Infinitude of time rests on immediate intuition because each magnitude of time is possible only through limitation and therefore the whole representation cannot be given through concepts. Concept of motion is possible only through and in the representation of time. Time is not something which exist of itself. It is the subjective condition under which alone intuition can take place in us. Time is the form of inner sense, that is, of the intuition of ourselves and our inner state.
Time is the formal a priori condition of all appearances.
It has objective validity only in respect to appearances, not for things abstracted or taken in general. The empirical reality of time is not absolute reality. Time and space taken together, are the pure forms of all sensible intuition , and so are what make a priori synthetic propositions possible. The Transcendental Aesthetic cannot contain more that these two elements. All intuition is nothing but the representation of appearances.