Authors/Thomas Aquinas/physics/L4/lect11: Difference between revisions

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==Lecture 10 The meaning of “void”—refutation of those positing the void ==
==Lecture 11 From motion there is shown to be no separated void ==
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|Lecture 10 The meaning of “void”—refutation of those positing the void   
|Lecture 11 From motion there is shown to be no separated void   


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|{{a|lib4l10n1|lib. 4 l. 10 n. 1}} Dixerat superius philosophus a tribus esse incipiendum: postquam ergo prosecutus est duo eorum, ponens scilicet opiniones negantium et affirmantium vacuum esse, hic prosequitur tertium, communes scilicet opiniones hominum de vacuo demonstrans. Circa hoc igitur tria facit: primo ostendit quid significetur nomine vacui; secundo ostendit quomodo vacuum aliqui esse posuerunt, ibi: quoniam autem de loco etc.; tertio excludit rationes ponentium vacuum esse, ibi: neque una autem et cetera. Circa primum duo facit: primo dicit de quo est intentio; secundo exequitur propositum, ibi: videtur autem et cetera.
|{{a|lib4l11n1|lib. 4 l. 11 n. 1}} Positis opinionibus aliorum de vacuo, et quid significetur nomine vacui, hic incipit inquirere veritatem. Et primo ostendit vacuum non esse separatum; secundo ostendit vacuum non esse corporibus inditum, ibi: sunt autem quidam et cetera. Circa primum duo facit: primo ostendit vacuum separatum non esse, ex parte motus; secundo ex consideratione qua ipsum vacuum consideratur secundum se, ibi: et per se autem et cetera. Circa primum duo facit: primo ostendit vacuum non esse ex parte motus; secundo ex parte velocitatis et tarditatis in motu, ibi: amplius autem et ex his et cetera.


|506. The Philosopher had said above that we I must start with three things. So now, having finished two of them, by giving, namely, the opinions of both of those who posited and of those who rejected the void, he now enters upon the third, by showing, namely, the general notions people have about the void.  Concerning this he does three things:  First he shows what is meant by the word “void”;  Secondly, how some thought that the void exists, at no. 513;  Thirdly, he rejects the reasons given by those who posit that a void exists, at no. 515.  As to the first he does two things:  First he reveals his intention;  Secondly, he executes it, at no. 509.   
|520. Having gone over others’ opinions about the void and having indicated what is meant by the word “void,” he now begins to search for the truth.  First, he shows that the void does not have a separate existence;  Secondly, that there is no void in bodies at no. 544 (L.14).  Concerning the first he does two things:  First he used motion to show that a separate void does not exist;  Secondly, by considering the void in itself, at no. 541.  As to the first he does two things:  First, from the fact of motion he shows there is no void;  Secondly from the fact of faster and slower motions, at no.527 (L.12).   


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|{{a|lib4l10n2|lib. 4 l. 10 n. 2}} Dicit ergo primo quod, cum dictum sit quod quidam posuerunt vacuum esse, quidam vero negaverunt; ad cognoscendum qualiter se habeat veritas, oportet accipere tanquam principium, quid significet nomen vacui. Sicut enim cum dubitatur an aliqua passio insit alicui subiecto, oportet accipere pro principio quid sit res, ita cum dubitatur de aliquo an sit, oportet accipere pro medio quid significet nomen. Quaestio enim quid est sequitur quaestionem an est.
|{{a|lib4l11n2|lib. 4 l. 11 n. 2}} Circa primum ponit sex rationes. Circa quarum primam dicit quod oportet iterum dicere quod non est vacuum separatum, sicut quidam dicunt. Ideo autem apponit iterum, quia hoc etiam aliqualiter ostensum est ex parte loci: si enim locus non sit spatium, sequitur quod vacuum nihil sit, ut supra dictum est. Sed nunc iterum idem ostendit ex parte motus: ponebant enim vacuum, ut dictum est, propter motum. Sed propter motum non est necessarium ponere vacuum. Maxime enim videtur quod esset causa motus localis: sed propter motum localem non oportet ponere vacuum, quia omnia corpora simplicia habent motus locales naturales, sicut motus naturalis ignis est sursum, et motus terrae est deorsum et ad medium. Et sic manifestum est quod natura uniuscuiusque corporis est causa motus localis, et non vacuum. Quod quidem esset, si propter necessitatem vacui aliqua corpora naturalia moverentur. Si autem non ponitur causa motus localis, nullius alterius motus causa poni potest, neque alterius rei. Frustra igitur vacuum esset.


|507. He says first, therefore [349 {{physics|4|bk213b30|213 b30}}], that since it was pointed out that some people affirmed a void and others denied it, in order to get at the truth we must begin by the meaning of the word “void.” For just as, when there is question about some property existing in a subject, we must begin by agreeing what the thing is, so when there is question about the existence of something, we must begin by taking as the middle form the meaning of the word. For the question of what something is comes after the question of whether it exists.   
|521. In regard to the first point he gives six reasons. In regard to the first of which he says [360 {{physics|4|bk214b12|214 b12}}] that we must repeat that there is no separated void as some assert. He says “repeat,” because this was already somewhat proved from the notion of place: for if place is not space, it follows that the void is nothing, as was said above. But now he proves the same point again from motion: for void was posited, as we said, on account of motion. But motion does not necessarily require a void. For it would seem especially to be the cause of local motion. But it is not necessary to posit a void in order to explain local motion, because all simple bodies have natural local motions, as the natural motion of fire is upward and that of earth downward toward the center. Thus it is clear that it is the nature of each body that causes its local motion and not the void. The latter would be the cause if any natural bodies were moved due to the necessity of a void. But if it is not set down as the cause of local motion, it cannot be considered the cause of any other motion or of any other thing. The void therefore would exist without a purpose.   


