Ps.-Dionysius the Areopagite, Mystical Theology 1.2

Take care that none of the uninitiated should hear these words. I refer to those who are bound up in things that are and imagine that there is nothing beyond these entities, nothing that transcends being itself, but instead think to know through their own knowledge the one who has established “darkness as his hiding place.” If this mystical invitation into the divine is beyond these people, what may we even begin to say about the truly uninitiated, who define the cause that lies beyond everything as deriving from what is and who say that there is nothing beyond the varied forms that they have concocted, forms without divinity? In the face of this transcendent cause, we must establish and assert certain theses, as it is the cause of all things, and still more properly negate them, as it transcends all things. Moreover, we mustn’t think that these assertions are opposed to the negations, but rather that this cause is beyond all lack and is beyond both assertion and negation.