"What is it to perceive, to feel emotion, to hold a belief, or to have a purpose?" asks Armstrong (225). Do we have a soul, or are we purely physical? Are these questions even mutually exclusive? The Identity Theorist argues that the mind is completely physical on the grounds that mental states and brain states causally interact and therefore, mental states must be brain states. Although one may object that it could be possible for the mind and body to interact without being identical, Identity Theorists adequately argue that we should believe the simplest explanation of everything.
The Identity Theorist believes that science and philosophy must work together in order for us to see the whole picture of the mind. On their own, each comes up with an incomplete idea of the nature of the human mind. According to Armstrong, as philosophers, we must not leave out scientific methods, and must consider a scientific consensus to be reliable. The scientific consensus about the human mind is a Materialist account, which suggests that everything in the world is material. Therefore, the mind is entirely physico-chemical, and all behaviors, experiences and sensations can be explained by brain processes in the central nervous system. J.J.C. Smart argued that sensations are identical with brain processes. Identity Theorists use identity in the strict sense of the word; when Smart claims that sensations are brain processes, he does not mean that they are of the same type of thing, but that they are numerically identical. "When I say that sensation is a brain process?I do not mean just that the sensation is somehow spatially or temporally continuous with the brain process?" explains Smart ...