Professor Shelly Kagan:
All right. We've been talking about
arguments that might give us reason to believe in the
existence of an immaterial soul. The kinds of arguments we've
been considering so far all fall under the general rubric of
"inference to the best explanation."
We posit--or the fans of souls posit--the existence of souls so
as to explain something that needs explaining about us.
I've gone through a series of such arguments,
and the one that we ended with last time was the suggestion
that we need to believe in the existence of a soul in order to
explain the fact that we've got free will.
The fact that we've got free will is something that most of
us take for granted about ourselves.
But the complaint then, or the objection to the
physicalist, takes the form that we couldn't be a merely physical
entity because no merely physical entity could have free
will. But we've got free will,
so there's got to be something more to us than just being a
physical object. Now, if we push the dualist to
explain what is it about free will that rules out the
possibility that we are merely physical objects,
I think the natural suggestion to spell out the argument goes
like this, and this is where we were at the end of last time.
The thought is that, there's a kind of
incompatibility with being free and being determined.
I mean, after all from the physicalist's point of view,
we're just a kind of glorified robot,
able to do all sorts of things that most robots in most science
fiction movies can do. But still, in a sense,
we're just a glorified physical object.
We're just a robot. And robots, the objection goes,
are programmed; they necessarily follow their
program. More generally speaking,
we might say, they're subject to
deterministic laws--that, as physical objects,
it's true of them that they must do what the laws of physics
and laws of nature require that they do.
And the laws of physics are--take a deterministic form,
determinism being a bit of philosopher's jargon for when
it's true of these laws that--or a physical--or a system--that if
you set it up a certain way, cause and effect plays out such
that, given that initial setup, the very same effect must
follow. It's determined by the laws of
nature that the effect that follows will follow from that
cause. And so, if you rewind the tape
and play it again over and over and over again,
each time you set things up the very same way they must move or
transform or change or end up in the very same state.
Well, that's what determinism is all about.
And intuitively, it seems plausible to many
people that you couldn't have free will and be subject to
determinism. Because the notion of free will
was that even if I was in the very same spot again,
the very same situation again, I could've chosen differently.
So I wasn't determined or predetermined to make that
choice. So if we were to spell out the
argument somewhat more fully, it might be,
"We have free will, but you can't both have free
will and be subject to determinism or subject to
deterministic laws." And every physical object,
or every purely physical object, is subject to
deterministic laws because the laws of physics are
deterministic. You put these things together
and you get the conclusion that we, since we've got free will,
can't be a purely physical object.
There must be something more than the purely physical to us.
That's the argument I put up on the board at the end of last
class. And here we've got it up here
now. One, we have free will.
Two, nothing subject to determinism has free will.
Three, all purely physical systems are subject to
determinism. So--a conclusion--we are not a
purely physical system. To explain the fact that we've
got free will, so the objection goes,
we have to appeal to--we have to posit--the existence of a
soul, something non-physical,
something more than purely physical.
Well, that's the argument. But I don't myself find the
argument compelling. Now, the first thing to notice
is that to get the conclusion we need all three premises.
Give up the conclusion that we've got--Give up the premise
that "we've got free will," it won't follow that we're
non-physical. Even if something that did have
free will would have to be non-physical,
it wouldn't follow that we're non-physical.
That's true for each one of the premises.
Give it up, the conclusion doesn't go through.
And the interesting thing is that each one of these premises
could be plausibly challenged. Now, as I said last time,
the subject of free will--or free will, determinism,
causation and responsibility, this cluster of problems--is an
extremely difficult and complicated physical problem.
And we could easily devote an entire semester to discussing
it. So all we're doing here is the
most quick and superficial glance.
But still, let me quickly point out why you could resist the
argument from free will to the existence of a soul.
First of all, as I just noted,
the argument needs premise number one.
It's got to be the case, to prove that we've got a
soul--at least for this argument to work to prove that we've got
a soul--it's got to be the case that we've got free will.
Now, that could be challenged. There are philosophers who have
said we certainly believe that we've got free will,
but it's an illusion. We don't really have free will.
Indeed, why don't we have free will?
