But what common element is there in alteration, growth and generation, and their contraries? What is there in common between these movements, and the displacement in space, when you consider the four movements, as such?[425] The common element is that the moved thing, after the movement, is no longer in the former state; that it no more remains quiet, and does not rest so long as the movement lasts. It ceaselessly passes to another state, alters, and does not remain what it was; for the movement would be vain if it did not make one thing other than it was. Consequently "otherness" does not consist in one thing becoming other than it was, and then persisting in this other state, but in ceaseless alteration. Thus, time is always different from what it was because it is produced by movement; for it is movement measured in its march and not in its limit of motion, or stopping point; it follows, carried away in its course. Further, one characteristic common to all kinds of movement is that it is the march (or process) by which potentiality and possibility pass into actualization; for every object in movement, whatever be the nature of this movement, succeeds in moving only because it formerly possessed the power of producing an action, or of experiencing the passion of some particular nature. MOVEMENT FOR SENSE-OBJECTS. 23. For sense-objects, which receive their impulse from without, movement is a stimulus which agitates them, excites them, presses them, prevents them from slumbering in inertia, from remaining the same, and makes them present an image of life by their agitation and continual mutations. Besides, one must not confuse the things that move with movement; walking is not the feet, but an actualization of the power connected with the feet. Now as this power is invisible, we perceive only the agitation of the feet; we see that their present state is quite different from that in which they would have been, had they remained in place, and that they have some addition, which however, is invisible. Thus, being united to objects other than itself, the power is perceived only accidentally, because one notices that the feet change place, and do not rest. Likewise, alteration in the altered object, is recognized only by failure to discover in it the same quality as before. MOVEMENT AS INFLUX.