Professor Shelly Kagan:
We've been talking about the
question, "What arguments might
be offered for the existence of
a soul?"
And the family of arguments
that we're considering initially
are arguments that get known as
inference or inferences to the
best explanation.
The thought is that there's
something about us that needs
explaining.
We can't explain it in terms
of… in purely physical terms.
And so we need to appeal to,
we need to posit,
the existence of,
a soul.
Now, I'll come back to that
sort of argument in just a
minute, but let me bracket that
for a moment and say something
about Plato.
Starting next week,
we're going to be looking at
Plato's dialogue,
the Phaedo.
And so although I'll be saying
a great deal about the
Phaedo once we turn to
it,
I want to just take a minute or
two and say a couple of
introductory remarks.
I don't know how many of you
have not read any Plato before,
but for those of you who
haven't, I actually think you're
in for a treat.
Plato is not only one of the
greatest philosophers in
history, he wrote his philosophy
in the form of dialogues.
That is to say,
plays, in which various
characters sit around or stand
around and argue about
philosophical positions.
The particular dialogue that
we're going to be reading,
the Phaedo,
is set at the death scene of
Socrates.
As I'm sure you know,
Socrates was put on trial,
condemned to death for
corrupting the youth of
Athens--and perhaps,
among other things,
for arguing philosophy with
them.
And he's given hemlock,
poison, and he drinks it and he
dies.
Now, this is a historical event.
Socrates had a circle of
friends and disciples that he
would argue philosophy with.
One of his disciples was Plato.
Plato then grew up and wrote
philosophical works.
Plato does not typically appear
in his own dialogues.
Or, if he does,
he's only there as a minor
character.
In fact, if I recall correctly,
Plato's mentioned as not being
there on the day that Socrates
dies.
So, how do we know,
if we've got this play,
whose position is Plato's
position?
And the answer--the short
answer--is, Socrates,
the character Socrates in the
play, represents Plato,
the author of the play's,
philosophical views.
Now, in fact,
if this were a class in ancient
philosophy, we'd have to
complicate that picture,
because it's fairly clear that
by late in Plato's career Plato
has philosophical views that are
very much unlike the views of
his teacher, Socrates.
And yet Plato continues to not
appear in the dialogue.
Socrates continues to be sort
of the hero.
And so scholars debate which of
the views put forward by
Socrates in which ones of the
dialogues represent views that
belong to the actual historical
figure Socrates,
and which of the views put
forward by the character
Socrates in which of the
dialogues represent views that
are actually not held by the
historical Socrates,
but were instead held by the
historical Plato and were merely
put in the mouth of the
character Socrates.
Scholars distinguish between
the early Platonic dialogues,
the so-called Socratic
dialogues,
where the thought is,
those are the views of
Socrates, the actual historical
figure.
And then there's the late
dialogues, where even though
Socrates appears,
most scholars believe those are
probably not the views that the
historical Socrates actually
believed.
You have middle dialogues where
you have to worry about whose
views are whose.
But we're not going to worry.
This is not a class in ancient
philosophy.
So for our purposes,
we don't have to ask ourselves
when Socrates in the dialogue
says something,
is this a view that the dead
man Socrates actually would have
held or is this simply a view
that the dead man Plato put in
the mouth of the character
Socrates?
For our purposes,
it won't really matter.
I'll take every view that
Socrates puts forward as a view
of Plato's, though I'll
typically sort of run back and
forth sort of in a careless
fashion.
I'll say, "Plato holds" or
"Socrates argues," because for
our purposes it's all the same.
But there's one other
complication that you've got to
be warned about,
which is this.
Because these are dialogues and
they take the form of
philosophical arguments,
people put forward views and
then, over the course of the
discussion, change their minds
about things.
And they take them back.
And maybe something similar is
going on when Socrates says
something.
Because, after all,
this isn't Plato saying,
"Here's what I believe
explicitly."
He's just writing a dramatic
play about philosophy.
And so sometimes we'll find
ourselves thinking,
"You know, there's an argument
here that Socrates is putting
forward.
But maybe it's not a very good
argument."