For precisely the reasons that are pointed to by the rest of
the argument. They might say,
"Oh, well, you know, we're physical objects;
determinism is true of us. No physical object that's
subject to determinism could have free will,
so we don't have free will. Of course, we mistakenly
believe we've got free will. We are physical objects that
labor under the illusion that we have free will,
but after all, free will isn't something that
you can just see, right?
You can't peer into your mind and see the fact that you've got
free will. Yes, we've got the sense that
we could've acted differently, but maybe that's an illusion."
As I say, there are philosophers who've argued that
way, have denied that we have free will and if we do conclude
that we don't actually have free will,
then we no longer have this argument for the existence of a
soul. It's a way to avoid the
argument; although, for what it's worth,
I should mention I don't myself believe that it's false that we
have free will. That is to say,
I do think premise one is true. I myself think we do have free
will. So although I don't like,
I don't believe the argument is sound--premise one doesn't
happen to be the premise I myself would want to reject. But there are other,
there are two other key premises.
What about premise number three, "All purely physical
systems are subject to determinism."
Well, we need that premise as well to make the argument go.
Suppose we think, "Look, you can't have free will
and determinism. You can't combine them."
The view that you can't combine them is sometimes known as
"incompatibilism" for the obvious reason.
It's the view that these two things are incompatible.
You can't have determinism and free will.
Suppose we do believe in incompatibilism and believe that
we've got free will. It would follow then that we're
not subject to deterministic laws.
Well, the dualist says, "That shows us that we have to
believe that there's something non-physical about us.
Because after all, premise three:
‘All purely physical systems are subject to determinism.'
Isn't it true after all that the basic laws of physics are
deterministic laws?" And the answer is,
"Well it's not so clear that it is true."
Which is just to say that premise three of the argument
can be rejected as well. Now, at this point I have to
just confess, as I've confessed at other
times before, three is a claim about
empirical science. What does our best theory about
the laws of nature tell us? And I'm no scientist and I'm no
specialist in sort of empirical matters, and believe me,
I'm no authority on quantum mechanics, our best theory of
fundamental physics. Still, I take it--I
gather--here's what I'm told--that the standard
interpretation of quantum mechanics says that,
despite what many of us might've otherwise believed,
the fundamental laws of physics are not,
in fact, deterministic. What does that mean?
Suppose we've got some sort of radioactive atom,
which has a certain chance of decaying.
What does that mean? Well, it means that,
you know, there's maybe, let's say, an 80 percent chance
that in the next 24 hours it will break down.
Eighty percent of atoms that are set up like that break down
in the next 24 hours; 20 percent of them don't.
Now, according to quantum mechanics under the standard
interpretation, that's all there is to say
about it. You have an atom like that,
80 percent chance in the next 24 hours it will break down.
Suppose it does break down! Can we say why it broke down?
Sure. We can say, "Well,
after all there was an 80 percent chance that it would."
Take an atom that after 24 hours hasn't broken down.
Can we say why it hasn't broken down?
Sure. There was a 20 percent chance
that it wouldn't. Can we explain why the ones
that do break down break down and the ones that don't break
down don't break down? No.
All we can say is, there was an 80 percent chance
it would, 20 percent chance it wouldn't, so most of them do,
some of them don't. That's as deep as the
explanation goes. There is nothing more.
Now, you know, when we've got our
deterministic hats on, we think to ourselves,
"There's got to be some underlying causal explanation,
some feature about the break-down atoms that explains
why they broke down and that was missing from the non-break-down
atoms that explains why they don't break down.
After all, determinism, right? If you set up the atoms exactly
the same way, they've always got to break
down." But the answer is,
according to the standard interpretation of quantum
mechanics, that's not how it works.
All there is to say is, "Some of these are going to
break down, and some of these won't."
The fundamental laws of physics, according to the
standard interpretation of quantum mechanics,
are probabilistic. Determinism is not true at the
level of fundamental physics. Well, that's what I'm told.
Believe me, I'm in no position to say, but that's what I'm
told. And of course,
if that's true, then premise three is false.
It just isn't true that all purely physical systems are
subject to determinism. So even if it does turn out
that you can't have free will and determinism,
that doesn't rule out the possibility that we are purely
physical objects, because not all purely physical
systems are subject to determinism. If determinism isn't true of us
at the fundamental level, then even if you couldn't both
have determinism and free will, we could still have free will,
and yet, for all that, still be purely physical
systems. While I'm busy pointing out
ways in which the argument doesn't succeed,
I also want to just take a moment and mention that premise
two is also subject to criticism.
