever is its own cause of something must possess it primarily, i.e., first, because what is first in any group is the cause of what comes after it. Hence fire, the cause of heat for itself and for other things, is the first hot thing. But, in Book VII Aristotle showed that there is no first in motion, whether on the side of time or the magnitude or the mobile—for they are all divisible. Therefore, it is impossible to find a first whose motion does not depend on a prior, for the motion of the whole depends on the motions of the parts and is divided into those motions, as was proved in Book VI. Aristotle, therefore, thus shows the cause why no mobile moves itself: it is because there cannot be a first mobile whose motion does not depend on its parts any more than the first being can be a divisible, for the existence of any divisible depends on the parts. Hence this conditional is true “If the part is not being moved, neither is the whole,” just as this one is true “If the part does not exist, the whole does not.”
lib. 7 l. 1 n. 7 Unde et Platonici, qui posuerunt aliqua movere seipsa, dixerunt quod nullum corporeum aut divisibile movet seipsum; sed movere seipsum est tantummodo substantiae spiritualis, quae intelligit seipsam et amat seipsam: universaliter omnes operationes motus appellando; quia et huiusmodi operationes, scilicet sentire et intelligere, etiam Aristoteles in tertio de anima nominat motum, secundum quod motus est actus perfecti. Sed hic loquitur de motu secundum quod est actus imperfecti, idest existentis in potentia, secundum quem motum indivisibile non movetur, ut in sexto probatum est, et hic assumitur. Et sic patet quod Aristoteles, ponens omne quod movetur ab alio moveri, a Platone, qui posuit aliqua movere seipsa, non dissentit in sententia, sed solum in verbis.	890. Hence even the Platonists, who assumed that some things move themselves, said that no body or divisible thing moves itself; rather to move itself is a prerogative of a spiritual substance which understands and loves itself (here all operations are being called “motions,” just as Aristotle in Book III of On the Soul calls sensing and understanding by the name of “motions” in the sense that motion is the act of a perfect thing). However, in this Book VII he takes motion as the act of an imperfect thing, i.e., of a thing existing in potency. It is in this sense of motion that no indivisible is moved, as was proved in Book VI and is here taken for granted. And so it is clear that Aristotle, in stating that whatever is moved is moved by some other, and Plato, in stating that some things move themselves, are here not apart in their opinions but solely in their words.