The German-born artist Hans Haacke uses art to pose questions about art. Turning the medium onto itself, his works have explored subjects like corporate sponsorship of art institutions, provenance, and the restitution of artworks, as well as local and global politics. A new retrospective displays over 30 works from the artist’s career, and serves as the New York premiere of Gift Horse (2014): an equine skeleton in bronze, tagged with a Bloomberg-esque digital ribbon that lists stock prices in real time. —J.V.