Premise two was the incompatibilist claim that,
"nothing subject to determinism has free will."
You can't combine them. They're incompatible.
Now, incompatibilism, I take it, is probably
something like the common-sense view here.
It's the view that probably most of you believe,
but again, it's worth noting that philosophically it can be
challenged. There are philosophers--and
here I'll tip my hat and say, I'm one of them--there are
philosophers who believe that, in fact, the idea of free will
is not incompatible with determinism.
So even if determinism were true of us, that wouldn't rule
out our having free will, because you can--appearances to
the contrary notwithstanding--have both
determinism and free will. They're compatible.
Hence, this view is known as compatibilism.
If we accept compatibilism, we'll be able to say,
"Look, maybe we have free will and determinism is true of us;
but for all that, we're still just purely
physical systems." Even if quantum mechanics was
wrong and somehow, you know, at the macro level
all the indeterminism boils out--whatever--and at the macro
level we are deterministic systems,
so what? If a deterministic system could
nonetheless have free will, we could still be purely
physical systems. Now, mind you,
I haven't said anything today to convince you of the truth of
compatibilism, nor am I going to try to do
that. My point here was only to say
we shouldn't be so quick to think that we have to believe in
the existence of a soul in order to explain our having free will.
It takes all of the premises of the argument to get the
conclusion that the soul exists. And each one of the premises
can be challenged. And here I mean not merely,
well, logically speaking, you know, of course you can
reject any premise of any argument.
No. I mean, there are reasonable
philosophical or scientific grounds for worrying about each
one of the premises. The argument requires a lot.
That doesn't prove that the argument fails,
but it does mean that you're going to have your work cut out
for you if you're going to use this route to arguing for the
existence of a soul. All right.
Let's recap. As I said, we've been
considering different kinds of arguments for the existence of a
soul, each of which appeals to some
feature about us--our creativity, our ability to feel,
the fact that we have a qualitative aspect of
experience, our ability to reason--what have you.
Some fact about us that calls out for explanation,
and the claim on the part of the dualists was,
we couldn't explain it without appealing to a soul.
And I've argued--I've shared with you my reasons for thinking
that those arguments are not compelling.
But notice that all of the kinds of considerations I
pointed to so far are what we might think of as everyday,
familiar features about us. It's an everyday occurrence
that we can think and reason and feel and be creative,
or choose otherwise and have free will.
Maybe the better arguments for the soul focus not on the
everyday but on the unusual, on the supernatural.
Here we might then have an entire other family of
arguments, set of arguments--again,
still of the form "inference to the best explanation."
Maybe we need to posit the soul in order to explain ghosts.
Maybe we need to posit the soul in order to explain ESP;
maybe we need to posit the soul in order to explain near-death
experiences. Maybe we need to posit the soul
in order to explain what goes on in séances or communications
from the dead or what have you. For any one of those,
we could again run an argument where we say,
"Look, here is something that needs explaining.
The best explanation appeals to the soul."
Now, I'm going to be rather quicker in discussing this
family of arguments, but let me take at least a
couple of minutes and do something about that.
Take, for example, near-death experiences.
This is something that you read a bit about in the selection
from Schick and Vaughn in your course packet.
The basic idea was probably familiar to most of you anyway,
that the following thing happens with people who,
you know, maybe their heart goes into a cardiac arrest--what
have you. They die on the operating
table, but then they're brought back to life,
as we put it. And many such people,
when we question them afterwards, have a very striking
experience. And one of the things that's
striking is, how similar the experience is from person to
person and from culture to culture--that they've got some
notion, as they were dead on the
operating table, of leaving their body.
Perhaps they begin to view their body from up--floating up
above it. Eventually, perhaps,
they leave the operating room altogether in this experience
that they're having, and they have a feeling of joy
and euphoria; they have some experience of
going through a tunnel, seeing some light at the end of
the tunnel. Perhaps at the other end of the
tunnel they begin to have some communications or see some loved
one who has died previously or perhaps some famous religious
person in their--in the teaching of their tradition--their
religious tradition. They have the sense that what
they've done is basically died and gone to heaven.
