CLEINIAS: Certainly.
ATHENIAN: And which of these ten motions ought we to prefer as being the mightiest and most efficient?
CLEINIAS: I must say that the motion which is able to move itself is ten thousand times superior to all the others.
ATHENIAN: Very good; but may I make one or two corrections in what I have been saying?
CLEINIAS: What are they?
ATHENIAN: When I spoke of the tenth sort of motion, that was not quite correct.
CLEINIAS: What was the error?
ATHENIAN: According to the true order, the tenth was really the first in generation and power; then follows the second, which was strangely enough termed the ninth by us.
CLEINIAS: What do you mean?
ATHENIAN: I mean this: when one thing changes another, and that another, of such will there be any primary changing element? How can a thing which is moved by another ever be the beginning of change? Impossible. But when the self-moved changes other, and that again other, and thus thousands upon tens of thousands of bodies are set in motion, must not the beginning of all this motion be the change of the self-moving principle?