Professor Shelly Kagan:
Today we're going to take up the
discussion where we left it last
time.
We were talking about two main
positions with regard to the
question, "What is a person?"
On the one hand,
we have the dualist view;
that's the view that we spent a
fair bit of time sketching last
meeting.
The dualist view,
according to which a person is
a body and a soul.
Or perhaps, strictly speaking,
what we should say is the only
part that's essential to the
person is the soul,
though it's got a rather
intimate connection to a
particular body.
That's the dualist view.
In contrast to that,
we've got the physicalist view,
according to which there are
just bodies.
A person is just a body,
as we might put it.
Now, the crucial point here,
the point I was turning to as
we ended last time,
is that although a person on
the physicalist view is just a
body, a person isn't just any
old body.
A person is a body that has a
certain set of abilities,
can do a certain array of
activities.
People are bodies that can
think, that can communicate,
that are rational,
that can plan,
that can feel things,
that can be creative,
and so forth and so on.
Now, we might argue about
what's the exact best list of
those abilities.
For our purposes,
I think that won't be crucial,
and so I'll sometimes talk
about this set of abilities
without actually having a
canonical list.
Just think of them as the set
of abilities that people have,
the things that we can do that
other physical objects--chalk,
radios, cars--those things
can't do.
Call those the abilities that
make something a person.
To just introduce a piece of
jargon, we could call those the
P abilities,
P for person.
Or we could talk about the
various kinds of ways--this is
the physicalist way of thinking
about it--according to the
physicalist,
a person is just a body that
has the ability to fulfill the
various P functions.
And we can talk,
then, about a person as a
P-functioning body.
Or we could say that a person
is a body that is
P-functioning.
It's important to see that the
idea is, although it's a body,
it's not just any old body.
Indeed, it's not just any old
human body.
After all, if you rip out your
gun, shoot me in the heart,
I bleed to death,
we still have a human body in
front of us.
But we don't have a
P-functioning body.
We don't have a body that's
able to think,
a body that's able to plan,
to communicate,
to be creative,
to have goals.
So the crucial thing about
having a person is having a
P-functioning body.
Now, what's a mind on this view?
On the physicalist view,
it's still perfectly legitimate
to talk about minds.
The point, though,
is that from the physicalist
perspective, the best thing to
say is,
talk about a mind is a way of
talking about these various
mental abilities of the body.
We nominalize it.
We talk about it using a noun,
the mind.
But talk of the mind is just a
way of talking about these
abilities that the body has when
it's functioning properly.
This is similar,
let's say, to talking about a
smile.
We believe that there are
smiles.
Physicalists don't deny that
there are minds.
Just like we don't deny,
we all believe,
that there are smiles.
But what is a smile?
Well, a smile is just a way of
talking about the ability of the
body to do something.
This characteristic thing we do
with our lips exposing our teeth
and so forth.
It's a smile,
a rather dorky smile,
but there's a smile.
Now, if you were listing the
parts of the body,
you would list the teeth,
you would list the lips,
you would list the gums,
you would list the tongue,
but you wouldn't list the
smile.
So, should we conclude,
as dualists,
that smiles are these extra
nonphysical things that have a
special intimate relationship
with bodies?
Well, you could imagine a view
like that, but it would be
rather a silly view.
Talk about a smile is just a
way of talking about the body's
ability to smile.
There's no extra part.
Even though we have a noun,
the smile, that if you're not
careful might lull you into
thinking there must be a thing,
the smile.
And then you'd have all these
metaphysical conundrums.
Where is the smile located?
It seems to be in the vicinity
of the mouth.
But the smile isn't the lips.
The smile isn't the teeth.
So it must be something
nonphysical.
No, that would just be a silly
way to think about smiles.
Talk of smiles is just a way of
talking about the ability of the
body to smile,
to form a smile.
That's an ability that we have,
our bodies have.
Similarly, then,
according to the physicalist,
talk of the mind,
despite the fact that we have a
noun there,
is just a way of talking about
the abilities of the body to do
various things.
The mind is just a way of
talking about the fact that our
body can think,
can communicate,
can plan, can deliberate,
can be creative,
can write poetry,
can fall in love.
