Functionalism - PowerPoint Presentation

Slide1

FunctionalismSlide2

Summary from last timeSlide3

“Multiple Realizability

”Slide4

Mental Multiple RealizabilitySlide5

The Argument

1. According to the Identity Theory, the belief (type) that Earth has water on it is identical to a certain brain-state type. Anyone who has a token of this belief type (anyone who believes the Earth has water on it)

must have

a token of that particular brain-state type.Slide6

2a. If we discover aliens, it is unlikely that they will have anything resembling human physiology. The probably won’t have “brains” as we know them, and they won’t have any of the same brain-state types we do.Slide7

2b. No robot, android, or computer has a brain. They are built out of metal and run electrically, not bio-chemically. Slide8

Therefore, if the Identity Theory is true:

3a. It is impossible for aliens to believe that Earth has water on it.

3b. It is impossible for robots, androids, or computers to believe that the Earth has water on it.Slide9

Since the same argument works for any belief state type, it follows that:

4. If the Identity Theory is true, then

it is impossible for aliens, robots, androids, and computers to have any beliefs at all

(or at least any beliefs that humans can also have).Slide10

And since the same argument works for any

mental

state type, it follows that:

4. If the Identity Theory is true, then

it is impossible for aliens, robots, androids, and computers to have any mental states at all

(or at least any mental states that humans can also have).Slide11

If the Identity Theory is true, it’s

impossible

for computers to want to take over the world.Slide12

If the Identity Theory is true, it’s

impossible

for aliens to want to take over the world.Slide13

Most philosophers say: big budget Hollywood movies are right. It

IS

possible for aliens or robots to want to take over the world.

Therefore,

the Identity Theory is false

.Slide14

functionalismSlide15

Functional Types

How do we understand the multiple

realizability

of the mental?

One way is to recognize that functional types are in general multiply realizable.Slide16

Functional Types

A functional type is a type of something that performs a certain task, does a particular job, or plays a certain role.

Any object that performs that task, does that job, or plays that role is a token of that type.Slide17

Example: Wings

From

Wikipedia: “A

wing

is a type of fin with a surface that produces lift for flight or propulsion through the

atmosphere.”

Any thing that is a fin, and produces lift for flight (or propulsion), is a wing.Slide18
Slide19

Example: Boat

From

Wikipedia: “A

boat

is a watercraft of any size designed to

float [hydrostatic lift]

or plane [hydrodynamic lift], to work or travel on water.”Anything designed to stay on top of water for the purpose of work or travel is a boat.Slide20
Slide21

Functionalism

So what is the job (function) of mental states? For different mental states, the answer is different.Slide22

Example: Pain

For example, the job of pain seems to be (1) to register bodily damage and (2) to cause aversion to the source of the damage.

So the functionalist might say:

any state

(not just human brain states) that performs these jobs is a pain stateSlide23

Example: Beliefs and DesiresSlide24

Comparison to Behaviorism

Stimulus

ResponseSlide25

Functionalism

Stimulus

Response

Other Mental StatesSlide26

Functionalism and the six features of mental statesSlide27

1. Some MSs

A

re Caused by the World

Brain states are caused by states of the world.

Brain states are what (in humans) play the pain roles, and the belief roles, and the desire roles.

According to functionalism, whatever plays the pain role

IS pain, whatever plays the belief role

IS belief, etc.Slide28

1. Some MSs

A

re Caused by the World

5. Therefore, according to functionalism, some mental states are caused by states in the world.Slide29

2. Some MSs Cause Actions

[A similar argument can be given here.]Slide30

3. Some MSs Cause Other MSs

(In Reason-Respecting Ways)

[Ravenscroft punts. CTM later.]Slide31

4. Some MSs are Conscious

[Ravenscroft punts. Zombies and inverted spectra to come.]Slide32

5. Some MSs Are Representational

[Ravenscroft punts. Conceptual role semantics later.]Slide33

6. MSs are Correlated with Brain States

Since brain states realize the functional roles of mental states, it’s not surprising that there’s a close connection here.

