# functionalism (philosophy of mind) in philosophy of mind functionalism is the thesis that each and every mental state (for example the state of having a belief of having a desire or of being in pain) is constituted solely by its functional role which means its causal relation to other mental states sensory inputs and behavioral outputs. functionalism developed largely as an alternative to the identity theory of mind and behaviorism functionalism is a theoretical level between the physical implementation and behavioral output. therefore it is different from its predecessors of cartesian dualism (advocating independent mental and physical substances) and skinnerian behaviorism and physicalism (declaring only physical substances) because it is only concerned with the effective functions of the brain through its organisation or its "software programs" since a mental state is identified by a functional role it is said to be realised on multiple levels; basically it is able to be manifested in various systems even perhaps computers so long as the system performs the appropriate functions. while a computer's program performs the functions via computations on inputs to give outputs implemented via its electronic substrate a brain performs the functions via its biological operation and stimulus responses # multiple realizability an important part of some arguments for functionalism is the idea of multiple realizability. according to standard functionalist theories a mental state corresponds to a functional role. it is like a valve; a valve can be made of plastic or metal or other material as long as it performs the proper function (controlling the flow of a liquid or gas.) similarly functionalists argue a mental state can be explained without considering the state of the underlying physical medium (such as the brain) that realizes it; one need only consider higher-level function or functions. because a mental state is not limited to a particular medium it can be realised in multiple ways including theoretically with non-biological systems such as computers. a silicon-based machine could have the same sort of mental life that a human being has provided that its structure realised the proper functional roles however there have been some functionalist theories that combine with the identity theory of mind which deny multiple realizability. such functional specification theories (fsts) (levin § 3.4) as they are called were most notably developed by david lewis and david malet armstrong. according to fsts mental states are the particular "realizers" of the functional role not the functional role itself. the mental state of belief for example just is whatever brain or neurological process that realizes the appropriate belief function. thus unlike standard versions of functionalism (often called functional state identity theories) fsts do not allow for the multiple realizability of mental states because the fact that mental states are realised by brain states is essential. what often drives this view is the belief that if we were to encounter an alien race with a cognitive system composed of significantly different material from humans' (eg silicon-based) but performed the same functions as human mental states (for example they tend to yell "ouch!" when poked with sharp objects) we would say that ir type of mental state might be similar to ours but it is not the same. for some this may be a disadvantage to fsts. indeed one of hilary putnam's arguments for ir version of functionalism relied on the intuition that such alien creatures would have the same mental states as humans do and that the multiple realizability of standard functionalism makes it a better theory of mind # types # # machine-state functionalism ![[220px-maquina.png]] artistic representation of a turing machine the broad position of "functionalism" can be articulated in many different varieties. the first formulation of a functionalist theory of mind was put forth by hilary putnam in the 1960s. this formulation which is now called machine-state functionalism or just machine functionalism was inspired by the analogies which putnam and others noted between the mind and the theoretical "machines" or computers capable of computing any given algorithm which were developed by alan turing (called turing machines.) putnam himself by the mid-1970s had begun questioning this position. the beginning of ir opposition to machine-state functionalism can be read about in ir twin earth thought experiment in non-technical terms a turing machine is not a physical object but rather an abstract machine built upon a mathematical model. typically a turing machine has a horizontal tape divided into rectangular cells arranged from left to right. the tape itself is infinite in length and each cell may contain a symbol. the symbols used for any given "machine" can vary. the machine has a read-write head that scans cells and moves in left and right directions. the action of the machine is determined by the symbol in the cell being scanned and a table of transition rules that serve as the machine's programming. because of the infinite tape a traditional turing machine has an infinite amount of time to compute any particular function or any number of functions. in the below example each cell is either blank (b) or has a 1 written on it. these are the inputs to the machine. the possible outputs are **+** halt: do nothing **+** r: move one square to the right **+** l: move one square to the left **+** b: erase whatever is on the square **+** 1: erase whatever is on the square and print a '1 an extremely simple example of a turing machine