If our representational forms do not apply to things in themselves, those things are cognitively inaccessible beyond their bare existence.

So, Kant concludes, in order to be necessarily true throughout their domain, the synthetic a priori propositions about space and time—and this includes not just the specific propositions of geometry or mathematics more generally but also the general propositions derived in the metaphysical expositions, such as that space and time are infinite singular wholes with parts rather than instances—must be true only of the representations on which we impose our own forms of intuition, and cannot be true