Jack Levine, George Segal, Audrey Flack, Larry Rivers, and R. B. Kitaj have long been considered central artists in the canon of twentieth-century American art: Levine for his biting paintings and prints of social conscience, Segal for his quiet plaster figures evoking the alienation inherent in modern life, Flack for her feminist photorealist canvases, Rivers for his outrageous pop art statements, and Kitaj for his commitment to figuration. Much...