And it will,
at least, be worth pausing
periodically to ask ourselves,
maybe Plato realized it wasn't
a very good argument.
We can often better understand
the dialogues by seeing Socrates
as putting forward certain
positions that he does not think
are altogether adequate.
And he modifies them or revises
them or introduces new positions
to deal with some of the
difficulties that he was setting
himself to be open to earlier.
As I say, don't worry about any
of those details now,
but it's a point to keep in
mind as you read the dialogues.
So that's all I really wanted
to say by way of introduction.
You should start reading the
Phaedo for next week.
We'll be talking about the
Phaedo starting some time
next week and we'll continue the
discussion of the Phaedo
for at least a bit of,
maybe all of,
the week after that.
In the case of Plato,
I'm going to make an exception.
Normally, I will mention our
readings, but I won't spend a
lot of time actually discussing
them in detail.
That's why you have to think of
the readings as complementing
the lectures or think of the
lectures as complementing the
readings.
I'm not just giving the Cliff
Notes, as it were,
of the readings.
Nonetheless,
in the case of the
Phaedo,
I am going to spend more time
actually saying,
"Here's what I think the first
main argument is.
Let's try to reconstruct it in
terms of its premises and its
conclusions.
Here are some objections I
raise.
Here is then the next argument
that Plato offers.
Let's try to get that up in
premises."
Even there, I won't be spending
time reading out loud long
passages from the Phaedo.
But, in some sense,
I'll be giving a closer
commentary of the Phaedo
than I'll do for the other
readings.
So, still, what you should do
is start reading it for next
week.
The topic of the Phaedo,
as I say, is set on Socrates'
last day.
At the end of the dialogue,
he drinks the hemlock and he
dies.
And perhaps unsurprisingly,
what he does with his friends
up until that moment is,
he argues about the immortality
of the soul.
Quite strikingly,
Socrates is not upset.
He's not worried about the fact
that he's going to die.
He actually welcomes this in a
certain way, because he believes
his soul is immortal.
And so, in addition to
philosophical arguments for and
against the existence and
immortality of the soul,
we end the dialogue with a
quite moving death scene,
one of the great death scenes,
if we could call it that,
of western civilization.
Anyway, as I say,
that's all for next week.
So let's return now to the
question, "How might we argue
for the existence of the soul?"
Initially, last time,
we considered a set of or a
subset of arguments that
basically said,
"Look, there's got to be more
to us than just material
objects.
People can't just be machines,
because machines can't reason.
Machines can't think."
And I said, "That doesn't seem
to be a compelling argument."
After all, chess-playing
computers, it seems,
can reason.
They have beliefs about what
I'm likely to do next.
They have desires about the
goals that they're trying to
achieve.
They reason about how best to
defeat me.
And it's worth pointing out
that--a point that I didn't make
last time--it's worth pointing
out that,
what the computers,
at least the best chess-playing
computers don't do.
Indeed, no computer actually
does this.
You might think that what a
computer, what a chess-playing
computer does is just this.
It calculates every possible
branch, every possible game from
here on out.
And then it sort of works
backwards.
"Oh, these are the ones where
I'll win."
And so it only makes the move
where it can sort of look ahead
20 moves, right,
and see which branches have the
computer winning.
That is not the way
chess-playing programs work.
For the simple reason that the
number of possible chess games
is so huge, that computers can't
calculate it.
They'd be busy for thousands of
years.
We can do that sort of:
When you play tic-tac-toe with
your seven-year old nephew or
niece, you just look ahead and
work backwards.
"Well, if I do that,
he'll do that and he'll do that
and then he wins,
so I won't do that," right?
But we can't do that with chess.
There's just too many games.
So how do chess-playing
programs, and particularly the
best chess-playing programs,
how do they work?
Well, they play chess the same
way you do.
They have various ideas about
which pieces are more powerful
and so they're more important to
protect.
They've got various ideas about
which strategies tend to be
successful.
What sorts of dangers come
along with them?
If you're a serious chess
player, you might study some of
the great games of chess
history.