Talk of all of those things is
what we mean by the mind,
but there's no extra thing,
the mind, above and beyond the
body.
That's the physicalist view.
So it's important,
in particular,
to understand that from the
physicalist's point of view,
the mind is not the brain.
You might think,
"Look, according to
physicalists minds are just
brains."
And that wouldn't be a
horrendously misleading thing to
say, because according to the
best science that we've got,
the brain is the part of the
body that is the seat or house
or the underlying mechanical
structure that gives us these
various abilities.
These P functions are
functions that we have by virtue
of our brain.
So that might tempt you into
saying the mind on the
physicalist view is just a
brain.
But we probably shouldn't say
that.
After all, if you shoot me,
there's my corpse lying on the
stage.
Well, there's my brain.
My brain is still there in my
head.
But we no longer have a person.
The person has died.
The person, it seems,
no longer exists.
Whether strictly that's the
best thing to say or not is a
question we'll have to come to
in a couple of weeks.
But it seems pretty clear that
the mind has been destroyed,
even though the brain is still
there.
So I think, at least when
there's the need to be
careful--maybe we don't normally
have a need to be careful--but
when there's the need to be
careful,
we should say,
talk of the mind is a way of
talking about the
P-functioning of the
body.
Our best science suggests that
a well-functioning body can
perform these things,
can think and plan and fall in
love by virtue of the fact that
the brain is functioning
properly.
That's the physicalist view.
On the dualist view,
what was death?
Death is presumably the
separation of the mind and the
body, perhaps the permanent
separation, with the destruction
of the body.
What's death on the physicalist
view?
Well, there is no extra entity,
the soul.
The mind is just the proper
P-functioning of the
body.
So, the mind gets destroyed
when the ability of the body to
function in that way has been
destroyed.
Death is, roughly,
the end of this set of
functioning.
Again, this probably should be
cleaned up and in a couple of
weeks we'll spend a day or half
period trying,
to clean it up and make it
somewhat more precise.
But there's nothing mysterious
about death from the physicalist
point of view,
at least about the basic idea
of what's going on in death.
I've got a stereo.
Suppose I hold up my boombox
for you and it's playing music.
It's one of the things it can
do.
And I drop in on the ground,
smashing it.
Well, it no longer can function
properly.
It's broken.
There's no mystery why it can't
function once it's broken.
Death is basically just the
breaking down of the body,
on the physicalist point of
view, so that it no longer
functions properly.
One other point worth
emphasizing and sketching the
physicalist view is this.
So, as I said,
physicalists don't deny that
there are minds.
Even though we say "we're just
bodies," that doesn't mean that
we're just any old body.
It's not as though the
physicalist view is,
"we're bodies that have some
illusion of thinking."
No, we're bodies that really do
think.
So there really are minds.
We could, on the physicalist
point of view,
call those souls.
Just like there's no danger in
talking of the mind from the
physicalist perspective,
there wouldn't be any serious
danger in talking about a soul.
And so, in certain contexts,
I'm perfectly comfortable--in
my physicalist moods,
I am perfectly
comfortable--talking about this
person's soul.
He's got a good soul,
a bad soul, how the soul soars
when I read Shakespeare,
or what have you.
There's nothing upsetting or
improper about the language of
the soul, even on the
physicalist point of view.
But in this class,
just to try to keep us from
getting confused,
as I indicated before and I
want to remind you,
I'm going to save the word
"soul";
I'm going to at least try to
save the word "soul" for when
I'm talking about the dualist
view.
So we might put it this way.
The neutral term is going to be
"mind."
We all agree that people have
minds, sort of the house or the
seat of our personalities.
The question is,
"What is a mind?"
The dualist position is that
the mind is a soul and the soul
is an immaterial object.
So when I use the word "soul,"
I will try to reserve it for the
metaphysical view,
according to which souls are
something immaterial.
In contrast to that,
we've got the physicalist view.
Physicalists also believe in
minds.
But minds are just a way of
talking about the abilities of
the body.
So physicalists do not believe
in any immaterial object above
and beyond the body that's part
of a person.
Just to keep things clear,
I will say that physicalists,
materialists,
do not believe in souls.