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|{{a|lib4l10n3|lib. 4 l. 10 n. 3}} Deinde cum dicit: videtur autem vacuum etc., ostendit quid significet nomen vacui: et primo ponit significationem communiorem; secundo significationem secundum usum Platonicorum, ibi: alio autem modo et cetera. Circa primum tria facit: primo ostendit quid significet nomen vacui; secundo quid oportet addere ad illam significationem, ibi: sed inconveniens est etc., tertio removet quandam dubitationem, ibi: unde et si et cetera.
|{{a|lib4l11n3|lib. 4 l. 11 n. 3}} Secundam rationem ponit ibi: amplius, si est etc.: quae talis est. Si ponatur vacuum esse, non potest assignari causa motus naturalis et quietis naturalis. Manifestum est enim quod corpus naturale movetur ad locum suum naturalem et quiescit in eo naturaliter, propter convenientiam quam habet cum ipso, et quia non convenit cum loco a quo recedit. Sed vacuum non habet aliquam naturam per quam possit convenire vel disconvenire a corpore naturali. Si ergo ponatur aliquod vacuum, quasi quidam locus privatus corpore, non poterit assignari ad quam partem illud corpus naturaliter moveatur. Non enim potest dici quod feratur ad quamlibet partem, quia hoc videmus ad sensum esse falsum, quia ab una parte naturaliter recedit, et naturaliter accedit ad aliam. Et haec eadem ratio valet contra eos qui ponunt locum esse quoddam spatium separatum, in quod corpus mobile fertur. Non enim erit assignare quomodo corpus positum in tali loco, vel moveatur vel quiescat: quia dimensiones spatii nullam habent naturam per quam possit attendi similitudo vel dissimilitudo ad corpus naturale. Et merito congruit eadem ratio de vacuo et de sursum et deorsum, idest de loco, cuius partes sunt sursum et deorsum. Quia illi qui ponunt vacuum, dicunt ipsum esse locum. Et non solum ponentes vacuum, et ponentes locum esse spatium, non possunt assignare quomodo aliquid moveatur et quiescat secundum locum: sed etiam non possunt convenienter assignare quomodo aliquid sit in loco vel in vacuo. Si enim locus ponatur esse spatium, oportet quod totum corpus inferatur in illud spatium; et non sicut accidit apud ponentes locum esse terminum corporis continentis, quod locatum est in loco sicut in aliquo separato, et sicut in quodam corpore continente et sustentante. Et hoc videtur esse de ratione loci, quod aliquid sit in loco sicut in separato et seorsum existente: quia si pars alicuius corporis non ponatur seorsum ab ipso corpore, non erit in eo sicut in loco, sed sicut in toto. Est igitur de ratione loci et locati, quod locus seorsum sit a locato. Et hoc non accidit si spatium sit locus, in quod totum mergitur totum corpus. Non igitur spatium est locus. Et si spatium non est locus, manifestum est quod vacuum non est.


|508. Then [350 {{physics|4|bk213b31|213 b31}}] he shows that it meant by the word “void”. First he gives the more common meaning;  Secondly, what the Platonists took it to mean at no. 512. As to the first he does three things:  First he shows what the word “void” means;  Secondly, what should be added to that meaning at no. 510;  Thirdly, he clears up a doubt, at no. 511.   
|522. He then gives the second reason [361 {{physics|4|bk214b17|214 b17}}]. If a void be postulated, no reason can be assigned for natural motion and rest. For it is clear that a natural body is moved toward its own natural place and rests there naturally on account of the kinship it has with its place and because it has no kinship to the place from which it departs. But the void has no nature by which it could be akin or hostile to a natural body. Therefore, it there were a void, considered as a certain place without a body in it, one could not assign any part to which the body would be naturally moved. For we cannot say that it would be borne to just any part, because observation shows that this is wrong, for a body naturally goes from one place and naturally approaches another.  This same reason is valid against those who posit place as a separate space into which a mobile body is borne. For it would be impossible to explain how a body in such a place could either be moved or be at rest: for the dimensions of space have no nature to which a natural body could be similar or dissimilar. Deservedly, then, the same argument applies to the void as to “up” and “down,” i.e., to place, whose parts are “up” and “down”; for those who posit a void call it place. Moreover, not only are those who posit a void and those who posit place to be space unable to explain how something is moved and at rest In respect to place, but also how something exists in place or in the void. For if place is supposed to be space, then the whole body would have to be enclosed inside that space, and not as happens with those who agree that place is the boundary of the containing body and that a thing is in place as in something separate and as in a body that contains and sustains it. Indeed, it seems to be of the very nature of place that something be in place as in something separated and existing apart from it: for if any part of a body is not laid down as separated from the body, it will exist in that body not as in a place but as in the whole. Therefore, it pertains to the very nature of place and of the thing in place that one be separated from the other. But this does not happen if place is space into whose entirety the entice body is immersed. Therefore space is not place. And if space is not place it is clear that no void is place.   


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|{{a|lib4l10n4|lib. 4 l. 10 n. 4}} Dicit ergo quod secundum opinionem hominum, videtur vacuum nihil aliud significare quam locum in quo nihil sit. Et huius causa est, quia proprie vacuum dicitur esse, in quo non est aliquod corpus: quia soli corpori convenit quod sit in loco; et vacuum nihil aliud potest significare quam locum absque locato. Sed quia homines opinantur quod omne ens sit corpus, sequitur secundum eorum opinionem quod ubi non est corpus, nihil sit. Et ulterius opinantur quod omne corpus sit tangibile, id est habens tangibiles qualitates. Et huiusmodi corpus est quod est grave vel leve: nondum enim erat notum quod corpus caeleste esset praeter naturam quatuor elementorum. Unde cum proprie de ratione vacui sit quod sit locus in quo non est aliquod corpus, sequitur quod vacuum sit in quo non est corpus grave vel leve: non quidem quod hoc sit de ratione vacui secundum primam impositionem nominis, sed secundum quandam syllogisticam deductionem ex communi opinione hominum, opinantium omne corpus esse grave vel leve: sicut etiam secundum opinionem communem hominum existimantium omne ens esse corpus, sequitur vacuum esse in quo nihil est. Sic igitur tribus modis potest accipi huius nominis significatio: una est propria, scilicet vacuum est locus in quo non est corpus: aliae duae secundum opinionem hominum; quarum una est communior, scilicet vacuum est locus in quo nihil est; alia vero est magis coarctata, scilicet vacuum est locus in quo non est corpus grave vel leve.
|{{a|lib4l11n4|lib. 4 l. 11 n. 4}} Tertiam rationem ponit ibi: accidit autem dicentibus et cetera. Et dicit quod, cum antiqui philosophi ponerent quod necesse est vacuum esse si est motus, e converso accidit: quia si est vacuum, non est motus. Et hoc probat per quoddam simile. Quidam enim dixerunt quod terra quiescit in medio propter similitudinem partium circumferentiae undique: et sic terra, cum non habeat quare moveatur magis versus unam partem circumferentiae quam versus aliam, quiescit. Et eadem ratione necesse est in vacuo quiescere. Non enim est assignare quare magis moveatur, ad unam partem quam ad aliam: quia vacuum, inquantum huiusmodi, non habet differentias in suis partibus; non entis enim non sunt differentiae.


