The feverish nature of the art market during the Second World War, and ever since, offers at least one straightforward reason for both the Nazi art theft itself and for why items have never been restituted. “There is no cultural genre in which money plays as big a role as visual arts,” Rein Wolfs, the director of the Bonn Museum of Modern Art, told me. “Dance, or theater, they aren’t about goods. But art, it’s about goods. There’s so much confusion around it because there’s so much money involved.”