And indeed, when they program
these things,
the programmers will feed in
game after game after game of
the great chess games in
history.
And then armed with all of
that, you sort of do your best.
And when you lose a game,
you kind of make a mental note
to yourself, "That really
screwed me up.
Let me try something different
next time."
And you avoid those sorts of
moves.
That's how chess-playing
programs work as well.
Jumping ahead,
let me make a remark about
this, because this is going to
be relevant for something I'll
get to in a couple of minutes.
What this means--what this,
the implication--is that if
you're playing a great
chess-playing program,
it's not as though the way to
tell what it's going to do is to
study its program and think it
through.
The people who design these
programs, presumably fairly
decent chess players themselves,
the people who design these
programs, when they're playing
the programs they're not
thinking to themselves,
"Let's see.
I programmed this computer so
that when I move a queen forward
to this space,
it should come out with a
bishop."
That's hopeless.
Because the program is
constantly revising its
strategies, in light of what's
worked and what hasn't worked in
the past.
When the programmers play these
programs or indeed when anybody,
a good chess player,
plays these programs,
the best way to try to beat
them is simply ask yourself,
"What's the best move to make
right now?"
The odds are the computer's
going to make the best possible
move.
Treat the computer as though it
were just a great chess player.
And indeed, the best programs
are great chess players.
There was a period of time in
which, although there were
decent, chess-playing programs
couldn't beat the best
chess-playing humans.
That ended some years ago when
the best programs began to beat
grand masters.
And now it's in fact the case
that the best programs can beat
pretty much anybody.
In the current world champion
of chess, I think Vladimir
Kramnik, was defeated in
December by a chess-playing
program.
So Kramnik's simply treating
this as an awesome opponent.
And that's the best way to deal
with these things.
All right.
So, bracket some of those
thoughts for a moment.
We'll come back to them a
little bit later when we start
talking about the question,
"Could machines be creative?"
Tipping my hand,
it seems pretty clear that that
seems like the right thing to
say about these chess-playing
programs.
So we had the question,
"Could machines,
could machines reason?"
And although we don't have
machines that can reason about a
lot of subjects yet,
it seems pretty clear.
It seems like the natural thing
to suggest, machines can reason
in at least some areas.
And so it doesn't seem
plausible to suggest that we
people must not be physical,
merely physical,
because after all,
we can reason and no machine
can reason.
No, machines could reason.
But this prompts a different
move on the part of the defender
of souls.
Perhaps the argument shouldn't
be, "we have to believe in souls
because no mere physical object
could reason."
Perhaps the argument should be,
"we have to believe in souls
because no mere physical object,
no machine could feel."
You know, we have emotions.
We love.
We're afraid.
We're worried.
We'll get elated.
We get depressed.
So perhaps the argument should
go "Yeah, yeah,
thinking, that's the sort of
thing a machine can do.
You know, we call them thinking
machines.
But feeling,
that's the sort of thing no
machine could do.
No purely physical object could
feel anything,
could have emotions.
And so, since we clearly do
feel things, there must be more
to us than a physical object."
Now, I think it is plausible to
suggest that unlike the case of
chess-playing computers,
we don't yet have machines that
feel things.
But the question isn't, "do we?"
The question is,
"could there be a machine that
could feel something,
could have an emotion of some
sort?"
So let's go a little science
fictiony and think about some of
the robots that have been shown
in science fiction movies,
some of the computer programs
that have been shown in science
fiction movies,
science fiction novels,
or what have you.
When I was a kid there was a
television show called Lost
in Space.
I'm afraid I've forgotten the
name of the robot that was on
that show.
But as it was a TV show and so
sure enough, every single
episode, some new dramatic
danger would take place.
And the robot would start
whizzing and binging and shout
out, "Danger,
Commander Robinson!"
"Danger, Will Robinson!" that
was it.
"Danger, Will Robinson!"
It seemed as though the robot
was worried.
More recent example.
A number of you have probably
read some of Douglas Adams'
books The Hitchhiker's Guide
to the Galaxy and the
sequels to that.
There's a robot in those books,
Marvin, who's --depressed,
I think is the simple word
about it.
