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Professor Shelly Kagan:
At the end of last class,
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I suggested that from here on
out I'm going to be assuming
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that there is no soul.
I'm going to be discussing the
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issues that we turn to hereafter
from the perspective of the
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physicalist,
the person who says that a
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person is basically just a fancy
body--a body that can do certain
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special tricks,
a body that can function in
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certain ways that we associate
with being a person,
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a body that can P-function,
as we put it.
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Now, I've given you my reasons
for believing there are no
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souls.
Basically, that the various
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arguments that might be offered
for believing in souls don't
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seem very compelling upon
examination,
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so there's no good reason to
posit this extra entity.
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For the most part,
then, I'm going to be putting
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aside soul talk.
Periodically,
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I'll come back and talk about
how some issue that we are
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considering might look from the
perspective of somebody who does
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believe in souls.
But, as I say,
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for the most part,
I'm going to be assuming there
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are no souls.
For those of you who still do
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believe in the existence of
souls, I suppose you could take
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a great deal of the discussion
that follows as some form of
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large conditional or
subjunctive.
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If there were no souls,
then here's what we'd have to
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say.
So although I'll be largely
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talking from the perspective of
the physicalist,
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if you haven't become convinced
of the truth of physicalism,
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so be it.
We'll at least explore what
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will we say about death if we've
decided that people are
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basically just bodies?
Now, you'll recall that at the
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start of the semester I said,
in thinking about the question,
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could I survive my death?
there were two basic things we
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had to get clear on.
First, we had to get clear on,
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what am I?
What are my parts?
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That's why we spent the last
several weeks worrying about the
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question, am I just a body?
Am I a body and an immaterial
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soul as well?
Or perhaps, strictly speaking,
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just the soul?
Having looked at that question,
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we're now going to turn to the
second basic question,
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what would it be to survive?
What would it be for a thing
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like that to continue to exist?
Now, of course,
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we're going to ask most
particularly,
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what would it be for a thing
like that to survive the death
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of the body?
Could it even make sense for a
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person to survive the death of
his body?
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You might think the answer to
that is no, if we are
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physicalists,
but in fact,
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it's not so clear the answer to
that is no.
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But in order to address that
particular question--What is for
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me to survive the death of my
body?
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Is that even a possibility or
not?--we first have to get clear
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about the more general question,
what is it for me to survive,
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period?
Take the more familiar hum-drum
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case.
Here I am lecturing to you
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today, Thursday.
Somebody's going to be here,
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no doubt, lecturing to you next
week, next Tuesday.
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The question of survival can be
asked about that very simple
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case.
Is the person who's going to be
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lecturing to you on Tuesday the
very same person as the person
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who is standing in front of you
lecturing to you now?
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Will that person survive the
weekend?
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I certainly expect to survive
the weekend.
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But what is it to survive the
weekend?
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What is it?
We might say,
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look, we've already got the
beginnings of an answer.
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For me to survive until
Tuesday, presumably is for there
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to be somebody,
some person alive lecturing to
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you on Tuesday,
and--here's the crucial
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point--for that person lecturing
to you on Tuesday to be the very
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same person as the person
lecturing to you today,
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on Thursday.
If I were to be killed in a
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plane accident this weekend and
there was a guest lecturer for
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you on Tuesday,
there'd be somebody alive
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lecturing to you.
But, of course,
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that wouldn't be me.
So the question we want to get
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clear on is, what is it for
somebody on Tuesday to be the
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same person as the person here
talking to you on Thursday?
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We can ask the question more
grandly, about larger expanses
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of time.
Suppose there's somebody alive
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40-odd years from now,
in the year 2050.
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Could that be me?
To ask, have I survived until
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2050?
is to ask, is that person who's
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alive in 2050 the very same
person as the person who's
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standing here now lecturing to
you?
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What is it for somebody in the
future to be the very same
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person as this person who's here
now today?
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Now, in thinking about this
question, it's important not to
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misunderstand what we're asking.
Some of you may misunderstand
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what I'm asking.
Some of you may want to say,
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"Look, the person lecturing to
you now has at least a fair bit
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of his hair.
He's got a beard.
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Let's suppose that the person
alive in 2050 is bald and bent
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over, has no beard.
How could they be the same
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person?
One's got hair, one doesn't.
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One's got a beard, one doesn't.
One stands straight,
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one's crooked.
