mind continued

The type identity theory of mind seems fairly straightforward, but is not without its flaws. One objection to this theory involves the concept of the plasticity of the human brain. Plasticity is a word used to describe the brain's ability to adapt to new conditions. People who suffer brain damage may lose the ability to be in certain mental states (they may be unable to recognize their mother, as an example). Because of this unique feature of the brain however, some patients may regain the ability to recognize their mother over a period of time. This is because when one area of the brain is damaged, another can take its role. This argument, called the argument of multiple realizability, shows that although the subject is in the same mental state (recognizing his mother), he is not in the same brain state. Thus it follows that brain states are not identical to mental states, which is the central claim of the type identity theory.

Although this argument seems to disprove the main point of the identity theory, some of the details can be modified to make the issue not so clear. A type identity theorist may in turn reply that the brain damaged patient actually is in a different, albeit subtly different mental state than previously, even though in both instances he is recognizing his mother. They may argue that the patient isn't recognizing his mother in the same exact way that he used to. This is however somewhat difficult to prove (does the patient feel different in some unexplainable way every time he looks at his mother?)

It seems that this still may be a problem for the type identity theorist.