He sort of--He is very smart.
He's thought about the
universe, thinks life is
pointless and he acts depressed.
He talks to another robot,
depresses the other robot.
The other robot commits suicide.
All right.
Seems natural to ascribe
depression to Marvin,
the robot.
That's how he behaves.
Or, my favorite example,
the movie 2001:
A Space Odyssey.
Now, I've got to tell you,
for those of you who have not
seen this movie,
I'm about to spoil it.
All right?
So you cover your ears.
In 2001: A Space
Odyssey, we get some kind of
indication that there's life on
another planet.
It's all very mysterious and we
send off a spaceship to
investigate the markings,
the radio signals from the
other place.
This is a very important
mission and so there is a
computer program named Hal that
helps run the ship and takes a
lot of the burdens off of the
part of the human astronauts who
are on the ship.
Hal's got the goal--in terms of
reasoning and desires and so
forth and so on--Hal's got the
goal of making sure the mission
is successful.
But Hal thinks to himself
fairly plausibly,
humans really screw things up.
This is a very important
mission.
Let's kill the humans to make
sure they don't screw things up.
One of the astronauts,
discovering the plot,
attempts to stop Hal.
And proceeds to do the only
thing he can do to defend
himself against Hal,
which is shut down the program,
basically killing--if we can
talk that way--killing Hal.
Meanwhile, as all this is going
on, Hal and Dave,
the human astronaut,
are talking to each other.
Hal realizes what's going on.
Hal tries to stop Dave,
understandably enough.
And Hal says,
as Dave begins to shut down
Hal's circuits,
"I'm afraid.
I'm afraid, Dave."
What's he afraid of?
He's afraid of dying.
It seems perfectly natural to
ascribe fear to Hal.
Hal is behaving in exactly the
way you would expect him to
behave, or it to behave,
if it felt fear.
It's got reason to be afraid.
It's behaving appropriately.
It's telling us that it's
afraid.
It seems natural to say Hal's
afraid.
Now, you could continue to sort
of fill in examples like this.
As I say, of course,
they're all science fiction,
but the fact that we can
grasp--and it's not as though we
go running away saying,
"Oh no!
This was outrageous," right?
"It makes no sense to think a
computer could have said,
‘I'm afraid.'
It makes no sense to think that
it could try to kill the people
who are trying to shut it down
and so forth."
That seems to me to be
prejudice, as I said last time.
The natural inclination here is
to say, "These computer
programs, these robots are
feeling emotion."
But there's no particular
reason to think there's anything
going on there than the
circuits.
They're just physical objects,
programs on machines.
If that's right,
if that's the right thing to
say, then what we have to say
is,
"We don't need to appeal to
souls in order to explain
emotions and feelings.
Physical objects could have,
mere physical objects could
have, emotions and feelings.
So we have no reason to posit
the existence of a soul."
Now, I think the best response
on the part of the dualist to
this reply is to distinguish two
aspects of feelings,
two aspects of emotions.
There's the behavioral aspect
of feeling fear,
let's say.
The behavioral aspect is when
you're aware in the environment
of something that poses a danger
to you,
that will harm you or destroy
you, or in the case of a
computer program,
turn you off,
then you take various kinds of
behaviors in opposition to that
to try to disarm the danger,
to try to neutralize it.
This is just a matter of
beliefs, goals,
responses, planning,
the sort of thing that we
already saw the chess-playing
computer can do,
that behavioral side of emotion.
It seems pretty plausible to
think robots could do that.
Physical objects could do that.
But, and here's the crucial
point of this objection,
there's another side or another
aspect to emotions and feelings.
It's the sensation of what it's
feeling like--that's why we call
them feelings after all--what
it's feeling like on the inside,
as it were, while all this
behavioral stuff's going on.
When I'm afraid,
I have this certain sort of
clammy feeling or my heart's
going poundingly.
Your blood is racing.
When you're afraid,
you've got this sinking feeling
in the stomach.
When you're depressed,
there are these,
well, we could call them
experiences, though the word
"experience" is also somewhat
ambiguous.