Because, for the purposes of
this class, I'm going to reserve
the word "soul" for the
immaterialist conception of the
mind.
In other contexts--no harm in
talking about souls.
So these are the two basic
positions: the dualist view on
the one hand,
the physicalist view on the
other.
The question we need to turn
to--I take it that just as the
dualist view is a familiar one,
so it's true that the
physicalist view is a familiar
one.
Whether or not you believe it,
you are familiar with the fact
that some people believe it,
or at least you wonder whether
it's true.
Does science require that we
believe in the physicalist view
or not?
The question we want to turn
to, then, is,
"Which of these two views
should we believe:
the dualist position or the
physicalist position?"
And the crucial question,
presumably, is,
"Should we believe in the
existence of a soul?"
Both sides believe in bodies.
As I say, the dualist position,
as we're understanding it,
is not a view that says there
are only minds,
there are no bodies.
Dualists believe that there are
bodies.
They believe that there are
souls as well as bodies.
Physicalists believe there are
bodies but no souls.
So there's an agreement that
there are bodies.
Here is one.
Each one of you is sort of
dragging one around with you.
There's agreement that there's
bodies.
The question is,
"Are there anything beyond
bodies?"
Is there anything beyond the
body?
Is there a soul?
Are there souls?
That's the question that's
going to concern us for a couple
of weeks.
If we ask ourselves,
"What reasons do we have to
believe in a soul?"
we might start by asking,
what reasons do we have to
believe in anything?
How do we prove the existence
of things?
For lots of familiar everyday
objects, the answer is fairly
straightforward.
We prove their existence by
using our five senses.
We just see them.
How do I know that there are
chairs?
Well, there are some chairs in
front of me.
Open my eyes, I see them.
How do I know that there is a
lectern?
Well, I see it.
I can touch it.
I feel it.
How do I know that there are
trees?
I see them.
How do I know that there are
birds?
I see them.
I hear them.
How do I know that there are
apples?
I see them.
I taste them.
So forth and so on.
That approach pretty clearly
isn't going to work for souls,
because a soul--and again,
we've got in mind this
metaphysical view,
according to which its
something immaterial--isn't
something we see.
It's not something we taste or
touch or smell or hear.
We don't directly observe souls
with our five senses.
You might wonder,
well, don't I sort of directly
observe it in myself that I have
a soul?
Although I guess there have
been people who've made that
sort of claim,
it seems false to me.
I can only ask each of you to
sort of introspect for a second.
Turn your mind's eye inward and
ask.
Do you see a soul inside you?
I don't think so.
I see things outside me.
I feel certain sensations in my
body, but it doesn't seem as
though I observe a soul.
Even if I believe in a soul,
I don't see it.
How do we prove the existence
of things we can't see or hear
or taste and so forth?
The usual method,
maybe not the only method,
but the usual method is
something like this.
Sometimes, we posit the
existence of something that we
can't see so as to explain
something else that we all agree
takes place.
Why do I believe in the
existence of atoms?
I don't see individual atoms.
Why do I believe in the
existence of atoms so small that
I can't see them?
Because atomic theory explains
things.
When I posit the existence of
atoms with certain structures
and certain sort of ways of
interacting and combining and
building up,
when I posit atoms,
suddenly I can explain all
sorts of things about the
physical world.
So, I infer the existence of
atoms based on the fact that
doing that allows me to explain
things that need explaining.
This is a kind of argument that
we use all the time.
How do I posit--why do I
believe in x-rays,
even though I don't see them?
Because doing that allows me to
explain certain things.
Why do I believe in certain
planets too far away to be
observed directly through a
telescope?
Because positing them allows
you explain things about the
rotation of the star or the
gravitational fluctuations,
what have you.
We make inferences to the
existence of things we can't
see, when doing that helps us to
explain something we can't
otherwise explain.
This pattern of argument,
which is ubiquitous,
is called "inference to the
best explanation."
I want to emphasize this bit
about "best explanation."
What we're justified in
believing are those things that
we need, not simply when they
would offer us some kind of
explanation,
but when they offer us the best
explanation that we can think
of.
So look, why am I justified in
believing in germs,
various kinds of viruses that I
can't see, or bacteria or what
have you, that I can't see?
