Identity theory argues that the mind is identical to the brain and that mental events are identical to brain events, ultimately the theory enlightens materialism in that everything is physical and to further precision it enlightens material monism in believing that only material substances and their states exist (K. T. Maslin, 2007, 65). To some extent it exemplifies physicalism that humans are fully material beings that can be explained using ideally complete physics which it is essential to point out do not currently exist. The theory in summary states that when we experience something in our minds it will be identical to an event in the brain, for example pain will be experienced at the same time as the firing of c-fibres in the brain (Gareth Southwell, 2009, http://www.philosophyonline.co.uk). In this essay I will further discuss the different versions of the identity theory such as type-type and token-token. And I will prove that despite strengths such as explaining why changes in the brain through injury or otherwise accompany alterations in the mental functioning no version of the identity theory of mind are ultimately acceptable due to its inability to explain the locations of thoughts or emotions, the subconscious or conscious states, the qualia of experiences or the intentional mental states with further critique by the American philosopher Kripke. There are two types of identity theory and the first one I will discuss is the type-type identity theory. This theory believes that any given mental state will be identical to a brain state (K. T. Maslin, 2009, 68). This theory tries to identify the connection of mental phenomena with physical processes in the brain. This theory utilises the discoveries of science as identical with the possible connections of mental states with brain states, it states that the discovery of water as an element of oxygen and hydrogen as well as the identification of physical phenomena such as lightning with the pattern of electrical discharges it can connect the experience and feeling of pain with the physical process in the brain and central nervous system of the firing of C-fibres. The extension of this theory places impetus on reductionism. This is where it is argued that the meanings of different mental and physical phrases exactly match at their core concepts. This can be explained in terms of water and H20, two groups of phenomena that appear numerically contrasting turn out to be one set of existents and not two. Ultimately they state that mental and physical concepts will turn out to be a single type of property described by two different terminologies. They believe the true nature of phenomena can be provided by the base to which it is reduced for example pain can be reduced to the behaviour of neurons in the central nervous system.>