So--we'll use it for the
moment--there's an experience
that goes along with each
emotion.
There's what it feels like to
you when you're afraid.
What it feels like to you when
you're worried or depressed or
joyful or in love.
And the thought,
and I think this is a pretty
powerful thought,
is that even if the robots are
behaving behaviorally,
they've got the behavior side
of the emotions down,
they don't have the feeling
side at all.
Now, once you start thinking
these thoughts,
there's no need to restrict
yourself to emotions.
The missing stuff,
the missing thing is there in
all sorts of familiar humdrum
ways as well.
So right now I'm looking at the
chairs in the auditorium.
They're some kind of shade of
blue.
Think about--Look at some
places in the room where the
curtains with their red.
Think about what it's like to
see red, the sensation of seeing
red.
Now again, we've got to
distinguish between what I'll
continue to call the behavioral
side of seeing red and the
experiential side of seeing red.
It's easy enough for us to
build a machine that can tell
red from blue.
It just checks and sees what
kind of light frequencies are
bouncing off the object.
So we can build a machine that
could sort red balls from blue
balls.
My son has a little robot that
can do that.
Still, when you think to
yourself, what's the--what's
going on inside the machine?
What does it feel like to be
the machine while it's looking
at--while it's got its little
light sensors pointed at--the
red ball?
Does it have the sensation of
seeing red?
What I suppose you want to say,
certainly what I want to say
is, "No, no, it doesn't have
that sensation at all."
It's sorting things based on
the light frequencies,
but it doesn't have the
experience of seeing red.
What we're trying to get at
here is--it can be very elusive,
but I imagine most of you are
familiar with it.
It's the sort of thing you
wonder about when you ask
yourself, "If somebody was born
blind, could he possibly know
what it's like to see color?"
He might be a scientist and
know all sorts of things about
how light works.
You use such and such
frequencies, and which objects,
and you hand him an apple and
he'll say, "Oh,
it must be very red," right?
Maybe he points his little
light detector at it and it
reads out.
It says, "This is such and such
a frequency."
And he says,
"Oh, this is a very red apple,
much redder than that tomato"
or whatever.
But for all that,
we've got the notion,
not only is he not seeing red,
he can't even imagine what it's
like to see red,
never having had these
experiences.
And once you start to see this,
we realize, of course,
our life is filled with this
aspect.
Things have colors.
Things have sounds.
Things have smells.
There is the qualitative aspect
of experience.
And the point that I started
with earlier,
about the internal aspect of
emotions, is it's not just out
there, but inside as well.
We have certain kinds of
sensations inside our body,
the characteristic sensation of
fear or joy or depression.
All right.
So the suggestion then might be
this.
What no physical object can get
right, because no physical
object can get at all,
is the qualitative aspect of
experience.
That's the aspect that we're
after when we ask ourselves,
"What's it like to see red?
What's it like to smell coffee
or to taste pineapple?"
Now, it's pretty--Philosophers
sometimes call these things
qualia,
because of the notion of the
qualitative aspects of things.
Our experiences have
qualitative properties.
And the suggestion then might
be, no physical object,
no mere machine could possibly
have qualitative experience.
But we've got it,
so we're no mere physical
object.
We're no mere machine.
All right.
Now, that's the objection.
It's a pretty good objection.
And then the question is,
"What can the physicalist say
in response?"
Now, the best possible response
would be for the physicalist to
say, "Here's how to build a
machine that can be conscious in
this sense.
That is, have a qualitative
experience.
Here's how to do it.
Here's how to--Just like we can
explain in materialist,
physicalist terms how to get
desires and beliefs and the
behavioral stuff down,
here's how to get the feeling,
qualitative aspect of things
down, too."
It would be best if the
physicalist could give us that
kind of story.
I think the truth of the matter
has to be--I think the answer
right now is,
we don't know how to give that
story.
Consciousness,
if what we mean by
consciousness is this
qualitative aspect of our mental
life, consciousness remains a
pretty big mystery.
We don't know how to explain it
in physicalist terms.