Because doing that allows me to
explain why people get sick.
But there's other things that
would allow me to explain that
as well.
How about demons?
I could believe in demons and
say, "Why does a person get sick
and die?
Well, it is demonic possession."
Why aren't I justified in
believing in the existence of
demons?
It's a possible explanation.
But what we seem to be
justified in believing is not
just any old explanation,
but the "best explanation."
So we've got two rival
explanations.
We've got, roughly,
germ theory and we've got demon
theory.
We have to ask ourselves,
"Which of these does a better
job of explaining the facts
about disease?"
Who gets what kinds of diseases?
How diseases spread,
how they can be treated or
cured, when they kill somebody.
The fact of the matter is,
demon theory doesn't do a very
good job of explaining disease,
while germ theory does do a
good job.
It's the better explanation.
So we're justified in believing
in germs, but not demons.
It's a matter of inference,
not just to any old
explanation, but inference to
the best explanation.
All right, so,
what we need to ask ourselves,
then, is, "What about the
soul?"
We can't observe souls.
But here's a possible way of
arguing for them.
Are there things that need to
be explained that we could
explain if we posited the
existence of a soul,
an immaterial object,
above and beyond the body?
Are there things that the
existence of a soul could
explain and explain better than
the explanation that we would
have if we had to limit
ourselves to bodies?
You might put it this way as
sort of the easiest version of
this kind of argument,
for our purposes.
Are there things about us that
the physicalist cannot explain?
Are there mysteries or puzzles
about people that the
physicalist just draws a blank,
but if we become dualists,
we can explain these features?
Suppose there was a feature
like that, feature F.
Then we'd say,
"Look, although we can't see
the soul, we have reason to
believe in the soul,
because positing the existence
of a soul helps us to explain
the existence of feature F,
which we all agree we've got."
Suppose it was true that you
couldn't explain love from the
physicalist perspective.
But we all know that people do
fall in love,
but souls would allow us to
explain that.
Boom, we'd have an argument for
the existence of a soul.
It would be an example of
"inference to the best
explanation."
Now, the crucial question,
of course, is,
"What's the relevant feature
F?"
Is there some feature that the
physicalist can't explain and so
we need to appeal to something
extra-physical to explain it?
Or the physicalist can only do
a rotten job of explaining,
like demon theory did?
And then, if we were to appeal
to something nonphysical,
we would do a better job of
explaining.
If we could find the right
F, and make out the
argument, the physicalist can't
explain it or does a bad job of
explaining it and the dualist
does a better job of explaining
it,
we'd have reason to believe in
the soul.
Like all arguments in
philosophy, it would be a
tentative argument.
We'd sort of have some reason
to believe in the soul until we
sort of see what next argument
comes down the road.
But at least it would give us
some reason to believe in the
soul.
What I want to do is ask,
"What might feature F
be?"
Is there any such feature
F?
It's probably also worth
underlining the fact that what
I've really been doing is
running through a series of
arguments.
"Inference to the best
explanation" is not a single
argument for the soul.
It's rather the name for a
kind of argument.
Depending on what F you
fill in the blank with,
what pet feature or fact you're
trying to explain by appeal to
the soul,
you get a different argument.
So let's ask ourselves,
"Are there things that we need
to appeal to the soul in order
to explain these things about
us?"
Here's a first try.
Actually, let me start by
saying I'm going to distinguish
two broad families of
characteristics we might appeal
to.
We might say,
one set of approaches focus on
ordinary, familiar,
everyday facts about us.
The fact that we love,
the fact that we think,
the fact that we experience
emotions, what have you--these
are ordinary features of us.
I'm going to start with those
and then I'll turn,
eventually, to another set of
possible things that might need
explaining,
which we might think of as
extraordinary,
supernatural things.
Maybe there are certain
supernatural things about
communication from the dead or
near-death experiences that need
to be explained in terms of the
soul.
We'll get to those,
but we'll start with ordinary,
everyday, hum-drum facts about
us.
Even though they're ordinary
and familiar,
it still could turn out that we
need to appeal to souls in order
to explain them.
So, to start, how about this?
Start with a familiar fact,
which I've already drawn your
attention to a couple of times,
that you can have a body that's
dead.
