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. PERSISTENT MOVEMENT AND ITS INTERVAL ARE NOT TIME, BUT ARE WITHIN IT.