And it's because of that that I
think we shouldn't be dismissive
of the dualist when the dualist
says,
"We've got to believe in souls
in order to explain it."
We shouldn't be dismissive,
but that's not to say that I
think we should be convinced.
Because it's one thing to say
we don't yet know how to explain
consciousness in physical terms.
It's another thing to say we
won't ever be able to explain
consciousness in physical terms.
If we had the latter--excuse
me--If we had the bold claim
that no physical object could
see red,
taste honey,
then we'd have to conclude
since we can do all that,
we're not a physical object or
not merely a physical object.
But I don't think we're yet in
a position to say that.
I think the simple fact of the
matter is we don't know enough
about consciousness yet to know
whether or not it can be
explained in physical terms.
When I think about this
situation, an analogy always
occurs to me.
Imagine that we're somewhere
in, let's say,
the fourteenth century trying
to understand life,
the life of plants.
A plant is a living thing.
And we ask ourselves,
"Could it possibly be that life
could be explained in material
terms?"
It's got to seem very
mysterious to us.
How could it be?
When we think of the kinds of
examples of material machines
that we've got available to us
in the fourteenth century,
I try to imagine what would
somebody in the fourteenth
century think to himself or
herself when he entertains the
possibility that a plant might
just be a machine?
And then, I have this little
image of some plant made out of
gears, right?
And the gears begin turning and
the bud opens,
dot, dot, dot,
dot.
And the person's just going to
say, "My god!
That wouldn't be alive!"
So it's pretty obvious that no
machine could be alive.
No material object could be
alive.
In order to explain life,
we have to appeal to something
more than just atoms.
They didn't have atoms,
but more than just matter.
Life requires something
immaterial above and beyond
matter to explain it.
That would have been an
understandable position to come
to in the fourteenth century,
but it would have been wrong.
We didn't have a clue back then
how to explain life in material
terms.
But that didn't mean it
couldn't be done.
I'm inclined to think the same
thing is true right now for us
and consciousness.
I know there are theories out
there.
But my best take is we're
pretty much like in the
fourteenth century.
We don't really have a clue
yet, or not much of a clue,
as to how you could even so
much as begin to--it's not that
merely that we don't have the
details worked out.
We don't even have the picture
in broad strokes as far as
consciousness is concerned,
of how it could be done in
physical terms.
But not seeing how it's
possible is not the same thing
as seeing that it's impossible.
If the dualist comes and says,
"Can't you just see that it's
not remotely possible,
it's not conceivably possible,
for a purely physical object to
have experiences,
to have qualia?"
what I want to say is,
"No, I don't see that it's
impossible.
I admit I don't see how to do
it, but I don't see that it's
impossible."
So I don't feel forced to posit
the existence of a soul.
Of course, the fan of the soul
could come back and say,
"But that's not fair.
The question isn't,
‘Is this explanation
impossible?'
The question is just,
‘Who's got the better
explanation?'
You guys can't offer any kind
of explanation at all,
yet.
I can offer an explanation.
How is consciousness possible?
We have souls.
Souls are really very different
from physical objects and so
they can be conscious."
But at this point,
I think it's crucial to
remember the point that it's not
just the question,
"Who's got an explanation?"
but, "Who's got the better
explanation?"
And before we say that the soul
view's got the better
explanation, we have to ask
ourselves,
just how much of an explanation
is it to say,
"Oh I can explain
consciousness.
Consciousness is housed not in
the body, but in the soul."
Okay.
"How exactly is it that a soul
can be conscious?"
we ask.
And then the soul theorist
says, "Well, uhm..
er..
ah..
it just can."
That's not really much of an
explanation.
I don't feel I've got any sort
of account going here as to how
consciousness works,
even if I become a dualist.
If the dualist were to start
offering us some elaborate
theory of consciousness,
"Well, there's these sorts of
soul structures,
and those sorts of soul
structures,
and these create these
sensations and those create
those sensations.
And here's a theory," well,
then, I'll begin to take it
seriously as an explanation.
But if all the soul theorist is
just saying is "Nah,
nah.