|509. He says therefore that according to common opinion, the void seems to signify nothing more than a place In which there is nothing. The reason for this is because properly that is said to be a void in which there is not any body, and since only a body can be in place, void seems to mean nothing more than a place without any thing in it. But because people suppose that every being is a body, it follows that according to their opinion where there is not body, there is nothing.  And further they believe that every body is tangible, i.e., that it has tactile qualities. And a body of this kind is heavy or light: for in their time it was not yet known that a heavenly body is different in nature from any of the four elements. Hence since it is the very nature of the void to be a place in which there is not a body, it follows that the void is that in which there is neither a light nor a heavy body. However, this is not to say that it belongs to the notion of the void according to the primary meaning of the word, but rather by reason of a certain syllogistic deduction that starts with the general opinion of people that every body is either heavy or light; just as the common opinion of people that every being is a body, leads to the conclusion that the void is that in which there is nothing.  Consequently, the meaning of this word “void” is three-fold: one is proper, namely, that the void is that in which there is not any body; the others come from the general opinion of people: the first is more common, namely, that the void is a place in which nothing exists; the second is more restricted, namely, that the void is a place in which there is neither a heavy nor a light body.   
|523. He gives the third reason [362 {{physics|4|bk214b28|214 b28}}] saying that, whereas the early philosophers claimed that the void had to be, if motion existed, the very opposite is the case: for if there were a void there would be no motion. And this he proves by a simile. For some have said that earth comes to rest at the center on account of the likeness of the parts on the whole circumference: consequently, earth, having no reason to be moved toward one part of the circumference more than another, rests. The same reason would cause rest in a void. For there would be no reason for earth to be moved to one part rather than to another, since the void, as such, does not have differences among its parts—for non-being does not possess differences.   


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|{{a|lib4l10n5|lib. 4 l. 10 n. 5}} Deinde cum dicit: sed inconveniens est etc., ostendit quid addendum sit ad hanc significationem. Dicit enim quod inconveniens est si dicatur quod punctum sit vacuum, cum tamen de puncto dici possit quod in puncto non sit corpus tangibile. Oportet ergo addere quod vacuum sit locus in quo non sit corpus tangibile, sed sit ibi spatium susceptivum corporis tangibilis: sicut caecum dicitur quod caret visu, natum autem habere. Et sic concludit quod uno modo dicitur vacuum, spatium quod non est plenum corpore sensibili secundum tactum, quod scilicet est grave vel leve.
|{{a|lib4l11n5|lib. 4 l. 11 n. 5}} Quartam rationem ponit ibi: deinde quoniam omnis motus etc.: quae talis est. Motus naturalis est prior violento, cum motus violentus non sit nisi quaedam declinatio a motu naturali. Remoto ergo motu naturali, removetur omnis motus; cum remoto priori, removeatur posterius. Sed posito vacuo, removetur motus naturalis; quia tollitur differentia partium loci, ad quas est motus naturalis, sicut et posito infinito, ut supra dictum est. Sed hoc interest inter vacuum et infinitum, quia posito infinito, nullo modo potest poni neque sursum neque deorsum neque medium, ut in tertio dictum est: posito autem vacuo, possunt haec quidem poni, sed non quod ad invicem differant; quia nullius et non entis, et per consequens vacui, cum sit non ens et privatio, non est aliqua differentia. Sed loci mutatio naturalis requirit locorum differentiam, quia diversa corpora ad diversa loca moventur. Unde oportet loca naturalia differre ad invicem. Si igitur ponatur vacuum, nullius erit naturalis loci mutatio. Et si non est loci mutatio naturalis, nulla loci mutatio erit. Unde si est aliqua loci mutatio, oportet quod vacuum non sit.


|510. Then [351 {{physics|4|bk214a4|214 a4}}] he shows that must be added to this meaning. For he says that it is not correct to say that a point is a void, even though in a point there is no tangible body. So we must add that the void to a place in which there is not a tangible body, but which has in it space to receive a tangible body, just as a blind person is said to be one who lacks sight but to apt to have it. And so he concludes that in one way the void is called a space which is not full of a body that is sensible by touch, i.e., a body that is heavy or light.   
|524. He gives the fourth reason [363 {{physics|4|bk215a1|215 a1}}]as follows. Natural motion is prior to compulsory since compulsory motion is only a departure from natural motion. Therefore, remove natural motion and all other motion is removed; for when the prior is removed, all that follows is removed. But if the void is posited, natural motion is removed; because the differences among the parts of place would be taken away and it is toward such parts that natural motions tend The same holds if the infinite be posited, as we said above.  There is, however, this difference between the void and the infinite, that after granting the infinite there is no way of positing “up” or “down” or “center,” as we pointed out in Book III; but after granting a void, these places could be posited, but it would not be because they were mutually different: for no difference can be assigned in the realm of nothing and non-being and, consequently, of the void, which is a non-being and a privation. Yet natural changes of place do require difference of place, because diverse bodies are moved to diverse places. Consequently, natural places must be different one from the other. Therefore, if a void be posited, nothing could undergo a natural change of place; and if there is no natural change of place, there will be no change of place of any sort. Hence, if there is any change of place, there can be no void.   


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|{{a|lib4l10n6|lib. 4 l. 10 n. 6}} Deinde cum dicit: unde et si dubitabit aliquis etc., removet quandam dubitationem, quae est: utrum si in aliquo spatio sit color vel sonus, dicendum sit vacuum vel non: et hoc propter definitionem primo datam, scilicet vacuum est in quo nihil est. Et solvit quod si spatium in quo est tantum sonus vel color, sit susceptivum corporis tangibilis, vacuum est: si vero non, non est vacuum. Et hoc ideo, quia haec non est propria definitio vacui, vacuum est in quo nihil est, nisi secundum opinionem credentium, ubi non est corpus nihil esse.
|{{a|lib4l11n6|lib. 4 l. 11 n. 6}} Quintam rationem ponit ibi: amplius, nunc quidem proiecta et cetera. Circa quam considerandum est quod solet esse quaedam dubitatio circa ea quae proiiciuntur: oportet enim movens et motum simul esse, ut infra in septimo probatur; et tamen illud quod proiicitur, invenitur moveri etiam postquam separatum est a proiiciente, sicut apparet in lapide proiecto, et sagitta emissa per arcum. Nunc igitur supposito quod vacuum non sit, solvitur ista dubitatio ex parte aeris, quo medium repletur. Et hoc dupliciter. Dicunt enim quidam quod ea quae proiiciuntur, moventur etiam postquam non tanguntur a proiiciente, propter antiperistasim, idest repercussionem vel contra-resistentiam: aer enim motus repercutitur ad alium aerem, et ille ad alium, et sic deinceps; et per talem repercussionem aeris ad aerem movetur lapis. Alii vero dicunt quod hoc ideo est, quia aer, qui continuus existens a proiiciente impellitur, velocius impellit corpus proiectum, quam sit motus quo corpus proiectum fertur naturaliter in proprium locum. Unde propter velocitatem motus aeris non permittitur corpus proiectum, ut puta lapis vel aliud huiusmodi, cadere deorsum; sed fertur secundum impulsionem aeris. Nulla autem istarum causarum posset poni, si esset vacuum; et ita corpus proiectum nullo modo ferretur nisi quandiu veheretur, puta a manu proiicientis, sed statim emissus a manu caderet; cuius contrarium videmus. Non ergo est vacuum.


