Summary: Physics (page 5)

Book V

Aristotle distinguishes between two types of motion: something moves either accidentally — as when the cook walks — or essentially, as when the athlete runs.

A further key distinction concerns:

- motion with respect to quality: alteration

- motion with respect to quantity: growth or diminution

- motion with respect to place: locomotion

All motion is continuous.

Book VI

Aristotle defines the continuous as that which is divisible into ever-divisible parts ¹.

Time contains something indivisible: the instant — which refutes Zeno of Elea's aporias, founded on the infinite division of time.

Book VII

Everything is moved by something else, but it is necessary that we stop and that there be a first thing that moves and is moved ².

Locomotion is the first of movements ³ — there is a primacy of motion with respect to place.

Four types of locomotion can be identified: Pulling, pushing, dividing, rolling ⁴. All other motions can be reduced to these types. Thus, expansion and condensation are repulsion and traction ⁵. Similarly, inspiration is traction, expiration is push ⁶.

Book VIII

Is motion eternal, or did it have a beginning?

Motion cannot exist without time — and since time is eternal, so is motion.

If everything that is moved is moved by something else, there is something that moves not by something else but by itself, or we will go on to infinity ⁷. This is the prime mover.

Since nothing moves it but itself, it must be immobile:

It is manifest from this that what originally moves is immobile ⁸.

This first mover is eternal, for that which moves first will be eternal, if it is one ⁹.

Circular motion is infinite, unified, and continuous — the only type of motion that possesses all these characteristics.

In conclusion, the first mover moves with an incessant motion and during an infinite time; it is therefore manifest that it is indivisible, without parts and without magnitude ¹⁰.

¹ Book VI, 231b
² livre VII, 242b
³ ibid., 243a
⁴ ibid.
⁵ ibid.
⁶ ibid.
⁷ VIII, 256a
⁸ ibid., 258b
⁹ ibid., 259a
¹⁰ ibid., 267b