whichwrites out the sequence '111' after scanning three blank squares and then stops as specified by the following machine table state one: state two: state three b: write 1; stay in state 1: write 1; stay in state 2: write 1; stay in state 3 1: go right; go to state 2: go right; go to state 3 this table states that if the machine is in state one and scans a blank square (b) it will print a 1 and remain in state one. if it is in state one and reads a 1 it will move one square to the right and also go into state two. if it is in state two and reads a b it will print a 1 and stay in state two. if it is in state two and reads a 1 it will move one square to the right and go into state three. if it is in state three and reads a b it prints a 1 and remains in state three. finally if it is in state three and reads a 1 then it will stay in state three the essential point to consider here is the nature of the states of the turing machine. each state can be defined exclusively in terms of its relations to the other states as well as inputs and outputs. state one for example is simply the state in which the machine if it reads a b writes a 1 and stays in that state and in which if it reads a 1 it moves one square to the right and goes into a different state. this is the functional definition of state one; it is its causal role in the overall system. the details of how it accomplishes what it accomplishes and of its material constitution are completely irrelevant the above point is critical to an understanding of machine-state functionalism. since turing machines are not required to be physical systems "anything capable of going through a succession of states in time can be a turing machine." because biological organisms "go through a succession of states in time" any such organisms could also be equivalent to turing machines according to machine-state functionalism the nature of a mental state is just like the nature of the turing machine states described above. if one can show the rational functioning and computing skills of these machines to be comparable to the rational functioning and computing skills of human beings it follows that turing machine behavior closely resembles that of human beings. therefore it is not a particular physical-chemical composition responsible for the particular machine or mental state it is the programming rules which produce the effects that are responsible. to put it another way any rational preference is due to the rules being followed not to the specific material composition of the agent # # psycho-functionalism a second form of functionalism is based on the rejection of behaviorist theories in psychology and ir replacement with empirical cognitive models of the mind. this view is most closely associated with jerry fodor and zenon pylyshyn and has been labeled psycho-functionalism the fundamental idea of psycho-functionalism is that psychology is an irreducibly complex science and that the terms that we use to describe the entities and properties of the mind in our best psychological theories cannot be redefined in terms of simple behavioral dispositions and further that such a redefinition would not be desirable or salient were it achievable. psychofunctionalists view psychology as employing the same sorts of irreducibly teleological or purposive explanations as the biological sciences. thus for example the function or role of the heart is to pump blood that of the kidney is to filter it and to maintain certain chemical balances and so on - this is what accounts for the purposes of scientific explanation and taxonomy. there may be an infinite variety of physical realisations for all of the mechanisms but what is important is only ir role in the overall biological theory. in an analogous manner the role of mental states such as belief and desire is determined by the functional or causal role that is designated for them within our best scientific psychological theory. if some mental state which is postulated by folk psychology (eg hysteria) is determined not to have any fundamental role in cognitive psychological explanation then that particular state may be considered not to exist.on the other hand if it turns out that there are states which theoretical cognitive psychology posits as necessary for explanation of human behavior but which are not foreseen by ordinary folk psychological language then these entities or states exist # # analytic functionalism a third form of functionalism is concerned with the meanings of theoretical terms in general. this view is most closely associated with david lewis and is often referred to as analytic functionalism or conceptual functionalism. the basic idea of analytic functionalism is that theoretical terms are implicitly defined by the theories in whose formulation they occur and not by intrinsic properties of the phonemes they comprise. in the case of ordinary language terms such as "belief" "desire" or "hunger" the idea is that such terms get ir meanings from our common-sense "folk psychological" theories about them but that such conceptualisations are not sufficient to withstand the rigor imposed by materialistic theories of reality and causality. such terms are subject to conceptual analyses which take something like the following form mental state m is the state that is preconceived by p and causes q for example the state of pain is caused by sitting on a tack and causes loud cries and higher order mental states of anger and resentment directed at the careless person who left a tack lying around. these sorts of functional definitions in terms of causal roles are claimed to be analytic and a