Authors/Thomas Aquinas/physics/L8/lect11

Lecture 11 How the parts of something moving itself are related

Latin	English
	Lecture 11 How the parts of something moving itself are related.
lib. 8 l. 11 n. 1 Postquam philosophus ostendit quod movens seipsum dividitur in duas partes, quarum una movet et non movetur, alia autem movetur; hic ostendit quomodo huiusmodi partes se habeant ad invicem. Et circa hoc tria facit: primo proponit quod intendit; secundo ostendit propositum, ibi: sit enim a movens etc.; tertio concludit conclusionem principaliter intentam ex omnibus praemissis, ibi: manifestum igitur ex his et cetera. Dicit ergo primo, quod cum movens dividatur in duo, quorum unum movetur etiam ab alio, aliud vero movens est immobile: et iterum mobile dividatur in duo; est enim quoddam mobile quod etiam movet, quoddam vero mobile quod nihil movet: oportet dicere quod movens seipsum componatur ex duabus partibus, quarum una sit sic movens quod tamen sit immobilis, alia vero sic moveatur quod tamen non moveat. Quod autem subdit ex necessitate, dupliciter potest intelligi: quia si intelligatur quod pars mota moventis seipsum non moveat aliquid quod sit pars moventis seipsum, sic legenda est littera, quod necessitas remaneat affirmata, cadens super hoc quod dicit non movente. Probat enim statim impossibile esse, quod eius quod primo movet seipsum, sit tertia pars, quae moveatur a parte mota. Si vero intelligatur quod pars mota non moveat aliquid extrinsecum, sic hoc quod dicit ex necessitate, cadit sub negatione: non enim est de necessitate moventis seipsum, quod pars eius mota moveat aliquid extrinsecum; nec tamen est impossibile.	1062. After showing that a thing which moves itself is divided into two parts, one of which causes motion and is not moved, and the other of which is moved, the Philosopher now shows how such parts are mutually related. About this he does three things: First he proposes what he intends; Secondly, he shows his proposition, at 1063; Thirdly, he reaches the conclusion chiefly intended by all the foregoing, at 1068. He says therefore First (831 258 a5) that since a mover is divided into two elements, one of which is also moved by something else, and the other of which is immobile, and again, since a mobile is divided into two, there being a mobile which also causes motion, and another which does not move anything, one must say that what moves itself is composed of two parts, one of which is such a mover as to be immobile, and the other of which is so moved as not to move anything else. And when he says that the latter does not move anything “of necessity,” it can mean two things: If it is understood as though the moved part of a self-mover does not move anything that is part of the self-mover, the word “necessity” should be interpreted in an affirmative sense, referring to his calling it “non-moving,” as meaning that of necessity it does not move anything else. For he at once proves that it is impossible for a thing that moves itself to have a third part which is moved by the moved part. But if the words are interpreted as meaning that the moved part does not move anything extrinsic, then the phrase, “of necessity,” must be given a negative meaning; for it is not necessary in a thing which moves itself that its moved part move something extrinsic, but neither is it impossible.
lib. 8 l. 11 n. 2 Qualiter autem hoc contingat, ostendit consequenter cum dicit: sit enim a movens et cetera. Et circa hoc duo facit: primo ostendit propositum; secundo solvit quandam dubitationem, ibi: dubitationem autem habet et cetera. Circa primum duo facit: primo ostendit qualiter partes moventis seipsum se habeant ad invicem; secundo qualiter secundum eas totum dicitur seipsum movere, ibi: si igitur continuum est et cetera. Circa primum duo facit: primo ostendit quod in movente seipsum sunt solae duae partes, quarum una movet et non movetur, alia movetur et non movet; secundo quomodo hae duae partes ad invicem coniungantur, ibi: contacta autem utraque et cetera. Primum ostendit sic. Si dicatur quod pars mota moventis seipsum, iterum moveat aliquid aliud, quod sit pars eiusdem moventis seipsum: sit ergo prima pars moventis seipsum a, quod sit movens immobile: secunda vero pars sit b, quod moveatur ab a, et moveat tertiam partem, quae est c, quae sic moveatur a b, quod nihil aliud moveat quod sit pars moventis seipsum. Non enim potest dici quod fiat descensus in infinitum in partibus moventis seipsum, scilicet quod pars mota iterum moveat aliam: quia sic movens seipsum esset in infinitum, quod est impossibile, ut supra ostensum est. Erit ergo aliqua pars moventis seipsum, quae est mota non movens, quam dicimus c. Et licet contingat per multa media quae sunt moventia et mota, pervenire in ultimum motum quod dicitur c; accipiatur loco omnium mediorum, unum medium quod sit b. Sic ergo hoc totum quod est abc movet seipsum. A quo toto si auferatur haec pars quae est c, adhuc ipsum ab movebit seipsum: quia una pars eius est movens, scilicet a, et alia mota, scilicet b, quod requirebatur ad hoc quod aliquid sit movens seipsum, ut supra ostensum est. Sed c non movebit seipsum, neque aliquam aliam partem, secundum supposita. Similiter etiam bc non movet seipsum sine a, quia b non movet nisi inquantum movetur ab alio quod est a, quod non est pars eius. Relinquitur ergo quod solum ab moveat seipsum primo et per se. Unde necesse est quod movens seipsum habeat duas partes, quarum una sit movens immobilis, alia vero sit mota, quam necesse est nihil movere quod sit pars moventis seipsum: hoc enim conclusum est per praemissam rationem. Vel nihil movens ex necessitate: quia non est de necessitate moventis seipsum, quod pars mota moveat aliquid aliud etiam extrinsecum.	