In Octo Libros Physicorum Aristotelis Expositio
Commentary on Aristotle’s Physics
The Principles of Natural Things
Materia et subiectum scientiae naturalis et huius libri. Procedendum ab universalioribus principiis nobis magis notis
The matter and subject of physics
Quoniam quidem intelligere et scire contingit circa omnes scientias, quarum sunt principia aut causae aut elementa, ex horum cognitione (tunc enim cognoscere arbitramur unumquodque, cum causas primas et prima principia cognoscimus, et usque ad elementa), manifestum quidem quod quae sunt circa principia scientiae quae de natura est, prius determinare tentandum.
Since, indeed, to understand and to know happen in all sciences of which there are principles, causes, or elements, it is through acquaintance with these that knowledge is attained. For we do not think that we know a thing until we know its first causes and first principles and have carried our analysis as far as its elements. Plainly, therefore, in the science of nature, as in other branches of study, our first task will be to try to determine what relates to its principles.
Innata autem est ex notioribus nobis via et certioribus, in certiora naturae et notiora. Non enim eadem nobis nota et simpliciter.
The natural way of doing this is to start from the things that are more knowable and certain to us and proceed toward those that are clearer and more knowable by nature; for the same things are not “knowable relatively to us” and “knowable” without qualification.
Unde quidem necesse secundum modum hunc procedere ex incertioribus naturae, nobis autem certioribus, in certiora naturae et notiora.
So, in the present inquiry, we must follow this method and advance from what is more obscure by nature but clearer to us toward what is more clear and more knowable by nature.
Sunt autem primum nobis manifesta et certa confusa magis: posterius autem ex his fiunt nota elementa et principia dividentibus haec. Unde ex universalibus ad singularia oportet procedere.
Now, what is plain and obvious to us at first is confused masses, the elements and principles of which become known to us later by analysis. Thus we must advance from universals to singulars.
Totum enim secundum sensum notius est: universale autem totum quoddam est. Multa enim comprehendit ut partes universale.
For it is a whole that is best known to sense perception, and a universal is a kind of whole, comprehending many things within it, like parts.
Sustinent autem idem hoc quodammodo et nomina ad rationem. Totum enim quoddam et indistincte significant, ut puta circulus. Definitio autem ipsius dividit in singularia.
Much the same thing happens in the relation of the name to the formula. A name, such as “round,” means vaguely a sort of whole: its definition divides into particular elements.
Et pueri primum appellant omnes viros patres et feminas matres: posterius autem determinant horum unumquodque.
Similarly, children begin by calling all men “father” and all women “mother,” but later on distinguish each of them.
1. Quia liber Physicorum, cuius expositioni intendimus, est primus liber scientiae naturalis, in eius principio oportet assignare quid sit materia et subiectum scientiae naturalis.
1. Because this book upon which we intend to comment here, the Physics, is the first book of natural science, it is necessary in the beginning to decide what is the matter and the subject of natural science.
Sciendum est igitur quod, cum omnis scientia sit in intellectu, per hoc autem aliquid fit intelligibile in actu, quod aliqualiter abstrahitur a materia; secundum quod aliqua diversimode se habent ad materiam, ad diversas scientias pertinent.
Since every science is in the intellect, it should be understood that something is rendered intelligible in act insofar as it is in some way abstracted from matter. And, inasmuch as things are differently related to matter, they pertain to different sciences.
Rursus, cum omnis scientia per demonstrationem habeatur, demonstrationis autem medium sit definitio; necesse est secundum diversum definitionis modum scientias diversificari.
Furthermore, since every science is established through demonstration, and since the definition is the middle term in a demonstration, it is necessary that sciences be distinguished according to the diverse modes of definition.
2. Sciendum est igitur quod quaedam sunt quorum esse dependet a materia, nec sine materia definiri possunt: quaedam vero sunt quae licet esse non possint nisi in materia sensibili, in eorum tamen definitione materia sensibilis non cadit. Et haec differunt ad invicem sicut curvum et simum. Nam simum est in materia sensibili, et necesse est quod in eius definitione cadat materia sensibilis, est enim simum nasus curvus; et talia sunt omnia naturalia, ut homo, lapis: curvum vero, licet esse non possit nisi in materia sensibili, tamen in eius definitione materia sensibilis non cadit; et talia sunt omnia mathematica, ut numeri, magnitudines et figurae.
2. It must be understood, therefore, that there are some things whose existence depends upon matter and that cannot be defined without matter. Further, there are other things that, even though they cannot exist except in sensible matter, have no sensible matter in their definitions. And these differ from each other as the curved differs from the snub. For the snub exists in sensible matter and sensible matter must fall in its definition, for the snub is a curved nose. And the same is true of all natural things, such as man and stone. But sensible matter does not fall in the definition of the curved, even though the curved cannot exist except in sensible matter. And this is true of all the mathematical objects, such as numbers, magnitudes, and figures.
