At the 1994 landmark conference "Toward a Scientific Basis for Consciousness," philosopher David Chalmers distinguished between the "easy" problems and the "hard" problem of consciousness research. According to Chalmers, the easy problems are to explain cognitive functions such as discrimination, integration, and the control of behavior; the hard problem is to explain why these functions should be associated with phenomenal experience. Why doesn't all this cognitive processing go on "in the dark," without any consciousness at all? In this book philosophers, physicists, psychologists, neurophysiologists, computer scientists, and others address this central topic in the growing discipline of consciousness studies. Some take issue with Chalmers's distinction, arguing that the hard problem is a nonproblem, or that the explanatory gap is too wide to be bridged. Others offer alternative suggestions as to how the problem might be solved, whether through cognitive science, fundamental physics, empirical phenomenology, or with theories that take consciousness as irreducible.