153
Socrates
SOC. No, Theaetetus, it is not. For the doctrine is amply proved by this, namely, that motion is the cause of that which passes for existence, that is, of becoming, whereas rest is the cause of non-existence and destruction; for warmth or fire, which, you know, is the parent and preserver of all other things, is itself the offspring of movement and friction, and these two are forms of motion. Or are not these the source of fire?
Theaetetus
THEAET. Yes, they are.
Socrates
SOC. And furthermore, the animal kingdom is sprung from these same sources.
5
Theaetetus
THEAET. Of course.
Socrates
SOC. Well, then, is not the bodily habit destroyed by rest and idleness, and preserved, generally speaking, by gymnastic exercises and motions?
Socrates
SOC. And what of the habit of the soul? Does not the soul acquire information and is it not preserved and made better through learning and practice, which are motions, whereas through rest, which is want of practice and of study, it learns nothing and forgets what it has learned?
Theaetetus
THEAET. Certainly.
10
Socrates
SOC. Then the good, both for the soul and for the body, is motion, and rest is the opposite?
Theaetetus
THEAET. Apparently.
