“I was interested in ideas,” said the artist Marcel Duchamp, “not merely in visual products.” That “merely” speaks to the brainy, conceptual breadth of Duchamp. Where would 20th-century art be without him? This exhibition celebrates an important collection of Duchamp’s art—more than 35 seminal works, including several of his most famous readymades—recently bestowed upon the Hirshhorn by Barbara and Aaron Levine. Included in the show are works by artists Duchamp influenced: Man Ray, Tristan Tzara, Henri Cartier-Bresson, Diane Arbus, Irving Penn, and more. An important gift. —J.V.