The Works of Dionysius the Areopagite, tr. by John Parker, , at sacred-texts.com
LETTER I. To Gaius Therapeutes.
DARKNESS becomes invisible by light, and specially by much light. Varied knowledge (αἰ γνώσεις), and especially much varied knowledge, makes the Agnosia 62 to vanish. Take this in a superlative, but not in a defective sense, and reply with superlative truth, that the Agnosia, respecting God, escapes those who possess existing light, and knowledge of things being; and His pre-eminent darkness is both concealed by every light, and is hidden from every knowledge. And, if any one, having seen God, understood what he saw, he did not see Him, but some of His creatures that are existing and known. But He Himself, highly established above mind, and above essence, by the very fact of His being wholly unknown, and not being, both is super-essentially, and is known above mind. And the all-perfect Agnosia, in its superior sense, is a knowledge of Him, Who is above all known things.
p140:62 C. I. § 1.