 Few people, if any, think zombies actually exist. But many hold that they are at least conceivable, and some that they are possible. It seems that if zombies really are possible, then physicalism is false and some kind of dualism is true. For many philosophers that is the chief importance of the zombie idea. But it is also valuable for the sharp focus it gives to philosophical theorizing about consciousness and other aspects of the mind (see for example Howell 2013; Kriegel 2011; Stoljar 2006; Tye 2008). Use of the zombie idea against physicalism also raises more general questions about the relations between imaginability, conceivability, and possibility. Finally, zombies raise epistemological difficulties: they reinstate the ‘other minds’ problem.