It can't be the same person."
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That's the mistake that it's
important for us to get clear
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about.
So I'm going to spend some time
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talking about examples that I
think we would not find
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puzzling,
and work our way back up to the
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case of personal identity.
So first I'm going to say some
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things about identity across
time--or indeed initially,
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identity across space--with
some familiar,
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hum-drum, material objects.
So, let's start.
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Suppose you and I are walking
along and we see a train.
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So let me draw the train first.
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I'm not a very good artist,
but all right.
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There's our train.
We start walking.
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I point to the caboose.
Let's make this look more like
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a caboose, slightly more like a
caboose.
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Just so it doesn't look too
much like the locomotive.
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I point to the caboose and I
say, "Look at that train."
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And we're walking along,
we're walking along,
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we're walking along.
We come to the end of the train
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and I point to the locomotive
and I say, "Wow!
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Look how long that train is!
That's the very same train I
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pointed to five minutes ago.
We've been walking along it all
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this time."
Now, imagine that you say--you
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wouldn't say anything as stupid
as this, but imagine that you
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said this--you say,
"This isn't the same train as
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the train we pointed to five
minutes ago.
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After all, right now what
you're pointing to is a
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locomotive, whereas five minutes
ago what you pointed to was a
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caboose.
A caboose isn't the same thing
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as a locomotive.
How could you possibly say it's
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the same thing?
Who could possibly make a
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mistake like that?
The locomotive's got smoke
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coming out of it.
The caboose doesn't.
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And so forth and so on.
There's a lot of differences
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between the two.
How could you make such a silly
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mistake?"
Well, of course,
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what I would then want to say
to you is, no,
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actually, you're the one who's
making the mistake.
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I agree, of course,
that a locomotive is not the
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same thing as a caboose.
But I wasn't claiming that it
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was.
Rather, initially when we
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started our walk,
I pointed to a caboose,
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but by pointing to the caboose,
I picked out a train.
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I said, "Look at that train."
And what I was referring to
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wasn't just the caboose,
but the whole,
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long, extended-through-space
object,
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the train, of which the caboose
was just a part.
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And when--At the end of our
walk when I pointed to a
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locomotive and said,
"Look at that train,"
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by pointing to the locomotive,
I was picking out a train,
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an entire train.
This long,
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extended-through-space object,
the train.
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And when I said,
"This train that I'm pointing
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to now is the very same train as
the train I pointed to five
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minutes ago,"
I'm not saying what is
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certainly false.
I'm not saying the locomotive
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is the same thing as the
caboose.
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Rather, what I'm saying is,
the entire
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extended-through-space train
that I'm pointing out now is the
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same train as the entire
extended-through-space train
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that I picked out five minutes
ago.
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And that claim,
far from being false,
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is true.
Now, as I say,
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none of us would make that
mistake.
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But it's a tempting mistake if
you're not being careful.
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And that mistake might mislead
us if we start thinking about
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the personal identity case.
But let's continue with the
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train for a bit.
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Suppose, as we're taking our
walk, part of the train isn't
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visible.
There's a large warehouse
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that's blocking the view.
We're walking along the way.
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We see a caboose.
I say, "Ha! There's a train."
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Then for a while we're walking,
we don't see anything because
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all you can see is the
warehouse.
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And then after we get past the
warehouse, a very long,
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block-long warehouse,
I see a locomotive and I say,
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"Hey look.
There's a train."
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And then I ask you,
"Do you think this is the same
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train as the train we pointed to
before?"
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Now again, it's important not
to misunderstand that question.
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That question is not asking,
is the locomotive that we're
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pointing to now the same as the
caboose that we pointed to
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earlier?
No, of course not.
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The locomotive's not the same
as the caboose.
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But that's not what I'm asking.
What I'm asking rather is,
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remember earlier when I pointed
to the caboose?"
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In doing so,
and I started talking about a
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train, I was picking out some
entire extended-through-space
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train.
Right now, in pointing to a
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locomotive, I'm picking out not
just the locomotive.
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I mean to be talking about an
entire train.
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Some entire
extended-through-space train.
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And I'm asking not about the
locomotive and the caboose,
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but rather I'm asking about the
trains that I pick out by means
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of the locomotive and caboose.
Are they the same train?
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And the answer is, "Don't know;
can't tell.
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The building's blocking the
view."