Quaedam vero sunt quae non dependent a materia nec secundum esse nec secundum rationem; vel quia nunquam sunt in materia, ut Deus et aliae substantiae separatae; vel quia non universaliter sunt in materia, ut substantia, potentia et actus, et ipsum ens.
There are still other things that do not depend upon matter, either according to their existence or according to their definitions. And this is either because they never exist in matter, such as God and the other separated substances, or because they do not universally exist in matter, such as substance, potency and act, and being itself.
3. De huiusmodi igitur est metaphysica: de his vero quae dependent a materia sensibili secundum esse sed non secundum rationem, est mathematica: de his vero quae dependent a materia non solum secundum esse sed etiam secundum rationem, est naturalis, quae physica dicitur.
3. Now metaphysics deals with things of this latter sort, while mathematics deals with those things that depend upon sensible matter for their existence but not for their definition. And natural science, which is called “physics,” deals with those things that depend upon matter not only for their existence but also for their definition.
Et quia omne quod habet materiam mobile est, consequens est quod ens mobile sit subiectum naturalis philosophiae. Naturalis enim philosophia de naturalibus est; naturalia autem sunt quorum principium est natura; natura autem est principium motus et quietis in eo in quo est; de his igitur quae habent in se principium motus, est scientia naturalis.
And because everything that has matter is mobile, it follows that mobile being is the subject of natural philosophy. For natural philosophy is about natural things, and natural things are those whose principle is nature. But nature is a principle of motion and rest in that in which it is. Therefore, natural science deals with those things that have in them a principle of motion.
4. Sed quia ea quae consequuntur aliquod commune, prius et seorsum determinanda sunt, ne oporteat ea multoties pertractando omnes partes illius communis repetere;
4. Furthermore, those things that follow from something common must be treated first and by themselves. Otherwise, it becomes necessary to repeat such things many times while discussing each instance of that which is common.
necessarium fuit quod praemitteretur in scientia naturali unus liber, in quo tractaretur de iis quae consequuntur ens mobile in communi; sicut omnibus scientiis praemittitur philosophia prima, in qua determinatur de iis quae sunt communia enti inquantum est ens.
Therefore, it was necessary that one book in natural science be set forth in which those things that are consequent upon mobile being in common are treated, just as first philosophy, in which those things that are common to being insofar as it is being are determined, is set forth for all the sciences.
Hic autem est liber Physicorum, qui etiam dicitur De physico sive naturali auditu, quia per modum doctrinae ad audientes traditus fuit: cuius subiectum est ens mobile simpliciter.
This, then, is the book, the Physics, or On Physics or of the Natural to be Heard, because it was handed down to hearers by way of instruction. And its subject is mobile being simply.
Non dico autem corpus mobile, quia omne mobile esse corpus probatur in isto libro; nulla autem scientia probat suum subiectum: et ideo statim in principio libri De caelo, qui sequitur ad istum, incipitur a notificatione corporis.
I do not, however, say “mobile body,” because the fact that every mobile being is a body is proven in this book, and no science proves its own subject. Thus, in the very beginning of the De caelo, which follows this book, we begin with the notion of body.
Sequuntur autem ad hunc librum alii libri scientiae naturalis, in quibus tractatur de speciebus mobilium: puta in libro De caelo de mobili secundum motum localem, qui est prima species motus; in libro autem de generatione, de motu ad formam et primis mobilibus, scilicet elementis, quantum ad transmutationes eorum in communi; quantum vero ad speciales eorum transmutationes, in libro Meteororum; De mobilibus vero mixtis inanimatis, in libro de mineralibus; de animatis vero, in libro De anima et consequentibus ad ipsum.
Moreover, after the Physics, there are other books of natural science in which the species of motion are treated: in De caelo, we treat the mobile according to local motion, which is the first species of motion; in De generatione, we treat of motion’s relation to form and of the first mobile things, the elements, with respect to their changes in general; but we consider their particular changes in Meteororum, and in De mineralibus, we consider the mobile mixed bodies that are non-living. Living bodies are considered in De anima and the books that follow it.
5. Huic autem libro praemittit Philosophus prooemium, in quo ostendit ordinem procedendi in scientia naturali. Unde duo facit:
5. To this book, then, the Philosopher writes a preface in which he shows the order in which natural science must proceed. In this preface, he does two things.
primo ostendit quod oportet incipere a consideratione principiorum;
First, he shows that it is necessary to begin with a consideration of principles.
secundo quod inter principia oportet incipere a principiis universalioribus, ibi: innata autem etc.
Second, at the natural way of doing this (184a16; ), he shows that, among principles, it is necessary to begin with the more universal principles.
