Dramatic shifts from foreboding dark to probing light, with minimal gradation in between; a realism that exposes all the flaws and folds of human flesh, eschewing Michelangelo's idealized bodies; a surgical explication of almost unbearably tense emotion; and the poised depiction of crucial moments at the lip of their unfolding: these were among the innovations of Michelangelo Merisi, known as Caravaggio. Without them, as the great Italian art writer Roberto Longhi once noted, "Ribera, Vermeer, L...