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Suppose we had x-ray vision and
could see through the building.
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Then the answer would be,
"Well look, if what we've got
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is something like this,
then of course,
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we do have one single train."
The extended-through-space
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train I picked out at the end of
our walk is the same as the
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extended-through-space train
that I picked out at the
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beginning of our walk.
But it might not turn out that
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way.
It might turn out if I had
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x-ray vision,
that what I'd see is this .
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Then the answer would be,
"Ah, there's not one train
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here, but two trains."
The extended-through-space
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train that I'm picking out when
I point to the locomotive turns
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out to be a different train from
the extended-through-space train
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I picked out when I pointed to
the caboose.
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I don't have x-ray vision.
I don't know which of these
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metaphysical hypotheses is the
correct one.
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All right, easy enough with
trains.
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We know how it works with
trains.
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Now let's talk about something
not a whole lot more
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complicated--cars.
I used to have a car I bought
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in 1990.
My ability to draw cars is even
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worse than my ability to draw
trains.
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There's my car in 1990.
It was new.
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It was sparkly.
Then I drove it for some years
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and I got some dents and so
forth and so on.
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Here's a smile.
By 1996 or 2000,
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it wasn't looking so good.
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The sparkle had gone.
It had a couple of dents.
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That was the car in 2000.
By 2006, it had a lot of dents,
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2006, when it finally died.
All right, now we all
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understand the claim that the
car I had in 2006 was the very
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same car as the car I had in
1990.
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Of course, again,
you've got to be careful not to
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misunderstand what's being said.
We all know that in 2006 the
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car had a lot of scratches and
had gotten banged in on one side
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and pretty sorry looking in
terms of the scrapes and the
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paint job and the rust.
Whereas, the car in 1990,
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new and shiny and smooth.
You might say the 2006 car
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stage is obviously not the same
thing as the 1990 car stage.
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That's like thinking that the
locomotive's the same thing as
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the caboose.
But when I say it's the same
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car, I don't mean to be talking
about car stages.
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I mean to be talking about a
single thing that was extended
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through time.
There I am, proud owner of my
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new car in 1990 and I say,
"This is a car.
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It's a car that will exist for
more than a few minutes.
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It's a car that will exist for
years and years and years,"
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though at the time I didn't
realize it was going to last 16
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years or longer.
When I refer to my car--as
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opposed to what we could dub the
car stage or the car slice--when
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I refer to the car in 1990,
I mean to be talking about the
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entire extended-through-time
object.
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In 2006, when I point to that
sad heap and talk about,
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"I've had that car for 16
years."
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Well, I haven't had that car
stage for 16 years.
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That car stage or that car
slice, if we wanted to talk
00:17:40
about it that way,
has only been around for
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however long,
months, years,
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a year.
It hasn't been around for 16
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years.
But when I talk about that car,
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I'm picking not just the
current slice or the current
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stage of the car,
but the entire
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extended-through-time object.
When I say, "That's the very
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same car I've had for 16 years,"
I mean, "Think of the object
00:18:08
extended through time that I'm
picking out by pointing to the
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current slice.
That's the very same
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extended-through-time object
that I picked out 16 years ago
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by pointing to what was then the
current slice.
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The slices aren't the same;
the car is the same.
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It's the very same car."
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Well, now let's imagine a
somewhat more difficult case.
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At the end of 2006,
my engine failed.
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I sold the car to a dealer,
junk dealer.
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Suppose that in 2010 I see a
car in the junk lot and it looks
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familiar to me.
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I say, "Whoa!
That's my car."
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Is it or isn't it my car?
This is sort of like the case
00:19:31
with the factory blocking the
view.
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1990 to 2006, very easy.
Saw the car every day in my
00:19:42
garage.
But here is a
00:19:44
four-year--Instead of a factory
blocking my view,
00:19:48
it's the mists of time blocking
my view.
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And I ask, "Same car or not?"
Again, by this time,
00:19:55
I imagine you don't need to be
warned, but let me just warn you
00:19:58
a couple more times.
I'm not asking,
00:20:01
"Is the car stage,
the 2010 car stage,
00:20:05
the same car stage as the 2006
car stage?
00:20:10
Maybe not.
Maybe obviously not.
00:20:13
I'm asking rather,
in pointing to the 2010 car
00:20:18
stage, I mean to be picking out
an entire extended-through-time
00:20:25
entity, the car.