Primo ergo ponit talem rationem. In omnibus scientiis quarum sunt principia aut causae aut elementa, intellectus et scientia procedit ex cognitione principiorum, causarum et elementorum; sed scientia quae est de natura, habet principia, elementa et causas; ergo in ea oportet incipere a determinatione principiorum.
Therefore, he first gives the following argument. In all sciences of which there are principles, causes, or elements (184a10), understanding and science proceed from a knowledge of the principles, causes, and elements. Now, the science that is about nature has principles, elements, and causes. Therefore, in that science it is necessary to begin with a determination of principles.
Quod autem dicit intelligere, refertur ad definitiones; quod vero dicit scire, ad demonstrationes. Nam sicut demonstrationes sunt ex causis, ita et definitiones; cum completa definitio sit demonstratio sola positione differens, ut dicitur in I Poster.
When he says, to understand, he refers to definitions, and when he says, to know, he refers to demonstrations. For as demonstrations are from causes, so also are definitions, since a complete definition is a demonstration differing only by position, as is said in Posterior Analytics 1.8.
Per hoc autem quod dicit principia aut causas aut elementa, non intendit idem significare. Nam causa est in plus quam elementum; elementum enim est ex quo componitur res primo et est in eo, ut dicitur in V Metaphys., sicut litterae sunt elementa locutionis, non autem syllabae: causae autem dicuntur ex quibus aliqua dependent secundum suum esse vel fieri;
When he speaks of principles or causes or elements, however, he does not intend to signify the same thing by each. For “cause” is wider in meaning than “element.” An element is a first component of a thing and is in the composed thing, as is said in Metaphysics 5. Thus, letters are elements of speech, but syllables are not. But those things are called “causes” upon which things depend for their existence or their coming to be.
unde etiam quae sunt extra rem, vel quae sunt in re ex quibus non componitur res primo, possunt dici causae, non tamen elementa. Principium vero importat quendam ordinem alicuius processus; unde aliquid potest esse principium, quod non est causa: sicut id unde incipit motus est principium motus, non tamen causa; et punctum est principium lineae, non tamen causa.
Thus, even that which is outside the thing or that which is in it—though the thing is not first composed of it—can be called a “cause,” though it cannot be called an “element.” But “principle” implies a certain order in any progression. Thus, something can be a principle that is not a cause, as that from which motion begins is a principle of motion but is not a cause, and a point is a principle of a line but not a cause.
Sic igitur per principia videtur intelligere causas moventes et agentes, in quibus maxime attenditur ordo processus cuiusdam; per causas autem videtur intelligere causas formales et finales, a quibus maxime dependent res secundum suum esse et fieri; per elementa vero proprie primas causas materiales.
Therefore, by principle he seems to mean moving causes and agents in which—more than in others—there is found an order of some progression. By causes he seems to mean formal and final causes upon which things most of all depend for their existence and their coming to be. By elements he means properly the first material causes.
Utitur autem istis nominibus disiunctim et non copulatim ad designandum quod non omnis scientia per omnes causas demonstrat. Nam mathematica non demonstrat nisi per causam formalem; metaphysica demonstrat per causam formalem et finalem praecipue, et etiam agentem; naturalis autem per omnes causas.
Moreover, he uses these terms disjunctively and not conjunctively in order to point out that not every science demonstrates through all the causes. For mathematics demonstrates only through the formal cause. Metaphysics demonstrates principally through the formal and final causes, but also through the agent. Natural science, however, demonstrates through all the causes.
Primam autem propositionem rationis inductae probat ex communi opinione, sicut et in libro Poster.: quia tunc quilibet opinatur se cognoscere aliquid, cum scit omnes causas eius a primis usque ad ultimas. Nec oportet ut aliter accipiamus hic causas et elementa et principia quam supra, ut Commentator vult, sed eodem modo.
He then proves the first proposition of his argument from common opinion. This is also proven in Posterior Analytics 1.2. For a man thinks that he knows something when he knows all its causes from the first to the last. The meanings here of causes, principles, and elements is exactly the same as we have explained above, even though the Commentator disagrees.
Dicit autem usque ad elementa, quia id quod est ultimum in cognitione est materia. Nam materia est propter formam; forma autem est ab agente propter finem, nisi ipsa sit finis: ut puta dicimus quod propter secare serra habet dentes, et ferreos oportet eos esse ut sint apti ad secandum.
Furthermore, Aristotle says, as far as its elements, because matter is the last to be known. For matter is for the sake of form, and form is from the agent for the sake of the end, unless it itself is the end. For example, we say that a saw has teeth in order to cut, and these teeth ought to be made of iron so they will be apt for cutting.
6. Deinde cum dicit: innata autem etc., ostendit quod inter principia oportet praedeterminare de universalioribus:
6. Next, at the natural way of doing this (184a16), he shows that, among principles, it is necessary to treat the more universal ones first.