Why would well-heeled folks dress up to attend a fancy gathering where they could admire a urinal? Because it’s art, of course! Or, at least, so they think. This spring’s Dada exhibit at the National Gallery of Art in Washington, D.C., celebrates what the Washington Post describes as “the most radical, irreverent, rule-breaking movement in the history of Western art.” In case you’re unfamiliar, the term dada means exactly what it sounds like: nonsense. As H. R. Rookmaaker described it, Dada “was a nihilistic creed of disintegration, showing the meaninglessness of all Western thought, art, morals, traditions.” It raises the...