Methodological functionalism is a theory about the nature of mental states. In particular, the original motivation for functionalism comes from the useful comparison of minds with computers. But that's just an analogy. In contrast to identity theory, functionalism introduces the idea that mental states multiply.
Evolution of Functionalism
The functionalist idea is, in some ways, quite old. In contemporary theories applied to the mind, the functions in question are usually taken as those that mediate between stimulus inputs (and psychological) and behavioral (and psychological) outputs. Hilary Putnam's contribution was to model these functions using the contemporary idea of machines and computer programs, where the machine's program fixes the way in which it mediates between its inputs and stop states, on the one hand, and the outputs and other states. stop, on the other.
Modern computers demonstrate that quite complex processes can be implemented on finite devices that operate on basic mechanical principles. If minds are functional devices of this type, then one can begin to understand how physical human bodies can produce the tremendous variety of actions and reactions that are associated with our full and rich mental lives. In this way, the best theory, according to Putnam's hypothesis, is that mental states are functional states, that the kind mind is a functional type.
The Initial Inspiration of Methodological Functionalism
The initial inspiration for functionalism comes from the useful analogy of minds with computing machines, as noted above. Putnam was certainly not the first to note that this comparison could be theoretically fruitful. But in his "functionalist papers" of the 1950s and 1960s, he methodically explored utility, and oversaw the transition from the idea of mere analogy to integral theory, culminating in his classic defense of the theory of the functional state in his paper on 1967, "The nature of mental states".
How is Methodological Functionalism applied?
Objectors to methodological functionalism generally argue that it classifies too many things as mental states, or at least more states than psychologists usually accept. The effectiveness of the arguments for and against functionalism depends in part on the particular variety in question, and whether it is a stronger or weaker version of the theory. In one version or another, functionalism remains the most widely accepted theory of the nature of mental states among contemporary theorists.
The central idea of Methodological Functionalism
Consider, for example, mouse traps. Mouse traps are devices for catching or killing mice. Mousetraps can be made of almost any material, and perhaps indefinitely or infinitely many designs could be employed. There are mousetraps designed with stickers, boxes, poisons, etc. All that matters for something is that a mousetrap, at the end of the day, is that it is capable of trapping or killing mice. Contrast the mousetraps with the diamonds.
Diamonds are valued for their hardness, their optical properties, and their rarity in nature. But not all hard, clear, white and rare crystals are diamonds, the most infamous alternative is cubic zirconia. Diamonds are carbon crystals with specific molecular structures. Being a diamond is a matter of being a certain type of physical material. (That cubic zirconia is not as clear or hard as diamonds explains something about why it is not equally valued. But even if it were just as hard and just as clear, a cubic zirconia crystal would therefore not be a diamond.) These examples can be used to explain the central idea of functionalism.
Distinction between Functionalism and other disciplines
Functionalism is the theory that mental states are more like mousetraps than diamonds. That is, what makes something a state of mind is more a matter of what it does, not what it is made of. This distinguishes functionalism from traditional mind-body dualism, such as that of René Descartes, according to which minds are made of a special type of substance, the res cogitans (the thinking substance.)
It also distinguishes functionalism from contemporary monisms such as JJC Smart's mind-brain identity theory. Identity theory says that mental states are particular kinds of biological states, that is, brain states, and therefore presumably have to be made up of certain kinds of things, namely things of the brain. Mental states, according to identity theory, are more like diamonds than mousetraps.
Functionalism is also distinguished from B. F. Skinner's behaviorism because it accepts the reality of internal mental states, rather than simply ascribing psychological states to the whole organism. According to behaviorism, a creature's mental states depend on how it behaves (or is willing to behave) in response to stimuli. On the contrary, functionalists often believe that internal and psychological states can be distinguished with a "finer grain" than behavior, that is, that different internal or psychological states could give rise to the same behaviors. So functionalists think that it is what internal states do that makes them mental states, not just what the creature of which they are a part does.
