The use of perspective in Renaissance painting caused a revolution in the history of seeing, allowing artists to depict the world from a spectator's point of view. But the theory of perspective that changed the course of Western art originated elsewhere--it was formulated in Baghdad by the eleventh-century mathematician Ibn al Haithan, known in the West as Alhazen. Using the metaphor of the mutual gaze, or exchanged glances, Hans Belting--preeminent...