I started reading Thomas Aquinas’s commentary on Aristotle’s Physics recently. The Physics isn’t actually about what we would call physics; it’s about what in modern terms would be called philosophy of nature. Anyways, Aristotle devotes large parts of this book to rebutting the opinions of other philosophers, and every time I see one of these rebutting sections I’m always amazed at how similar his contemporaries sound to modern philosophers. Here are a few parts I was reading over the past couple of days that particularly stood out to me. The Latin text is from the Corpus Thomisticum, and the translation is by yours truly.
Thomas Aquinas, Commentary on Aristotle’s Physics, book 2, reading 2
Postquam philosophus ostendit quid est natura, hic ostendit quot modis natura dicitur. Et primo ostendit quod natura dicitur de materia; secundo quod dicitur de forma, ibi: alio autem modo et cetera. Circa primum, sciendum est quod antiqui philosophi naturales, non valentes usque ad primam materiam pervenire, ut supra dictum est, aliquod corpus sensibile primam materiam omnium rerum ponebant, ut ignem vel aerem vel aquam: et sic sequebatur quod omnes formae advenirent materiae tanquam in actu existenti, ut contingit in artificialibus; nam forma cultelli advenit ferro iam existenti in actu. Et ideo similem opinionem accipiebant de formis naturalibus, sicut de formis artificialibus. Dicit ergo primo quod quibusdam videtur quod hoc sit substantia et natura rerum naturalium, quod primo inest unicuique, quod secundum se consideratum est informe: ut si dicamus quod natura lecti est lignum, et natura statuae est aes; nam lignum est in lecto, et secundum se consideratum non est formatum. Et huius signum dicebat Antiphon esse hoc, quod si aliquis proiiciat lectum ad terram, et ligna putrescendo accipiant potentiam ut aliquid ex eis germinet, illud quod generatur non erit lectus, sed lignum. Et quia substantia est quae permanet, et naturae est sibi simile generare, concludebat quod omnis dispositio quae est secundum quamcumque legem rationis vel artem, sit accidens: et illud quod permanet sit substantia, quae continue patitur huiusmodi dispositionum immutationem. Supposito igitur quod rerum artificialium formae sint accidentia, et materia sit substantia, assumebat aliam propositionem, quod sicut se habent lectus et statua ad aes et lignum, ita et quodlibet horum se habet ad aliquid aliud quod est materia ipsorum; ut aes et aurum ad aquam (quia omnium liquefactibilium materia videtur esse aqua), et ossa et ligna ad terram, et similiter est de quolibet aliorum naturalium. Unde concludebat quod illa materialia subsistentia formis naturalibus, sint natura et substantia eorum. Et propter hoc quidam dixerunt terram esse naturam et substantiam omnium rerum, scilicet primi poetae theologizantes; posteriores vero philosophi vel ignem vel aerem vel aquam, vel quaedam horum, vel omnia haec, ut ex superioribus patet. Quia tot de numero eorum dicebant esse substantiam omnium rerum, quot accipiebant esse principia materialia; et omnia alia dicebant esse accidentia horum, idest materialium principiorum, vel per modum passionis vel per modum habitus vel per modum dispositionis, vel cuiuslibet alterius quod reducatur ad genus accidentis. Et haec est una differentia quam ponebant inter principia materialia et formalia, quia dicebant ea differre secundum substantiam et accidens. Alia autem differentia est, quia dicebant ea differre secundum perpetuum et corruptibile. Nam quodcumque praemissorum corporum simplicium ponebant esse materiale principium, dicebant illud esse perpetuum: non enim dicebant quod transmutarentur invicem. Sed omnia alia dicebant fieri et corrumpi infinities: ut puta, si aqua sit principium materiale, dicebant aquam nunquam corrumpi, sed manere eam in omnibus sicut substantiam eorum; sed aes et aurum et alia huiusmodi dicebant corrumpi et generari infinities.
