The contemporary French artist Christian Boltanski has never been one to dwell: in the 60s he was doing short films; the 70s saw a turn to photography; in the 80s he started building altar-like installations that dealt with religious themes. “I ask questions,” Boltanski said in 2018, “but I don’t have any answers. Generally I don’t like people who think they have any answers. Those people are dangerous.” This large retrospective explores themes of history and memory. —J.V.