|511. Then [352 {{physics|4|bk214a9|214 a9}}] he clears up the following difficulty; If there is color or sound in a certain space, should it be called a void or not? This question arises because the definition first given says that the void is that in which there is nothing. And he answers by saying that if the space in which there is just sound or color has room for a tangible body, it is a void; if not, not. The reason is that the proper definition of the void is not “that in which there is nothing,” and such a definition is held only by people who believe that where no body is, nothing is.   
|525. The fifth reason is then given [364 {{physics|4|bk215a14|215 a14}}]. In regard to this it should be considered that some question exists about projectiles: for the mover and the thing moved must be always together, as will be proved below in Book VII (1-3). Yet a projectile is found to be in motion even after it is separated from the projector, as is evident in the case of a stone that is thrown, or of an arrow shot from a bow. Now on the supposition that there is no void this difficulty is solved by attending to the air with which the medium [the field of trajectory] is filled. And it is solved in two ways. For some assert that projectiles remain in motion even after they are no longer contact with what gave them impulse on account of antiperistasis, i.e., repercussion or counter-resistence: for the air that has been pushed, pushes against other air, and that against other air, and so on, and it is on account of this impact of air against air that the stone is moved. The other explanation is that the continuum of air that received the impact from the projector pushes the impelled body with more speed than the speed of the motion by which the projectile is naturally borne to its proper place. Hence the speed of the air movement prevents the projectile, for example, the stone, or some other such, from falling downward; but it is carried along by the impulse of the air.  Now neither of these explanations could be alleged if there were a void; consequently, a projectile could be moved only as long as it was carried, for example, in the hand of the one casting it: but as soon as it was released from the hand it would fall. But it is the opposite that happens. Therefore, there is not a void.   


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|{{a|lib4l10n7|lib. 4 l. 10 n. 7}} Deinde cum dicit: alio autem modo etc., ponit aliam significationem vacui secundum usum Platonicorum. Et dicit quod alio modo dicitur esse vacuum: in quo non est hoc aliquid, neque aliqua substantia corporea. Fit autem hoc aliquid per formam. Unde aliqui dicunt materiam corporis, secundum quod est absque forma, esse vacuum: qui etiam materiam dicunt esse locum, ut supra dictum est. Sed non bene dicunt: quia materia non est separabilis a rebus quarum est materia; sed homines quaerunt locum et vacuum, tanquam aliquid separabile a corporibus locatis.
|{{a|lib4l11n7|lib. 4 l. 11 n. 7}} Sextam rationem ponit ibi: amplius nullus utique etc.: quae talis est. Si motus sit in vacuo, nullus poterit assignare causam propter quid illud quod movetur, alicubi stat. Non enim est ratio quare magis quiescat in una parte vacui quam in alia; neque in his quae moventur naturaliter, cum non sit differentia in partibus vacui, ut supra dictum est; neque in his quae moventur motu violento. Nunc enim dicimus quod cessat motus violentus, ubi deficit repercussio vel impulsio aeris, secundum duas causas assignatas. Oportebit ergo quod vel quiescat omne corpus, et nihil moveatur; aut si aliquid moveatur, quod movetur in infinitum, nisi occurrat ei aliquod corpus maius, quod violentum motum eius impediat. Ad confirmationem autem huius rationis, subiungit causam quare ponunt aliqui motum fieri in vacuo; quia scilicet vacuum cedit, et non resistit mobili; unde cum vacuum similiter cedit ex omni parte, feretur in infinitum ex qualibet parte.


|512. Then [353 {{physics|4|bk214a11|214 a11}}] he gives the meaning of “void” as used by the Platonists. And he says that there is another meaning of the void: that in which there is no “this something” or any corporeal substance. Now a “this something” comes about on account of the form. Hence some claim that the matter of a body, insofar as it is apart from its form, is the void. These are the same who claim that matter is place, as was stated above (L.3). But this is poor judgment, for matter is not separable from the things of which it is the matter; whereas men inquire about place and the void as being separable from bodies in place. 
|526. He then gives the sixth reason [365 {{physics|4|bk215a19|215 a19}}]. If motion were in a void, no one could give a reason why the moving object should stop anywhere. For there is no reason why it should stop at one part of the void rather than another. This is true both in the case of objects that are moved naturally, because there is no difference among the parts of the void, as we have said, and in the case of objects moved by a compulsory motion. For now we say that a violent compulsory motion ceases when repercussions or impulsions of the air are lacking, on account of the two reasons already given. Therefore it will have to be admitted either that every body is at rest and nothing in motion or that, if anything be in motion, it will remain In motion to infinity unless it runs into a more powerful body that could impede its compulsory motion. In support of this reasoning, he gives the reason why some posit motion in the void. It is because the void yields to and does not resist the mobile; hence since the void yields in the same way, in all directions, a mobile thing should be moved in all directions ad infinitum.   
 