1063. How this happens he shows at (832 258 a9). About this he does two things: First he explains his proposition; Secondly, he solves a doubt, at 1066. About the first he does two things: First he shows how the parts of a thing that moves itself are related; Secondly, how with respect to them a whole is said to move itself, at 1065. About the first he does two things: First he shows that in a thing which moves itself there are just two parts, one of which causes motion and is not moved, and the other of which is moved and does not cause any motion; Secondly, how these two parts are joined to one another, at 1064. He explains the first part in this way (832 258 a9): If it be said that the moved part of a thing that moves itself does in turn move something else which is part of the very thing that moves itself, then let A be the first immobile part of this self-moving thing. Let B be the second part and let it be both the one moved by A and the mover of a third part C. which is so moved by B as to move nothing else that is a part of this self-moving thing. For it cannot be said that there is an infinite descent in the parts of a thing which moves itself, such that a moved part in turn moves another, for then it would be moving itself ad infinitum, which is impossible, as was shown above. There will be, therefore, in that self-moving thing a part which is moved but is not a mover, i.e., the part C. And although it might be that it is through many intermediate moved movers that the last moved part C is reached, we can accept B as the one intermediate taken in place of all these intermediates. Thus, therefore, does this whole, which is ABC, move itself. If from this whole there be taken away the part C, AB will still move itself, because one of its parts is a mover, namely A, and the other moved, namely B, which was required for a thing to be able to move itself, as was shown above. But C will not move itself, or move any other part, as we have assumed. Likewise, even BC does not move itself without A, because B does not cause motion except inasmuch as it is moved by something else, which is A, which is not a part of BC. It remains, therefore, that only AB moves itself first and per se. Hence a thing which moves itself must have two parts, one of which is an immobile mover, and the other of which is moved and necessarily does not move anything that is part of the whole thing that moves itself, for this was concluded by the foregoing argument. Or else it “moves nothing of necessity”—since it is not a necessity of a self-mover that the moved part move anything else, even anything extrinsic.
lib. 8 l. 11 n. 3 Deinde cum dicit: contacta autem utraque etc., ostendit quomodo hae duae partes se habeant ad invicem. Ubi considerandum est, quod Aristoteles nondum probavit primum movens non habere aliquam magnitudinem, quod infra probabit. Quidam autem antiqui philosophi posuerunt nullam substantiam absque aliqua magnitudine esse. Unde Aristoteles ante probationem hoc sub dubio secundum suam consuetudinem derelinquens, dicit quod duas partes moventis seipsum, quarum una est movens et alia mota, necesse est aliquo modo coniungi, ad hoc quod sint partes unius totius. Non autem per continuationem, quia supra dixit quod movens seipsum et motum non possunt continuari, sed necesse est ea dividi: unde relinquitur quod oportet has duas partes coniungi per contactum; aut ita ut ambae partes contingant se invicem, si ambae partes habeant magnitudinem; aut ita quod altera tantum pars contingatur ab alia, et non e converso, quod erit si movens non habet magnitudinem. Quod enim est incorporeum, potest quidem tangere corpus sua virtute movendo ipsum, non autem contingitur a corpore: duo autem corpora se invicem tangunt.	1064. Then at (833 258 a20) he shows how these two parts are mutually related. Here it must be considered that Aristotle has not yet proved that the first mover has no magnitude, as will be proved later. But some of the earlier philosophers posited that no substance can exist without magnitude. Hence Aristotle is keeping with his custom when he leaves this matter doubtful until it is proved; and he says that the two parts of a self-mover, of which one is a mover and the other moved, must be somehow conjoined if they are to be parts of one whole. But not by continuation, because above he has said that a self-mover and a moved thing cannot form a continuum but are necessarily divided. Hence it remains that these two parts must be joined by contact: either by both parts touching one another, if they have magnitude; or by just one of the parts touching the other and not vice versa, which will be the case if the mover has no magnitude. For what is incorporeal can indeed touch a body by means of its power and so move it, but it is not touched in turn by the body; two bodies, however, touch each other.