You could have a corpse,
and that's clearly not a
person.
It's not a living being.
It's not a person.
It doesn't do anything.
It just lies there;
whereas your body,
my body is animated.
I move my hands around,
my mouth is going up and down,
it walks from one part of the
stage to the other part of the
stage.
Maybe we need to appeal to the
soul in order to explain what
animates the body.
The thought would be,
when the soul and the body have
been separated--such the dualist
explains--the soul has lost its
ability to give commands to the
body.
So the body is no longer
animated.
So we've got a possible
explanation of the difference
between an animated and an
unanimated or an inanimate body
to it.
Is the soul in contact of the
right sort with the body?
There's a possible explanation.
You might say,
"Look, the physicalist can't
tell us that,
because all the physical parts
are still there when you've got
the corpse,
at least if it's a fresh corpse
before the decay has set in.
So, we need to appeal to the
existence of a soul in order to
explain the animation of bodies
like the ones that you and I
have."
Well, I said I was going to run
through a series of arguments
but that doesn't mean that--the
lights have just turned off;
I don't know why--that doesn't
mean that I think the arguments
will all work.
I announced on the first day of
class that I don't,
myself, believe in the
existence of a soul.
As such, it shouldn't be any
surprise to you that what I'm
going to do as we run through
each of these arguments is to
say,
"I'm not convinced by it and
here's why."
Now since I think that the
arguments I'm about to
sketch--and I've just started
sketching the first of is--fails
I hope you'll think it over and
you'll eventually come to agree
with me,
yeah, these arguments don't
really work after all.
But what's more important to me
is that you at least think about
each of these arguments.
Is this a convincing argument
for the existence of a soul?
If you think so,
what response do you want to
offer to the objections that I'm
giving?
If this argument doesn't work,
is there another argument for
the existence of a soul that you
think is a better one?
First argument,
you need the soul in order to
explain the animation of the
body.
From the physicalist point of
view, of course,
the answer is going to be "too
quick."
To have an animated body,
you need to have a functioning
body.
It's true that when you've got
a corpse, you've got all the
parts there, but clearly they're
not functioning properly.
But all that shows us is,
the parts have broken.
Remember my stereo?
I dropped my stereo.
It falls on the stage.
It doesn't work anymore.
It stops giving off music.
My boombox stops giving off
music.
That's not because
previously--we had a CD inside
of it, we had some batteries.
We dropped the whole thing.
It's not as though previously
there was something nonmaterial
there.
We've got all the same parts
there, but the parts are now
broken.
They're not connected to each
other in the right way.
The energy is not flowing from
the batteries through the wires
to the CD component.
There's nothing mysterious from
the physicalist perspective
about the idea that a physical
object can break.
Although we need to offer a
story about what makes the parts
work when they're connected with
each other and interacting in
the right way,
there's no need to appeal to
anything beyond the physical.
Suppose we try to refine the
argument.
Suppose we say,
"You need to appeal to the soul
in order to explain not just
that the body moves around,
flails, but the body acts
purposefully."
We need something to be pulling
the strings, to be directing the
body.
That's what the soul does,
so says the dualist.
In response,
the physicalist is going to
say, "Yes it's true that bodies
don't just move around in random
patterns."
Human bodies don't do that.
So we need something to direct
it, but why couldn't that just
be, one particular part of the
body plays the part of the
command module?
Suppose I've got a heat-seeking
missile which tracks down the
plane.
As the plane tries to dodge it,
the missile corrects its
course.
It's not just moving randomly,
it's moving purposefully.
There had better be something
that explains,
that's controlling,
the motions of the missile.
But for all that,
it could just be a particular
piece of the missile that does
it.
More gloriously,
we could imagine building some
kind of a robot that does a
variety of tasks.
It's not moving randomly,
but the tasks are all
controlled by the CPU within the
robot.
The physicalist says we don't
need to appeal to anything as
extravagant as a soul in order
to explain the fact that bodies
don't just move randomly,
but they move in purposeful
ways that are controlled.
For each objection,
there's a response.
You could imagine the dualist
coming back and saying,
"Look, in the case of the
heat-seeking missile or the
robot for that matter,
although it's doing things,
it's just obeying orders.
