TIME CONSIDERED EITHER AS MOTION; AS SOMETHING MOVABLE; OR SOMETHING OF MOTION.
To begin with, we may divide the generally accepted opinions about time into three classes: time as movement, as something movable, or as some part of movement. It would be too contrary to the notion of time to try to define it as rest, as being at rest, or as some part of rest; for time is incompatible with identity (and consequently with rest, and with what is at rest). Those who consider time as movement, claim that it is either any kind of movement, or the movement of the universe. Those who consider it as something movable are thinking of the sphere of the universe; while those who consider time as some part of movement consider it either as the interval of movement, or as its measure, or as some consequence of movement in general, or regular movement.
POLEMIC AGAINST THE STOICS; TIME IS NOT MOVEMENT.
7. (8). Time cannot (as the Stoics claim,[447]) be movement. Neither can we gather together all movements, so as to form but a single one, nor can we consider the regular movement only; for these two kinds of motion are within time. If we were to suppose that there was a movement that did not operate within time, such a movement would still be far removed from being time, since, under this hypothesis, the movement itself is entirely different from that in which the movement occurs. Amidst the many reasons which, in past and present, have been advanced to refute this opinion, a single one suffices: namely, that movement can cease and stop, while time never suspends its flight. To the objection that the movement of the universe never stops, we may answer that this movement, if it consist in the circular movement (of the stars, according to Hestius of Perinthus; or of the sun, according to Eratosthenes[447]) operates within a definite time, at the end of which it returns to the same point of the heavens, but it does not accomplish this within the same space of time taken up in fulfilling the half of its course. One of these movements is only half of the other, and the second is double. Besides, both, the one that runs through half of space, and the one that runs through the whole of it, are movements of the universe. Besides, it has been noticed that the movement of the exterior sphere is the swiftest. This distinction supports our view, for it implies that the movement of this sphere, and the time used to operate it, are different entities; the most rapid movement is the one that takes up the least time, and runs through the greatest amount of space; the slowest movements are those that employ the longest time, and run through only a part of that space.[448]
POLEMIC AGAINST THE PYTHAGOREANS: TIME IS NOT WHAT IS MOVABLE.
On the other hand, if time be not the movement of the sphere, evidently it is far less (than that which is movable, as thought the Pythagoreans,[449]) or (as Pythagoras thought), the sphere (of heaven) itself, as some have thought, because it moves. (This fact alone is sufficient to refute the opinion that confuses time with that which is movable).
POLEMIC AGAINST THE STOIC ZENO: TIME IS NO INTERVAL OF MOVEMENT.
Is time then some part of movement? (Zeno[450]) calls it the interval of movement; but the interval is not the same for all movements, even if the latter were of similar nature; for movements that operate within space may be swifter or slower. It is possible that the intervals of the most rapid and of the slowest movement might be measured by some third interval, which might far more reasonably be considered time. But which of these three intervals shall be called time? Rather, which of all the intervals, infinite in number as they are, shall time be? If time be considered the interval of the regular movement, it will not be the particular interval of every regular movement; otherwise, as there are several regular movements, there would be several kinds of time. If time be defined as the interval of movement of the universe, that is, the interval contained within this movement, it will be nothing else than this movement itself.