Identity theory is a physicalist theory which extends on the idea that the mind is ontologically dependent on the brain by asserting that mental states are neurological states as the mind and the brain are the same thing. The theory dictates that mental phenomena are results of physical and chemical reactions in our brains and neuronal reactions; therefore, the differences that our made in our brain causes a change in identity. The Identity Theory is also widely supported by neuroscientists as recent advances in scientific research have yielded the notion that much of our mental functioning can be associated with specific parts of the brain (eg. damage to posterior sectors of the left-brain hemisphere is associated with impaired literacy skills). Thoughts and feelings are said to be simply neurophysical reactions in our brain and electrical impulses sent between neurones. A real-life example of how identity theory seems to be pragmatic can be seen in the case study of Phineas Gage’s severe injury to the brain in 1848. The head injuries rendered Phineas a completely new person as he adopted different traits and emotions afterwards. The identity theory would surmise that his brain was significantly damaged due to the injury, which caused the mind and mental states to alter as well. This links into another idea of what it means to be human – the essential self. The Essential Self is a set of characteristics that can endure over time but as Phineas became a completely new person, it can be deduced that there is no such thing as the essential self. This case study points out to the approach to the essential self known as the Illusion Theory which asserts that we don’t have a fixed set of characteristics. To summarise the Identity Theory, it is the idea that our mental state and identity are merely our brain because mental states are neurological states.
In spite of the theory’s attractiveness, the Identity Theory does have its fair share of flaws. Firstly, I’d like to define the functions of a mind. A mind is a substance that should have the capacity to enable us to have self-awareness, dreams, fantasies, hopes and emotions; the mind also enables us to communicate, store and retrieve memories, and have sense-perception. If a person is not able to carry out these functions (mental states), they then don’t have a mind. The Identity Theory has a plausible explanation of how the majority of these mental states can be derived from neurological processes and neurological states but it fails to explain to explain the retrieval of memories and the capacity for thought. Neuroscientists have determined that episodic and semantic memories are stored in three regions of the brain but they have not yet been able to determine how memories are retrieved from the brain and acted upon. If the brain and the mind are the same thing, there should be an evident mechanism that is used to retrieve memories but, as there is not any mechanism as of yet, this disputes the notion that the brain and mind are the same entity. Furthermore, there is another crucial flaw in this theory explored by John Searle. John Searle proposed the thought experiment that the brain started to deteriorate and was slowly replaced, piece by piece, by silicon chips – a logical reasoning, he deduced, was that you would not lose mental functions as you would continue to have a constant mental life. This conclusion by John Searle weakened the premise of ‘wherever there is no brain, there is no mind’ as the functions of the human mind remained constant even though the brain was gone.