In this essay the writer explains the debate of the relations between a
mental state and a brain state. This essay looks at whether a mental state is
identical with a physical state. Here, the writer argues against the identity
theorists who claim that a mental state and a brain state are identical. According to the writer, the identity theorists cannot accommodate both ontological and epistemological objections. Finally, he argues that we cannot
know the qualities of mental state by only observing physical information
given by physical sciences of bodies including brains.

Keywords: a mental state, a brain state, Cartesian dualism, and
necessarily true.