improved, and preserved by study and attention, which are motions; but when
at rest, which in the soul only means want of attention and study, is
uninformed, and speedily forgets whatever she has learned?

THEAETETUS: True.

SOCRATES: Then motion is a good, and rest an evil, to the soul as well as
to the body?

THEAETETUS: Clearly.

SOCRATES: I may add, that breathless calm, stillness and the like waste
and impair, while wind and storm preserve; and the palmary argument of all,
which I strongly urge, is the golden chain in Homer, by which he means the
sun, thereby indicating that so long as the sun and the heavens go round in
their orbits, all things human and divine are and are preserved, but if
they were chained up and their motions ceased, then all things would be
destroyed, and, as the saying is, turned upside down.

THEAETETUS: I believe, Socrates, that you have truly explained his
meaning.

SOCRATES: Then now apply his doctrine to perception, my good friend, and
first of all to vision; that which you call white colour is not in your
eyes, and is not a distinct thing which exists out of them. And you must
not assign any place to it: for if it had position it would be, and be at
rest, and there would be no process of becoming.

THEAETETUS: Then what is colour?