Philosophy of Mind (Continued)
On Monday:
• Dualism
• Logical Behaviorism
• Methodological behaviorism
Today:
• The Mind/Brain Identity Theory
• Functionalism
The Mind/Brain Identity Theory
Water = H2O
Mind = Brain
The Mind/Brain Identity Theory
Water = H2O
Mind = Brain
This is a conclusion reached by science. You can’t tell
what the mind is just by thinking really hard, as
Descartes’ and Ryle’s arguments assumed.
The Mind/Brain Identity Theory
Materialism:
All physical events have physical
explanations, including human behavior.
The Materialist Slogan:
No mental difference without a physical
difference
The Materialist Slogan:
No mental difference without a physical
difference
Materialism:
There must be some physical difference
between someone who loves jazz and
someone who hates jazz.
Dualism:
Someone who loves jazz could be physically
identical to someone who hates jazz.
The Materialist Slogan:
No mental difference without a physical
difference
According to Identity Theory:
Dualism gets more and more implausible as we
learn more about the nervous system.
The Materialist Slogan:
No mental difference without a physical
difference
According to Identity Theory:
Dualism gets more and more implausible as we
learn more about the nervous system.
Dualism made sense before we had any way of
knowing which physical differences correlated
with loving jazz.
Now we know.
2,000 years ago, Lucretius was a materialist
before it was cool. He believed that the mind is
part of the body, so when the body dies, the
mind does too.
But Lucretius thought the mind was more like a
hormone—a chemical substance.
2,000 years ago, Lucretius was a materialist
before it was cool. He believed that the mind is
part of the body, so when the body dies, the
mind does too.
But Lucretius thought the mind was more like a
hormone—a chemical substance.
Since then, the materialist account of the mind
has gotten much better.
In the same manner, the materialist account of
lightning has also improved. In Lucretius’s time,
many seriously believed that lightning was
made by Zeus.
This was not just a cute story.
In the same manner, the materialist account of
lightning has also improved. In Lucretius’s time,
many seriously believed that lightning was
made by Zeus.
This was not just a cute story.
At the time, this was literally the best
explanation for lightning and thunder.
According to Identity Theory:
The materialist account of the mind has
gotten a lot better, just as the materialist
account of lightning has gotten a lot better.
According to Identity Theory:
The materialist account of the mind has
gotten a lot better, just as the materialist
account of lightning has gotten a lot better.
Indeed, materialism is now the best
explanation for both kinds of events.
Like Lucretius, we may not know exactly which
physical event correlates with each and every
mental event, but we can safely conclude that
some physical event correlates with each and
every mental event.
Like Lucretius, we may not know exactly which
physical event correlates with each and every
mental event, but we can safely conclude that
some physical event correlates with each and
every mental event.
Identity between mind and brain is offered
as the best explanation for these
correlations.
The best explanation for correlations
between mental events and neurological
events is identity:
The best explanation for correlations
between mental events and neurological
events is identity:
Why is activity in a specific part of the brain
always correlated with the enjoyment of
jazz?
Because that’s what it is to enjoy jazz:
activity in that part of the brain just is the
enjoyment of jazz.
The best explanation for correlations
between mental events and neurological
events is identity:
Why is activity in a specific part of the brain
always correlated with the enjoyment of
jazz?
Because that’s what it is to enjoy jazz:
activity in that part of the brain just is the
enjoyment of jazz.
Do you agree with this?
activity in that part of the brain just is the
enjoyment of jazz.
According to Identity Theory:
Dualism is like Vitalism. Both theories posit
some special substance as the best
explanation for something, but we can now
explain those same observations without
positing that substance.
Vitalism:
There is a physical substance—a “vital fluid”—
found only in living things. It is the best
explanation for what living things all share, and
for the differences between living and non-living
things.
Vitalism:
There is a physical substance—a “vital fluid”—
found only in living things. It is the best
explanation for what living things all share, and
for the differences between living and non-living
things.
Dualism:
There is a non-physical substance—a “soul”—
found only in humans. It is the best explanation
for mental events.
Vitalism posits a physical substance, while
Dualism posits non-physical substance.
Vitalism posits a physical substance, while
Dualism posits non-physical substance.
Still, Identity Theory says,
both posits are superfluous.
Identity Theory:
The concept of a soul does no
explanatory work.
(Like the concept of “vital fluid”)
Identity Theory:
The concept of a soul does no
explanatory work.
