181
Socrates
SOC. Then they must be examined, since you are so urgent. Now I think the starting-point of our examination of the doctrine of motion is this: Exactly what do they mean, after all, when they say that all things are in motion? What I wish to ask is this: Do they mean to say that there is only one kind of motion or, as I believe, two? But it must not be my belief alone; you must share it also, that if anything happens to us we may suffer it in common. Tell me, do you call it motion when a thing changes its place or turns round in the same place?
Socrates
SOC. Let this, then, be one kind of motion. Now when a thing remains in the same place, but grows old, or becomes black instead of white, or hard instead of soft, or undergoes any other kind of alteration, is it not proper to say that this is another kind of motion?
5
Theodorus
THEO. I think so.
Socrates
SOC. Nay, it must be true. So I say that there are these two kinds of motion: alteration, and motion in space.
Theodorus
THEO. And you are right.
Socrates
SOC. Now that we have made this distinction, let us at once converse with those who say that all things are in motion, and let us ask them, Do you mean that everything moves in both ways, moving in space and undergoing alteration, or one thing in both ways and another in one of the two ways only?
Theodorus
THEO. By Zeus, I cannot tell! But I think they would say that everything moves in both ways.
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