Indeed, as it was not possible to determine the time itself of the Soul, and to measure within themselves the parts of an invisible and uncognizable duration, especially for men who did not know how to count, the (world) Soul created day and night so that their succession might be the basis of counting as far as two, by the aid of this variety. Plato[464] indicates that as the source of the notion of number. Later, observing the space of time which elapses from one dawn to another, we were able to discover an interval of time determined by an uniform movement, so far as we direct our gaze thereupon, and as we use it as a measure by which to measure time. The expression "to measure time" is premeditated, because time, considered in itself, is not a measure. How indeed could time measure, and what would time, while measuring, say? Would time say of anything, "Here is an extension as large as myself?" What indeed could be the nature of the entity that would speak of "myself"? Would it be that according to which quantity is measured? In this case, time would have to be something by itself, to measure without itself being a measure. The movement of the universe is measured according to time, but it is not the nature of time to be the measure of movement; it is such only accidentally; it indicates the quantity of movement, because it is prior to it, and differs from it. On the other hand, in the case of a movement produced within a determinate time, and if a number be added thereto frequently enough, we succeed in reaching the knowledge of how much time has elapsed. It is therefore correct to say that the movement of the revolution operated by the universal Sphere measures time so far as possible, by its quantity indicating the corresponding quantity of time, since it can neither be grasped nor conceived otherwise. Thus what is measured, that is, what is indicated by the revolution of the universal Sphere, is time. It is not begotten, but only indicated by movement. MOVEMENT IS SAID TO BE MEASURED BY SPACE, BECAUSE OF ITS INDETERMINATION. The measure of movement, therefore, seems to be what is measured by a definite movement, but which is other than this movement. There is a difference, indeed, between that which is measured, and that which measures; but that which is measured is measured only by accident. That would amount to saying that what is measured by a foot-rule is an extension, without defining what extension in itself is. In the same way, because of the inability to define movement more clearly because of its indeterminate nature, we say that movement is that which is measured by space; for, by observation of the space traversed by movement, we can judge of the quantity of the movement. TIME IS MEASURED BY MOVEMENT, AND IN THAT SENSE IT IS THE MEASURE OF MOVEMENT.