You guys can't explain it and I
can, because I say this is an
explanation."
then, I find myself wanting to
say, "That's not really any
better.
That's no improvement at all."
There was a question or a
comment.
Student: [inaudible]
Professor Shelly Kagan:
Good.
So the question was--First,
it was the accusation before
the question,
that I'm holding a sort of
double standard.
I'm defending,
I'm defending the physicalist
by saying, "Don't blame us.
We don't know how to explain it
yet."
Why aren't I allowing the soul
theory to say,
"Don't blame us.
We don't know how to explain it
yet."
Good question.
And my answer is--And sometimes
I think this one's a tie.
I think the soul theorist
doesn't have an explanation.
The physical theorist doesn't
have an explanation.
As far as I can see,
right now nobody's got a good
explanation about how
consciousness works.
It's a bit of a mystery right
now.
So I don't mean--I hope I
haven't been doing this.
It's not so much a double
standard is needed;
it's a tie.
But notice if it's a tie,
that doesn't give us what we
were looking for.
What we were looking for,
after all, was some reason to
believe in souls.
And if the best the soul
theorist can say is,
"I can't explain it and neither
can you," that's not a reason to
believe this side.
We already believe there are
bodies.
We already know bodies can do
some pretty amazing things.
The question we're asking is,
"Is there a good reason to add
to our list of things there are?
Is there a good reason to add
the soul, something immaterial?"
And if the best that the soul
theorist has is,
"maybe we need this to explain
something that I don't see how
you guys can explain,
maybe this would help,
though I can't quite see how
either," that's not a very
compelling argument.
So what I'm inclined to think
with regard to this particular
strand or this particular
version of the argument is,
the jury's still out.
Maybe at the end of the day
we'll give it our best.
We'll decide you can't explain
consciousness in physical terms.
We'll begin to work out some
sort of alternative immaterial
theory.
Maybe at the end of the day we
will decide we need to believe
in souls.
But right now,
I don't think the evidence
supports that conclusion.
Still, there's other
possibilities.
Consider creativity.
Here's another version of an
argument that goes from
inference to the best
explanation.
Creativity.
It says, "People can be
creative."
We write new pieces of music.
We write poems.
We prove things in mathematics
that have never been proven
before or we find new ways to
prove these theorems or what
have you and we can be creative.
No mere machine can be creative.
So we must be something more
than a mere machine.
Well, then, the question is
going to be, "Could it be a case
that there could be a physical
object that's creative?"
And I'm inclined to think,
"Yes."
In fact, I already suggested as
much when I talked about the
chess-playing computers.
The chess-playing computer
programs think of moves,
think of strategies no one's
thought of before.
In the most straightforward
natural meaning of the term,
we have to say--I think the
program that beat the world
champion was called Deep Fritz.
So when Deep Fritz beat
Kramnik, it was being creative.
It made a move that Kramnik
didn't think of and perhaps
nobody had.
Perhaps no chess game before
had had this move.
Computers can do other sorts of
things of this sort.
There are mathematical
theorem-proving programs.
Now, some of these things can
prove things that are
mathematically way over my head.
But let's take something simple
like the Pythagorean Theorem,
which we all learned in high
school.
And we learned how to prove the
Pythagorean Theorem in Euclidean
geometry, starting with the
various axioms in Euclidean
geometry,
ba, ba-ba, ba-ba, ba-ba, ba bum.
This proves Pythagorean Theorem.
And it turns out there's a
variety of proofs of the
Pythagorean Theorem.
And, in fact,
a computer program has come up
with a proof that,
as far as was known,
nobody in the world had ever
come up with before.
Well, other than prejudice,
what would stop us from saying
the program was being creative?
Not just in sort of
mathematical things like chess
or math, there are,
as you know,
programs that can write music.
And I don't just mean throw out
some random assortment of notes.
Programs that can produce music
that have--that we recognize as
music, that have melodic
structure and develop themes,
resolve, music that nobody's
heard before.
Why not say the machine is
creative?
What, other than prejudice,
would stop us from saying that?
So if the argument's going to
be, "We need to posit the
existence of a soul in order to
explain creativity," again,
that just seems wrong.
