Dost Thou bid me assent, if any define time to be "motion of a body?" Thou dost not bid me. For that no body is moved, but in time, I hear; this Thou sayest; but that the motion of a body is time, I hear not; Thou sayest it not. For when a body is moved, I by time measure, how long it moveth, from the time it began to move until it left off? And if I did not see whence it began; and it continue to move so that I see not when it ends, I cannot measure, save perchance from the time I began, until I cease to see. And if I look long, I can only pronounce it to be a long time, but not how long; because when we say "how long," we do it by comparison; as, "this is as long as that," or "twice so long as that," or the like. But when we can mark the distances of the places, whence and whither goeth the body moved, or his parts, if it moved as in a lathe, then can we say precisely, in how much time the motion of that body or his part, from this place unto that, was finished. Seeing therefore the motion of a body is one thing, that by which we measure how long it is, another; who sees not, which of the two is rather to be called time? For and if a body be sometimes moved, sometimes stands still, then we measure, not his motion only, but his standing still too by time; and we say, "it stood still, as much as it moved"; or "it stood still twice or thrice so long as it moved"; or any other space which our measuring hath either ascertained, or guessed; more or less, as we use to say. Time then is not the motion of a body.
And I confess to Thee, O Lord, that I yet know not what time is, and again I confess unto Thee, O Lord, that I know that I speak this in time, and that having long spoken of time, that very "long" is not long, but by the pause of time. How then know I this, seeing I know not what time is? or is it perchance that I know not how to express what I know? Woe is me, that do not even know, what I know not. Behold, O my God, before Thee I lie not; but as I speak, so is my heart. Thou shalt light my candle; Thou, O Lord my God, wilt enlighten my darkness.