Various philosophers have composed and expounded theories to clarify their reasoning about the mind. Dualism, behaviorism, and identity theory are well-known theories supported by well-written explanations. A modern theory, functionalism provides broad insight into the main problem faced by philosophers, the mind/body problem. Functionalism was developed as a combination of behaviorist theory and identity theory. Behaviorism believes that being in a mental state is the same as a physical state, which is an evident behavioral characteristic. For example, if one says they are unhappy, their physical state might include a frowning expression or inappropriate posture. On the other hand, Identity Theory suggests when one experiences something; there is a corresponding neurological condition. The fallacy of these two theories is that behaviorism fails to incorporate mental states but attempts to do so by saying that the mental state is the observable behavior (Southwell). However, different behaviors can arise from the same stimuli and different stimuli can initiate the same reaction. The identity theory is incorrect because it states that mental and brain states are identical, however, this statement is presumably false (Garth). Functionalism includes elements of both theories to explain reasons and is based on both ideas. The Functionalist view can be defined as mental states established by their functional role; meaning mental states and its relation to other mental states, sensory inputs and behavioral outputs (Levin). In the article “Functionalism” by Ned Block, he illustrates this concept through a machine detecting an even or odd number of 1s. This system has two states, S1 and S2; one input,...... middle of paper......y.Works CitedLevin, Janet, "Functionalism", The Stanford Encyclopedia of Philosophy (Summer 2010 edition), Edward N. Zalta (ed.), URL = .Southwell, Gareth. "Philosophy of mind - Behaviorism - Introduction." Resources, reviews, discussions and books for students and general readers interested in philosophy - Philosophy Online. 2000. Network. 17 November 2011. .Chalmers, David. “Absent Qualia, Faded Qualia, Dancing Qualia.” David Chalmers. Conscious experience. Network. November 17, 2011. Cole, David, “The Chinese Room Argument,” The Stanford Encyclopedia of Philosophy (Winter 2009 Edition), Edward N. Zalta (ed.), URL = .