Well, there's a--question,
comment?
Student: [inaudible]
Professor Shelly Kagan:
Good.
The question was,
"When I talk about creativity
here, am I trying to build in
some appeal to the feeling that
we may have when we're being
creative?"
And the answer is, "No."
All I had in mind,
as you know,
is just--in talking about the
creativity issue--I just have in
mind producing something new,
producing something that hasn't
been around before.
And most particularly,
producing something that your
programmers didn't already have
in mind.
Remember, it's not as though
the people who designed the
chess-playing programs can beat
it.
The chess-playing program makes
moves these guys haven't thought
of.
All right.
The creativity argument may not
work, but there's something that
sort of immediately comes on its
heels.
Even if we could build a
program, even if we had built
programs that can be creative,
that can do things that
nobody's thought of before,
all the program is doing is
following its program,
right?
It's just a series of lines of
code.
And the robot or the computer
or what have you is just
automatically,
mechanically following the code
commands of the program.
We might say,
even if we are smart enough to
build programs that can,
by mechanistically following
the program,
do things we've never thought
of, still all the computer can
do, all the robot can do is
automatically,
necessarily,
mechanically follow the
program.
It doesn't have free will.
But we have free will.
So, here's a new argument for
the existence of the soul.
People have free will.
No merely mechanical object,
no robot, no computer could
have free will.
But since we've got free will,
we must be something more than
a merely physical object.
There must be something extra,
something immaterial about us,
the soul.
So maybe that's why we need to
believe in souls in order to
explain free will.
Now, the subject,
free will, is a very,
very--The subject of
consciousness is a very
complicated.
One could have an entire
semester devoted to thinking
about the philosophical problem
of consciousness.
And indeed, as it happens,
in our department this very
semester there is such a class
devoted, all semester,
to the topic of consciousness.
One could similarly have a
course devoted to the problem of
free will.
I'm going to spend all of two
minutes on it.
So it's by no means do I mean
to suggest, "Oh,
here's everything you need to
know about the subject."
I simply want to point out
enough about the problem to help
you see why I don't think free
will is a slam-dunk for the
soul.
So what's the argument?
Well, the thought seems to be
something like this.
One, we have free will.
Two--let me say something about
this.
What is it about the thought
that the computer is just
following a program?
Well, the thought,
I suppose is,
in philosopher's jargon,
that the computer is a
deterministic system.
It follows the laws of physics
and the laws of physics are
deterministic.
If you're in this state,
you will necessarily,
given the laws of physics and
the way the computer's
programmed and built and so
forth,
these wires will turn on,
turn off, these circuits will
turn on, turn off,
boom,
suddenly you'll be in that
state.
There are certain laws such
that, given that the computer's
in this state,
it must necessarily move in
that state.
When you've got a view about
cause and effect that works this
way--for everything that
happens,
there's some earlier thing that
caused it to happen such that
given that earlier cause,
the event had to follow--that's
a deterministic picture.
And the thought,
of course, is that the robot or
the computer is a deterministic
system and you can't have free
will if you're a deterministic
system.
So number one,
we have free will.
Two, nothing subject to
determinism has free will.
Put one and two together.
It follows, if nothing subject
to determinism has free will,
but we have free will,
it follows that we're not
subject to determinism.
Suppose we then add three,
all purely physical systems are
subject to determinism.
Well, one and two gave us that
we are not subject to
determinism.
Three says, all purely physical
systems are subject to
determinism.
Well, it would follow then from
one, two, and three that we are
not a purely physical system.
So, conclusion,
four, we are not a purely
physical system.
All right.
That's the argument from free
will.
Now, the argument is valid.
That's philosopher's jargon,
that is to say,
given the three premises,
the conclusion really does
follow.
The interesting question is,
"Are the three premises true?"
And they've got to all be true.
It's got to be that every
single one of them is so.
I'll just spend a minute more
on this starting next time.
But the point to think about
for next time is just,
is it really true that all
three of the premises are true,
or might one or more of them be
false?
All right.
That's where we'll start next
time.
 