And I'm asking,
00:20:28
"Is that the very same
extended-through-time entity as
00:20:31
the extended-through-time entity
that I used to own?"
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I wonder.
And the answer is, "Don't know."
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The mists of time are blocking
my view.
00:20:41
I don't know the answer.
But we know what the
00:20:43
possibilities are.
00:20:51
One possibility is that indeed
it's the very same--I won't draw
00:20:57
it all, 2008 and so forth.
It could be the very same car.
00:21:05
If we knew what it took to have
the various stages of a car add
00:21:11
up to the very same car,
then that would be one
00:21:15
possibility.
But there might be a different
00:21:20
possibility.
It could have been that after I
00:21:24
sold it to the junk dealer,
he crushed it,
00:21:27
turned it into a heap of metal
and that was the end of my car.
00:21:32
And the car I'm seeing on the
dealer's lot in 2010 might be
00:21:41
some other car with its own
history.
00:21:47
What we're wondering about is,
is there a single--well,
00:21:52
here's a piece of jargon--is
there a single "space-time worm"
00:21:57
here or are there two?
When I look at the car in 2010
00:22:02
and say, "There's a car.
I wonder if it's the same car,"
00:22:06
I'm asking about this thing
that's extended--well,
00:22:10
obviously through space,
since cars take up some
00:22:13
space--and through time.
Looks a bit like a worm.
00:22:17
So philosophers call them
space-time worms.
00:22:21
Is the space-time worm that
makes up this car the same
00:22:25
space-time worm as the one that
made up my car?
00:22:29
One worm there or two?
And the answer might be,
00:22:33
"Don't know,
need to have more facts."
00:22:36
But at least that's what the
question is.
00:22:39
Now metaphysically,
there's different ways of
00:22:44
trying to pose the set of issues
that I've begun to talk about.
00:22:52
Should we say,
as we might say with the train,
00:22:56
the train is made up out of the
various cars,
00:23:00
the locomotive,
the caboose,
00:23:03
and the intervening cars?
So the train--that's the way we
00:23:08
normally think about trains,
at least the way I normally
00:23:11
think about trains--the train's
a bit like a sandwich,
00:23:15
right?
The metaphysically fundamental
00:23:17
things are the caboose,
the locomotives,
00:23:19
the intervening trains.
If they're glued together in
00:23:22
the right way,
they make up a train.
00:23:26
What's the right kind of
metaphysical glue for trains?
00:23:28
Well, it's being connected with
those little locks.
00:23:35
That may or may not be the
right way to think about what
00:23:39
I've been calling car stages or
car slices.
00:23:42
On some metaphysical views,
you might say,
00:23:44
just exactly like with the
train,
00:23:46
the car stages are the
metaphysically fundamental
00:23:50
things and a car,
something extended through
00:23:53
time,
is glued together like a
00:23:58
sandwich from the car stages.
And then, we might worry about
00:24:04
what's the relevant metaphysical
glue for cars.
00:24:07
On other metaphysical views,
no what's really prior is the
00:24:11
car itself, and talking about
car stages is a certain
00:24:15
convenience,
a kind of way of chopping up
00:24:19
the fundamental thing,
the car.
00:24:21
So, to use an analogy that I
think David Kaplan,
00:24:25
a philosopher at UCLA offers,
it's as though you have to
00:24:29
think of it more like a bologna
or salami that you can slice.
00:24:33
If--For certain purposes you
can talk about slices,
00:24:36
but the fundamental thing's the
salami.
00:24:39
All right.
In thinking about cars,
00:24:43
should we say that the
fundamental thing is the car
00:24:46
stages and they get put together
like a sandwich to make cars?
00:24:51
Or should we think that the
fundamental thing is the car
00:24:54
extended through time and it can
be sliced up to make car stages?
00:24:58
For our purposes,
I think we won't have to go
00:25:00
there.
It doesn't really matter.
00:25:02
As long as we're comfortable
talking about entire space-time
00:25:06
worms, the cars,
and the slices or the stages.
00:25:10
We don't have to ask which is
metaphysically prior.
00:25:13
You should also notice that- I
should also mention that there
00:25:16
are other metaphysical views
about what goes on when an
00:25:19
object exists over time.
I've been here helping myself
00:25:23
to the suggestion that we should
think about extension over time
00:25:29
analogously to the way we think
about extension over space.