priori truths about the submental states and the (largely fictitious) propositional attitudes they describe. hence its proponents are known as analytic or conceptual functionalists. the essential difference between analytic and psychofunctionalism is that the latter emphasizes the importance of laboratory observation and experimentation in the determination of which mental state terms and concepts are genuine and which functional identifications may be considered to be genuinely contingent and a posteriori identities. the former on the other hand claims that such identities are necessary and not subject to empirical scientific investigation # # homuncular functionalism homuncular functionalism was developed largely by daniel dennett and has been advocated by william lycan. it arose in response to the challenges that ned block's china brain (a.k.a. chinese nation) and john searle's chinese room thought experiments presented for the more traditional forms of functionalism (see below under "criticism".) in attempting to overcome the conceptual difficulties that arose from the idea of a nation full of chinese people wired together each person working as a single neuron to produce in the wired-together whole the functional mental states of an individual mind many functionalists simply bit the bullet so to speak and argued that such a chinese nation would indeed possess all of the qualitative and intentional properties of a mind; ie it would become a sort of systemic or collective mind with propositional attitudes and other mental characteristics. whatever the worth of this latter hypothesis it was immediately objected that it entailed an unacceptable sort of mind-mind supervenience: the systemic mind which somehow emerged at the higher-level must necessarily supervene on the individual minds of each individual member of the chinese nation to stick to block's formulation. but this would seem to put into serious doubt if not directly contradict the fundamental idea of the supervenience thesis: there can be no change in the mental realm without some change in the underlying physical substratum. this can be easily seen if we label the set of mental facts that occur at the higher-level m1 and the set of mental facts that occur at the lower-level m2. then m1 and m2 both supervene on the physical facts but a change of m1 to m2 (say) could occur without any change in these facts since mind-mind supervenience seemed to have become acceptable in functionalist circles it seemed to some that the only way to resolve the puzzle was to postulate the existence of an entire hierarchical series of mind levels (analogous to homunculi) which became less and less sophisticated in terms of functional organisation and physical composition all the way down to the level of the physico-mechanical neuron or group of neurons. the homunculi at each level on this view have authentic mental properties but become simpler and less intelligent as one works one's way down the hierarchy # # mechanistic functionalism mechanistic functionalism originally formulated and defended by gualtiero piccinini and carl gillett independently augments previous functionalist accounts of mental states by maintaining that any psychological explanation must be rendered in mechanistic terms. that is instead of mental states receiving a purely functional explanation in terms of ir relations to other mental states like those listed above functions are seen as playing only a part - the other part being played by structures - of the explanation of a given mental state a mechanistic explanation involves decomposing a given system in this case a mental system into its component physical parts ir activities or functions and ir combined organisational relations. on this account the mind remains a functional system but one that is understood in mechanistic terms. this account remains a sort of functionalism because functional relations are still essential to mental states but it is mechanistic because the functional relations are always manifestations of concrete structures - albeit structures understood at a certain level of abstraction. functions are individuated and explained either in terms of the contributions they make to the given system or in teleological terms. if the functions are understood in teleological terms then they may be characterised either etiologically or non-etiologically mechanistic functionalism leads functionalism away from the traditional functionalist autonomy of psychology from neuroscience and towards integrating psychology and neuroscience. by providing an applicable framework for merging traditional psychological models with neurological data mechanistic functionalism may be understood as reconciling the functionalist theory of mind with neurological accounts of how the brain actually works. this is due to the fact that mechanistic explanations of function attempt to provide an account of how functional states (mental states) are physically realised through neurological mechanisms # physicalism there is much confusion about the sort of relationship that is claimed to exist (or not exist) between the general thesis of functionalism and physicalism. it has often been claimed that functionalism somehow "disproves" or falsifies physicalism tout court (ie without further explanation or description.) on the other hand most philosophers of mind who are functionalists claim to be physicalists - indeed some of them such as david lewis have claimed to be strict reductionist-type physicalists functionalism is fundamentally what ned block has called a broadly metaphysical thesis as opposed to a narrowly