Besides, this movement is a definite quantity. Either this quantity will be measured by the extension of the space traversed, and the interval will consist in that extension; but that extension is space, and not time. Or we shall say that movement has a certain interval because it is continuous, and that instead of stopping immediately it always becomes prolonged; but this continuity is nothing else than the magnitude (that is, the duration) of the movement. Even though after consideration of a movement it be estimated as great, as might be said of a "great heat"--this does not yet furnish anything in which time might appear and manifest; we have here only a sequence of movements which succeed one another like waves, and only the observed interval between them; now the sequence of movements forms a number, such as two or three; and the interval is an extension. Thus the magnitude of the movement will be a number, say, such as ten; or an interval that manifests in the extension traversed by the movement. Now the notion of time is not revealed herein, but we find only a quantity that is produced within time. Otherwise, time, instead of being everywhere, will exist only in the movement as an attribute in a substrate, which amounts to saying that time is movement; for the interval (of the movement) is not outside of movement, and is only a non-instantaneous movement. If then time be a non-instantaneous movement, just as we often say that some particular instantaneous fact occurs within time, we shall be forced to ask the difference between what is and what is not instantaneous. Do these things differ in relation to time? Then the persisting movement and its interval are not time, but within time. POLEMIC AGAINST STRATO: TIME IS NOT MOTION AND REST. Somebody might object that time is indeed the interval of movement, but that it is not the characteristic interval of movement itself, being only the interval in which movement exerts its extension, following along with it. All these terms lack definition. This (extension) is nothing else than the time within which the movement occurs. But that is precisely the question at issue, from the very start. It is as if a person who had been asked to define time should answer "time is the interval of the movement produced within time." What then is this interval called time, when considered outside of the interval characteristic of movement? If the interval characteristic of time be made to consist in movement, where shall the duration of rest be posited? Indeed, for one object to be in motion implies that another (corresponding object) is at rest; now the time of these objects is the same, though for one it be the time of movement, and for the other the time of rest (as thought Strato[451]). What then is the nature of this interval? It cannot be an interval of space, since space is exterior (to the movements that occur within it). POLEMIC AGAINST ARISTOTLE: TIME IS NOT THE NUMBER AND MEASURE OF MOVEMENT.