00:25:34
That's why I started with a
spatial example,
00:25:37
the train, and moved to the
temporal example,
00:25:40
the car.
And there are those
00:25:42
philosophers who think that's
exactly the right way to think
00:25:45
about it and those philosophers
that think no,
00:25:47
no, that's misleading.
When an object is extended over
00:25:51
time, really the entire object's
right there at every single
00:25:55
moment.
These are interesting and
00:25:58
difficult questions.
But again, I think for our
00:26:01
purposes, we don't have to go
there.
00:26:04
So I will help myself to this
language of space-time worms,
00:26:09
objects that extend not only
over space but also over time.
00:26:15
And distinguish the entire worm
from the various slices or
00:26:19
stages that either make up the
worm or that we could slice the
00:26:23
worm into.
The point that I've been
00:26:26
emphasizing is,
well first point,
00:26:29
of course, has been,
"Don't confuse the stages with
00:26:33
the entire space-time worm."
The stages can differ without
00:26:38
the entire space-time worm being
a different worm.
00:26:42
Second question I've hinted at
that we're about to turn to,
00:26:45
not literally turn to at the
moment,
00:26:47
but shortly we'll turn to is,
"What's the relevant glue?"
00:26:52
What makes two stages,
stages of the very same thing?
00:27:00
In the case of trains,
as I say, it's fairly obvious.
00:27:04
What is it in the case of cars?
What makes the 1990 car stage a
00:27:11
stage in the very same car,
the extended through space and
00:27:19
time worm car,
as the 2006 stage?
00:27:24
What's the metaphysical glue
that glues these stages
00:27:27
together?
And the answer,
00:27:29
not that there aren't puzzles
about it, but the answer is
00:27:33
roughly,
"It's the very same car if it's
00:27:38
the very same hunk of metal and
plastic and wires."
00:27:46
There was the car.
A car is just some metal and
00:27:52
plastic, rubber.
And that very same hunk
00:27:58
continued into 2000 and it
continued into 2006.
00:28:03
The glue, the key to identity
across time for cars,
00:28:13
is being the same hunk of
stuff.
00:28:19
Now, that doesn't mean it's got
to be the same atom for atom.
00:28:26
We know that's not true.
Look, think about my steering
00:28:29
wheel.
Every time I grabbed the
00:28:32
steering wheel to drive,
I wore away thousands of atoms.
00:28:43
You can lose some atoms and
still be the very same steering
00:28:49
wheel.
Every now and then,
00:28:52
I'd replace the tires on my
car.
00:28:55
But for all that,
it was the same hunk of stuff.
00:29:00
Now this raises an interesting
issue.
00:29:03
How many changes of the
constituent parts can you have
00:29:10
and still be the same hunk of
stuff?
00:29:15
If this was a class in which we
were going to worry about the
00:29:20
general problem of identity
across time,
00:29:24
this would be a problem we'd
have to directly face.
00:29:28
But since we are only looking
at enough of the problem of
00:29:33
identity to get to the question
that we really want to think
00:29:37
about,
the nature of personal identity
00:29:41
across time, I'm not going to
pursue that.
00:29:45
I just want to flag the thought
that you can be the very same
00:29:49
hunk of stuff,
even if some of the constituent
00:29:53
atoms have changed along the
way.
00:29:56
And even bigger parts.
You can replace the headlights
00:29:59
and still be the same hunk of
stuff.
00:30:02
At any rate,
that's what's gone on in the
00:30:06
car case, same hunk of stuff
1900-2006.
00:30:09
And when I see the car on the
junk dealer's yard in 2010 and
00:30:14
ask, "Is that my car or not?"
the answer lies in--if only we
00:30:19
could know--is that the same
hunk of stuff or not?
00:30:23
That's what the key,
the metaphysical glue is,
00:30:28
being the same hunk of stuff.
All right, let's turn now to
00:30:34
the case we really wonder about,
personal identity.
00:30:47
Here's somebody lecturing to
you in 2007, Shelly Kagan.
00:31:02
We imagine there's somebody in
2050 and we ask,
00:31:10
"Is that Shelly Kagan?"
We'll call him "Mr. X."
00:31:20
We ask, "Is that the same
person or not?"
00:31:23
Now again, at this point you're
not going to be tempted by the
00:31:28
mistake.
