This book investigates in unprecedented detail what David Papineau has called "the intuition of distinctness"--its seeming to us, when we attend introspectively to a phenomenal property of a current sensation, that this property couldn''t literally be an electro-chemical property of neural activity in a certain tiny region of our brain. This book argues that the intuition of distinctness is no mere curiosity, since it plausibly underlies much of the widespread feeling both inside and outside philosophy that phenomenal properties (or qualia) constitute an insuperable obstacle to physicalism (or materialism) about the mind. It goes on to argue against the natural suggestion that this feeling is warranted because the intuition of distinctness somehow gives us genuine reason to reject physicalism about phenomenal properties and to adopt property dualism instead; it argues that there is no plausible way in which it could. The volume develops a positive view of what phenomenal properties are, defending an unorthodox version of representationalism, and sketching accounts of what makes our introspective knowledge of phenomenal properties special, how introspection could tell us that an introspected property is physical, and what the subjectivity of phenomenal properties could be. The volume critically surveys previous attempts to explain consistently with physicalism how the intuition of distinctness arises in us. Finally, it elaborates an explanation of the intuition of distinctness.