But then suddenly they get yanked back, and they wake up,
you know, in the hospital room. So they've had near-death
experiences. Or perhaps a better way to put
it would be they've had death experiences but then have been
brought back to life. Now, there it is, right?
You survey people, and people have these
experiences. And now we have to ask
ourselves, "What explains this?" And here's a perfectly
straightforward and natural explanation.
These people died. Their bodies died,
and they went to the next world.
They went to the next life. They went to heaven but then
were yanked back. Now, their bodies were lying
there on the operating table; their bodies weren't in heaven.
So something non-bodily went to heaven.
That's how the explanation goes. It's a natural,
straightforward explanation of what's gone on here.
Hence, inference to the best explanation.
We need to posit the soul, something immaterial that
survives the death of the body, that can leave the body,
go up to heaven; though, as it happens in these
cases, the tie is never completely broken.
They get yanked back; the soul gets yanked back by
whatever cause, and reconnected to the body.
It's as though we might think of there being two rooms,
to use a kind of analogy here. There is the room that this
world represents, this life represents.
And what happens in these experiences is that your soul
leaves this room and goes into a second room,
the room of the next world or the next life,
but for various reasons, isn't allowed to stay in the
next room. It gets yanked back to this
room. Well, that's a possible
explanation. And in a moment,
I'll ask whether it's the best possible explanation,
but before we do turn to that question,
there is an objection to this entire way of looking at things
that's probably worth pausing for a moment and considering.
The objection is similar to the kind of dismissive attitude that
we saw at the beginning of the course about the question,
"Could I survive my death?" Well, duh.
Could there be life after there is no more life?
Well, of course not. Here the objection says,
this two-room notion's got to be mistaken.
It can't be that what's going on in near-death experiences is
that people are reporting about what it's like to be dead
because--so the objection says--they never really died.
After all, 20 minutes later, or whatever it is,
there they are up and about. Well, not up and about;
they're presumably lying in their hospital beds,
but they're clearly alive. Hence, it follows that they
never really died. Or, if you want,
you could say maybe they died, but since they obviously didn't
die permanently--after all they were brought back to life--how
could they possibly tell us what it's like to be permanently
dead? How can we take their
experiences as veridical reports of the afterlife?
Because what we want to know is what is like to be permanently
dead, and these people were never permanently dead.
So whatever unusual experiences they may be having,
they are not reports of the afterlife.
That's how the objection goes. Although, I think,
I was pausing for a moment to raise that objection,
it's not an objection that I think we should take all that
seriously. Suppose we were to agree,
all right, strictly speaking these people didn't die.
Or strictly speaking they didn't die, certainly at least,
permanently. Does it follow from that that
their experiences should not be taken as evidence of what the
afterlife is like? I think that's really a
misguided objection. Suppose somebody said,
"Look, I spent 20 years living in France, and then I came back
to the United States. And so I want to tell you what
it's like in France." And somebody says,
"You know, you never really moved to France permanently.
So your experiences in France, whatever they are--interesting
as they may be--can't really cast any light on what it would
be like to permanently move to France.
You'd say, "Give me a break!" Right?
"It's true that, of course, I didn't move to
France permanently. Still, I have some experience
of France. And so I can--a great deal
after all, 20 years--I can give you a pretty good idea of what
it's like to live in France, even if I didn't move there for
the rest of my life without ever coming back."
You can't say quite as much if you've only been in France for a
couple of days before coming back, but still you can say
something relevant. Indeed, suppose I never went
into France at all. Suppose all that happened was I
stood right on the border and peered into France,
talked to some people in France.
They were on the French side of the border, I was on the other
side, but I talked to them for a while.
Still, I never went in, but for all that I might have
something helpful to say about what it's like in France.
Well, if that's the right thing to say about the France case,
then why not say the same thing about the near-death experience
case? Even if these people didn't
stay in the second room, they didn't stay dead,
they had some experience of being dead.
Isn't that relevant to what it would be like to be dead?
Or even if we say, "No. Strictly speaking,
these people didn't die at all. They were just on the border
looking in. They never, strictly speaking,
died at all." So what?
They were on the border looking in.
To suggest that that couldn't be relevant evidence is like
saying I can't tell you anything interesting about what's going
on in the hallway right now, because after all I'm not in
the hallway; I'm here in the lecture hall.
