Henri Matisse is supposed to have encountered someone who complained that the arm of a woman in one of his portraits was too long. “Madam, you are mistaken,” he replied. “This is not a woman, this is a painting.” She might have replied, “That’s not an argument, that’s attitude.” The painter’s bon mot is what E.H. Gombrich (to whose classic study Art and Illusion I owe the anecdote) called “one of the paradoxes with which modern artists and critics like to tease the long-suffering public.” Such paradoxes can be hard to avoid. Gombrich thought the development of pictorial illusionism—that is, of the European canon of realistic representation—“was stimulated by the dissatisfaction which certain periods of Western civilization felt with images that failed to look convincing.” The statement is itself paradoxical, because it ignores the question of who wants to be convinced by an image. Long before Matisse, the Italian artists of the sixteenth century who came to be known as Mannerists were willing to twist their figures out of proportion, and they did so to create not convincing images, but convincing paintings.