Authors/Thomas Aquinas/physics/L4/lect13

Lecture 13 Non-existence of the void from the void itself

Latin	English
	Lecture 13 Non-existence of the void from the void itself
lib. 4 l. 13 n. 1 Hic ostendit vacuum non esse, rationibus acceptis ex parte ipsius vacui, absque consideratione motus: et hoc ostendit tribus rationibus. Dicit ergo primo: quod etiam considerantibus vacuum per se, absque motu, videbitur quod ita sit dictum ab aliquibus vacuum esse, sicut vere sonat nomen vacui. Nam vacuum sonat aliquid inane et quod non est; et inaniter et absque ratione et veritate dictum est, quod vacuum sit. Et hoc quidem sic ostendit. Quia si aliquis ponat in aqua aliquod corpus cubicum (scilicet quod habet sex superficies quadratas), oportet quod tanta quantitas aquae recedat a loco suo, quanta est quantitas cubi. Et sicut est de aqua, ita est et de aere; licet non sit ita manifestum, eo quod aqua est magis sensibilis quam aer. Eadem igitur ratione, quandocumque aliquid immittitur in aliquod corpus, quod natum est transmutari in aliquam partem, necesse est quod, nisi partes cohaereant per condensationem aut subintrationem partium in invicem, quod transmutetur: vel secundum conditionem corporis cedentis (quando habet exitum liberum), utpote quod corpus grave, ut terra, cedat deorsum, et corpus leve, ut ignis, cedat sursum, et corpus quod est respectu alicuius grave et respectu alicuius leve, cedat in utramque partem, sicut aer et aqua: vel quod corpus cedat secundum conditionem corporis impositi, quando scilicet corpus cedens coarctatur a corpore imposito, ut non possit moveri secundum suam exigentiam, sed secundum exigentiam corporis impositi. Universaliter tamen hoc verum est, quod oportet corpus cedere in quod alterum corpus immittitur, ne sint duo corpora simul. Sed hoc non potest dici de vacuo, quod cedat corpori immisso: quia vacuum non est aliquod corpus; omne autem quod movetur quocumque modo, est corpus. Sed si sit aliquod spatium vacuum, et aliquod corpus immittatur in illud spatium, oportet quod corpus impositum transeat per illud spatium, quod prius erat vacuum, scilicet simul cum eo existens; sicut si aqua non cederet ligneo cubo neque aer, sed ista corpora transirent per ipsum corpus ligneum cubicum, ita quod aer et aqua subintrarent ipsum corpus cubicum, et essent simul cum eo. Sed hoc est impossibile, scilicet quod corpus cubicum ligneum sit simul cum spatio vacuo: quia corpus cubicum ligneum habet tantam magnitudinem, quantam habet vacuum, quod ponitur quoddam spatium dimensionatum sine corpore sensibili. Et quamvis corpus ligneum cubicum sit calidum vel frigidum, aut grave vel leve, nihilominus tamen ipsum corpus cubicum alterum est secundum rationem ab omnibus passionibus sensibilibus sibi accidentibus: quamvis non sit separabile ab eis secundum rem. Hoc autem quod est secundum rationem alterum a passionibus, est ipsum corpus lignei cubi, idest quod pertinet ad corporeitatem eius. Si ergo separetur hoc corpus ab omnibus quae sunt alia ab ipso secundum rationem, ita quod non sit neque grave neque leve, sequitur quod contineat vel occupet de spatio vacuo aliquid aequale sibi. Et sic in eadem parte sibi aequali, quae est pars loci et vacui, erit simul corpus lignei cubi. Quo supposito, non videtur quod sit assignare differentiam inter corpus cubi, et dimensiones loci vel vacui. Nam sicut dimensiones loci vel vacui sunt sine qualitatibus sensibilibus, ita et dimensiones corporis cubici, ad minus secundum rationem, sunt aliae ab huiusmodi passionibus. Duae autem magnitudines aequalis quantitatis non possunt differre, nisi secundum situm. Non enim potest imaginari quod haec linea sit alia ab illa sibi aequali, nisi inquantum imaginamur utramque in alio et alio situ. Unde si ponantur duae magnitudines simul, non videtur quod possint differre: et sic si duo corpora aequalia dimensionata sint simul, sive sint cum passionibus sensibilibus sive non, sequitur quod duo corpora sint unum. Vel si adhuc corpus cubicum, et spatium quod est locus vel vacuum, remaneant duo et simul sint, non potest assignari ratio quare non quaecumque alia corpora simul possint esse in eodem. Et ita, sicut corpus cubicum simul est cum spatio loci aut vacui, ita etiam simul cum utroque poterit adhuc esse aliud tertium vel etiam quartum corpus: quod est impossibile. Non enim potest dici quod simul cum corpore cubico ligneo non possit esse simul aliud corpus sensibile, propter materiam: quia corpori non debetur locus ratione materiae, nisi secundum quod materia continetur sub dimensionibus. Unde quod duo corpora non possint esse simul, non est ex parte materiae vel passionum sensibilium, sed solum ex ratione dimensionum, in quibus non potest esse diversitas si sint aequales, nisi secundum situm, ut dictum est. Unde cum dimensiones sint in spatio vacuo sicut in corpore sensibili, sicut duo corpora sensibilia non possunt esse simul, ita nec corpus sensibile simul cum spatio vacuo. Hoc est igitur unum inconveniens et impossibile, quod sequitur ex praemissa positione, quod duo corpora sunt simul.	