lib. 8 l. 11 n. 4 Deinde cum dicit: si igitur continuum est etc., ostendit qua ratione totum dicatur movens seipsum, una parte movente et alia mota. Et supponamus quantum ad praesens, quod utraque pars sit continua, idest magnitudinem habens; quia de eo quod movetur, in sexto probatum est quod sit aliquid continuum; et accipiatur nunc idem de movente, antequam veritas probetur. Hac igitur suppositione facta, ipsi toti composito ex duobus tria attribuuntur, scilicet moveri, movere, et movere seipsum. Sed hoc quod est movere seipsum, attribuitur ei non propter hoc quod aliqua pars eius moveat seipsam, sed ipsum totum seipsum movet: sed hoc quod est movere et moveri, attribuitur toti ratione partis. Non enim totum movet neque totum movetur; sed movet una pars eius, scilicet a, reliqua vero pars eius solum movetur, scilicet b: iam enim ostensum est quod non est aliqua tertia pars, ut c, quae moveatur ab ipso b. Impossibile est enim hoc, si accipiatur id quod primo movet seipsum, sicut supra ostensum est.	1065. Then at (834 258 a21) he shows by what reason a whole is said to move itself with one part causing motion and the other part being moved. And let us suppose at first that each part is continuous, i.e., having a magnitude, because in Book VI it has been proved of anything that is moved that it is a continuum, and let the same thing be supposed at the present time for the mover, before the truth is proved. Therefore, using this supposition, three things are attributed to this whole composed of two parts: it is moved, it causes motion, and it moves itself. But self-movement is attributed to it not because a part moves itself but because the entire whole move itself, while to cause motion, and to be moved, are attributed to the whole by reason of the part. For the whole neither moves nor is moved, but one part A moves, and the other part B is moved only; and it has already been shown that there is no third part C which is moved by B. For this is impossible, if we are dealing with a thing that moves itself primarily, as has been shown above.
lib. 8 l. 11 n. 5 Deinde cum dicit: dubitationem autem habet etc., movet quandam dubitationem circa praemissa. Et primo movet eam; secundo solvit, ibi: aut potentia quidem et cetera. Habet autem haec dubitatio ortum ex hoc quod supra probaverat, quod in primo movente seipsum non sunt nisi duae partes, quarum una movet et alia movetur; quia si esset tertia, etiam ea remota compositum ex primis duabus movet seipsum, et sic ipsum est primum movens seipsum. Ex hoc ergo sequitur dubitatio talis. Ponamus quod pars moventis seipsum quae est movens immobile, ut a, sit quoddam continuum: de parte autem eius quae movetur, scilicet b, manifestum est quod est aliquid continuum, secundum prius probata. Omne autem continuum est divisibile: est ergo dubitatio, si auferatur aliqua pars per divisionem ab a aut a b, utrum reliqua pars moveat aut moveatur. Quia si reliqua pars moveat aut moveatur, adhuc residua pars de ab movebit seipsum, et sic ab non primo movebat seipsum. Et sic sequitur ulterius, quod nihil erit primo movens seipsum.	1066. Then at (835 258 a27) he raises a doubt about the foregoing. First he raises it; Secondly, he solves it, at 1067. This doubt springs from what he had previously proved, namely, that in a thing that moves itself in a primary sense, there are but two parts, of which one moves and the other is moved, on the ground that, if there were a third, even if this third were removed, the composite of the first two would still move itself, and thus the latter is the primary self-mover. From this, therefore, the following doubt follows (835 258 a27). Let us suppose that the immobile but motion-causing part A of a self-moving whole is a continuum. Now it is clear that its part B, which is the moved part, is a continuum, according to what has been previously proved. But every continuum is divisible. Therefore the doubt is this: If through division a part be removed from A or R, would the remaining part be a mover or a moved part? Because if it is either, the part of AB that remains will move itself and, accordingly, AB will not be some-thing that moves itself in a primary sense. Thus it further follows that nothing will be a self-mover in a primary sense.
