“I begin with an idea,” the German painter Georg Baselitz has said, “but as I work, the picture takes over.” The result is six decades’ worth of paintings featuring lively colors and forceful brushstrokes—and often displayed upside down—as well as sculptures and prints. A new retrospective marks the first time the Venice Accademia has dedicated an exhibition to a living artist, and runs as a collateral event of the 58th Venice Biennial. —J.V.