Functionalism: A materialist Theory of the Mind
Introduction
According to the Identity Theory of Mind (which we discussed earlier), all mental states and events such as thoughts, desires, decisions, pains and so on are identical with physical states (of the brain). There was a problem with this view: multiple realizability. The extraterrestrial being ET wanted to phone home. Not only that but ET obviously experienced a fairly wide range of emotions. In other words, ET was the subject of mental states. Yet ET, we may suppose, did not have a human brain or maybe any brain at all. So ET's mental states were not identical with brain states. This points to the fact that the identity of a mental state is not to be found in what constitutes it – brain state or otherwise. A mental state such as “wanting to phone home” may apply to beings with very different brains from ours – perhaps a future cybernaut with a silicon based brain, or to beings with no brain at all – ET. Another similar example is the state “multiplying 8 by 9”. This can apply to a calculator, computer, person and maybe many other beings as well. Mental states are “multiply realizable”. This means that they can have a wide range of physical instantiations – person, dolphin, ET, robot, etc. This phenomenon is fairly widespread. The term “table” is multiply realizable. A table can be made out of wood, metal, cardboard, stone and other materials as well. It is easy to see how multiple realizability presents a problem for the Identity Theory. According to the theory a mental state such as wanting to phone home would be identical with some brain state A. However, for ET the mental state of wanting to phone home would be identical with some different (physical) state B. It would follow that A = B, and this is false since A and B are different – A is a state of a human brain whereas B is not. For a being to be the subject of a mental state does not, it seems, depend on the subject's physical constitution. Functionalism is a theory which, as we will see, though similar to the identity theory is importantly different in the account it gives of the nature of mental states. According to the theory of Functionalism a mental state is a functional state.What exactly is a functional state?
Functional states and roles
It is common to describe something in terms of what it does rather than in terms of what it is made of, for instance. For example, the human heart is that organ which circulates blood, a saw is a tool used for cutting wood (usually), the radiator in a car is that part which cools the engine. That is to say that we describe hearts, saws and radiators in functional terms. This is often expressed by saying that radiators, saws and hearts have a certain “functional role”. And the point is that very different physical objects can carry out any given functional role. Whatever carries out the functional role of circulating the blood in the human body is a heart, whether it is made of normal heart tissue, plastic, metal or whatever. It doesn't matter what it's made of as long as it efficiently circulates blood. A heart, like a radiator or saw, is identified by its functional role rather than by its physical constitution. In other words, if you want to know what a heart is, look at what at what it does rather than at what it's made of. And similarly for saws and radiators (and many others).Functional role and the mind
How exactly does the notion of functional role apply to the mind and mental states? According to the theory of the mind called Functionalism, a mental state is identified by its functional role rather than by (as asserted by the Identity Theory) its physical constitution. According to functionalism, a mental state M is identified by three types of causal relation.- The causal links between the environment and M. For instance, the slamming of the door may cause me to have a certain experience, namely the hearing of a sound.
- The causal links between M and other mental states. For instance, the hearing of a sound may cause me to become angry or frightened.
- The causal links between M and physical behaviour. For instance, the hearing of the sound may cause me to get up out of my chair.
Now, to say that a mental state is identified by its functional role rather than by its being, say, a brain state is incomplete. For it would be open to the dualist to say that a mental state is a functional state which is fundamentally non-physical. Functionalism is a physicalist theory however. Thus it asserts that a mental state has a physical realization. A “physical realization” is a certain physical state, event or process with which the given mental state is identical. Of course, as seen in the case of ET, the particular physical realization may not be a state of the brain. Functionalism is not too far removed from the identity theory. Yet there is a difference. The physical realization of a (functionally specified) mental state for human beings will normally be a state of the brain – this is where functionalism is fundamentally similar to the identity theory. Indeed the form of functionalism presented here is called the “functionalist identity theory”. The two theories differ in that for functionalism it is not essential that a mental state be a state of the brain. Any physical realization will do – machine state, silicon state or whatever. Whatever the internal organization of ET's head, it is the state of this internal organization which is the physical realization of ET's desire to phone home. Functionalism is a physicalist theory. Mental states are physical states but are not necessarily states of a human brain. There are, then, two parts to a functionalist identity theory of the mind.