541. Now the Philosopher taking his arguments from the void itself, without any mention of motion, shows that the void does not exist. He shows this by three reasons. He says therefore first [375 216 a26] that even considering the void on its own merits, without motion, it will be seen that the void spoken of by some is just what the name “void” implies. For “void” means something empty and non-existent—and the claim that it exists is vain and without reason and truth. And he shows this as follows. If anyone places a cubic body in water (i.e., a body having six square surfaces) an amount of water equal to the quantity of the cube must be displaced. And what is true of water is true of air, although it is not so evident, because water is more perceptible to sense than air. By the same reasoning applied to the case of any body that can be displaced, in some part, it must, if the parts are not compressed, or enter into each other, be dislodged either (1) according to the state of a yielding body (when it has free exit); for example, if it is a heavy body such as earth it will yield downwards, and if it is a light body such as fire it will yield upwards, and if it is a body which is light in relation to one body and heavy in relation to another, it will yield in both directions, such as do air and water; or (2) because the body yields on account of the condition of the newly imposed body, i.e., when the yielding body is prevented by the imposed body, i.e., when the yielding body is prevented by the imposed body from being moved according to its demands but is moved according to the demands of the imposed body. And in general it can be held as true that a body must yield to an inserted one, lest two bodies be in the same place. But this will not be true in the case of the void, i.e., that it must yield to the inserted body, since the void is not a body, whereas whatever is moved in any manner whatsoever is a body. But if there be empty space and a body inserted therein, then the inserted body must pass through that space which previously was empty and cohabit the same space as the void—just as if water or air were not to yield to a wooden cube, but were to pass into the cube in such a way that the air and water would penetrate that cubic body and cohabit with it. But it is impossible for a wooden cube to exist with empty space; for the wooden cube has the same magnitude as the empty space, which is supposed to be a certain dimensional space without a sensible body. And even though the wooden cube be hot or cold, heavy or light, nevertheless the cubic body is other in notion from all the sensible qualities, that are its accidents, although it be not separable from them in reality. Now what is in conception distinct from the qualities is the body of a wooden cube, i.e., that which pertains to its corporeity. Now if this body be separated from whatever is distinct from it in notion, so that it is neither heavy nor light, it follows that it will occupy a volume of empty space equal to itself. Thus in the same part equal to it, which is part of the place and of the void, the body of the wooden cube will be. On this assumption it does not seem possible to find a difference between the body of the cube and the dimensions of the place or void. For just as the dimensions of the place or void exist without sensible qualities, so too the dimensions of the cubic body, at least according to notion, are distinct from its sensible qualities. But two magnitudes of equal quantity can differ only in situs. For we cannot imagine one line as distinct from another of equal length, unless we imagine one in one situs and the other in another. Hence, if two magnitudes are imagined together, it does not seem that they can differ: consequently, if two bodies of equal dimensions are together, whether accompanied by their sensible qualities or not, it follows that two bodies are one, or if the cubic body and the space which is the place or void remain two, but are still together, there is no reason why any number of bodies cannot be there. In that case, just as the cubic body is together with the space of the place or void, along with both a third or even a fourth body ought to be able to be inserted. This, of course, is impossible. For we cannot say that it is because of matter that some other sensible body cannot exist together with the wooden cubic body, for place does not belong to a body because of its matter, except in the sense that the matter is contained under dimensions. Hence the impossibility for two bodies to be together is not on account of the matter or of the sensible qualities, but only on account of the dimensions, in which no diversity can be found if they are equal except a diversity based on situs, as was said. Wherefore since there are dimensions in empty space just as there are in a sensible body, then, just as two sensible bodies cannot be together, so neither can a sensible body be together with empty space. So this is one unacceptable result and impossibility that follows from the aforementioned premise: namely, that two bodies would be in the same place.