(Like the concept of “vital fluid”)
We need a materialist theory anyway, to
explain physical things. This same theory can
now explain everything Dualism was supposed
to explain, but without positing any special
substances.
Identity Theory:
The materialist theory of the mind is a
better explanation for mental events
than dualism.
Identity Theory:
The materialist theory of the mind is a
better explanation for mental events
than dualism.
What makes it better?
Identity Theory:
The materialist theory of the mind is a
better explanation for mental events
than dualism.
What makes it better?
Parsimony.
We need a materialist theory anyway.
We need to explain physical phenomena regardless
of what we say about mental phenomena.
If this same theory can also explain all
mental phenomena, then why bring in some
different, additional theory to explain those
phenomena?
Materialism explains both physical phenomena
and mental phenomena, in one unified theory.
Dualism only explains mental phenomena.
Materialism explains both physical phenomena
and mental phenomena, in one unified theory.
Dualism only explains mental phenomena.
All else being equal, a theory that both explains
and unifies provides a better explanation than
one that just explains, without unifying.
Materialism explains both physical phenomena
and mental phenomena, in one unified theory.
Dualism only explains mental phenomena.
All else being equal, a theory that both explains
and unifies provides a better explanation than
one that just explains, without unifying.
Thus, materialism provides a better
explanation for mental events than dualism.
Materialism explains both physical phenomena
and mental phenomena, in one unified theory.
Dualism only explains mental phenomena.
All else being equal, a theory that both explains
and unifies provides a better explanation than
one that just explains, without unifying.
???
Thus, materialism provides a better
explanation for mental events than dualism.
In Groups:
Provide support for this premise. Why is a
unifying theory better than a non-unifying
theory?
All else being equal, a theory that both explains
and unifies provides a better explanation than
one that just explains, without unifying.
???
By definition, non-unified theories employ novel
concepts, which can’t be defined in terms of
concepts we are already committed to.
By definition, non-unified theories employ novel
concepts, which can’t be defined in terms of
concepts we are already committed to.
The Principle of Parsimony
Only posit novel concepts when you really have
to, because your existing concepts can’t do the
job.
According to Identity Theory, existing
concepts can do the job.
The Principle of Parsimony
Only posit novel concepts when you really have
to, because your existing concepts can’t do the
job.
In Groups:
Do you agree that we should only posit novel
concepts when our existing concepts prove
inadequate?
Are parsimonious theories more likely to be true, or
is parsimony good for some other reason?
(Recall the justification of induction...)
Functionalism
Functionalism
Functionalism shares the Identity Theory’s
commitment to materialism, and its rejection
of dualism.
However, it also finds problems with the
Identity Theory.
Functionalism
Functionalism agrees with Identity Theory
that every token mental state is identical with
some token brain state.
But it disagrees that every type of mental
state is identical with some type of brain
state.
What does this mean?
Tokens vs. Types
Tokens: particular, specific, concrete
instances.
Example: the particular instance of redness
displayed by a particular apple
Types: general kinds, or properties, which
may take many different instances.
Example: the property of being red in general.
Tokens vs. Types
Tokens: particular, specific, concrete
instances.
My homesickness, when I was at summer camp at
age 10, is a token mental state.
Types: general kinds; properties that may
have many different instances.
Homesickness in general, across all particular
instances, is a mental type.
Functionalism agrees that token mental
states are identical with token brain states.
My homesickness, when I was at summer camp at
age 10, was identical with a certain state of my brain
at the time.
Functionalism agrees that token mental
states are identical with token brain states.
My homesickness, when I was at summer camp at
age 10, was identical with a certain state of my brain
at the time.
But it denies that types of mental state are
identical with types of brain state.
Homesickness in general is not identical with any
one type of brain state.
According to Functionalism:
Psychological types, or properties, can be
realized in multiple ways.
According to Functionalism:
Psychological types, or properties, can be
realized in multiple ways.
Multiple Realizability sounds complicated, but
it’s very simple. It just means that a property or
type can be instantiated in physically different
ways.
A wooden spoon and a metal spoon are physically
different, but they’re still instances of the same
type: spoon.
According to Functionalism:
Psychological types, or properties, can be
realized in multiple ways.
Just as two objects can be physically different
and yet both be spoons, two mental states can
be physically different and yet both be
instances of the same kind of mental state.
There were probably a few physical differences
between E.T.’s nervous system and our
nervous systems.
