Authors/Thomas Aquinas/physics/L8/lect15

Lecture 15 Local motion alone can be continuous and perpetual

Latin	English
	Lecture 15 Local motion alone can be continuous and perpetual.
lib. 8 l. 15 n. 1 Postquam philosophus ostendit quod motus localis est primus inter omnes motus, hic ostendit quis motus localis sit primus. Et quia, sicut supra dixit, necesse est eundem esse motum continuum et primum, dividitur haec pars in partes duas: in prima ostendit quis motus possit esse semper continuus; in secunda ostendit quod ille motus est primus, ibi: quod autem lationum circularis et cetera. Prima autem pars dividitur in partes tres: in prima ostendit quod nullus motus potest esse continuus nisi localis; in secunda quod nullus motus localis potest esse continuus praeter circularem, ibi: quoniam autem contingit esse quendam etc.; in tertia ostendit quod motum circularem contingit esse continuum, ibi: qui autem in circulari et cetera. Circa primum duo facit: primo proponit quod intendit; secundo probat propositum, ibi: omnes enim ex oppositis et cetera. Dicit ergo primo, quod cum ostensum sit quod loci mutatio est prima inter omnes species motus, nunc ostendendum est quae loci mutatio sit prima; quia eius etiam sunt multae species, ut in septimo ostensum est. Et simul etiam secundum eandem methodum, idest artem, idest secundum eandem artificialem considerationem, erit manifestum id quod nunc paulo supra diximus, et quod etiam prius suppositum est in principio huius octavi, quod contingit aliquem motum esse continuum et perpetuum. Oportet enim quod idem sit primus et continuus, ut supra ostensum est; et ideo sub eadem consideratione utrumque eorum cadit. Quod ergo nulla alia species motus praeter loci mutationem possit esse continua et perpetua, manifestum est ex his quae dicentur.	1097. After proving that local motion is the first of all motions, the Philosopher now shows which local motion is the first. And because, as he said above, the motion must be the same which is continuous and first, this treatment is divided into two parts: First he shows which motion can be always continuous; Secondly, he shows that such a motion is the first, (L. 19). The first part is divided into three sections: In the first he shows that no motion but local can be continuous; In the second that no local motion but a circular one can be continuous, (L. 16); In the third that a circular motion can be continuous, (L. 19). About the first he does two things; First he proposes what he intends; Secondly, he proves his proposition, at 1098. He says therefore first that since it has been shown that change of place is the first among all types of motion, we must now show which change of place is first, because there are many types of it, as was proved in Book VII, And at the same time, according to the same method, i.e., art, i.e., according to the same technical consideration, there will be plain what we have just said and what was also previously assumed at the beginning of Book VIIII namely, that there exists a motion which is continuous and perpetual. Now the first and the continuous must be the same, as was proved above. For that reason both of them fall under the same consideration. That no other type of motion, however, but local motion can be continuous and perpetual will be clear from what will be said.