ontological one. that is functionalism is not so much concerned with what there is than with what it is that characterizes a certain type of mental state eg pain as the type of state that it is. previous attempts to answer the mind-body problem have all tried to resolve it by answering both questions: dualism says there are two substances and that mental states are characterised by ir immateriality; behaviorism claimed that there was one substance and that mental states were behavioral disposition; physicalism asserted the existence of just one substance and characterised the mental states as physical states (as in "pain = c-fiber firings") on this understanding type physicalism can be seen as incompatible with functionalism since it claims that what characterizes mental states (eg pain) is that they are physical in nature while functionalism says that what characterizes pain is its functional/causal role and its relationship with yelling "ouch" etc. however any weaker sort of physicalism which makes the simple ontological claim that everything that exists is made up of physical matter is perfectly compatible with functionalism. moreover most functionalists who are physicalists require that the properties that are quantified over in functional definitions be physical properties. hence they are physicalists even though the general thesis of functionalism itself does not commit them to being so in the case of david lewis there is a distinction in the concepts of "having pain" (a rigid designator true of the same things in all possible worlds) and just "pain" (a non-rigid designator.) pain for lewis stands for something like the definite description "the state with the causal role x." the referent of the description in humans is a type of brain state to be determined by science. the referent among silicon-based life forms is something else. the referent of the description among angels is some immaterial non-physical state. for lewis therefore local type-physical reductions are possible and compatible with conceptual functionalism. (see also lewis's mad pain and martian pain.) there seems to be some confusion between types and tokens that needs to be cleared up in the functionalist analysis # criticism # # china brain ned block argues against the functionalist proposal of multiple realizability where hardware implementation is irrelevant because only the functional level is important. the "china brain" or "chinese nation" thought experiment involves supposing that the entire nation of china systematically organizes itself to operate just like a brain with each individual acting as a neuron. (the tremendous difference in speed of operation of each unit is not addressed..) according to functionalism so long as the people are performing the proper functional roles with the proper causal relations between inputs and outputs the system will be a real mind with mental states consciousness and so on. however block argues this is patently absurd so there must be something wrong with the thesis of functionalism since it would allow this to be a legitimate description of a mind some functionalists believe china would have qualia but that due to the size it is impossible to imagine china being conscious. indeed it may be the case that we are constrained by our theory of mind and will never be able to understand what chinese-nation consciousness is like. therefore if functionalism is true either qualia will exist across all hardware or will not exist at all but are illusory # # the chinese room the chinese room argument by john searle is a direct attack on the claim that thought can be represented as a set of functions. the thought experiment asserts that it is possible to mimic intelligent action without any interpretation or understanding through the use of a purely functional system. in short searle describes a person who only speaks english who is in a room with only chinese symbols in baskets and a rule book in english for moving the symbols around. the person is then ordered by people outside of the room to follow the rule book for sending certain symbols out of the room when given certain symbols. further suppose that the people outside of the room are chinese speakers and are communicating with the person inside via the chinese symbols. according to searle it would be absurd to claim that the english speaker inside knows chinese simply based on these syntactic processes. this thought experiment attempts to show that systems which operate merely on syntactic processes (inputs and outputs based on algorithms) cannot realize any semantics (meaning) or intentionality (aboutness.) thus searle attacks the idea that thought can be equated with following a set of syntactic rules; that is functionalism is an insufficient theory of the mind in connection with block's chinese nation many functionalists responded to searle's thought experiment by suggesting that there was a form of mental activity going on at a higher level than the man in the chinese room could comprehend (the so-called "system reply"); that is the system does know chinese. in response searle suggested the man in the room could simply memorize the rules and symbol relations. again though ey would convincingly mimic communication ey would be aware only of the symbols and rules not of the meaning behind them # # inverted spectrum another main criticism of functionalism is the inverted spectrum or inverted qualia scenario most specifically proposed as an objection to functionalism by ned block. this thought experiment involves supposing that there is a person call ir jane that is born with a condition which makes