Transcript Functionalism

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 multiplerealizability 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 nonphysical 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.”