Before Kant, John Locke and Hume thought pure reason can only know analytic ideas--things that are contained in the definitions. [To the empiricists the only real knowledge is what can be verified by observation. ] Kant expanded the areas of what can be known.  He said reason can know synthetic a priori-[i.e. universals, like causality]-but only within the conditions of possibity of experience. Jacob Fries expanded that further. To Fries, God, and the soul are areas where knowledge is possible, but not by reason, rather by a sort of knowledge that is not reason nor based on sense perception.

[I think that both Kant and the Friesian School of Kelley Ross have tremendous points, but I can not tell if the truth is only in one camp or the other.

Rav Nahman in the Le/M [I think in the left out portions that were later added back in] says when God created the world the midot like wisdom would expand indefinitely. Then God set a limit to them. 

Rav Nahman wrote this specifically about wisdom [Reason]. This goes along with Jacob Fries that we have knowledge beyond conditions of possibility of experience [i.e. Faith.] but this knowledge is not by reason.