I think I ought to make Kant clear. There is knowledge that is known by way of reason, for example things known by definition. And there are things known by the five senses. But can we know things like universals [things that particulars have in common]?-Yes. Things are in the realm of possibility of experience. We can know them by structures in the mind like computer chips. [E.G. the ideas of time space and causality. But outside of the conditions of possible experience we can not know.

There are some attempts to get past this blockage, and one approach is that of Jacob Fries--and that is to say there is knowledge that is known, but not by reason and not by the senses.

[This is different from reason first Kant [the first interpretation] and from sensibility first Kant [Robert Hanna, Sperber].] This Kant-Friesian approach says neither reason nor sense perception is first. See Kelley Ross's web site To get an idea about this Kant-Friesian approach I think the best idea is to learn the books of Leonard Nelson who is a lot more clear than Fries himself, even though I think most are still in  German.