So what? Even though I'm here in the
lecture hall, I can see into the hallway and
tell you what's going on in it. So attempts to dismiss the
appeal to near-death experiences on what we might call
philosophical grounds--this would be the bad notion of
philosophy--on philosophical grounds,
I think that's got to be misguided.
Still, that doesn't mean that we should believe the argument
for the existence of the soul from near-death experiences,
because the question remains, "What's the best explanation of
what's going on in near-death experiences?"
Now, one possibility, as I suggested,
was what I called a second ago the "two-room explanation."
There's the room of this life, and there's the room of the
next life and people who have near-death experiences either
temporarily were in the second room or else at least they were
glancing into the second room. That's one possible explanation.
But of course, there's a different possible
explanation--the one-room explanation.
There's just life, this life, and as you come very
close to the wall of the room, things end up looking and
seeming and feeling rather different than they do in the
middle of the room. Now, maybe the one-room
metaphor is not the best metaphor, because it immediately
prompts the question, "Well, what's on the other side
of the wall?" And of course,
the physicalist's suggestion is there isn't anything on the
other side of the wall. So maybe a better way to talk
about it would just be: Life's a biological process;
we're all familiar with that process, sort of,
in its middle stretches. In its closing stretches,
some fairly unusual biological processes kick in.
In rare, but not unheard of, cases, some people begin to
have those unusual biological processes and then return to the
normal biological processes and can talk about what was
happening in the unusual biological processes.
Which is just to say, we need to offer a
biological/physical explanation of what goes on in near-death
experiences. Now, mind you,
that's not yet to offer the physical explanation;
it's just a promissory note. We now have two rival
explanations, the soul, dualist,
explanation that we went into the other world and the
physicalist, promissory note that we can
explain the white lights and the feeling of euphoria and seeing
your body from a distance in physical terms.
We don't really have very much of a physical explanation until
we begin to offer scientific accounts of each of those
aspects of near-death experience.
But this is, in fact, an area on which
scientists work. And you saw some of the
beginnings of an explanation offered in the reading by Schick
and Vaughn. So, for example,
when the body is in stress, as would likely happen toward
the end of the biological processes,
when the body is in stress, certain endorphins get released
by the body. Perhaps that explains the
feelings of euphoria. When the body is in stress,
we have various unusual stimulations of the visual
sections of the brain, and perhaps that explains the
white light or the feeling of compression in the tunnel.
Now, again, I'm not any kind of scientist and so I'm not in any
position to say, "Look, here are the details of
the explanation." But you get the beginnings of
that sketched in the readings, and it's a judgment call you've
got to make. Does it seem more plausible
that we can explain these experiences in terms of the
traumatic stress that your body and brain is going through when
you are near dying? Or is it more plausible to
suggest, "No. What's happened here is a soul
has been released from connection with the body."
For my money, I find the beginnings of the
scientific explanation sufficiently persuasive and
sufficiently compelling that I don't find the argument from
near-death experience--as an argument for the existence of a
soul--I don't find it especially persuasive. Of course, there are various
other things we could appeal to in terms of supernatural
occurrences, right? I've only mentioned--only
discussed now in detail--one of them.
But there are a variety of things about people who can
communicate from the dead or ghosts or séances or what have
you. And what the physicalist would
need to do for each one of those--For each one of those you
can imagine a dualist who says, "We need to believe in a soul
so as to explain séances. How do we explain the fact that
the person who's conducting the séance knows things about,
your history that only your dead uncle would know?"
The dualist can explain that by appealing to ghosts and the
like. How does the physicalist
explain things like that? Short answer is, I don't know.
I'm not the kind of person who makes it his business to try to
explain away those things in physicalist,
naturalistic, materialistic,
scientific terms. But there are people who make
it their business. So, for example,
there's a magician--The question is not,
could I explain to you how the séance manages to do the
amazing things that it does? You're wasting your time asking
somebody like me. The person to ask is a
magician, somebody whose profession it is to fool people
and make it look like they can do things with magic.
So in fact, there are professional magicians who make
it their business to debunk people who claim to genuinely be
in contact with the dead and the like.
There's a magician, I think his name is The Amazing
Randi, who has a sort of standing offer;
he says, "You show me what happened in the séance or in
communication with the dead or what have you,
and I'll show you how to do it. I'll debunk it for you."