After the Philosopher has shown what nature is, he here shows how many meanings “nature” has. And first he shows that nature is said of matter; second that it is said of form, there: “But in another way,” etc. Concerning the first, it must be noted that the ancient natural philosophers, unable to arrive at prime matter, as was said above, held some sensible body to be the first matter of all things, like fire, or air, or water: and thus it followed that all forms came to matter as to something already existing in act, as occurs with artificial things; for the form of a knife comes to iron that already exists in act. And therefore they held a similar opinion on natural forms and artificial forms. He [Aristotle, citing objections?] says then first that to some it seems that this is the substance and nature of all natural things, that which is in each of them first, which considered in itself has no form: as if we should say that the nature of a bed is wood, and the nature of a statue is bronze; for wood is in the bed, and considered in itself is not formed. And Antiphon said that a sign of this fact is this, that if someone throws a bed to the ground, and the wood by rotting actualizes [?] its potency to have something germinate out of it, that which is formed will not be a bed, but wood. And because substance is that which remains, and it is characteristic of nature to create something similar to itself, he concluded that every arrangement that follows some law of reason or some skill, is accidental: and that which remains is substance, which uninterruptedly undergoes such arrangements and changes. Given then that the forms of artificial things are accidents, and their matter is their substance, he adopted another proposition, that as a bed and a statue is to wood and bronze, so also any of these things is to any other thing that is its matter; as bronze and gold are to water (for the matter of all liquefiable things seems to be water), and bones and wood to earth, and it is similar with any other natural thing. From this he concluded that those materials underlying natural forms, are their nature and substance. And because of this some have said that the earth is the nature and substance of all things, namely the first theologizing [?] poets; philosophers afterward said that fire or air or water, or some of these, or all of them [were the nature and substance of all things], as is clear from what was said above. For they said as many of those were the substance of all things, as they held to be material principles*; and everything else they said were accidents of these, that is of the material principles, either in the manner of passion [“passion” in the sense of receiving rather than causing change; opposed to action] or in the manner of a habit* or in the manner of an arrangement, or of whatever other thing that falls under the genus of accident. And this, they said, is one difference between material and formal principles, for they said they differed as substance and accident. And another difference is, that they said they differed as permanent and corruptible. For whichever of the aforementioned simple bodies they said was a material principle, they said that that was permanent: for they said that they [the principles] were not changed into each other. But all other things they said came into being and passed away an infinite number of times: as for example, if water was a material principle, they said water never passed away, but remained in all things as their substance; but bronze and gold and other such things they said passed away and came into being an infinite number of times.
(*I’m not entirely sure how to translate “principium”; literally it just means “beginning,” but it often carries the connotation that it’s a source rather than just a beginning. Translations of Aquinas usually just translate “principium” as “principle” everywhere, so since I’m not entirely sure what Aquinas means, I’m just falling back on that. Similarly, I’m also not sure how to translate “habitus”; literally it just means “a[n act of] having,” which could mean any one of a number of things. But most translations of Aquinas just render this as “habit,” so I’m falling back on that.)
It might be hard to understand this if you don’t know all the technical terminology Aquinas uses, but the basic idea is that the ancient philosophers thought that any complex thing exists only as a feature or arrangement of the parts that make it up, rather than the whole being a thing in itself. They thought that the elements were never created or destroyed, only rearranged to form different things. They also thought that there was no ontological difference between living things and artificial machines. All of these are positions taken for granted by modern philosophers and scientists, though we have different elements now. This contrasts with the position Aristotle came up with; he held that natural things (“natural” being defined as “having within itself a principle of motion and rest, which is in it primarily and essentially and not accidentally” (book 2, reading 1)) are things in their own right rather than simply sums of their parts.
ibid., book 2, reading 7
… sicut Empedocles, qui dixit quod aer non semper adunatur superius supra terram quasi hoc ei sit naturale, sed quia ita accidit a casu. Dicit enim quod quando mundus est factus, lite distinguente elementa, accidit quod aer se collegit in istum locum, et sicut tunc cucurrit, ita semper stante isto mundo cursum habebit: sed multoties in aliis mundis, quos ponebat infinities fieri et corrumpi, ut supra dictum est, aer aliter ordinatur inter partes universi. Et similiter dicebat quod plurimae partes animalium fiunt a fortuna; sicut quod in prima constitutione mundi fiebant capita sine cervice.