lib. 8 l. 15 n. 2 Deinde cum dicit: omnes enim ex oppositis etc., ostendit propositum. Et circa hoc duo facit: primo ostendit quod nulla alia species mutationis praeter localem potest esse continua et perpetua, una et eadem existens; secundo quod nec duae mutationes aliae oppositae possunt sibi succedere sine interpositione quietis, ibi: amplius in generatione et cetera. Circa primum duo facit: primo ostendit propositum; secundo excludit quasdam obiectiones, ibi: nihil enim differt et cetera. Circa primum duo facit: primo ostendit propositum in motibus; secundo in mutationibus, ibi: similiter autem et in mutationibus et cetera. Proponit ergo primo unam propositionem, quae communiter vera est tam in motibus quam in mutationibus, quod scilicet omnes motus et mutationes sunt ex oppositis in opposita: a qua generalitate excipitur quodammodo loci mutatio, ut in fine sexti dictum est. Generatio enim et corruptio, quae sunt mutationes, habent pro terminis esse et non esse; alterationis vero termini oppositi sunt contrariae passiones, idest passibiles qualitates, ut calidum et frigidum, album et nigrum; augmenti vero et diminutionis oppositi termini sunt magnum et parvum, sive perfectum et imperfectum in magnitudine seu quantitate. Manifestum est autem ex his quae dicta sunt in quinto, quod motus qui sunt in contraria sunt contrarii: motus igitur qui est in album, contrarium est motui qui est in nigrum. Sed contraria non possunt esse simul: ergo dum aliquid movetur ad album, non simul movetur ad nigrum. Quod ergo incipit moveri ab albo in nigrum motu denigrationis, etiamsi moveretur motu dealbationis dum fieret album, tamen manifestum est quod non poterat simul moveri motu denigrationis. Quod autem prius existebat, si non semper movebatur aliquo motu determinato, necesse est dicere quod prius quiescebat quiete opposita huic motui: quia omne quod est natum moveri, vel quiescit vel movetur. Manifestum est ergo quod id quod movetur in aliquod contrarium, aliquando quiescebat quiete opposita tali motui. Nullus ergo motus qui est in aliquod contrarium, potest esse continuus et perpetuus. Si ergo huic conclusioni addatur quod primo positum est, scilicet quod omnis motus alterationis vel augmenti vel decrementi sit in aliquod contrarium, sequetur quod nullus huiusmodi motus possit esse continuus et perpetuus.	1098. Then at (864 261 a32) he proves the proposition. And about this he does two things: First he shows that no other species of change but local can be continuous and perpetual, remaining one and the same; Secondly, that two changes which are opposite cannot succeed one another without an interval of rest, at 1103. About the first he does two things: First he proves the proposition; Secondly, he excludes some objections, at 1100. About the first he does two things: First he proves the proposition in motions; Secondly, in changes, at 1099. He proposes therefore First (864 261 a32) one proposition which is true in common both for changes and motions, namely, that all changes and motions are from opposites to opposites. But local motion is in a sense excluded from this generality, as was said at the end of Book VI. For generation and ceasing-to-be, which are changes, have, for their termini, existence and non-existence; the opposite termini of alteration are contrary passions, i.e., passible qualities, such as hot and cold, black and white; and the opposite termini of growth and decrease are large and small, or perfect and imperfect in magnitude, or quantity. But it is plain from what was said in Book V that motions toward contrary termini are contrary. Therefore, a motion to white is contrary to a motion to black. But contraries cannot be together; therefore, while something is being moved to white, it cannot at the same time be undergoing a motion to back, Hence what begins to be moved from white to black by the motion of blackening, even though it should be moved by the motion of whitening while becoming white, it could not simultaneously be moved by the motion of blackening, But what was existing previously, if it was not always being moved by some definite motion, must be considered as having been previously resting with a rest opposite to this motion, for whatever is apt to be moved is either at rest or being moved. Therefore, it is plain that what is being moved to a contrary was at one time resting with a rest opposite to that motion. Hence no motion to a contrary can be continuous and perpetual. If, therefore, to this conclusion be added what was first assumed, namely, that every motion of alteration, or growth or decrease is to a contrary, it follows that none of these motions can be continuous and perpetual.
lib. 8 l. 15 n. 3 Deinde cum dicit: similiter autem etc., ostendit idem in mutationibus, idest in generatione et corruptione; quia generatio et corruptio opponuntur et universaliter secundum communem oppositionem entis et non entis, et iterum in singulari, sicut generatio ignis opponitur corruptioni ignis, secundum oppositionem esse ipsius et non esse. Unde si impossibile est simul esse oppositas mutationes, sequetur quod nulla mutatio sit continua et perpetua, eodem modo sicut et prius de motibus: sed necesse erit inter duas generationes eiusdem, intervenire medium tempus in quo erat corruptio; et similiter inter corruptiones tempus generationis.	1099. Then at (865 261 b3) he proves the same thing for changes, i.e., for generation and ceasing-to-be: these, indeed, are opposed universally according to the common opposition of being and non-being, and also in the singular thing, as the generation of fire is opposed to the ceasing-to-be of fire, according to the opposition of its existence and its non-existence. Hence, if opposite changes cannot co-exist, it will follow that no change is continuous and perpetual in the same way that it followed previously for motions, and that between two generations of the same thing, there must intervene a time in which ceasing-to-be occurred. In like manner, a time of generation interrupts instances of ceasing-to-be.
