Hilary Putnam, who wrote the article “the nature of mental states”, was a functionalist whom in this article argues whether pain states are brain states. By this Putnam means to challenge Identity Theorists on the idea that pain or a state of pain, and not just the feeling of pain or a reaction to pain, but pain itself, is a brain state; states that occur as physical-chemical occurrences in the brain. According to Putnam not only are the logistics of this theory false but the physical or chemical occurrences are redundant when discussing pain states: he claims that “the state of being in pain is a functional state of the whole organism.” The focus of this article, as explained by Putnam, is not what is pain (like what is temperature, since we know that temperature is molecular kinetic energy) but what is the concept of pain. He makes the argument that it is false to assume that the concept of such things can be the same as the physical identity of them. He states that for those who then do not know the exact molecular kinetic energy involved in a particular temperature or maybe they do not even understand that concept in itself, then according to the physicalist theory those people would be unable to experience temperature if the temperature and the concept were one and the same.

            Identity theory explains pain states as being brain states in that all mental events (feelings, beliefs etc.) happen in physical-chemical reactions in the brain, while functionalism debates that it is not even the matter in which such things occur that is relevant. The functionalist believes that consciousness and mental states can occur in anything, cream cheese or computers.  Putnam describes an idea of Turing functionalism to explain his “what is the concept of pain” argument. He compares the Turing Machine processes to the ways that mental states occur in humans: receives input, carries out the instructions of the input program, changes its internal state, and produces an appropriate output based on the input and instructions. According to this comparison, Putnam claims that humans are probabilistic automatons. Probabilistic because the transition that occurs in organisms between states (pains or other mental states) are not, nor are they required to be, deterministic. From this explanation Putnam defines the basis for his reasoning regarding pain as a functional state of an organism as follows: All organisms capable of feeling pain are probabilistic automata, being able to experience pain is to possess the appropriate kind of functional organization for it, no organism capable of feeling pain can be decomposed into parts which separately possess these functional organizations, and for every set of functional organizations there exists a subset of sensory inputs that allow that organism that state when its sensory inputs are in that subset.

            Putnam states that this hypothesis is a mechanical model of an organism and that this is in fact what psychology aims to do, therefore supporting the functional view. Although functionalism and Identity theory have been understood as theories to replace dualism, Putnam explains that in his theories of state-functionalism can coexist with dualistic theories; He claims that a body or a soul can be probabilistic automatons. Putnam goes on to argue that functionalism is simply easier to make sense of than identity theory. He explains that organisms without brains could not feel pain if the physical-chemical theory were true, and as he points out octopus do not have brains and yet are capable of feeling pain. Putnam also explains the weakness in assuming that similar behaviors in two organisms is equivalent to the two having similarities in actual physical details (brain states), whereas it can easily be suspected that the two have similar functional organization. Functionalism also leaves out the need for the discovery of neurophysiological laws for “brain-states” in each independent species. Putnam remains clear that it is the input, output and the entire organisms experience of them that is the focus of functionalism and that these are the only relevant aspects.