Principle: What is real in the material element of appearances, i.e., that which corresponds to sensation rather than the forms of intuition, has an intensive magnitude (degree).
Kant proposes this as a general principle governing every object which we represent through sensation, regardless of the nature of the sensation itself. However, we know from the Aesthetic that Kant considered some of the sensible properties of objects to be their impenetrability, hardness, and color. The claim here is somewhat startling, namely, that we can know prior to sensation that our sensations themselves will have intensive magnitude (cf. the empiricists' claim that all sensation has a certain "vivacity"), and that this is a reflection of the magnitude in the objects which cause the sensations. Pure intuition of empty space and time would have the magnitude 0, which can be increased up to any required magnitude.
"Between reality and negation there is a continuity of possible realities and of possible smaller perceptions. Every color, as for instance red, has a degree which, however small it may be, is never the smallest; and so with heat, the moment of gravity, etc." (A169/B211).
Kant claimed that the reason we can move from the infinite gradations of sensation to such intensive magnitudes in the objects of sensation is that the latter have "a degree of influence on the sense [which] must be ascribed to all objects of perception, insofar as the perception contains sensation" (A166/B208).
The difference between intensive and extensive magnitudes of the real is explained in terms of the relation between part and whole. The extensive magnitude, as has been said, is whole synthesized through the successive addition of parts. An intensive magnitude, however, is perceived instantaneously in apprehension.
One important claim made in this section is that an empty space or time is not an object of experience. First, it would involve an absence of sensation, while we can only sense through the presence of sensations. Secondly, even if we could not consciously detect an object of some degree (e.g., when staring out into interstellar space), it might yet exist in an extremely minute degree. this argument undercuts the claim of the atomists and vacuists that empty spaces can be created and detected by various experiments.