lib. 8 l. 15 n. 4 Deinde cum dicit: nihil enim differt etc., excludit tres obiectiones. Primo quia posset aliquis dicere quod cum mutationes opponantur secundum oppositionem terminorum; termini autem generationis et corruptionis non sunt contrarii, sed oppositi secundum contradictionem; videtur sequi quod generatio et corruptio non sunt contraria: et sic non erit eadem ratio de eis et de motibus qui sunt contrarii. Huic ergo obiectioni respondet, dicens quod nihil differt mutationes quae differunt secundum contradictorios terminos, esse contrarias vel non contrarias, dummodo hoc solum verum sit, quod impossibile sit ambas eidem simul inesse. Hoc enim quod est esse contrarium vel non contrarium, nihil est utile ad rationem praemissam.	1100. Then at (866 261 b7) he dismisses three objections. First of all, someone could say that since changes are opposed according to the opposition of their termini, whereas the termini of generation and ceasing-to-be are not contrary but contradictory, it seems to follow that generation and ceasing-to-be are not contrary; consequently, the same argument will not apply to them and to motions that are contrary. To this objection he replies that it makes no difference whether changes which differ according to contradictory termini are contrary or not contrary, as long as this alone is true, that it is impossible for both to be in the same thing at the same time, For to be contrary or not contrary has no bearing on the argument given.
lib. 8 l. 15 n. 5 Secundam obiectionem excludit ibi: neque si non necesse et cetera. Posset enim aliquis dicere, quod necesse est illud quod non semper movetur prius quiescere, quia motus opponitur quieti; sed hoc non habet locum in mutationibus generationis et corruptionis, quibus non opponitur quies proprie loquendo, ut in quinto dictum est. Huic ergo obiectioni respondet, dicens quod nihil etiam differt quantum ad propositam rationem, si non est necesse quiescere in aliquo contradictoriorum terminorum; neque etiam si mutatio non contrariatur quieti (quia fortasse illud quod non est, non potest quiescere: corruptio autem est in non esse: unde videtur quod in termino corruptionis non possit esse quies): sed hoc solum sufficit ad propositum, si sit tempus medium inter duas generationes aut inter duas corruptiones. Sic enim consequens erit quod neutra istarum mutationum sit continua. Post hoc autem redit ad primam obiectionem: et dicit quod ideo non differt contrarias aut non contrarias esse secundum contradictionem mutationes, quia neque etiam in prioribus, in quibus agebatur de motibus, non erat utile ad propositum quod in eis est contrarietas, sed quod non contingit eos simul esse; quod non est proprium contrariorum, sed commune omnibus oppositis.	1101. The second objection he dismisses at (867 261 b10). For someone could say that it is necessary for what is not always being moved to be previously at rest, because motion is the opposite of rest. But this does not occur in generation and ceasing-to-be, to which, properly speaking, rest is not opposed, as was said in Book V. To this objection he responds that it makes no difference to the argument given whether there is rest in either of the contradictory termini or not, or whether change is not contrary to rest (because perhaps what does not exist cannot rest, and ceasing-to-be tends to non-existence, whence it seems that rest cannot occur in the terminus of a ceasing-to-be): but the proposition is sufficiently proved if an intermediate time exists between two generations or two instances of ceasing-to-be. For the consequence will be that neither of these changes is continuous. After this he returns once more to the first objection and says that the reason why it makes no difference whether the changes between contradictory termini are contrary or not is that in the earlier discussions about motions likewise, it was not the question of contrariety that played a part in the proofs but the fact that the two changes could not occur at one and the same time. And this is not a peculiarity of contraries, but is common to all opposites.