I'm not asking,
00:31:31
"Is this person stage Mr.
X the same person stage as SK
00:31:39
2007?"
Obviously not.
00:31:42
SK 2007 has still got his hair,
has the beard,
00:31:47
stands up more or less
straight.
00:31:50
Mr.
X is bald, doesn't have a
00:31:52
beard.
I suppose I should have drawn
00:31:56
him bent.
Can I do that?
00:31:59
A little cane.
I'm not asking,
00:32:04
"Is the person stage Mr.
X the same as the person stage
00:32:09
SK 2007?"
Sounds like a computer or
00:32:13
something.
Get the SK 2007!
00:32:15
I'm not asking that.
I'm asking, I'm saying,
00:32:19
"Look, when you look at the
current stage,
00:32:24
the current person slice and
think about the entire
00:32:29
extended-through-time entity,
the person that makes up Shelly
00:32:37
Kagan, or that is Shelly Kagan,
is that the very same person as
00:32:45
the extended-through-time person
that you got in mind when you
00:32:52
point to the Mr.
X 2050?"
00:32:56
The stages are obviously
different.
00:32:58
But by looking at the stages,
we pick out a space-time worm
00:33:04
that makes up a person.
And we're asking,
00:33:08
"Is that the very same
space-time worm as the one we
00:33:12
picked out previously or a
different space-time worm than
00:33:17
the one we picked out
previously?"
00:33:20
And the answer,
presumably, is going to be,
00:33:24
"Well it depends on getting
clear on whether the stages are
00:33:30
glued together in the right
metaphysical way."
00:33:35
And so, what we'd like to know
is, well, what does it take for
00:33:41
two person stages to make up or
be part of the very same
00:33:47
extended-through-time person?
What's the metaphysical glue
00:33:53
that underlies being a single
extended-through-time person?
00:33:58
What's the key to personal
identity?
00:34:04
If we could get clear about
what the answer to that
00:34:08
metaphysical question,
the key to personal identity,
00:34:11
we'd at least know what we
needed to find out to answer the
00:34:18
question, "Is this one person or
two?"
00:34:22
Are the pieces glued together
in the right way?
00:34:29
Different question,
the question that we're
00:34:33
ultimately hoping to get an
answer to.
00:34:36
Could I survive my death?
Well look, think again about
00:34:40
the question we started with.
Could I survive the weekend?
00:34:45
To survive the weekend,
there's got to be somebody
00:34:50
who's alive, some person on
Tuesday and that person's got to
00:34:56
be the very same person as the
person you're looking at now,
00:35:03
you're thinking about now.
Or to put it in terms of
00:35:09
stages, that person's got to
be--that stage,
00:35:15
that slice has to be part of
the very same
00:35:20
extended-through-time space-time
worm as this stage is.
00:35:28
They've got to be glued
together in the right way.
00:35:31
We can't tell whether that's
true until we know what the glue
00:35:34
is.
But at least we anticipate
00:35:36
that, well, there will be
somebody here on Tuesday who is
00:35:40
glued together in that way,
the right way,
00:35:43
whatever that turns out to be.
The stages will be glued
00:35:46
together in the right way.
Suppose I asked then,
00:35:52
"Will I survive my death?"
All right, so I'm going to be
00:35:57
optimistic.
I'm going to assume that I make
00:36:01
it to 2040.
2040… I won't even be 90 yet.
00:36:04
That's not too wildly
optimistic.
00:36:06
It's optimistic,
but not wildly optimistic.
00:36:10
So here's the SK 2040.
We know that there's an
00:36:19
extended through space and time,
space-time worm,
00:36:25
a person.
Then let's suppose,
00:36:30
sadly, 2041 my body dies.
And I ask, "Could I survive my
00:36:38
death, that is to say,
the death of my body?"
00:36:42
Well, we want to know,
after 2041, let's say 2045,
00:36:51
is there somebody who's a
person, call him Mr.
00:36:59
X.
Could it be the case that
00:37:04
there'd be a person in 2045,
after the death of my body in
00:37:12
2041,
could it be the case that
00:37:15
there's a person who is part of
the very same space-time worm
00:37:21
that you're thinking about right
now?
00:37:26
Could that be or not?
We can't answer that question
00:37:32
until we are clearer about what
does it take to have identity
00:37:38
across time.
What's the key to personal
00:37:42
identity?
