Abstract
Consciousness is extremely familiar yet it is at the limits—beyond the limits, some would say—of what one can sensibly talk about or explain. Perhaps this is the reason its study has drawn contributions from many fields including psychology, neuroscience, philosophy, anthropology, cultural and literary theory, artificial intelligence, physics, and others. The focus of this entry is on: the varieties of consciousness, different problems that have been raised about these varieties, and prospects for progress on these problems.