If we imagine a space in itself with which the perceiving subject contrives to coincide, for example, if I imagine that my hand perceives the distance between two points as it spans it, how could the angle formed by my fingers, and indicative of that distance, come to be judged, unless it were so to speak measured out by the inner operation of some power residing in neither object, a power which, ipso facto, becomes able to know, or rather effect, the relation existing between them?