"The madman is not the man who has lost his reason. The madman is the man who has lost everything except his reason... The sane man knows that he has a touch of the madman, but the madman thinks he is entirely sane... The whole secret of mysticism is this: that man can understand everything by the help of what he does not understand... [The mystic] knows the world is larger than his mind, while the madman makes his mind larger than the world."
G.K. Chesterton
Orthodoxy, Chapter 2