And the orders were given to it
from something outside itself."
Something programmed the robot
or the missile.
So don't we need there to be
something outside the body that
programs the body?
That could be the soul.
That's a harder question.
Must there be something outside
the body that controls the body?
One possibility,
of course, is,
why not say that people are
just robots as well and we get
our commands from outside?
On a familiar religious view,
God built Adam out of dirt,
out of dust.
Adam is just a certain kind of
robot then.
God breathes into Adam.
That's sort of turning it on.
Maybe people are just robots
commanded from outside by God.
But that doesn't mean that
there's anything more to us than
there is to the robot.
That's one possible response.
A different response,
of course, is why couldn't we
have robots that just build more
robots?
Then, if you ask,
"Where did the commands come
from?"
the answer is,
"When they were built,
they were built in such a way
as to have certain instructions
that they begin to follow out."
Just like people have a genetic
code, perhaps,
that gives us various
instructions that we begin to
follow out,
or certain innate psychology or
what have you.
The argument quickly becomes
very, very messy.
The fan of the soul begins to
want to protest,
"Look, we're not just robots.
We're not just robots with some
sort of program in our brain
that we're following.
We've got free will.
Robots can't have free will.
So there's got to be something
more to us than robots.
We can't just be physical
things."
This is an interesting
argument, and I think it's a new
argument.
We started with the idea you
needed to appeal to souls in
order to roughly explain why
human bodies move,
why we're animated or why we
move in nonrandom ways.
I think it's fairly clear that
you don't need to appeal to
souls in order to do that.
Appeal to a physical body
suffices, I think,
to have an explanation as to
the difference between an
animated and an inanimate body,
how bodies will move in
nonrandom ways.
If the brain is our CPU,
then we'll behave in
deliberate, purposeful ways just
like a robot will behave in
deliberate, purposeful ways.
So this initial argument,
I think, is not compelling.
Still, we might wonder,
what about this new argument?
What about the fact that--We
said there's a family of
arguments, all of which have the
general structure,
inference to the best
explanation, you need souls in
order to explain feature
F.
Plug in a different feature
F and you get a new
argument.
The one we started with--you
need the soul to explain the
animation of the body--that
argument, I think,
doesn't work.
Now we've got a new one.
You need the soul in order to
explain free will.
Let me come back to that
argument later.
It's a good argument.
It's an argument well worth
taking seriously,
but let's come back to it
later.
First, let's run through some
other things that might be
appealed to as candidates for
feature F.
Suppose somebody says,
"Look, it's true that we don't
need to appeal to souls in order
to explain why bodies move
around in a nonrandom fashion.
But people have a very special
ability"--and so the argument
goes--"that mere bodies couldn't
have, physicalists can't
explain.
That's the ability to think.
It's the ability to reason.
People have beliefs and desires.
And based on their beliefs
about how to fulfill their
desires, they make plans.
They have strategies.
They reason about what to do.
This tightly connected set of
facts about us--beliefs,
desires, reasoning,
strategizing,
planning--you need to appeal to
a soul"--so the argument
goes--;"to explain that.
No mere machine could believe.
No mere machine has desires.
No mere machine could reason."
It's easy to see why you might
think that sort of thing when
you stick to simple machines.
It's pretty clear that there
are lots of machines that it
doesn't seem natural to ascribe
beliefs or desires or goals or
reasoning to.
My lawnmower,
for example,
doesn't want to cut the grass.
Even though it does cut the
grass, it doesn't have the
desire.
It doesn't think to itself,
"How shall I get that blade of
grass that's been eluding me?"
So it's easy to see why we
might be tempted to say no mere
machine could think or reason or
have beliefs or desires.
That argument's much less
compelling nowadays than I think
it would have been 20 or 40
years ago.
In an era of computers with
quite sophisticated computer
programs, it seems,
at the very least,
natural to talk about beliefs,
desires, and reasoning and
strategizing.
So suppose, for example,
we've got a chess-playing
computer.
On my computer at home I've got
a program that allows my
computer to play chess.
I, myself, stink at chess.
This program can beat me blind.
I move my bishop,
the computer moves its queen.
What do we say about the
computer?
