J. Warner Wallace

While physical states can be publicly known, mental states are only privately known. This characteristic of the mind is not shared with the brain; the properties of the brain and the mind are not identical.

Physical brains are subject to the laws of physics; mental states are subject to the laws of logic. Those who think mental states are entirely physical hold a logically contradictory position. In order to think rationally about their thoughts , they must have the freedom to do so, but this freedom is unavailable if the laws of physics and chemistry are controlling their thoughts.