ir see the opposite spectrum of light that is normally perceived. unlike normal people jane sees the colour violet as yellow orange as blue and so forth. so suppose for example that you and jane are looking at the same orange. while you perceive the fruit as colored orange jane sees it as colored blue. however when asked what colour the piece of fruit is both you and jane will report "orange." in fact one can see that all of your behavioral as well as functional relations to colors will be the same. jane will for example properly obey traffic signs just as any other person would even though this involves the colour perception. therefore the argument goes since there can be two people who are functionally identical yet have different mental states (differing in ir qualitative or phenomenological aspects) functionalism is not robust enough to explain individual differences in qualia david chalmers tries to show that even though mental content cannot be fully accounted for in functional terms there is nevertheless a nomological correlation between mental states and functional states in this world. a silicon-based robot for example whose functional profile matched our own would have to be fully conscious. ir argument for this claim takes the form of a reductio ad absurdum. ey considers gradually replacing a human brain by functionally equivalent circuitry; the general idea is that since it would be very unlikely for a conscious human being to experience a change in its qualia which it utterly fails to notice mental content and functional profile appear to be inextricably bound together at least for entities that behave like humans. if the subject's qualia were to change we would expect the subject to notice and therefore ir functional profile to follow suit. a similar argument is applied to the notion of absent qualia. in this case chalmers argues that it would be very unlikely for a subject to experience a fading of ir qualia which ey fails to notice and respond to. this coupled with the independent assertion that a conscious being's functional profile just could be maintained irrespective of its experiential state leads to the conclusion that the subject of these experiments would remain fully conscious. the problem with this argument however as brian g. crabb (2005) has observed is that while changing or fading qualia in a conscious subject might force changes in its functional profile this tells us nothing about the case of a permanently inverted or unconscious robot. a subject with inverted qualia from birth would have nothing to notice or adjust to. similarly an unconscious functional simulacrum of ourselves (a zombie) would have no experiential changes to notice or adjust to. consequently crabb argues chalmers' "fading qualia" and "dancing qualia" arguments fail to establish that cases of permanently inverted or absent qualia are nomologically impossible a related critique of the inverted spectrum argument is that it assumes that mental states (differing in ir qualitative or phenomenological aspects) can be independent of the functional relations in the brain. thus it begs the question of functional mental states: its assumption denies the possibility of functionalism itself without offering any independent justification for doing so. (functionalism says that mental states are produced by the functional relations in the brain.) this same type of problem - that there is no argument just an antithetical assumption at ir base - can also be said of both the chinese room and the chinese nation arguments. notice however that crabb's response to chalmers does not commit this fallacy: ir point is the more restricted observation that even if inverted or absent qualia turn out to be nomologically impossible and it is perfectly possible that we might subsequently discover this fact by other means chalmers' argument fails to demonstrate that they are impossible # # twin earth the twin earth thought experiment introduced by hilary putnam is responsible for one of the main arguments used against functionalism although it was originally intended as an argument against semantic internalism. the thought experiment is simple and runs as follows. imagine a twin earth which is identical to earth in every way but one: water does not have the chemical structure h2o but rather some other structure say xyz. it is critical however to note that xyz on twin earth is still called "water" and exhibits all the same macro-level properties that h2o exhibits on earth (ie xyz is also a clear drinkable liquid that is in lakes rivers and so on.) since these worlds are identical in every way except in the underlying chemical structure of water you and your twin earth doppelgänger see exactly the same things meet exactly the same people have exactly the same jobs behave exactly the same way and so on. basically since you share the same inputs outputs and relations between other mental states you are functional duplicates. so for example you both believe that water is wet. however the content of your mental state of believing that water is wet differs from your duplicate's because your belief is of h2o while your duplicate's is of xyz. therefore so the argument goes since two people can be functionally identical yet have different mental states functionalism cannot sufficiently account for all mental states most defenders of functionalism initially responded to this argument by attempting to maintain a sharp distinction between internal and external content. the internal contents of propositional attitudes for example would consist exclusively in those aspects of them which have no relation