Functionalism Lecture 1 (1)

7/31/2019 Functionalism Lecture 1 (1)

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Functionalism

Functionalism came about as response to the perceived failings ofbehaviourism and type-identity theory.

Behaviourism: worry that mental states were not internal states that

were causes of behaviour or that could explain

behaviour

worry that no non-circular analysis could be given

Identity theory: worry about multiple realisability

Functionalism does not suffer from these worries.


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Functionalism:

mental states are the states they are in virtue of their function

Which function they have is defined in terms of the causal relations

that the states either actually, typically, or ought to, bear to other

states.

MentalState

Other mental states

Non-mental causes e.g.

objects in theenvironment,stimulation of the

sensory organs, etc.

Non-mental effects

e.g. bodilymovements, movingof objects in the

environment, etc.


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There are many things that seem to be the type of thing that they are

in virtue of their causal role:

Carburettors: mix oxygen and fuel for combustion

Thermometers: things that provide a variable output depending on

and correlating with the temperature.

Eyes: organs that allow a creature to gather information from its

environment using light waves.

In all these cases, the specific material that composes the thing seems

to be irrelevant.


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An example of a (crude) functional definition:

A state is a pain state if and only if it:

is typically caused by damage to the body

typically causes fear and anxiety and a desire to avoid the pain

stimulus

typically causes crying, wincing and groaning and attempts toavoid the pain stimulus.

We can see that just from such a definition there is no commitment to

whether the pain state should be a physical or non-physical state.

But most functionalists are physicalists and hold that mental states

are physical states.


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Over-coming previous problems:

Mental states can be internal states that cause behaviour and thatexplain behaviour.

Mental states can be multiply realised.

We can give a non-circular analysis via ramsification.

MentalState

Other mental states

Non-mental causes e.g.objects in theenvironment,

stimulation of thesensory organs, etc.

Non-mental effects

e.g. bodilymovements, moving

of objects in theenvironment, etc.


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Ramsification

Imagine explaining a game of

football to someone.

One might explain what a striker is

by reference to what a goalkeeper

is and vice versa

but you could give enough

information about the relationships

between all the players

and their relationships to the non-

players: ball, the net, the refereeetc.

so that if someone went to the football

game they could identify who was the

striker and who was the goal-keeper even

though these roles were inter-defined.


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Ramsification

Now imagine explaining the game

without mentioning goalkeepers

and strikers and just talking of two

different kinds of people and how

they interact.

And imagine defining a striker asbeing identical to one of the two

people so described.

This is ramsification: showing howone can take inter-defined terms

and define one of them with no

explicit reference to the others.


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Ramsification

Frank Plumpton Ramsey

(1903 - 1930)

Made fundamental contributions to

- economics

- mathematics

- probability and decision theory

- logic

- philosophy

Radio programme Better Than the Stars about Ramsey:

http://www.dspace.cam.ac.uk/handle/1810/3484


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Ramsification

Imagine a simple mental theory like this:

If a subject Ssuffers tissue damage and desires to avoid thatstimulus then S is in pain

Bold = mental states, Italic = non-mental terms

We can ramsify this theory by existentially generalising over the

mental terms:

There exists M1 and M2 such that if a subject Ssuffers tissue damage

and is in M2 then S is in M1.

Equivalently:

M1, M2 [T(M1, M2)](Note we have got rid of all talk of mental states.)

Now we can define pain:

S is in pain =def

M1

, M2

[T(M1

, M2

) and S is in M1

]


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Ramsification

Now we can define pain:

S is in pain = defM1, M2 [T(M1, M2) and S is in M1]

This says that S is in pain if and only if there is a mental state that is

related to other mental and non-mental states in the way that thetheory specifies and S is in that mental state.

But the other mental states are defined abstractly by their causalrelations to other states - so no worry about vicious circularity.


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While all functionalists agree on the above, there are many different

kinds of functionalism.

Here are some of the dimensions along which functionalist theoriescan vary:

(1) The vocabulary which the input and output relations are

characterised.

- Folk-psychology

- Various scientific vocabularies: e.g. neuroscience; computational

terms; scientific psychology

(2) The way in which one determines what the functional

specifications of mental states should be.

- a priori (yielding analytic or common-sense functionalism)

- a posteriori (yielding forms of empirical functionalism)


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(3) The width of the functional system

- inside the central nervous system

- inside the body- including the environment

(4) Whether the mental state is a role state or realiser state

Realiser state model:

MentalState

Other mental states

Non-mental causes e.g.objects in theenvironment,

stimulation of the

sensory organs, etc.