… like Empedocles, who said that air does not always rise upward above the eath as if this is natural to it, but because it occurs thus by chance. For he says that when the world was made, with strife [incompatibility? repulsion?] separating the elements, it happened that air went to that place, and as when it ran there then, so will it always take that course as long as the world stands thus: but often in other worlds, which he thought were created and passed away an infinite number of times, as was said above, air is otherwise ordered among the parts of the universe. And similarly he said that most parts of animals occur by chance; as when in the first creation of the world heads were made without necks.
And here we have the multiverse with the laws of nature changed at each iteration.
ibid., book 2, reading 12
Circa primum sciendum quod ponentes naturam non agere propter aliquid, hoc confirmare nitebantur removentes id ex quo natura praecipue videtur propter aliquid operari. Hoc autem est quod maxime demonstrat naturam propter aliquid operari, quod ex operatione naturae semper invenitur aliquid fieri quanto melius et commodius esse potest, sicut pes hoc modo est factus a natura, secundum quod est aptus ad gradiendum; unde si recedat a naturali dispositione, non est aptus ad hunc usum; et simile est in ceteris. Et quia contra hoc praecipue opponere nitebantur, ideo dicit quod potest opponi quod nihil prohibet naturam non facere propter aliquid, neque facere semper quod melius est. Invenimus enim quandoque quod ex aliqua operatione naturae provenit aliqua utilitas, quae tamen non est finis illius naturalis operationis, sed contingit sic evenire; sicut si dicamus quod Iupiter pluit, idest Deus vel natura universalis, non propter hunc finem, ut frumentum augmentet, sed pluvia provenit ex necessitate materiae. Oportet enim, inferioribus partibus ex propinquitate solis calefactis, resolvi vapores ex aquis; quibus sursum ascendentibus propter calorem, cum pervenerint ad locum ubi deficit calor propter distantiam a loco ubi reverberantur radii solis, necesse est quod aqua vaporabiliter ascendens congeletur ibidem, et congelatione facta, vapores vertantur in aquam; et cum aqua fuerit generata, necesse est quod cadat deorsum propter gravitatem: et cum hoc fit, accidit ut frumentum augeatur. Non tamen propter hoc pluit ut augeatur; quia similiter in aliquo loco frumentum destruitur propter pluviam, ut cum est collectum in area. Non tamen propter hoc pluit, ut destruatur frumentum, sed hoc casu accidit, pluvia cadente; et eodem modo videtur casu accidere quod frumentum crescat per accidens, pluvia cadente. Unde videtur quod nihil prohibeat sic etiam esse in partibus animalium, quae videntur esse sic dispositae propter aliquem finem: utpote quod aliquis dicat quod ex necessitate materiae contingit quod quidam dentes, anteriores scilicet, sint acuti et apti ad dividendum cibum, et maxillares sint lati et utiles ad conterendum cibum. Non tamen ita quod propter istas utilitates natura fecerit dentes tales vel tales: sed quia dentibus sic factis a natura propter necessitatem materiae sic decurrentis, accidit ut talem formam consequerentur, qua forma existente sequitur talis utilitas. Et similiter potest dici de omnibus aliis partibus, quae videntur habere aliquam determinatam formam propter aliquem finem.
