In the ars gratia artis view, works of art are their own end and shouldn’t serve any external purpose, but most of us use art all the time. J. S. Bach composed a piece of music, now known as the Goldberg Variations, that was reportedly meant to occupy the restless mind of a patron while he tried to get to sleep. More recently, composer Max Richter (whom I wrote about here) crafted an eight-hour-long project called Sleep, which is meant to be heard while sleeping. Part of his rationale, from a...