29. I once heard a learned man say that the motions of the sun, moon, and stars constituted time; and I did not agree. For why should not the motions of all bodies constitute time? What if the lights of heaven should cease, and a potter's wheel still turn round: would there be no time by which we might measure those rotations and say either that it turned at equal intervals, or, if it moved now more slowly and now more quickly, that some rotations were longer and others shorter? And while we were saying this, would we not also be speaking in time? Or would there not be in our words some syllables that were long and others short, because the first took a longer time to sound, and the others a shorter time? O God, grant men to see in a small thing the notions that are common to all things, both great and small. Both the stars and the lights of heaven are "for signs and seasons, and for days and years." This is doubtless the case, but just as I should not say that the circuit of that wooden wheel was a day, neither would that learned man say that there was, therefore, no time.
30. I thirst to know the power and the nature of time, by which we measure the motions of bodies, and say, for example, that this motion is twice as long as that. For I ask, since the word "day" refers not only to the length of time that the sun is above the earth (which separates day from night), but also refers to the sun's entire circuit from east all the way around to east--on account of which we can say, "So many days have passed" (the nights being included when we say, "So many days," and their lengths not counted separately)--since, then, the day is ended by the motion of the sun and by his passage from east to east, I ask whether the motion itself is the day, or whether the day is the period in which that motion is completed; or both? For if the sun's passage is the day, then there would be a day even if the sun should finish his course in as short a period as an hour. If the motion itself is the day, then it would not be a day if from one sunrise to another there were a period no longer than an hour. But the sun would have to go round twenty-four times to make just one day. If it is both, then that could not be called a day if the sun ran his entire course in the period of an hour; nor would it be a day if, while the sun stood still, as much time passed as the sun usually covered during his whole course, from morning to morning. I shall, therefore, not ask any more what it is that is called a day, but rather what time is, for it is by time that we measure the circuit of the sun, and would be able to say that it was finished in half the period of time that it customarily takes if it were completed in a period of only twelve hours. If, then, we compare these periods, we could call one of them a single and the other a double period, as if the sun might run his course from east to east sometimes in a single period and sometimes in a double period.
Let no man tell me, therefore, that the motions of the heavenly bodies constitute time. For when the sun stood still at the prayer of a certain man in order that he might gain his victory in battle, the sun stood still but time went on. For in as long a span of time as was sufficient the battle was fought and ended.
I see, then, that time is a certain kind of extension. But do I see it, or do I only seem to? Thou, O Light and Truth, wilt show me.