To ask for the proof of intellection — hence of a direct, adequate and infallible knowledge of the supernatural — is to prove that one does not have access to it, and, analogically speaking, it is like asking for the proof of the adequacy of our elementary sensations, which no one doubts, on pain of not being able to live. But the absence of metaphysical intellection in most men of the “iron age” does not for all that close the door to the saving supernatural, as is shown by the phenomenon of revelation, and the subsequent phenomenon of faith, both of which presuppose a kind of elementary — but in no way insufficient — intuition, which we could term “moral” and sometimes even “aesthetic”; for in fact, the reality of God penetrates all our being. To doubt this is to make of oneself “a house divided against itself.”
Frithjof Schuon, “The Primacy of Intellection”. Available on the website Studies in Comparative Religion. Read the entire essay clicking here.