Spoiler alert. And he has a standing offer,
he says, "I'll pay whatever the amount is, $10,000 to the first
person who can document some effect done in supernatural
terms that I can't reproduce through trickery."
So far he's never had to pay out.
Well again, that doesn't prove the dualist is wrong.
It could be that there are genuine séances.
It could be that there really are ghosts.
It could be that there really is communication from the dead. As is typically the case,
you've got to decide for yourself what strikes you as the
better explanation. Is the supernatural,
dualist explanation the more likely one?
Or is the physicalist explanation the more likely one?
Look, you have a dream where your dead mother has come back
to talk to you. One possible explanation,
the dualist, that's the ghost of your
mother, immaterial soul that she is, communicating to you while
you're asleep. Second possible explanation,
it's just a dream. Of course you dream about your
mother because your unconscious cares about her.
What's the better explanation? We don't have the time here to
go case, by case, by case, and ask ourselves,
"How does the evidence fall down one side versus the other?"
But when I review the evidence, I come away thinking there's no
good reason to move beyond the physical.
So again, let's recap. One group of arguments for the
existence of a soul says, "We need to posit a soul in
order to explain something, whether it's something everyday
or something supernatural." The existence of a soul would
be the beginnings of a possible explanation.
But the question is never, "Is that a possible
explanation?" but, "Is it the best
explanation?" And when I review these various
arguments, I come away thinking the better explanation falls
with the physicalist. Mind you, I don't want to deny
that there are some things the physicalist has not yet done a
very compelling job of explaining.
In particular, as I've mentioned previously,
I think there are mysteries and puzzles about the nature of
consciousness, the qualitative aspect of
experience, what it's like to smell coffee or taste pineapple
or see red. It's very hard to see how you
explain that in physicalist terms.
So to that extent, I think we can say the jury may
still be out. But I don't think what we
should say is, "The better explanation lies
with the dualist." Because I think positing a soul
doesn't really yet offer us the explanation.
It just holds out the promise of an explanation.
So at best that's a tie, and hence, no compelling reason
to accept the existence of a soul. It would be one thing if we
could see that no conceivable physicalist explanation could
possibly work. But I don't think we're in that
situation. All we're in right now is,
perhaps in existence of that with regard to consciousness,
maybe some other things, we don't yet see how to explain
it. But not yet seeing how to
explain it is not the same thing as seeing that it can't be
explained on physicalist terms. Of course, again,
if we had a dualist explanation with some details really worked
out, maybe we'd have to say, "Look, this is the better
explanation." But dualism doesn't so much
offer the explanation typically as just say, "Well,
maybe we'd be better off positing something immaterial."
That, I think, is not a very compelling
argument. Well, let's ask.
What other kinds of arguments could be offered for the
existence of a soul? I want to emphasize the point
that the various arguments that I have been talking about so
far, although they have this common
strand--"inference to the best explanation"--are each separate
and distinct arguments. One of them might work even
though the other ones don't work.
But I want to turn now to a rather different kind of
argument. The argument I'm about to
sketch is a purely philosophical argument, not really so much a
matter of who can explain this or that feature of us better
than anybody else. It's an argument that doesn't
seem to have any empirical premises;
it works from purely armchair philosophical reflection.
And the striking thing is that many people find this a pretty
compelling argument. The argument I'm going to give
traces back to Descartes, the great early modern
philosopher. Well, I'm not going to follow
the details of this argument, but the basic idea goes back to
Descartes. And it starts by asking you to
imagine a story. So I'm going to tell the story
in the first person. I'm going to tell about myself,
but you know, you'll find the argument sort
of, perhaps more persuasive if,
as I tell the story, you imagine the story being
told about you. So each one of you should
translate this into a story about yourself.
You know, your morning. So this is a story about my
morning. Imagine--this didn't,
of course, actually happen, but imagine--the crucial point
here is simply that we can imagine this story happening,
not even that we think it's empirically possible,
just it's conceivable, it's an imaginable story.
All right. So suppose that I woke up this
morning, that is to say, at a certain point I look
around my room and I see the familiar sights of my darkened
bedroom. I hear, perhaps,
the sounds of the cars outside my house, my alarm clock
ringing, what have you. I move out of the room toward
the bathroom, planning to brush my teeth.
