Abstract: Thomas Nagel investigates the status of a priori knowledge in the context of the mind-body problem. A priori reflection on the concepts of mental and physical properties seems to show that mental state and event types could not be identical with physical state event types. Nagel wishes to block the conclusion that it really does show this because he finds the resultant property dualism profoundly unsatisfactory.

Keywords: a prior, mental properties, mind-body problem, Thomas Nagel, physical properties, property dualism,