lib. 4 l. 13 n. 2 Secundam rationem ponit ibi: amplius autem manifestum est et cetera. Et dicit manifestum esse quod cubus, qui transmutatur et ponitur in spatium vacuum, habet hoc quod habent omnia alia corpora, scilicet dimensiones. Si ergo dimensiones corporis cubici non differunt a dimensionibus loci secundum rationem, quare oportet facere aliquem locum corporibus extra proprium corpus uniuscuiusque, si locus nihil aliud est quam corpus impassibile, idest absque passionibus sensibilibus? Ex quo enim corpus habet proprias dimensiones, ad nihil videtur esse necessarium quod ponantur circa ipsum aliquae aliae dimensiones spatii aequalis suis dimensionibus. Accidit igitur, si ponatur vacuum vel locus esse quoddam spatium separatum, quod non est necessarium corpora esse in loco.	542. He then gives the second reason [376 216 b6], saying that it is clear that a cube which is transferred to an empty space has what all other bodies have, namely, dimensions. If therefore the dimensions of the cube do not differ from the dimensions of the place according to conception, why is it necessary to find for a body a place distinct from its own body, if place is nothing more than “impossible body,” i.e., a body without sensible qualities? In view of the fact that a body has its own dimensions, there seems to be no necessity for it to be surrounded by other dimensions of a space equal to its own dimensions. Consequently if the void is presumed, or place as a certain separated space, it follows that bodies do not have to be in place.
lib. 4 l. 13 n. 3 Tertiam rationem ponit ibi: amplius oportet etc.; et dicit quod si aliquid esset vacuum, oporteret quod manifestaretur in istis mobilibus. Sed nunquam apparet aliquid vacuum infra mundum: quia plenum aere, quod videtur vacuum, non est vacuum. Aer enim est aliquid, licet visu non percipiatur. Quia si etiam pisces essent ferrei, et haberent similem apparentiam cum aqua, non posset aqua discerni ab eis per visum; nec tamen sequeretur quod aqua non esset, vel etiam pisces: quia non solum visu, sed etiam tactu discernitur illud quod tangitur. Et sic patet aerem aliquid esse: quia tactu percipitur calidus vel frigidus. Ex his igitur apparet quod vacuum non sit aliquod spatium separatum, neque infra mundum neque extra mundum.	543. He gives the third reason [377 216 b12] when he says that if there were a void, it would have to be evident in mobile things. But there is no evidence of a void anywhere in the world, because what is full of air seems to be a void, though it to not. For air is something, although not perceptible to sight. Now if fish were made of iron and had the same appearance as water, our sight would not be able to distinguish them from water; but it would not follow that the water, or even the fish, were non-existent: for it is not only by sight but also by touch that we can discern what is touched. Consequently, it is evident that water is something, because touch can perceive whether it be hot or cold. From all this it appears that there is no separate void either within or outside the universe.