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|{{a|lib4l10n8|lib. 4 l. 10 n. 8}} Deinde cum dicit: quoniam autem de loco etc., ostendit quomodo aliqui ponebant vacuum esse. Et primo quid dicebant esse vacuum; secundo propter quid vacuum ponebant, ibi: et propter eadem acceptum et cetera. Dicit ergo primo, quod quia vacuum est locus privatus corpore, et determinatum est de loco quomodo sit et quomodo non sit (dictum est enim quod locus non est aliquod spatium, sed terminus continentis); manifestum est etiam quod neque vacuum est spatium separatum a corporibus, neque intrinsecum corporibus, sicut ponebat Democritus. Et hoc ideo, quia ponentes vacuum quocumque istorum modorum, volunt quod vacuum non sit corpus, sed spatium corporis. Ideo enim videbatur aliquid esse vacuum, quia locus aliquid est: et sicut locus videbatur esse spatium, ita et vacuum. Si ergo locus non est aliquod spatium praeter corpora, neque vacuum potest esse spatium praeter corpora. Et cum de ratione vacui sit quod sit spatium corporis praeter corpora, ut supra dictum est, sequitur quod vacuum non sit.
 
|513. Then [354 {{physics|4|bk214a16|214 a16}}] he tells how some posited existence of a void;  First, what they said the void was;  Secondly, why they posited it, at no. 514.  He says therefore first that since the void is a place without a body in it, and since we have already decided how place exists and how it does not (for we have said that place is not a space but the boundary of a container), it is clear that the void is neither a space separated from bodies nor intrinsic to them as Democritus supposed. This is so because those who suppose that space exists in either of those two ways, intend the void to be not a body, but the space of a body. For they thought that the void was something because place was something, and just as place seems to be space, so also the void. But if place is not a space outside of bodies, neither can the void be a space outside of bodies. And since it is the very nature of the void to be a bodily space existing outside of bodies, as was said above, it follows that the void does not exist. 
 
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|{{a|lib4l10n9|lib. 4 l. 10 n. 9}} Deinde cum dicit: et propter eadem acceptum etc., ostendit quare posuerunt vacuum. Et dicit quod propter idem acceperunt vacuum esse, propter quod acceperunt locum esse, scilicet propter motum, ut supra dictum est: quia provenit ut salvetur motus secundum locum, tam secundum illos qui dicunt locum aliquid esse praeter corpora quae sunt in loco, quam secundum illos qui ponunt vacuum esse. Negantibus autem locum et vacuum, non provenit motum secundum locum esse. Et sic vacuum quodammodo opinantur causam esse motus eo modo quo et locum, ut in quo scilicet est motus.
 
|514. Then [355 {{physics|4|bk214a21|214 a21}}] he shows why they posited a void. And he says that they admitted the existence of the void for the same reason that they admitted place, namely, on account of motion, as we said above: for it comes about that local motion is saved, both for those who assert that place is something over and above the bodies which are in place and for those who claim that the void exists. But for those who deny place and the void, there cannot be local motion. Consequently, some believed that the void is a cause of motion in the way that place is, i.e., as that in which motion takes place. 
 
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|{{a|lib4l10n10|lib. 4 l. 10 n. 10}} Deinde cum dicit: neque una autem necessitas est etc., excludit rationes ponentium vacuum esse. Et non intendit hic rationes praemissas vera solutione solvere; sed instantiam dare ex qua ex ipso aspectu apparet, quod rationes non ex necessitate concludunt. Primo ergo excludit rationes ponentium vacuum separatum; secundo ponentium vacuum in corporibus, ibi: contingit autem densari et cetera.
 
|515. Then [356 {{physics|4|bk214a26|214 a26}}] he rejects the arguments of those who posit existence of the void. He does not, however, intend here to give a true solution to the aforesaid arguments, but to bring an objection which at a glance shows that their arguments do not conclude with necessity.  First therefore he rejects the reasons given by those who posit a separated void;  Secondly, the arguments of those who posit a void existing in bodies, at no. 517. 
 
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|{{a|lib4l10n11|lib. 4 l. 10 n. 11}} Primam autem rationem excludit dupliciter. Primo quidem, quia non est necessarium si motus sit quod vacuum sit. Et si loquamur universaliter de qualibet specie motus, manifeste apparet quod nequaquam est necessarium. Nihil enim prohibet id quod est plenum, alterari: solus enim motus localis excludi videtur si vacuum non ponatur. Et hoc latuit Melissum, dum credidit remoto vacuo omnem speciem motus auferri. Secundo excludit eandem rationem per hoc quod neque motus localis tollitur, si vacuum non sit. Dato enim quod nullum spatium separabile sit praeter corpora quae moventur, potest motus localis esse per hoc quod corpora subintrent se invicem per modum inspissationis, et sic aliquid in plenum movetur, et non in vacuum. Et hoc apparet manifeste in generationibus corporum continuorum, et praecipue in humidis, sicut videtur in aqua. Si enim proiiciatur lapis in aliquam magnam latitudinem aquae, manifeste apparet fieri quasdam circulationes circa locum percussionis, quousque pars aquae depulsae commoveat aliam et subintret ipsam: unde quia modica pars aquae subintrat per quandam diffusionem in maiorem aquam, circulationes praedictae a parvo in maius procedunt, quousque totaliter deficiant.
 
|516. He rejects the first reason in two ways: First, because even though motion exists, it does not necessarily follow that the void exists. And if we speak generally of any species of motion, it is clear that the void is not necessary at all. For nothing prevents the full from being altered [i.e., having motion in quality], since only local motion seems to be excluded if the void is not posited. Yet Melissus did not see this, for he believed that if there were no void, no motion of any kind could exist.  Secondly, he rejects the same reason on the ground that not even local motion is destroyed, if there is no void. For, assuming that there is no separable space over and above moving bodies, local motion can take place, if bodies make room for one another by contracting: thus they would be moving into the full rather than into the empty. This is evident in the generations of continuous bodies, especially in liquids, such as water. For if a stone is thrown into a large surface of water, circles appear around the place of entry as long as one part of the moving water agitates another part and enters it. Hence, because a small portion of water by a process of diffusion enters a larger section, the circles grow from small to large until they cease entirely. 
 
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|{{a|lib4l10n12|lib. 4 l. 10 n. 12}} Deinde cum dicit: contingit autem densari etc., excludit rationes ponentium vacuum in corporibus. Et primo rationem quae procedebat ex condensatione. Et dicit quod contingit corpora condensari, et partes corporis subintrare sibi invicem, non propter hoc quod pars subintrans vadat in locum vacuum; sed ideo quia erant aliqua foramina, plena aliquo corpore subtiliori, quod facta condensatione elabitur: sicut quando aqua colliditur et inspissatur, aer qui intus erat, excluditur. Et haec maxime apparent in spongia, et in huiusmodi corporibus porosis. Haec igitur solutio non ostendit causam condensationis, quam inferius ponit: sed ostendit quod etiam per hunc modum manifeste excludi potest necessitas vacui.
 
|517. Then [357 {{physics|4|bk214a32|214 a32}}] he rejects the reasons given by those who posit a void in bodies. And first of all the reason based an condensation. And he says that bodies happen to become condensed, and parts of a body mutually penetrate, not because the invading part is entering an empty place but because there were certain openings, full of a more subtle body which escapes under condensation, just when water is compressed and contracted, the air that was present is expelled. This takes place manifestly in a sponge and other like porous bodies. Therefore this solution does not give the reason for condensation (he will give this later [L.14]: but it does show that also in this way, the need of a void can be clearly eliminated. 
 