As I enter the bathroom, it's much more light,
I look in the mirror and--here's where things get
really weird--I don't see anything.
Normally, of course, when I look in the mirror I see
my face. I see my head;
I see the reflection of my torso.
But now, as I'm looking into the mirror, I don't see anything
at all. Instead, I see the shower
reflected behind me. Normally, that's blocked of
course by me, by my body.
But I don't see my body. Slightly freaked out,
I reach for my head, or perhaps we should say I
reach for where I would expect my head to be,
but I don't feel anything there.
Glancing down at my arms, I don't see any arms.
Now, I'm really panicking. As I begin trying to touch my
body, I don't feel anything. I don't--Not only can't I feel
anything with my fingers, I don't have any sensations
where my body should be. Now, we could continue this
story, but I've probably said enough for you to grant that
what I've just started doing--a novelist could do a better job
of telling the story than I just did--but what I've just done was
basically imagine--I've imagined a story in which I discover that
my body doesn't exist. Or I've imagined a story in
which my body has perhaps ceased to exist, or I've imagined a
story in which I exist, or at least my mind exists.
You know, I'm thinking thoughts like, "Why can't I see my body
in the mirror? Why can't I feel my head?
What's going on?" I'm panicking, right?
We've got a story in which I'm thinking all sorts of thoughts;
my mind clearly exists, and yet, for all that,
my body does not exist. We could--certainly it
seems--imagine that possibility. Now, the brilliant thing about
this argument is it goes from that to a conclusion about there
being a difference between my mind and my body.
What we've just done, after all, is imagine that my
mind exists but my body does not.
Now, what does that show? Descartes says what it shows is
the mind and the body must be two logically distinct things.
The mind and the body cannot be the same thing.
Because, after all, what I just did was imagine my
mind existing without my body. How could I even do that,
even in imagination? How could it even be possible
to imagine my mind without my body, if talking about my mind
is just a way of talking about my body?
If they're really, bottom line,
metaphysically speaking, the same thing,
then you couldn't have one without the other after all.
So here's a podium. Try to tell a story in which
this podium exists but this podium does not exist.
You can't do it, right? The podium is just one thing,
the podium. And if it is just one thing,
you could tell a story in which it exists;
you could tell a story in which it doesn't exist.
But you can't tell a story in which it exists and doesn't
exist. If I can tell a story in which
A exists and B doesn't exist, it's got to follow that A and B
are not the same thing. Because if B was just another
word for, another way of talking about, A, then to imagine A
existing but B not existing would be imagining A existing
but--well, B is just A--A not existing.
But of course, you can't imagine a world in
which A exists but A doesn't exist.
Put the same point the other way around: If I can imagine A
without B, then A and B have to be logically distinct things.
They cannot be identical. But since I can imagine my mind
existing without my body, it follows that my mind and my
body have to be logically distinct things.
They cannot be identical. My mind cannot just be a way of
talking. Talking about my mind cannot
just be a way of talking about my body.
Now, it's a very cool argument. You know, philosophers love
this argument. And I've got to tell you,
to this day there's a debate in the philosophical community
about whether or not this argument works. It's one thing to be clear--a
couple of things to be clear about.
What exactly is this argument not doing?
The argument is not saying, "If something is possible,
if I can imagine it, it's true."
No. I can imagine unicorns.
It doesn't mean unicorns exist. That's not what the argument is
saying. The argument is only making a
much more specific claim. If I can imagine one thing
without the other, they must be separate things.
Now, of course, it could still be that in the
real world the one thing cannot exist without the other.
There may be some sort of metaphysical laws that tie the
two things so tightly together that you'll never actually get
one without the other. That's not the question.
The point is just if I can at least imagine the one thing
without the other, they must in fact be two
separate things. Because if there was really
just one thing there, you couldn't imagine it without
it. Since I can imagine my mind
without my body, it must be the case that my
mind is something separate and distinct from my body.
Otherwise, how could I imagine it existing without the body?
If they were the same thing, I couldn't--I can't imagine the
body existing without the body. If the mind is just a way of
talking about the body, how could I imagine the mind
without the body? Since I can imagine the mind
without the body, it follows that they're
separate. So the mind is not the body
after all. It's something different.
It's the soul. Is that a good argument or not?
That's where we'll start next time.