lib. 8 l. 15 n. 6 Tertiam obiectionem excludit ibi: non oportet autem turbari et cetera. Dixerat enim supra, motus esse contrarios qui sunt in contraria: cum ergo motus sit contrarius quieti, videtur sequi quod uni sint duo contraria; quod est impossibile, ut probatur in X Metaphys. Ad hoc ergo excludendum dicit, quod non oportet de hoc turbari, quod videtur sequi idem esse contrarium pluribus, scilicet motus et quieti et motui qui est in contrarium. Sed hoc solum debemus accipere, quod unus motus contrarius opponitur quodammodo et motui contrario et quieti; motui quidem contrario secundum directam contrarietatem, quieti autem magis secundum oppositionem privativam; quae tamen habet aliquid de contrarietate, inquantum quies opposita est finis et complementum contrarii motus: sicut etiam aequale et commensurabile opponitur quodammodo duobus, scilicet excellenti et ei quod excellitur, sive magno et parvo, quibus opponitur secundum privationem magis, ut patet in X Metaphys. Et iterum hoc oportet accipere, quod non contingit simul esse neque oppositos motus neque oppositas mutationes.	1102. The third objection he dismisses at (868 261 b15). For he had said previously that motions which tend to contraries are contrary. Therefore, since motion is contrary to rest, it seems to follow that one thing has two contraries—which is impossible, as is proved in Metaphysics X. In order to exclude this he says that there is no need to be disturbed about the fact that one thing seems to be contrary to two things, i.e., a motion contrary to rest and to the motion which is to a contrary. Rather, the only thing we ought to take is that one contrary motion is in some manner opposed both to another contrary motion and to rest, to another contrary motion according to direct contrariety; but to rest, more according to privative opposition. Yet this latter opposition has some contrariety, inasmuch as an opposite rest is the end and complement of a contrary motion, just as “equal and commensurable” is opposed in a way to two things, namely, to the excelling and to what is excelled, i.e., to the large and the small, to which two it is opposed rather according to privation, as is plain in Metaphysics X. And once more, what is important to grasp is that opposite motions or opposite changes do not occur at one and the same time.
lib. 8 l. 15 n. 7 Deinde cum dicit: amplius in generatione et corruptione etc., ostendit quod non solum inter duos motus vel mutationes eiusdem speciei oportet esse medium tempus; et quod nulla mutatio una, quae est in aliquod oppositorum, potest esse perpetua et continua; sed etiam quod impossibile est quod oppositi motus aut mutationes sic succedant sibi invicem, quod non intercidat tempus medium. Hoc enim videtur penitus esse inconveniens in generatione et corruptione, si quando aliquid factum est, generatione completa, statim necesse sit quod corruptio incipiat; et quod nullo tempore permaneat id quod generatum est. Frustra enim aliquid generaretur, nisi generatum in esse permaneret. Unde ex his mutationibus potest fieri fides in aliis: hoc enim est naturale quod similiter se habet in omnibus, quia natura semper eodem modo operatur. Sicut ergo inconveniens videtur quod id quod generatur, statim cum generatum est corrumpatur; ita inconveniens videtur quod id quod dealbatur, statim cum factum est album denigretur, et quod id quod augetur statim decrescat. In omnibus enim his naturae intentio frustraretur.	1103. Then at (869 261 b22) he shows that there must not only be a time between two motions or changes of the same species, and that no single change which tends to one of two opposites can be perpetual and continual, but also that it is impossible for opposite motions or changes so to follow one upon the other that there is no time between them. For it seems to be utterly at odds with generation and ceasing-to-be that when something has come to be and its generation is complete, that immediately it begin to cease to be, so that there would be no period of time in which the generated thing would be permanent. For a thing would be generated in vain, if the generated thing were not to remain in existence. Hence from these changes of generation and ceasing-to-be, we can understand the others. For the natural is what occurs in a like way in all things, since nature always acts in the same way. Therefore, just as it seems unacceptable for something to cease to be as soon as it is generated, so, toot it seems unacceptable that a thing should start becoming black as soon as it became white, and..that a thing should begin to shrink as soon as it is grown. For in all these cases, the intention of nature would be frustrated.