What Is Functionalism?

Question 2: What exactly is functionalism, and how in particular is it meant to be an improvement over behaviorism? Be sure to explain how functionalists appeal to the notion of multiple realisability to motivate their view, especially in response to identity theory. Why does the resulting picture seem so compelling to many philosophers?

The essential concept of functionalism revolves around the role and function of mental states for which it is a part, instead of its internal make up. More precisely, functionalist propositions assume the identity of a mental state to be dictated by its causal relations to sensory inputs and behaviour outputs. As a common example, a functionalist may identify pain as a state that is caused by an injury, to create the belief that something is wrong with the body, a desire to escape that state, to produce stress, cause wincing, and nurse the injured area. Functionalists agree that anything that plays this role is a pain. According to this theory, all beings with internal states that carry out the above roles have the potential to feel pain.  

Functionalism can be understood as an enhanced development from behaviourism, and distinguishes causal connections between mental states. Overall, functionalism enables for more refined relationship between mental states than behaviourism as functionalism provides sufficient characterisations of mental states. Consequently, for the functionalist, acknowledgement of mental states must be holistic.

Putnam (1975) introduces the concept of multiple realisability. According to the identity theory, mental states are identical to physical brain states. For example, pain being identical to C-fibre firings, and lightning being identical to motion of electrical charges. Putnam refutes that pain correlates with only one physical kind. He argues that there are many ways that pain can be realised in the physical; therefore, not identical. Putnam emphasises the difficulties that confront the identity theorist by doubting that any one physical-chemical state correlates with pain in mammals, reptiles and molluscs (p. 436). Since identity relation is one-to-one, but the mental kind to physical kind relation is one-to-many, multiple realisability can be seen as an objection to the identity theory.

For instance, there is a specific kind of neural activity, C-fibre firings that meet these conditions. If so, then according to this theory, humans can be in pain by simply going through C-fibre stimulation. But the theory then permits creatures with very different physical constitutions to have mental states as well; if there are green-blobbed Martians, or inorganic states of androids that also meet these conditions, then these creatures can too be in pain. As functionalists put it, pain is realised by different types of physical states in different kinds of creatures, or multiply realised.