- A mental state (event or process) is a functional state as explained in the account (1) – (3) above.
- A mental state has a physical realization.
Some problems for functionalism
- The Chinese Room: This is a hypothetical counterexample to functionalism. Suppose that you are in a room where your task is to answer questions about a story written in Chinese. The questions are in Chinese and the answers have to be given in Chinese but you can neither read nor write any Chinese at all. The only thing you have is an instruction manual written in English. The manual contains rules for associating certain Chinese characters (the questions) with other Chinese characters (the answers). The manual allows you to answer the questions in a way which satisfies a Chinese speaker. It is suggested that this example presents a problem for functionalism in the following way. We can suppose that the relevant “input/output” relations are the same as for a native Chinese speaker. The input is a sentence in Chinese – the question - and the output is the appropriate Chinese sentence – the answer. Yet you understand no Chinese. You are “functionally equivalent” to a native speaker. This means that all the relevant causal relations could be the same, i.e. functionalism is a theory about the causal relations involving external stimuli, mental states and bodily behaviour. And to say that you are functionally equivalent to the native Chinese speaker means that all these causal relations are the same for you as for the native speaker. However, despite the functional equivalence you don't understand Chinese and so it appears that the relevant functional relations are not adequate as an account of what it is to understand Chinese. There is more to the mind than what is captured by functional equivalence. Functionalism seems inadequate as a theory of mind.
How can the functionalist respond to this objection? The Chinese Room argument aims to show that you are functionally equivalent to the Chinese speaker but despite this you do not understand Chinese. Therefore functional equivalence does not fully capture what it is to understand Chinese. That's the argument. However, as the case has been described, there is a question as to whether or not you really do understand Chinese (with the help of the instruction manual, of course). And this forms the basis of the functionalist's reply. For the functionalist wants to know this: Are you really functionally equivalent to the Chinese speaker? The test for this is whether or not you are able to reply to the Chinese questions in a sufficiently flexible and inventive way. If not – if your replies are too robot-like and repetitive - then you will not be functionally equivalent to the native speaker at all. And if so, the Chinese Room will no longer be a case of functional equivalence at all. The problem is that the more flexible and inventive your replies to the Chinese questions are, the more we are inclined to say that you do understand Chinese. Thus the functionalist can reply to the Chinese Room that it is simply not clear that it is a case of functional equivalence together with a non-equivalent mental state.
- The inverted spectrum: This objection is similar to the Chinese Room. Imagine two observers Bill and Ben. Ben is a normal observer, like us. Bill, however, is different. When Bill observes fire engines, post - boxes, tomato sauce and Communist flags he has the experience of seeing something green. And when he observes healthy grass, cucumbers and traffic lights indicating “Go” he has the experience of seeing something red. Bill's colour spectrum has been systematically inverted. The problem for functionalism is this: all Bill and Ben's behaviour - their input/output relations – could be the same, and yet their actual visual experiences would be quite different – the reverse of normal. Again, despite all the functional relationships being the same, the actual mental states are different. Functionalism has failed to give an adequate account of mental experience. There seems to be more to more to mental experience than is expressed in the sort of functional relationships outlined above in (1) – (3).
A functionalist might reply as follows: Grant that there is more to visual experience (or any experience) than can be captured by the sort of causal relations in (1) – (3). So what more is required? Remember that the functionalist identity theory has two parts – firstly, the account of a mental state as a functional state and, secondly, the requirement that a mental state have a physical realization. It is by referring to the second part of the theory that the functionalist can reply to the objection. For even if Bill and Ben are functionally equivalent, the physical realization of their different mental states will not be the same. Ben sees red when looking at red things and green when looking at green things, whereas the situation is reversed for Bill. However, it seems plausible that their different visual experiences will be realized by different internal (brain) states – different ones for seeing red and for seeing green. Therefore, we can explain why Bill and Ben have different visual experiences (despite being functionally equivalent) in terms of the different internal states. The physical realization of “seeing red” is different from that of “seeing green”. Thus functionalism may be able to account for the problem of the inverted spectrum. Will this solve the problem of “qualia”? Remember that qualia are those properties of our experience such as the bitterness of a taste, the stinging of a pain, etc. Can a purely physicalist theory like functionalism account for these “mental” properties? Are qualia fundamentally non-physical?