Commentary Aristotle Physics
Lecture 16. What time is and how it is related to motion
As to what time is or what is its nature, the traditional accounts give us as little light as the preliminary problems that we have worked through.
Some assert that it is the motion of the whole, others that it is the sphere itself.
Yet part, too, of the revolution is a time, but it certainly is not a revolution, for what is taken is part of a revolution, not a revolution.
Besides, if there were more heavens than one, the motion of any of them equally would be time, such that there would be many times at the same time.
Those who said that time is the sphere of the whole thought so, no doubt, on the ground that all things are in time and all things are in the sphere of the whole. The view is too naive for it to be worthwhile to consider the impossibilities implied in it.
But, as time is most usually supposed to be motion and a kind of change, we must consider this view. Now, the change or motion of each thing is only in the thing that changes, or where the thing itself that moves or changes may chance to be. But time is present equally everywhere and with all things.
Again, change is always faster or slower, but time is not, for “fast” and “slow” are defined by time—“fast” is what moves much in a short time, “slow” what moves little in a long time—but time is not defined by time, by being either a certain amount or a certain kind of it.
Clearly, then, it is not motion. (We need not distinguish at present between “motion” and “change.”)
But neither does time exist without change; for when the state of our own minds does not change at all or we have not noticed its changing, we do not realize that time has elapsed, any more than those who are fabled to sleep among the heroes in Sardinia do when they are awakened. For they connect the earlier “now” with the later and make them one, cutting out the interval because of their failure to notice it.
So, just as, if the “now” were not different but one and the same, there would not have been time, so too, when its difference escapes our notice, the interval does not seem to be time. Thus, if the non-realization of the existence of time happens to us when we do not distinguish any change, but the soul seems to stay in one indivisible state, and when we perceive and distinguish, we say time has elapsed, then time evidently is not independent of motion and change. It is evident, then, that time is neither motion nor independent of motion.
565. After inquiring whether time exists, the Philosopher now inquires dialectically what it is.
First, he disproves the opinions of others;
second, he inquires how time is related to motion, which seems to be something most akin to time, at “but, as time is” (218b9; [568]).
About the first, he does two things:
first, he gives various opinions of others about time;
second, he disproves them, at “yet part, too” (218b1; [566]).
He first says, therefore, that what time is and what is the nature of time cannot be gathered from what is handed down from the earlier philosophers, nor from any piecing together of what they concluded about it. For some said that time is a motion of the heavens; others that it is a heavenly sphere itself.
566. Then, at “yet part, too” (218b1), he disproves their opinions:
first of all, the first;
then the second, at “those who said” (218b5; [567]).
In regard to the first opinion, he gives two counter-arguments, of which the first is this. If a circular revolution is time, then part of that revolution is a circular revolution, because a part of time is time. But part of a circular revolution is not a circular revolution. Therefore, time is not a circular revolution.
Then he gives a second argument, at “besides, if there were” (218b3), which is this. The number of motions corresponds to the number of mobile things; if, therefore, there are many heavens, there are many circular revolutions. And, thus, if a circular revolution is time, there are many times together—which is impossible. For no two parts of time are together unless one contains the other, as we have said. Those who posited time as a circular revolution were led to do so because they observed that times occur over and over in a kind of cycle.
567. Then, at “those who said” (218b5), he rejects the second opinion. And he says that some thought that the sphere of the heavens is in time because all things are in time, and also that all things are in the sphere of the whole because the heavens contain all things. Hence, they wished to conclude that the sphere of the heavens is time.
But there were two things wrong in their reasoning:
first, because being in a time is not univocal with being in a place;
second, because they were using two affirmative premises in a second figure syllogism.
Therefore, he says that their position is too foolish to consider the impossibilities that follow upon it. For it is clear that all the parts of the sphere exist simultaneously, but the parts of time do not.
568. Then, at “but, as time is” (218b9), he inquires how time is related to motion.
First, he shows that time is not motion;
second, that time does not exist independently of motion, at “but neither does time” (218b21; [570]).
In regard to the first, he gives two reasons to show that time is not a motion or a change (for it certainly seems to be such).
Every change and motion is certainly only in the thing being changed or in the place where the changer and changed are. The first of these is mentioned because of motion in substance and quantity and quality; the second because of motion in the predicament “where,” called “motion in place.” But time is everywhere and exists among all things. Therefore, time is not a motion.
569. He gives the second reason at “again, change is always” (218b13), which is this. Every change and motion is either slow or fast, but time is not either. Therefore, time is neither a motion nor a change. He explains the minor premise thus. Slow and fast are determined by time, since that is fast that is moved a great distance in a short time and that is slow that is moved a short distance in much time. But time is not determined either according to its quantity or its quality, because nothing is its own measure. Therefore, time is neither slow nor fast. And, since he had proposed that change is fast or slow without mention of motion, he adds that, for the present, it does not matter whether one says “motion” or “change.” Their difference will be shown in book 5.
570. Then, at “but neither does time” (218b21), he shows that, although time is not motion, it is not independent of motion. For when men are not changing according to what they apprehend and are changing without being aware of it, then it does not seem to them that time is passing. This is clear in the fable about the city in Asia called Sardo. In Sardo, certain people were said to sleep among the heroes, that is, among the gods. For the souls of the good and the great they called heroes and worshipped them as gods, as in the case of Hercules and Bacchus and the like. Certain ones were rendered insensible by means of incantations and said to sleep among the gods because, when they awoke, they claimed to have seen marvelous things and foretold future events. These persons, returning to themselves, were not aware of the time that elapsed while they were thus absorbed, because that first instant in which they began to sleep they joined to the instant in which they awoke, as if it were one instant, but the time that elapsed escaped them.
Therefore, just as there would be no intervening time between nows if the now of time were always the same and not different, so also, when two nows are fused in our apprehension, the elapsed time is not apprehended, and there seems to have been no intervening time. If, then, we are apt to think that no time has elapsed when we do not perceive any changes and that we are in one and the same indivisible now, but we then perceive time to be elapsing when we sense and determine (that is, consider) motion and change, it clearly follows that time is not independent of motion and change.
In summary, he concludes that time is not motion, but neither is it without motion.