Why did the computer move its
queen, or virtual queen?
Why did the computer move its
queen?
The natural thing to say is,
it's worried about the fact
that the king is exposed and
it's trying to block me by
capturing my bishop.
That is what we say about
computer-playing programs.
Think about what we're doing.
We're ascribing desires to the
program.
We're saying it's got an
ultimate desire to win the game.
A certain subsidiary desire is
to protect its king,
to capture my king.
A certain other subsidiary
desire is, no doubt,
to protect its various other
pieces along the way.
It's got beliefs about how to
do that by blocking certain
paths or by making other pieces
on my side vulnerable.
It's got beliefs about how to
achieve its goals.
Then, it puts those
combinations of beliefs and
desires into action by moving in
a way that's a rational response
to my move.
It looks as though the natural
thing to say about the
chess-playing computer is,
it does have beliefs.
It does have desires.
It does have intentions.
It does have goals.
It does reason.
It does all of this.
It's rational to this limited
extent.
It's only able to play chess.
But to that extent,
it's doing all these things and
yet we're not tempted to say,
are we, that the computer has a
nonphysical part?
We can explain how the computer
does all of this in strictly
physical terms.
Of course, once you start
thinking of it this way,
it's natural to talk this way
across a variety of things that
the computer may be trying to
do.
It's perfectly open to you,
as dualists,
to respond by saying,
"Although we personify the
computer,
we treat it as though it was a
person, as though it had beliefs
and desires and so forth,
it doesn't really have the
relevant beliefs and desires,
because it doesn't have any
beliefs and desires,
because no physical object
could have beliefs and desires."
In response to that,
I just want to say,
"Isn't that just prejudice?"
Of course, it is true that if
we simply insist no physical
object could really have beliefs
or desires,
then it will follow that when
we are tempted to ascribe
beliefs and desires to my
chess-playing computer,
we're falling into an illusion.
That will follow once we assume
that no physical object has
beliefs or desires.
But what reason is there for
saying it has no beliefs or
desires?
What grounds are there for
withholding ascriptions of
beliefs and desires to the
computer?
That's far from obvious.
Here's a possibility.
Desires, at the very least,
seem to be, at least in typical
cases, very closely tied to a
series of emotions.
You get excited when you're
playing chess at the prospect of
capturing my queen and crushing
me.
You get worried when your
pieces are threatened.
Of course, more generally,
you get excited,
your heart goes pitter-pat,
when your girlfriend or
boyfriend says they love you.
Your stomach sinks,
you have that sinking feeling
in the pit of your stomach,
when you get a bad grade on a
test.
Maybe what's really going on is
the thought that there's an
aspect of desire that has a
purely behavioral side,
that's moving pieces around in
a way that would make sense if
you had this goal.
And maybe machines can do that.
But there's an aspect of
desires, the emotional side,
that machines can't have,
but we clearly do have.
Maybe we want to build that
emotional side into talk of
desires.
So maybe if we want to say
machines don't have a mental
life and couldn't have a mental
life,
what we really mean is no
machine could feel anything
emotionally.
So let's distinguish.
Let's say there's a way of
talking about beliefs and
desires which is just going to
be captured in terms of
responding in a way that makes
sense given the environment.
Maybe computers and robots
could do that.
But there's clearly a side of
our mental life,
the emotional side,
where we might really worry,
could a robot feel love?
Could it be afraid of anything?
Again, our question was,
"Do we need to appeal to souls
to explain something about us?"
The physicalist says "no";
the dualist says "yes."
If what we mean is the mental,
but that the aspect,
the behavioral aspect of the
mental,
where even a chess-playing
computer probably has it,
then that's not a very
compelling argument.
The physicalist will say,
"Look, that aspect of the
mental is pretty clear.
We can explain it in physical
terms."
But let's just switch the
argument.
What about emotions?
Can a robot feel emotions?
Could a purely physical being
fall in love?
Could it be afraid of things?
Could it hope for something?
The latest version of our
argument then is,
"People can feel emotions.
But if you think about it,
it's pretty clear no robot
could feel emotions.
No merely physical thing could
feel emotions.
So there must be more to us
than a merely physical thing."
That's the argument we'll start
with next time.
 
