“Appropriation is a stupid name,” the German artist Hans-Peter Feldmann said in 2010. “But, to steal is okay. If I discover something in art that I really like, I take it.” Feldmann’s approach suggests that the artist is not a unique creator, but one who modifies history, the secondhand, and the found to unexpected effect. An austere oil portrait will acquire a red nose. A handful of purchased paintings are grouped to tell a new story. This exhibition presents sculpture, photography, and collage from Feldmann’s five-decade career. —E.C.