They are not presented a priori They are not just forms of sensible intuition . Unity of synthesis of the manifold and consequently, a combination to which everything represented in space and time conform, is given a priori as the condition of the synthesis of all apprehension. Without or within us. Not in, but with these intuitions . Therefore all synthesis in subject to the categories .
Categories prescribe laws a priori to appearances and therefore nature.
The laws do not exist in the appearances but only relative to the subject. Pure understanding is not in a position to prescribe through categories any a priori laws other than those which are involved in a nature in general. Empirical laws cannot be derived from categories but are subject to them. We cannot think an object save through the categories . We cannot know an object so thought save through intuitions corresponding to these concepts.