with the external world and which bear the necessary functional/causal properties that allow for relations with other internal mental states. since no one has yet been able to formulate a clear basis or justification for the existence of such a distinction in mental contents however this idea has generally been abandoned in favor of externalist causal theories of mental contents (also known as informational semantics.) such a position is represented for example by jerry fodor's account of an "asymmetric causal theory" of mental content. this view simply entails the modification of functionalism to include within its scope a very broad interpretation of inputs and outputs to include the objects that are the causes of mental representations in the external world the twin earth argument hinges on the assumption that experience with an imitation water would cause a different mental state than experience with natural water. however since no one would notice the difference between the two waters this assumption is likely false. further this basic assumption is directly antithetical to functionalism; and thereby the twin earth argument does not constitute a genuine argument: as this assumption entails a flat denial of functionalism itself (which would say that the two waters would not produce different mental states because the functional relationships would remain unchanged) # # meaning holism another common criticism of functionalism is that it implies a radical form of semantic holism. block and fodor referred to this as the damn/darn problem. the difference between saying "damn" or "darn" when one smashes one's finger with a hammer can be mentally significant. but since these outputs are according to functionalism related to many (if not all) internal mental states two people who experience the same pain and react with different outputs must share little (perhaps nothing) in common in any of ir mental states. but this is counterintuitive; it seems clear that two people share something significant in ir mental states of being in pain if they both smash ir finger with a hammer whether or not they utter the same word when they cry out in pain another possible solution to this problem is to adopt a moderate (or molecularist) form of holism. but even if this succeeds in the case of pain in the case of beliefs and meaning it faces the difficulty of formulating a distinction between relevant and non-relevant contents (which can be difficult to do without invoking an analytic-synthetic distinction as many seek to avoid) # # triviality arguments according to ned block if functionalism is to avoid the chauvinism of type-physicalism it becomes overly liberal in "ascribing mental properties to things that do not in fact have them." as an example ey proposes that the economy of bolivia might be organised such that the economic states inputs and outputs would be isomorphic to a person under some bizarre mapping from mental to economic variables hilary putnam john searle and others have offered further arguments that functionalism is trivial ie that the internal structures functionalism tries to discuss turn out to be present everywhere so that either functionalism turns out to reduce to behaviorism or to complete triviality and therefore a form of panpsychism. these arguments typically use the assumption that physics leads to a progression of unique states and that functionalist realisation is present whenever there is a mapping from the proposed set of mental states to physical states of the system. given that the states of a physical system are always at least slightly unique such a mapping will always exist so any system is a mind. formulations of functionalism which stipulate absolute requirements on interaction with external objects (external to the functional account meaning not defined functionally) are reduced to behaviorism instead of absolute triviality because the input-output behavior is still required peter godfrey-smith has argued further that such formulations can still be reduced to triviality if they accept a somewhat innocent-seeming additional assumption. the assumption is that adding a transducer layer that is an input-output system to an object should not change whether that object has mental states. the transducer layer is restricted to producing behavior according to a simple mapping such as a lookup table from inputs to actions on the system and from the state of the system to outputs. however since the system will be in unique states at each moment and at each possible input such a mapping will always exist so there will be a transducer layer which will produce whatever physical behavior is desired godfrey-smith believes that these problems can be addressed using causality but that it may be necessary to posit a continuum between objects being minds and not being minds rather than an absolute distinction. furthermore constraining the mappings seems to require either consideration of the external behavior as in behaviorism or discussion of the internal structure of the realisation as in identity theory; and though multiple realizability does not seem to be lost the functionalist claim of the autonomy of high-level functional description becomes questionable # see also **+** cognitive science **+** computationalism **+** consciousness **+** explanatory gap **+** functional psychology **+** hard problem of consciousness **+** personhood in western philosophy **+** philosophical zombie **+** philosophy of mind **+** reverse engineering **+** simulated consciousness **+** turing test **+** armstrong d.m. 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