*David Chalmers *is University Professor of Philosophy and Neural Science and co-director of the Center for Mind, Brain, and Consciousness at New York University. He is best known for his work on consciousness, including his formulation of the “hard problem” of consciousness; Daniel C. Dennett is University Professor and Austin B. Fletcher Professor of Philosophy and director of the Center for Cognitive Studies at Tufts University. He is the author of a dozen books, including Consciousness Explained, and, most recently, From Bacteria to Bach and Back: The Evolution of Minds