“Physics” by Aristotle

Contraries as Principles

All philosophers identify their principles with the contraries. They differ, however, from one another in that some assume contraries which are more knowable in the order of explanation, i.e. universal, others those more familiar to sense, i.e., particular. ‘The great and the small’, for example, belong to the former class, ‘the dense and the rare’ to the latter. In any one genus there is only one contrariety, and substance is one genus.

Admitting that there is the form, Aristotle holds that there are two other principles, the one contrary to it, the other such as of its own nature to desire and yearn for it. The form cannot desire itself, for it is not defective; nor can the contrary desire it, for contraries are mutually destructive. The truth is that what desires the form is matter. Matter, which persists, is a joint cause, with the form, of what comes to be-a mother, as it were. But the negative part of the contrariety may often seem, not to exist at all.

Substance from Substratum

Only substances are said to ‘come to be’ in the unqualified sense. Now in all cases other than substance it is plain that there must be some subject, namely, that which becomes. For we know that when a thing comes to be of such a quantity or quality or in such a relation, time, or place, a subject is always presupposed, since substance alone is not predicated of another subject, but everything else of substance. But that substances too, and anything else that can be said ‘to be’ without qualification, come to be from some substratum. For we find in every case something that underlies from which proceeds that which comes to be; for instance, animals and plants from seed.

Parmenides: Being is One

Parmenides assumes not only that ‘being’ has the same meaning, of whatever it is predicated, but further that it means (1) what just is and (2) what is just one. Aristotle draws a distinction between ‘whiteness’ and ‘that which is white’ in his definition — as quality and substance, not in the sense that they can exist apart from each other. But Parmenides does not draw this distinction.

Parmenides states that a thing may come to be without qualification from not being; if the substratum is one numerically, it must have also only a single potentiality-which is a very different thing.


Motion is the fulfilment of the movable qua movable, the cause of the attribute being contact with what can move so that the mover is also acted on. (The mover or agent will always be the vehicle of a form, which, when it acts, will be the source and cause of the change, e.g. the full-formed man begets man from what is potentially man.) It is the fulfilment of this potentiality, and by the action of that which has the power of causing motion; and the actuality of that which has the power of causing motion is not other than the actuality of the movable, for it must be the fulfilment of both.


The view that there is an infinite body is plainly incompatible with the doctrine that there is necessarily a proper place for each kind of body.

The infinite has a potential existence, but, there will not be an actual infinite. The infinite exists both in the sense that things may occur and are actually occurring: one thing is always being taken after another, and each thing that is taken is always finite, but always different, in a process of coming to be or passing away.

Contrary to popular opinion, it is not what has nothing outside it that is infinite, but what always has something outside it. On the other hand, what has nothing outside it is complete and whole. For thus we define the whole-that from which nothing is wanting. Nothing is complete (teleion) which has no end (telos); and the end is a limit. IOW, what matter is to form is what infinite is to whole.

Place and Void

For just as in change of quality there is something which was formerly black and is now white, viz. the matter exists-so place, because it presents a similar phenomenon, is thought to exist. But matter is neither separable from the thing nor contains it, whereas place has both characteristics.

Place is the boundary of the containing body at which it is in contact with the contained body. (By the contained body is meant what can be moved by way of locomotion.)

The natural locomotion of the elementary bodies-namely, fire, earth, and the like-show not only that place is something, but also that it exerts a certain influence, certain distinct potency. Each is carried to its own place, if it is not hindered, the one up, the other down. Therefore, place cannot be the matter or the form, which makes no distinction of up and down.

For the same reason, void doesn’t exist, because it admits no differences of place. Why should a thing stop here rather than there? It will either be at rest or must be moved ad infinitum, unless something more powerful get in its way. Further, things are now thought to move into the void because it yields; but in a void this quality is present equally everywhere, so that things should move in all directions.


Time does not exist without change; for when the state of our own minds does not change at all, or we have not noticed its changing, we do not realize that time has elapsed. It is only when we have perceived ‘before’ and ‘after’ in motion, that is, when we think of the extremes as different from the middle and the mind pronounces that the ‘nows’ are two, one before and one after, it is then that we say that there is time.

Time is number of movement in respect of the before and after, and is continuous since it is an attribute of what is continuous. If there were no time, there would be no ‘now’, and vice versa. just as the moving body and its locomotion involve each other mutually, so do the number of the moving body and the number of its locomotion. For the number of the locomotion is time, while the ‘now’ corresponds to the moving body, and is like the unit of number.

“To be in time” is to have one’s being measured by time. All things grow old through time, and that there is oblivion owing to the lapse of time, but we do not say the same of getting to know or of becoming young or fair. For time is by its nature the cause rather of decay, since it is the number of change, and change removes what is.

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5 thoughts on ““Physics” by Aristotle

  1. Great review, Nemo. I picked this one up at the library yesterday and I confess, I’m a little scared. 🙂 I have enjoyed his aesthetic works, but that is probably because it’s a field I am more comfortable in (as wide as it is lol). Physics, ancient or not, is not something I have studied. Would you suggest this one next or a different one?

    1. Your original plan to read the Organon is good, because much of Aristotle’s woks are based on his form of logic. But, they can become tedious very quickly, unlike his aesthetic works. On second thought, you might want to read his works on Ethics and Politics next, they are closer in style and content to the aesthetic works.

      1. I have had a hard time finding the Organon in full. 😦 I guess I will have to do a interlibrary loan to read the last couple of sections. (I would buy it, but I am under oath not to purchase books for a year. :D) So I have to put it off for another little bit. I will follow your suggestion and hit Ethics next.

  2. Thanks for reminding me. I actually checked out the Perseus site when we talked about translations before, but found the format a little weird (that was with Poetics). Having all that extra “stuff” on either side of the text distracted me. Lol After trying to read it for a bit, it really started to drive me crazy. So I got a hard copy instead. I forgot about Adelaide. I like the format much better.

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