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|{{a|lib4l10n13|lib. 4 l. 10 n. 13}} Secundo ibi: et augmentari etc., excludit rationem quae procedit ex augmento. Et dicit quod augmentum contingit esse non solum per additionem alicuius corporis ingredientis in corpus augmentatum, ut sic necesse sit esse vacuum, sed etiam per alterationem: sicut cum ex aqua fit aer, maior fit quantitas aeris quam erat aquae. Et haec etiam non est vera solutio rationis inductae: sed solum instantia quaedam, ne sit necesse ponere vacuum. Vera autem solutio ponitur in libro de generatione, ubi ostenditur quod alimentum non sic transit in id quod augetur, quasi sit aliud corpus ab ipso; sed quia convertitur in substantiam eius, sicut ligna apposita igni, convertuntur in ignem.
 
|518. Secondly [358 {{physics|4|bk214b1|214 b1}}] he rejects the argument based on growth. And he says that growth occurs not only by the addition of some body invading the growing body so as to make the void necessary but also by alteration, as, when air comes to be from water, the quantity of air becomes greater than the quantity of water. This too is not the true solution of their argument but merely an objection showing that it is not necessary to posit a void. The true solution is given in the book “De Generatione, where it is shown that food does not pass into that which grows as to be a body distinct from it; rather it is converted into its substance, as wood added to fire is converted into fire. 
 
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|{{a|lib4l10n14|lib. 4 l. 10 n. 14}} Tertio ibi: omnino autem et quae est de augmento etc., excludit simul et rationem de augmento et rationem de aqua effusa in cinerem: et dicit quod utraque ratio impedit seipsam. Quod sic patet. Est enim circa augmentum haec dubitatio. Videtur enim vel quod non totum augeatur; vel quod augmentum non fiat per additionem corporis, sed per additionem alicuius incorporei; aut quod contingat duo corpora esse in eodem loco. Hanc igitur dubitationem, quae communiter videtur esse tam contra ponentes vacuum, quam contra non ponentes, volunt solvere. Sed tamen non demonstrant quod vacuum sit; vel oportet eos dicere, si augmentum sit propter vacuum, quod totum corpus sit vacuum, cum totum corpus augeatur. Et similiter dicendum est de cinere: quia si vas plenum cinere recipit tantum de aqua quantum vacuum, oportet dicere quod totum sit vacuum. Non est igitur hoc propter vacuitatem: sed propter commixtionem in aqua. Aqua enim commixta cineri condensatur, et aliqua pars eius exhalat; et iterum partes cineris magis inspissantur humefactione: cuius signum est, quod non potest extrahi tantum de aqua, quantum prius fuit. Ultimo autem concludit quod manifestum est, quod facile est solvere ea ex quibus demonstrant vacuum esse.
 
|519. Thirdly [359 {{physics|4|bk214b3|214 b3}}] he rejects together both the argument about increase [in growth] and that about water poured on ashes and says that each of these arguments blocks the other. This is evident as follows. For there is in respect to increase this difficulty: it seems either that the whole body is not being increased, or that increase does not come about by the addition of body but by the addition of something incorporeal, or that two bodies can be in the same place. Now it is this difficulty, which seems to be against both these who posit a void and against those who do not, that they wish to solve. But they do not show that the void exists, or, if increase is due to the void, then they would have to say that the whole body is a void, since the whole body is increased.  Likewise, in regard to the ashes: for if a vessel full of ashes can take as much water as the empty vessel, then one has to say that the whole container must be a void. Therefore this is not due to empty space but to being mixed in with the water. For when water is mixed with ashes it condenses and part of it evaporates; moreover, parts of the ash are condensed on account of the moisture, and a sign of this is that not as much water can be recovered as was put in.  Finally, he concludes that it is clearly easy to solve the arguments by which they prove the existence of a void.   


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Latest revision as of 16:30, 30 October 2014

