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.