Sec. 24. The radical and typical case of the first kind of unity in variety is found in the perception of extension itself. This perception, if we look to its origin, may turn out to be primitive; no doubt the feeling of "crude extensity" is an original sensation; every inference, association, and distinction is a thing that looms up suddenly before the mind, and the nature and actuality of which is a datum of what -- to indicate its irresistible immediacy and indescribability -- we may well call sense. Forms are seen, and if we think of the origin of the perception, we may well call this vision a sensation. The distinction between a sensation of form, however, and one which is formless, regards the content and character, not the genesis of the perception. A distinction and association, or an inference, is a direct experience, a sensible fact; but it is the experience of a process, of a motion between two terms, and a consciousness of their coexistence and distinction; it is a feeling of relation. Now the sense of space is a feeling of this kind; the essence of it is the realization of a variety of directions and of possible motions, by which the relation of point to point is vaguely but inevitably given. The perception of extension is therefore a perception of form, although of the most rudimentary kind. It is merely _Auseinandersein,_ and we might call it the _materia prima_ of form, were it not capable of existing without further determination. For we can have the sense of space without the sense of boundaries; indeed, this intuition is what tempts us to declare space infinite. Space would have to consist of a finite number of juxtaposed blocks, if our experience of extension carried with it essentially the realization of limits.