Lecture 11 From motion there is shown to be no separated void

Latin English
Lecture 11 From motion there is shown to be no separated void
lib. 4 l. 11 n. 1 Positis opinionibus aliorum de vacuo, et quid significetur nomine vacui, hic incipit inquirere veritatem. Et primo ostendit vacuum non esse separatum; secundo ostendit vacuum non esse corporibus inditum, ibi: sunt autem quidam et cetera. Circa primum duo facit: primo ostendit vacuum separatum non esse, ex parte motus; secundo ex consideratione qua ipsum vacuum consideratur secundum se, ibi: et per se autem et cetera. Circa primum duo facit: primo ostendit vacuum non esse ex parte motus; secundo ex parte velocitatis et tarditatis in motu, ibi: amplius autem et ex his et cetera. 520. Having gone over others’ opinions about the void and having indicated what is meant by the word “void,” he now begins to search for the truth. First, he shows that the void does not have a separate existence; Secondly, that there is no void in bodies at no. 544 (L.14). Concerning the first he does two things: First he used motion to show that a separate void does not exist; Secondly, by considering the void in itself, at no. 541. As to the first he does two things: First, from the fact of motion he shows there is no void; Secondly from the fact of faster and slower motions, at no.527 (L.12).
lib. 4 l. 11 n. 2 Circa primum ponit sex rationes. Circa quarum primam dicit quod oportet iterum dicere quod non est vacuum separatum, sicut quidam dicunt. Ideo autem apponit iterum, quia hoc etiam aliqualiter ostensum est ex parte loci: si enim locus non sit spatium, sequitur quod vacuum nihil sit, ut supra dictum est. Sed nunc iterum idem ostendit ex parte motus: ponebant enim vacuum, ut dictum est, propter motum. Sed propter motum non est necessarium ponere vacuum. Maxime enim videtur quod esset causa motus localis: sed propter motum localem non oportet ponere vacuum, quia omnia corpora simplicia habent motus locales naturales, sicut motus naturalis ignis est sursum, et motus terrae est deorsum et ad medium. Et sic manifestum est quod natura uniuscuiusque corporis est causa motus localis, et non vacuum. Quod quidem esset, si propter necessitatem vacui aliqua corpora naturalia moverentur. Si autem non ponitur causa motus localis, nullius alterius motus causa poni potest, neque alterius rei. Frustra igitur vacuum esset. 521. In regard to the first point he gives six reasons. In regard to the first of which he says [360 214 b12] that we must repeat that there is no separated void as some assert. He says “repeat,” because this was already somewhat proved from the notion of place: for if place is not space, it follows that the void is nothing, as was said above. But now he proves the same point again from motion: for void was posited, as we said, on account of motion. But motion does not necessarily require a void. For it would seem especially to be the cause of local motion. But it is not necessary to posit a void in order to explain local motion, because all simple bodies have natural local motions, as the natural motion of fire is upward and that of earth downward toward the center. Thus it is clear that it is the nature of each body that causes its local motion and not the void. The latter would be the cause if any natural bodies were moved due to the necessity of a void. But if it is not set down as the cause of local motion, it cannot be considered the cause of any other motion or of any other thing. The void therefore would exist without a purpose.
lib. 4 l. 11 n. 3 Secundam rationem ponit ibi: amplius, si est etc.: quae talis est. Si ponatur vacuum esse, non potest assignari causa motus naturalis et quietis naturalis. Manifestum est enim quod corpus naturale movetur ad locum suum naturalem et quiescit in eo naturaliter, propter convenientiam quam habet cum ipso, et quia non convenit cum loco a quo recedit. Sed vacuum non habet aliquam naturam per quam possit convenire vel disconvenire a corpore naturali. Si ergo ponatur aliquod vacuum, quasi quidam locus privatus corpore, non poterit assignari ad quam partem illud corpus naturaliter moveatur. Non enim potest dici quod feratur ad quamlibet partem, quia hoc videmus ad sensum esse falsum, quia ab una parte naturaliter recedit, et naturaliter accedit ad aliam. Et haec eadem ratio valet contra eos qui ponunt locum esse quoddam spatium separatum, in quod corpus mobile fertur. Non enim erit assignare quomodo corpus positum in tali loco, vel moveatur vel quiescat: quia dimensiones spatii nullam habent naturam per quam possit attendi similitudo vel dissimilitudo ad corpus naturale. Et merito congruit eadem ratio de vacuo et de sursum et deorsum, idest de loco, cuius partes sunt sursum et deorsum. Quia illi qui ponunt vacuum, dicunt ipsum esse locum. Et non solum ponentes vacuum, et ponentes locum esse spatium, non possunt assignare quomodo aliquid moveatur et quiescat secundum locum: sed etiam non possunt convenienter assignare quomodo aliquid sit in loco vel in vacuo. Si enim locus ponatur esse spatium, oportet quod totum corpus inferatur in illud spatium; et non sicut accidit apud ponentes locum esse terminum corporis continentis, quod locatum est in loco sicut in aliquo separato, et sicut in quodam corpore continente et sustentante. Et hoc videtur esse de ratione loci, quod aliquid sit in loco sicut in separato et seorsum existente: quia si pars alicuius corporis non ponatur seorsum ab ipso corpore, non erit in eo sicut in loco, sed sicut in toto. Est igitur de ratione loci et locati, quod locus seorsum sit a locato. Et hoc non accidit si spatium sit locus, in quod totum mergitur totum corpus. Non igitur spatium est locus. Et si spatium non est locus, manifestum est quod vacuum non est. 522. He then gives the second reason [361 214 b17]. If a void be postulated, no reason can be assigned for natural motion and rest. For it is clear that a natural body is moved toward its own natural place and rests there naturally on account of the kinship it has with its place and because it has no kinship to the place from which it departs. But the void has no nature by which it could be akin or hostile to a natural body. Therefore, it there were a void, considered as a certain place without a body in it, one could not assign any part to which the body would be naturally moved. For we cannot say that it would be borne to just any part, because observation shows that this is wrong, for a body naturally goes from one place and naturally approaches another. This same reason is valid against those who posit place as a separate space into which a mobile body is borne. For it would be impossible to explain how a body in such a place could either be moved or be at rest: for the dimensions of space have no nature to which a natural body could be similar or dissimilar. Deservedly, then, the same argument applies to the void as to “up” and “down,” i.e., to place, whose parts are “up” and “down”; for those who posit a void call it place. Moreover, not only are those who posit a void and those who posit place to be space unable to explain how something is moved and at rest In respect to place, but also how something exists in place or in the void. For if place is supposed to be space, then the whole body would have to be enclosed inside that space, and not as happens with those who agree that place is the boundary of the containing body and that a thing is in place as in something separate and as in a body that contains and sustains it. Indeed, it seems to be of the very nature of place that something be in place as in something separated and existing apart from it: for if any part of a body is not laid down as separated from the body, it will exist in that body not as in a place but as in the whole. Therefore, it pertains to the very nature of place and of the thing in place that one be separated from the other. But this does not happen if place is space into whose entirety the entice body is immersed. Therefore space is not place. And if space is not place it is clear that no void is place.