Methodological Functionalism as a philosophical theory
As explained so far, functionalism is a theory about the nature of mental states. As such, it is an ontological or metaphysical theory. And this is how it will be discussed, below. But it's also worth noting that functionalism comes in other varieties as well. Functionalism can be a philosophical theory about psychological explanations (that psychological states are explained as functional states) or about psychological theories (that psychological theories take the form of functional theories).
Functionalism can also be used as a theory of mental content, both as an account of the intentionality of mental states in general (what makes some states intentional is that they function in certain ways) or of a particular semantic content (what makes some state have the content "tree" is that it plays a certain role with respect to trees). Finally, functionalism can be considered as a methodological account of psychology, the theory that psychology should be pursued by studying how psychological systems work. (For a detailed examination of these variations, see Polger, 2004, ch. 3.)
Being is Doing
Before examining the arguments for and against functionalism, it is necessary to clarify the idea that, for mental states, being is doing. It is plausible that a physical material such as diamond has a physical or structural essence, that is, that it is a thing of a certain composition or constitution, regardless of what it does or can do.
It happens that diamonds can cut glass, but also many other things that are not diamonds. But it is also plausible that not all things are done this way. Some things can be essentially made up of their relationships to other things, and what they can do. The most obvious examples are artifacts like mouse traps and keys. Being a key is not a matter of being a physical thing with a certain composition, but it is a matter of being a thing that can be used to perform a certain action, namely to open a lock. The lock is also not a type of physical thing, but a type that only exists in relation to (among other things) the keys.
There may be metal, wood, plastic, digital, or keyword keys. What makes something a key is not its material composition or the lack of it, but rather what it does, or could do, or is supposed to do. (Making sense of the claim that there is something some kinds of things are supposed to do is one of the major challenges for functionalists.) The activities that a key does, could do, or is supposed to do can be called its functions. So you can say that keys are essentially things that have certain functions, that is, they are functional entities.
Application of Methodological Functionalism
The most famous arguments of functionalism are responses not to behaviorism but to mind-brain identity theory. According to identity theory, "sensations are brain processes" (Smart 1959). If the types of mental states are (identical to) the types of brain states, then there is a one-to-one relationship between the types of mental states and the types of brain states. The obvious implication is that the mind-brain identity theory is false. Other mammals, reptiles, and mollusks can experience pain, but they don't have brains like ours. It seems to follow that there is not a one-to-one relationship between brain sensations and processes, but rather a one-to-many relationship. Mental states, therefore, are not uniquely realized (as required by identity theory); instead, they are carried out multipliedly.
Arguments in favor of Methodological Functionalism
If by chance it turns out that mammals, reptiles, and mollusks all have similar brains (so there is indeed a one-to-one correlation), you can certainly recognize the possibility that terrestrial or extraterrestrial creatures experiencing pain but they don't have brains like human beings. So surely there need not be a one-to-one relationship between types of mental states and types of brain states, but that is exactly what identity theory would require.
This is bad news for identity theory, but good news for functionalism. Because functionalism says that what makes something a state of mind is what it does, and it is fully compatible with the various brains of mammals, reptiles and mollusks that all have mental states because their different brains do the same things, that is , they work the same way. Functionalism is supported because it is a theory of mind that is compatible with the probable degree of multiple realization of mental states.
Other Arguments In Favor
Another couple of arguments in favor of methodological functionalism are what can be called the optimistic and pessimistic arguments. For example, the possibility of artificial intelligence seems to require the truth of something like functionalism. Functionalism views the mind in the same way as an engineer: minds are mechanisms, and there is usually more than one way to build a mechanism. The optimistic argument, therefore, is a variation on the multiple realization argument discussed earlier; But this version does not depend on the empirical facts about what our world really is like, as does the argument from multiple realization.
Block, N. (ed.) 1980a. Readings in Philosophy of Psychology, Volume One. Cambridge, MA: Harvard University Press.
Kim, J. 2005. Physicalism, or Something Near Enough. Princeton: Princeton University Press.
Sober, E. 1985. Panglossian Functionalism and the Philosophy of Mind. Synthese 64: 165-193.
Wright, L. 1973. Functions. Philosophical Review 82, 2: 139-168.
Also you might be interested in Research Methodology in Legal Studies