BUT, functionalism does not require that the correlation between my brain states and my mental states is the same as the correlation between your

b.s.s

and

m.s.s

. But it is!Slide34

Two famous arguments against functionalismSlide35

The “Blockhead” Objection

The first famous argument against functionalism was put forward by Ned Block.Slide36

Decision TableSlide37

You don’t have to be intelligent to use a decision table. To find out what to do, look up what the current situation is and do whatever the table tells you to do.Slide38

Logarithm TablesSlide39

Logarithm Tables

Logarithms are very difficult to calculate. But with a log table, anyone– no matter what their mathematical ability is– can figure out log

4

(372).Slide40

Block’s Decision Table

Block wants us to imagine him sitting down and writing a GIANT decision table. In it, he describes what he would do

in every possible situation

.

A lot of the entries require a lot of thought and intelligence– how he would respond to difficult questions, what he would do in morally ambiguous cases, etc.Slide41

Blockhead

Then Block imagines building a robot (“Blockhead”) and programming it like this:

The robot’s program includes the entire decision table and only one instruction: if you are in situation S, find situation S in the table, then do what the table tells you to do in situation S.Slide42

Blockhead

The robot now behaves exactly like Ned Block would in every situation.

It appears to be extremely intelligent– it answers difficult philosophical and mathematical questions. It says things that seem very heartfelt to Ned Block’s loved ones. It describes paintings in moving detail.Slide43

Blockhead is a Blockhead

BUT, we who know the robot’s programming know that it is not intelligent.

The robot didn’t make that clever observation because it was clever. Ned Block is clever: he made that observation. The robot is just repeating it, because that’s what’s in the decision table.Slide44

The Argument

Blockhead behaves in every possible situation just like Ned Block.

Therefore, Blockhead is functionally equivalent to Ned Block.

Therefore, if functionalism is true, Blockhead has all the same mental states as Ned Block.

Ned Block loves his daughter.

But Blockhead does not love Ned Block’s daughter– he’s just behaving as he’s told.Slide45

Objection

The inference from #1 to #2 is wrong. Block has confused functionalism and behaviorism.Slide46

Behaviorism

Stimulus

ResponseSlide47

Functionalism

Stimulus

Response

Other Mental StatesSlide48

Blockhead

Stimulus

ResponseSlide49

The China BrainSlide50

Functionalism and M.R.

Functionalism is committed to the multiple-

realizability

of mental states.

It does not matter

what

realizes a mental state– it can be a brain state, a state of an alien’s nervous system, a state in a computer, or a non-physical state of a non-physical substance– all that matters is that the state play that mental state’s functional roleSlide51

It does not matter that the realizers of my mental states are neurons that communicate with one another by chemical signals.Slide52

If you replaced one of them with something that sent the same signals in the same circumstances, then I would have the same mental states.Slide53

If you replaced

all

of them with something that sent the same signals in the same circumstances, then I would have the same mental states.Slide54

And if you replaced the chemical signals with radio signals, it wouldn’t matter as long as the pattern was the same.Slide55

The China BrainSlide56

The China Brain

Block suggests how we can thus make an intelligent creature out of people.

STEP 1: Identify and number every neuron in my brain. Slide57

The China Brain

Block suggests how we can thus make an intelligent creature out of people.

STEP 2: Find that many people in China and give them each a number and a cell phone.Slide58

The China Brain

Block suggests how we can thus make an intelligent creature out of people.

STEP 3: If neuron 54,820 sends a chemical signal to neuron 36 when it receives signals from neurons 946,777 and 342,001, then tell person 54,820 to call person 36 when she receives a call from person 946,777 and 342,001.Slide59

The China Brain

Block suggests how we can thus make an intelligent creature out of people.

STEPS 4 through 86,000,000,000: Do the same for every other neural connection. Make the people connected in exactly the same way as my neurons are connected.Slide60

The China Brain

Now the pattern of cell phone calls between people in China is EXACTLY LIKE the pattern of neural communications between neurons in my brain.

Since functionalism says that only the pattern matters, not the realizers, it doesn’t matter that people and phones realize this mind.Slide61

Ravenscroft’s Response

Ravenscroft suggests that it’s chauvinism to assume the China brain is not thinking/ is not conscious.

Other philosophers, notably Dan Dennett, have held the same view.Slide62

Wings Again

But I disagree. I don’t think the China brain has thoughts/ is conscious. But I also don’t think this is an objection to functionalism.

Being a wing is a multiply realizable property. It doesn’t matter what a thing is made of

as long as it can fly

.Slide63

Functionalism

Similarly, being a pain is multiply realizable. It doesn’t matter what it is,

so long as it is caused by bodily damage and causes avoidance behavior

.

But the China brain doesn’t have a body and it doesn’t avoid anything when it’s in “pain.”