From THE CLOUD OF UNKNOWING
This, the clearest of all the classics of mysticism, but with the fuzziest title, is a gem from late 14th century England. The author's name is unknown - not an unfitting circumstance for a mystical writer. The book's principal theme is that God cannot be grasped by the mind but by love alone.
You will ask me, 'How am I to think of God himself, and what is he?' and I cannot answer you except to say 'I do not know!' for with this question you have brought me into the same darkness, the same cloud of unknowing where I want you to be! For though we through the grace of God can know fully about all other matters, and think about them - yes, even the very works of God himself - yet of God himself can no one think. Therefore I will leave on one side everything I can think, and choose for my love that thing which I cannot think! Why? Because he may well be loved, but not thought. By love he can be caught and held, but by thinking never. 