lib. 4 l. 11 n. 4 Tertiam rationem ponit ibi: accidit autem dicentibus et cetera. Et dicit quod, cum antiqui philosophi ponerent quod necesse est vacuum esse si est motus, e converso accidit: quia si est vacuum, non est motus. Et hoc probat per quoddam simile. Quidam enim dixerunt quod terra quiescit in medio propter similitudinem partium circumferentiae undique: et sic terra, cum non habeat quare moveatur magis versus unam partem circumferentiae quam versus aliam, quiescit. Et eadem ratione necesse est in vacuo quiescere. Non enim est assignare quare magis moveatur, ad unam partem quam ad aliam: quia vacuum, inquantum huiusmodi, non habet differentias in suis partibus; non entis enim non sunt differentiae. 523. He gives the third reason [362 214 b28] saying that, whereas the early philosophers claimed that the void had to be, if motion existed, the very opposite is the case: for if there were a void there would be no motion. And this he proves by a simile. For some have said that earth comes to rest at the center on account of the likeness of the parts on the whole circumference: consequently, earth, having no reason to be moved toward one part of the circumference more than another, rests. The same reason would cause rest in a void. For there would be no reason for earth to be moved to one part rather than to another, since the void, as such, does not have differences among its parts—for non-being does not possess differences.
lib. 4 l. 11 n. 5 Quartam rationem ponit ibi: deinde quoniam omnis motus etc.: quae talis est. Motus naturalis est prior violento, cum motus violentus non sit nisi quaedam declinatio a motu naturali. Remoto ergo motu naturali, removetur omnis motus; cum remoto priori, removeatur posterius. Sed posito vacuo, removetur motus naturalis; quia tollitur differentia partium loci, ad quas est motus naturalis, sicut et posito infinito, ut supra dictum est. Sed hoc interest inter vacuum et infinitum, quia posito infinito, nullo modo potest poni neque sursum neque deorsum neque medium, ut in tertio dictum est: posito autem vacuo, possunt haec quidem poni, sed non quod ad invicem differant; quia nullius et non entis, et per consequens vacui, cum sit non ens et privatio, non est aliqua differentia. Sed loci mutatio naturalis requirit locorum differentiam, quia diversa corpora ad diversa loca moventur. Unde oportet loca naturalia differre ad invicem. Si igitur ponatur vacuum, nullius erit naturalis loci mutatio. Et si non est loci mutatio naturalis, nulla loci mutatio erit. Unde si est aliqua loci mutatio, oportet quod vacuum non sit. 524. He gives the fourth reason [363 215 a1]as follows. Natural motion is prior to compulsory since compulsory motion is only a departure from natural motion. Therefore, remove natural motion and all other motion is removed; for when the prior is removed, all that follows is removed. But if the void is posited, natural motion is removed; because the differences among the parts of place would be taken away and it is toward such parts that natural motions tend The same holds if the infinite be posited, as we said above. There is, however, this difference between the void and the infinite, that after granting the infinite there is no way of positing “up” or “down” or “center,” as we pointed out in Book III; but after granting a void, these places could be posited, but it would not be because they were mutually different: for no difference can be assigned in the realm of nothing and non-being and, consequently, of the void, which is a non-being and a privation. Yet natural changes of place do require difference of place, because diverse bodies are moved to diverse places. Consequently, natural places must be different one from the other. Therefore, if a void be posited, nothing could undergo a natural change of place; and if there is no natural change of place, there will be no change of place of any sort. Hence, if there is any change of place, there can be no void.
lib. 4 l. 11 n. 6 Quintam rationem ponit ibi: amplius, nunc quidem proiecta et cetera. Circa quam considerandum est quod solet esse quaedam dubitatio circa ea quae proiiciuntur: oportet enim movens et motum simul esse, ut infra in septimo probatur; et tamen illud quod proiicitur, invenitur moveri etiam postquam separatum est a proiiciente, sicut apparet in lapide proiecto, et sagitta emissa per arcum. Nunc igitur supposito quod vacuum non sit, solvitur ista dubitatio ex parte aeris, quo medium repletur. Et hoc dupliciter. Dicunt enim quidam quod ea quae proiiciuntur, moventur etiam postquam non tanguntur a proiiciente, propter antiperistasim, idest repercussionem vel contra-resistentiam: aer enim motus repercutitur ad alium aerem, et ille ad alium, et sic deinceps; et per talem repercussionem aeris ad aerem movetur lapis. Alii vero dicunt quod hoc ideo est, quia aer, qui continuus existens a proiiciente impellitur, velocius impellit corpus proiectum, quam sit motus quo corpus proiectum fertur naturaliter in proprium locum. Unde propter velocitatem motus aeris non permittitur corpus proiectum, ut puta lapis vel aliud huiusmodi, cadere deorsum; sed fertur secundum impulsionem aeris. Nulla autem istarum causarum posset poni, si esset vacuum; et ita corpus proiectum nullo modo ferretur nisi quandiu veheretur, puta a manu proiicientis, sed statim emissus a manu caderet; cuius contrarium videmus. Non ergo est vacuum. 525. The fifth reason is then given [364 215 a14]. In regard to this it should be considered that some question exists about projectiles: for the mover and the thing moved must be always together, as will be proved below in Book VII (1-3). Yet a projectile is found to be in motion even after it is separated from the projector, as is evident in the case of a stone that is thrown, or of an arrow shot from a bow. Now on the supposition that there is no void this difficulty is solved by attending to the air with which the medium [the field of trajectory] is filled. And it is solved in two ways. For some assert that projectiles remain in motion even after they are no longer contact with what gave them impulse on account of antiperistasis, i.e., repercussion or counter-resistence: for the air that has been pushed, pushes against other air, and that against other air, and so on, and it is on account of this impact of air against air that the stone is moved. The other explanation is that the continuum of air that received the impact from the projector pushes the impelled body with more speed than the speed of the motion by which the projectile is naturally borne to its proper place. Hence the speed of the air movement prevents the projectile, for example, the stone, or some other such, from falling downward; but it is carried along by the impulse of the air. Now neither of these explanations could be alleged if there were a void; consequently, a projectile could be moved only as long as it was carried, for example, in the hand of the one casting it: but as soon as it was released from the hand it would fall. But it is the opposite that happens. Therefore, there is not a void.
lib. 4 l. 11 n. 7 Sextam rationem ponit ibi: amplius nullus utique etc.: quae talis est. Si motus sit in vacuo, nullus poterit assignare causam propter quid illud quod movetur, alicubi stat. Non enim est ratio quare magis quiescat in una parte vacui quam in alia; neque in his quae moventur naturaliter, cum non sit differentia in partibus vacui, ut supra dictum est; neque in his quae moventur motu violento. Nunc enim dicimus quod cessat motus violentus, ubi deficit repercussio vel impulsio aeris, secundum duas causas assignatas. Oportebit ergo quod vel quiescat omne corpus, et nihil moveatur; aut si aliquid moveatur, quod movetur in infinitum, nisi occurrat ei aliquod corpus maius, quod violentum motum eius impediat. Ad confirmationem autem huius rationis, subiungit causam quare ponunt aliqui motum fieri in vacuo; quia scilicet vacuum cedit, et non resistit mobili; unde cum vacuum similiter cedit ex omni parte, feretur in infinitum ex qualibet parte. 526. He then gives the sixth reason [365 215 a19]. If motion were in a void, no one could give a reason why the moving object should stop anywhere. For there is no reason why it should stop at one part of the void rather than another. This is true both in the case of objects that are moved naturally, because there is no difference among the parts of the void, as we have said, and in the case of objects moved by a compulsory motion. For now we say that a violent compulsory motion ceases when repercussions or impulsions of the air are lacking, on account of the two reasons already given. Therefore it will have to be admitted either that every body is at rest and nothing in motion or that, if anything be in motion, it will remain In motion to infinity unless it runs into a more powerful body that could impede its compulsory motion. In support of this reasoning, he gives the reason why some posit motion in the void. It is because the void yields to and does not resist the mobile; hence since the void yields in the same way, in all directions, a mobile thing should be moved in all directions ad infinitum.

Notes

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