“To understand music, you must listen to it. But so long as you are thinking, “I am listening to this music,” you are not listening. To understand joy or fear, you must be wholly and undividedly aware of it. So long as you are calling it names and saying, “I am happy,” or “I am afraid,” you are not being aware of it. Fear, pain, sorrow, and boredom must remain problems if we do not understand them, but understanding requires a single and undivided mind. This, surely, is the meaning of that strange saying, “If thine eye be single, thy whole body shall be full of light.”