BOOK ELEVEN
CHAPTER XXIV
31. Dost thou command that I should agree if anyone says that time is “the motion of a body”? Thou dost not so command. For I hear that no body is moved but in time; this thou tellest me. But that the motion of a body itself is time I do not hear; thou dost not say so. For when a body is moved, I measure by time how long it was moving from the time when it began to be moved until it stopped. And if I did not see when it began to be moved, and if it continued to move so that I could not see when it stopped, I could not measure the movement, except from the time when I began to see it until I stopped. But if I look at it for a long time, I can affirm only that the time is long but not how long it may be. This is because when we say, “How long?”, we are speaking comparatively as: “This is as long as that,” or, “This is twice as long as that”; or other such similar ratios. But if we were able to observe the point in space where and from which the body, which is moved, comes and the point to which it is moved; or if we can observe its parts moving as in a wheel, we can say how long the movement of the body took or the movement of its parts from this place to that. Since, therefore, the motion of a body is one thing, and the norm by which we measure how long it takes is another thing, we cannot see which of these two is to be called time. For, although a body is sometimes moved and sometimes stands still, we measure not only its motion but also its rest as well; and both by time! Thus we say, “It stood still as long as it moved,” or, “It stood still twice or three times as long as it moved”–or any other ratio which our measuring has either determined or imagined, either roughly or precisely, according to our custom. Therefore, time is not the motion of a body.