lib. 8 l. 11 n. 6 Deinde cum dicit: aut potentia quidem etc., solvit positam dubitationem. Ubi considerandum est quod Aristoteles prius in sexto probavit quod in motu non est aliquid primum, neque ex parte mobilis neque ex parte temporis neque ex parte rei in qua est motus, praecipue in augmento et motu locali: et hoc ideo, quia tunc loquebatur de motu in communi, et de mobili secundum quod est quoddam continuum, nondum applicando ad determinatas naturas. Et secundum hoc sequeretur quod non esset aliquid primo motum, et per consequens nec aliquid primo movens, si movens sit continuum: et ita etiam non esset aliquid primo movens seipsum. Sed nunc iam Aristoteles loquitur de motu, applicando ad determinatas naturas: et ideo ponit aliquid esse primo movens seipsum. Et solvit praemissam dubitationem sic: quod nihil prohibet esse divisibile in potentia ex eo quod sunt continua (scilicet movens et motum) si utrumque sit continuum, aut ad minus alterum tantum, scilicet quod movetur, quod necesse est esse continuum. Sed tamen possibile est quod aliquod continuum, sive sit movens sive motum, habeat talem naturam, ut non possit actu dividi, sicut patet de corpore solis. Et si contingat quod aliquod continuum dividatur, non retinebit eandem potentiam ad hoc quod moveat vel moveatur, quam prius habebat; quia huiusmodi potentia sequitur aliquam formam; forma autem naturalis requirit quantitatem determinatam. Unde si sit corpus incorruptibile, dividi non potest in actu. Si autem sit corruptibile, si dividatur in actu, non retinebit eandem potentiam, sicut patet in corde. Unde nihil prohibet in iis quae sunt divisibilia in potentia, esse unum primum.	1067. Then at (836 258 a32) he resolves this doubt. Now it should be remembered here that in Book VI Aristotle has proved that there is no first in motion, either on the part of the mobile, or of the time or of the sphere of motion, and that this is especially true in growth and local motion: the reason being that he was then speaking of motion in common and of the mobile as it is a certain continuum, without yet making application to particular natures. And according to this, it would follow that there would not be anything that is first moved and, consequently, no first mover, if the mover were a continuum. Likewise, there would also not be anything that is a first mover. But now Aristotle is speaking of motion and applying his doctrine to definite natures and for that reason he posits that there is a first mover of self. And he resolves the doubt in the following manner, stating, namely, that there is nothing to prevent the mover and moved from being divisible in potency, due to the fact that they are continua, i.e., if both are continua, or at least one of them, namely, the one that is moved, which necessarily is a continuum. But yet it is possible that some continuum, whether it be a mover or something moved, have such a nature that it cannot be actually divided, as is evident of the body of the Sun. And if it happens that some continuum is divided, it will not retain the same potency for causing motion or being moved as it had before—because such a potency follows upon the form, and a natural form requires a determinate quantity. Hence, if it is an incorruptible body, it cannot be actually divided. But if it is a corruptible one, then if it be divided, it will not retain the same potency, as is evident with respect to the heart. Hence, there is nothing to prevent, in things potentially divisible, there being one first.
lib. 8 l. 11 n. 7 Deinde cum dicit: manifestum igitur ex his etc., infert conclusionem principaliter intentam ex omnibus praemissis. Et dicit manifestum esse ex praemissis, quod necesse est ponere primum movens immobile. Cum enim non procedatur in infinitum in moventibus et motis ab alio, sed necesse sit stare ad aliquod primum, quod est immobile vel movens seipsum; sive moventia et mota stent ad aliquod primum immobile, sive ad aliquod primum quod movet seipsum, utrobique accidit quod primum movens sit immobile; propter hoc quod moventis etiam seipsum una pars est movens immobile, ut nunc ostensum est.	1068. Then at (837 258 b4) he infers the conclusion mainly intended from all this. And he says that from the foregoing it is clear that it is necessary to posit a first mover that is immobile. For since there is not an infinite process in movers and moved things, but a halt must be made at a first which is immobile or self-moving, then, whether the movers and moved stop at some first immobile or at some first that moves itself, in either case it turns out that the first mover is immobile, because one part even of a thing that moves itself is an immobile mover, as has just been proved.