Functionalism. SUMMARY FROM LAST TIME “Multiple Realizability”

Functionalism

SUMMARY FROM LAST TIME

“Multiple Realizability”

Mental Multiple Realizability

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.

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.

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

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.

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).

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).

If the Identity Theory is true, it’s impossible for computers to want to take over the world.

If the Identity Theory is true, it’s impossible for aliens to want to take over the world.

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.

FUNCTIONALISM

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.

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.

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.

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.

Functionalism

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

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 state

Example: Beliefs and Desires

Comparison to Behaviorism

Stimulus Response

Functionalism

Stimulus Response

Other Mental States

FUNCTIONALISM AND THE SIX FEATURES OF MENTAL STATES

1. Some MSs Are Caused by the World

1. Brain states are caused by states of the world.

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

3. According to functionalism, whatever plays the pain role IS pain, whatever plays the belief role IS belief, etc.

1. Some MSs Are Caused by the World

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

2. Some MSs Cause Actions

[A similar argument can be given here.]

3. Some MSs Cause Other MSs(In Reason-Respecting Ways)

[Ravenscroft punts. CTM later.]

4. Some MSs are Conscious

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

5. Some MSs Are Representational

[Ravenscroft punts. Conceptual role semantics later.]

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!

TWO FAMOUS ARGUMENTS AGAINST FUNCTIONALISM

The “Blockhead” Objection

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

Decision Table

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.

Logarithm Tables

Logarithm Tables

Logarithms are very difficult to calculate. But with a log table, anyone– no matter what their mathematical ability is– can figure out log4(372).

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.

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.

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.

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.

The Argument

1. Blockhead behaves in every possible situation just like Ned Block.

2. Therefore, Blockhead is functionally equivalent to Ned Block.

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

4. Ned Block loves his daughter.5. But Blockhead does not love Ned Block’s

daughter– he’s just behaving as he’s told.

Objection

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

Behaviorism

Stimulus Response

Functionalism

Stimulus Response

Other Mental States

Blockhead

Stimulus Response

The China Brain

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 role

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

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.

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.

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

The China Brain

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.

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.

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.

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.

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.

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.

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.

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.”