Et quia posset aliquis dicere quod semper vel ut in pluribus tales utilitates consequuntur; quod autem est semper vel frequenter, conveniens est esse a natura: ideo ad hanc obiectionem excludendam, dicunt quod a principio constitutionis mundi, quatuor elementa convenerunt ad constitutionem rerum naturalium, et factae sunt multae et variae dispositiones rerum naturalium: et in quibuscumque omnia sic acciderunt apta ad aliquam utilitatem, sicut si propter hoc facta essent, illa tantum conservata sunt, eo quod habuerunt dispositionem aptam ad conservationem, non ab aliquo agente intendente finem, sed ab eo quod est per se vanum, idest a casu. Quaecumque vero non habuerunt talem dispositionem sunt destructa, et quotidie destruuntur; sicut Empedocles dixit a principio fuisse quosdam generatos, qui ex una parte erant boves, et ex alia parte erant homines.
Concerning the first, it must be noted that those who held that nature does not act for an end, tried to prove this by taking away the cases because of which nature especially seems to work for an end. And this is what most seems to show that nature works for an end, that out of the operation of nature a thing is always found such that it can be so much the better and more convenient, as the foot is made in this way by nature, so that it is fit for stepping; so that if it departs from its natural arrangement, it is not fit for this use; and it is similar in everything else. And because they wanted to argue against this especially, therefore he [Aristotle, citing objections?] says that it can be objected that nothing prevents nature from not acting for an end and always making what is better. For we find all the time that out of some work of nature some useful thing comes forth, which is still not the end of that natural operation, but happens to occur this way; as if we say that Jupiter rains [?]*, that is God or all of nature [?]*, it is not for this end, that it should make fruit grow, but the rain comes forth out of the necessity of matter. For it is necessary, when lower areas have been warmed by their closeness to the sun, for vapors to be released out of water; and these ascending because of their heat, when they have arrived at a place where heat is insufficient because of its distance from the place where the rays of the sun are rebounded, it is necessary that the water, ascending as a vapor, be congealed there, and once it has congealed, that the vapors be turned into water; and when the water has been formed, it is necessary that it fall downward because of its weight: and when this occurs, it so happens that fruit grows. But it is not for the sake of this, so that the fruits should grow, that it rains; because similarly in another place fruit is destroyed because of rain, as when it is gathered together in an area. But it is not for this purpose, that the fruits should be destroyed, that it rained, but this happened by accident, when the rain was falling; and in the same way it seems to occur by chance that the fruit grows accidentally, while the rain is falling. From which it seems that nothing prevents things from also being this way with the parts of animals, which seem to be so arranged for some end: namely that someone should say that out of the necessity of matter it so happens that some teeth, that is the front teeth, are sharp and fit for cutting food, and molars are broad and useful for grinding food. But it is not that nature made teeth in such or such a way for these uses: but that, when teeth had been so made by nature because of the necessity of matter running down [?] in this way, it happened that it followed such a form, and once such a form existed, such a use followed. And it can similarly be said of all other parts, which seem to have some definite form for some end.
(*I think this might be one of those cases where the ancient Greeks and Romans used the name of a god metonymically to stand for the thing that that god is a god of. So in Virgil, you often find lines where he says “Venus” but means “love.” Here, I’m guessing Aristotle is saying “Zeus” to mean “the sky,” or “all of nature” as Aquinas says, and since Aquinas is using a Latin translation (he didn’t know Greek), that’s rendered as “Jupiter.”)
And because someone could say that such uses follow always or for the most part; that is, always or frequently, it is fitting that this be by nature: therefore to preclude this objection, they say that from the beginning of the formation of the world, the four elements came together to the formation of natural things, and the many and varied arrangements of natural things were made: and whichever things happened to be fit for some use, as if they had been made for this, only those were preserved, because they had an arrangement fit for preservation, not from some agent intending that end, but from that which in itself is empty, that is by chance. On the other hand whatever did not have such an arrangement was destroyed, and is destroyed every day; as Empedocles said some people were formed in the beginning, who in one part were bulls, and in the other part were men.
Now, is it just me, or does this whole section, and particularly the underlined part (the underline is mine, by the way), sound exactly like evolution and natural selection?
After Aristotle devoted so much of this book to rebutting these philosophers, it looks like nothing has changed.