For instance, an adept was sitting in a ship with an ordinary person. And this person said, "Oh, how terrible this noise is, continually going on! It breaks my nerves to pieces. Terrible, terrible, terrible! Day and night, to hear this going on. It almost drives me mad!" The adept said, "I did not hear it until you reminded me of it. I hear it when I want to hear it; I do not hear it when I do not want to hear it." That is the idea. Both had the sense of hearing, but one had the power to close it and to open it; the other had the doors of his hearing sense open but he could not close them.