Still, isn’t E.T. capable of
homesickness, just as we
are? Isn’t that type of mental
state still the best explanation
of his behavior? Why would
physical details about how
homesickness is realized make
any difference?
Still, isn’t E.T. capable of
homesickness, just as we
are? Isn’t that type of mental
state still the best explanation
of his behavior? Why would
physical details about how
homesickness is realized make
any difference?
Homesickness is a mental type that can be
realized within different physical systems.
If Michael Jackson can get homesick, so can
E.T. It doesn’t matter what their brains are like.
According to functionalism, mental states
are defined by their functions (like spoons).
And functions are multiply realizable.
According to functionalism, mental states
are defined by their functions (like spoons).
And functions are multiply realizable.
Functions are defined by goal-states—what matters
is just that some goal is achieved. It doesn’t matter
how the goal achieved.
Wooden spoons and metal spoons both achieve the
goal of scooping food, so they’re both spoons.
Likewise, a heart and a pacemaker perform the
same function, but in physically different ways.
Likewise, a heart and a pacemaker perform the
same function, but in physically different ways.
Functionalism implies that it’s possible (in
principle) to have ”mental pacemakers”—
artificial brain systems that perform the
functions of the mind.
Likewise, a heart and a pacemaker perform the
same function, but in physically different ways.
Functionalism implies that it’s possible (in
principle) to have ”mental pacemakers”—
artificial brain systems that perform the
functions of the mind.
As long as artificial systems perform the
functions of the mind, they are the mind.
So Functionalism makes an identity claim of its
own:
Mental states and processes are identical
to the functional properties of the brain.
Mind = “design facts” of the brain
Mind/Brain Identity: mental states and
processes are identical to the physical
properties of the brain.
Mind/Brain Identity: mental states and
processes are identical to the physical
properties of the brain.
Functionalism: mental states and processes
are identical to the functional properties of the
brain.
Mind/Brain Identity: mental states and
processes are identical to the physical
properties of the brain.
To instantiate the same mental state, you must
instantiate the same
physical
properties.
Functionalism:
mental
states
and processes
are identical to the functional properties of the
brain.
Mind/Brain Identity: mental states and
processes are identical to the physical
properties of the brain.
To instantiate the same mental state, you must
instantiate the same
physical
properties.
Functionalism:
mental
states
and processes
are identical to the functional properties of the
brain.
So anything that performs these functions can count
as a mental state or process—it doesn’t have to be a
brain at all.
anything that performs these functions can count
as a mental state or process—it doesn’t have to be a
brain at all.
As long as artificial systems perform the
functions of the mind, they are the mind.
anything that performs these functions can count
as a mental state or process—it doesn’t have to be a
brain at all.
As long as artificial systems perform the
functions of the mind, they are the mind.
Artificial intelligence—along with the rest
of cognitive science—is based on
functionalism.
anything that performs these functions can count
as a mental state or process—it doesn’t have to be a
brain at all.
Discuss:
Suppose a woman is in a car accident, and suffers
brain damage. As a result, she loses the ability to add
and subtract.
Now suppose neurosurgeons implant a calculator
directly in her brain, so she’s able to add and subtract
again.
Are the activities of the calculator literally the
woman’s own mental processes?
Functionalism in Different Fields
On Monday we discussed the difference between
psychology and philosophy of mind, and I just
said that cognitive science is founded on
functionalism.
So let’s consider how functionalism fares in
each of these three separate fields:
1) Cognitive Science
2) Psychology
3) Philosophy of Mind
Functionalism in Different Fields
First, what was the difference between
psychology and philosophy of mind?
Functionalism in Different Fields
First, what was the difference between
psychology and philosophy of mind?
Philosophy has a wider scope than
psychology:
While psychology is limited to questions about how
the mind predicts and explains behavior, philosophy
can address any question about the mind.
Functionalism in Different Fields
Now, what is the difference between
psychology and cognitive science?
Functionalism in Different Fields
Now, what is the difference between
psychology and cognitive science?
Cognition = representation
Cognitive science, too, is limited to explanation and
prediction—it’s a science, after all.
But it doesn’t focus on behavior. Computer science
is cognitive science, because it’s based on using
representations (symbols of code).
Functionalism in Different Fields
Last, (to be thorough) what is the difference
between cognitive science and philosophy?
Functionalism in Different Fields
Last, (to be thorough) what is the difference
between cognitive science and philosophy?
Again, philosophy is wider in scope.
