Philosophy of mind concerns questions about mental phenomena that empirical research alone can't settle, such as the nature of mental states and which sorts of things can have them-only living things, or also machines? Settling them requires reflection on such phenomena as consciousness, rationality, and intentionality; the 'explanatory gaps' that seem to exist between these; and underlying physical phenomena and the different strategies-dualist, eliminativist, physicalist, and functionalist-that have been proposed for dealing with them. (C) 2010 John Wiley & Sons, Ltd. WIREs Cogn Sci 2010 1 648-657