Non-mental effectse.g. bodily

movements, movingof objects in the

environment, etc.


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Role state model:

Being in a mental state is being in a second-order state: the state of

having the functional role occupied by some state

Both agree that someone is in pain iff someone is in state playing thepain role.

But the realiser view allows mental states like pain to be causes of

behaviour associated with theme.g. recoiling.

The role state view does not.


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In future lectures we will look at different types of functionalism that

vary along some of these dimensions.

First we will look at an influential form of functionalism:

Computational (or machine) functionalism:

the relation of the mind to the brain is that of a computer programme

to hardware.

Psychological states are defined in terms of computational processes

defined over psychological states.

We can explain what computational processes are by introducing the

notion of a Turing machine.

This type of functionalism is the philosophical theory behind

artificial intelligence.


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Alan Turing

(1912-1954)

- mathematician

- logician

- theoretical biologist

- philosopher

- enigma code-breaker in second world-war

- father of computing science

- great portrayal of his life by Derek Jacobi in the filmBreaking the

Code

-thought up the Turing machine


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A Turing machine has certain internal states.

You can input things into it and the machine can provide various

outputs.

The nature of each machine is specified by two functions:

(1) Tells the machine what to output when it is in its internal states

and some input comes in.

(2) Tells the machine what internal state to go into when it is in itsinternal states and some input comes in.

The functions will be conditionals like this:

If the machine is in internal state S1 and receives input I1 it will emit

output O1 and go into internal state S2.

A Turing machine has a finite number of internal states and inputs

and outputs.

The functions specify how the machine should behave for everypossible combination of input and internal state.


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Let's look at a very simple Turing machine:

a coke machine that gives you change.

- coke costs 1-it accepts 1 and 50p coins

The machine table for such a machine:

S1 S2

50p input

1 input

Emit nothing

Go to S2

Emit coke

Go to S1

Emit coke

Stay in S1

Emit cokeand 50p

Go to S1


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Instead of input being 50p or 1, and the output 50p and/or a coke,

we could imagine the input to be 50 cents or $1 and the output 50

cents and Irn Bru.

Often, people imagine the input and output of a Turing machine to besymbols on a tape.

Abstracting away from these differences we would get an abstract

specification of a machine table.

S1 S2

Input 1

Input 2

Output 1

Go to S2

Output 2

Go to S1

Output 2Stay in S

1

Output 1& 2Go to S1


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Machines can be made that implement different machine tables.

Turing showed how to make a machine that would implement any

machine table.

You could feed the machine different machine tables to act in

accordance with.

The machine table is a computer programme.

Such a machine is called a UniversalTuring Machine, fore-runner of the

general purpose computer.

By specifying the appropriate machine table

we can get a computer to do many differentthings

- add, divide, work out complex mathematical

functions, play chess, do word processing,

run Tomb Raider.


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A Turing machine that would produce our behaviour, given

appropriate inputs could either reflect the causal workings of our

brain or not reflect them.

Some philosophers think that any Turing machine that replicates theappropriate behaviour (outputs), given the right inputs specifies an

adequate psychology for a creature

Such philosophers believe in input-output functionalism.

Others require that the causal relations specified by the machine table

be of a certain kind, for example:

must be suitably complex must be like the actual causal processes in the human brain/mind.


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Turing was an input-ouput functionalist.

He developed the Turing Test - an operational test for mentality.

Operationalism: a programme in philosophy of science that aims to

define scientific concepts via experimental procedures and empirical

tests.

The idea is that is if a Turing machine can do as well as humans on

certain appropriate intellectual tasks then they must be judged to be

no less psychological (intelligent or thinking) than humans.


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"If the meanings of the words 'machine' and 'think' are to be found by

examining how they are commonly used it is difficult to escape the

conclusion that the meaning and the answer to the question, 'Canmachines think?' is to be sought in a statistical survey such as a

Gallup poll. But this is absurd. Instead of attempting such a definition

I shall replace the question by another, which is closely related to it

and is expressed in relatively unambiguous words.

- Alan Turing (1950) in "Computing Machinery and Intelligence" in

Minds, Brains and Computers, edited by Cummins and Cummins,

2000, Blackwell, p. 153.


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"'Can machines think?' should be replaced by 'Are there imaginable

digital computers which would do well in the imitation game?'"

-Alan Turing (ibid. p. 158)

Next time, Ill describe what the imitation game is.

Functionalism Lecture 1 (1)

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