Cognitive science is limited to the role of
representations in explaining and predicting things.
Philosophy can ask any kind of question about
representations.
Functionalism in Different Fields
Cognitive science doesn’t actually need to
address questions about the mind at all.
You can build a robot whether or not you believe
that the robot truly has a mind, and whether or not
you think its cognitive operations are genuinely
mental operations.
Functionalism in Different Fields
Cognitive science doesn’t actually need to
address questions about the mind at all.
You can build a robot whether or not you believe
that the robot truly has a mind, and whether or not
you think its cognitive operations are genuinely
mental operations.
Still, all of cognitive science is based on the
functions of representations.
Functionalism in Different Fields
So cognitive science is based on a functionalist
notion of cognition.
It’s a separate question whether this view of
cognition should also be the basis for our
concept of mind.
Functionalism in Different Fields
So cognitive science is based on a functionalist
notion of cognition.
It’s a separate question whether this view of
cognition should also be the basis for our
concept of mind.
This is not a question of prediction.
Functionalism in Different Fields
So cognitive science is based on a functionalist
notion of cognition.
It’s a separate question whether this view of
cognition should also be the basis for our
concept of mind.
This is not a question of prediction.
Whether the mind is identical with functional
states is a question for philosophy, not cognitive
science.
Functionalism in Different Fields
What about functionalism in psychology?
Functionalism in Different Fields
What about functionalism in psychology?
Psychology is mostly based on
functionalism.
In my opinion, it should be entirely based on
functionalism.
Functionalism in Different Fields
Good psychology (my opinion):
Jack recognized Jill because in his mind there is a
system with the function of face-recognition.
The system has this function for the same reason that
Jack’s heart has its function: natural selection.
We explain behavior by positing systems
that have functions.
Functionalism in Different Fields
In practice, however, much of psychology is
devoted simply to observing behavior,
without really explaining it.
CLAIM: People have a “need for mystery” that causes
them to resist scientific explanations.
Is this an explanation, or just a description?
Functionalism in Different Fields
In practice, however, much of psychology is
devoted simply to observing behavior,
without really explaining it.
CLAIM: People have a “need for mystery” that causes
them to resist scientific explanations.
Is this an explanation, or just a description?
The mind does not contain a Need-for-Mystery
System, with a function determined by
selection.
Functionalism in Different Fields
What about functionalism in philosophy of
mind?
Since philosophy can ask any question about
the mind, I think it identifies some questions
that functionalism doesn’t answer very well.
The biggest one is the question of conscious
experience.
Chalmers (1995):
“The really hard problem of consciousness is the
problem of experience. When we think and perceive,
there is a whir of information-processing, but there is
also a subjective aspect. As Nagel (1974) has put it,
there is something it is like to be a conscious
organism. This subjective aspect is experience....
Why is it that when our cognitive systems engage in
visual and auditory information-processing, we have
visual or auditory experience: the quality of deep blue,
the sensation of middle C?”
Chalmers (1995):
“The really hard problem of consciousness is the
problem of experience. When we think and perceive,
there is a whir of information-processing, but there is
also a subjective aspect. As Nagel (1974) has put it,
there is something it is like to be a conscious
organism. This subjective aspect is experience....
Why is it that when our cognitive systems engage in
visual and auditory information-processing, we have
visual or auditory experience: the quality of deep blue,
the sensation of middle C?”
How can knowledge of functional systems
explain what mental events feel like to the
subject?
Functionalism in Different Fields
We can implant a calculator in someone’s
brain, thereby restoring the informationprocessing functions of addition and
subtraction.
But what could this tell us about what it’s like,
from the woman’s subjective point of view, to
do addition and subtraction with an implant?
Scientific explanations of behavior are
objective, not subjective. We can’t observe
and measure what it’s like to experience things.
Yet, the ordinary, common-sense concept of the
mind often involves features of subjective
experience.
Imagine your doctor saying this:
“Objectively, this is going to hurt. You’ll probably contort
your face and scream out loud. But don’t worry. There’s
no evidence that you’ll actually feel anything from the
subjective point of view.”
So functionalism seems to work beautifully
in science.
(Even better than many psychologists recognize.)
So functionalism seems to work beautifully
in science.
(Even better than many psychologists recognize.)
But when we start asking non-scientific
questions about the mind—questions that
aren’t about predicting observable
behavior—it’s not clear that functionalism
fares as well.
The “Big” Essays and the review session
are due next Wednesday.