What's the metaphysical glue?
00:37:44
Once we get clear about what
the relevant metaphysical glue
00:37:48
is, we'll be in a position to
start asking,
00:37:50
"Could this happen or not?"
00:38:02
All right, that's the question
I want to turn to,
00:38:05
then.
What are the possible positions
00:38:08
on this question?
What's the key to personal
00:38:12
identity?
What's it to be the very same
00:38:15
person?
As we might put it somewhat
00:38:19
misleadingly,
what is it for "two" people to
00:38:23
really be the same single
extended-through-time person?
00:38:29
Suppose we believed in souls.
Then here would be a natural
00:38:34
proposal.
The metaphysical key to
00:38:38
personal identity is having the
very same soul.
00:38:44
So suppose I was a dualist.
I'd say, "Look,
00:38:47
you're looking at a body,
but connected in this intimate
00:38:51
way with this body is a
particular soul,
00:38:53
the soul of Shelly Kagan.
What makes it true that the
00:38:58
person lecturing to you next
Tuesday is Shelly Kagan,
00:39:03
the very same person,
what makes that true is that
00:39:07
it's the very same soul.
As long as this soul is here
00:39:12
again on Tuesday,
It'll be Shelly Kagan.
00:39:17
If it's a different soul,
it's not Shelly Kagan."
00:39:25
That's the natural thing to
suggest if we believe in the
00:39:29
soul view.
The key to personal
00:39:32
identity--not the only thing a
soul theorist can say,
00:39:37
but the natural thing for a
soul theorist to say--the key to
00:39:42
personal identity is having the
very same soul.
00:39:47
Same soul, same person.
Different soul,
00:39:53
different person.
Imagine that God or a demon or
00:39:59
what have you,
for whatever perverse reason,
00:40:04
severs the ordinary connection
between my body and my soul and
00:40:11
then reconnects the wires,
as it were, so that there's a
00:40:17
different soul animating and
controlling this body on
00:40:23
Tuesday.
For whatever perverse reasons,
00:40:26
maybe to make some sort of
philosophical point,
00:40:29
that person decides to come in
anyway on Tuesday and lecture to
00:40:34
you about philosophy.
According to the view that
00:40:39
we're taking,
which we'll now call the soul
00:40:42
view, according to the soul
view, it won't be me lecturing
00:40:46
to you on Tuesday.
Why not?
00:40:49
Because we've just stipulated
it's not the same soul.
00:40:53
It's a different soul.
The key to personal identity,
00:41:00
according to the soul theory of
personal identity,
00:41:05
the key to personal identity is
having the same soul.
00:41:11
When I ask myself,
"Will I survive the weekend?"
00:41:16
what I'm asking is,
"Will my soul still be around
00:41:18
come Tuesday?"
00:41:23
As long as my soul still exists
and is functioning,
00:41:26
it's still me.
I'm still around.
00:41:30
In fact--peeking ahead of
course, and this is why we are
00:41:34
often drawn to soul views--even
if my body dies,
00:41:38
as long as my soul continues to
exist, I continue to exist.
00:41:44
The key to personal identity,
according to the soul view,
00:41:47
is having the same soul.
As long as my soul continues to
00:41:50
exist, it's still me,
whether or not my body's still
00:41:53
alive.
00:41:59
And it's precisely for this
reason that at least the soul,
00:42:02
belief in the soul,
combined with the soul theory
00:42:06
of personal identity,
holds out the possibility of
00:42:09
surviving my death.
We may not know that the soul
00:42:13
will continue to exist after the
destruction of the body,
00:42:17
but at least it seems like a
possibility.
00:42:19
Plato of course,
as we know, tried to argue that
00:42:22
we could know,
that there was--there were good
00:42:24
grounds for believing the soul
would continue to exist.
00:42:27
I've said I don't find those
grounds so convincing.
00:42:31
But even if we didn't think we
could show that the soul would
00:42:34
continue to exist,
at least it could,
00:42:37
it would make perfect sense to
think about it continuing to
00:42:42
exist.
And so I could survive the
00:42:45
death of my body.
In contrast,
00:42:47
it looks--Prospects don't look
so promising for surviving my
00:42:53
death of my body if we don't
believe in dualism,
00:42:57
if we're physicalists.
If a person's just a
00:43:00
P-functioning body,
how could it be that after the
00:43:03
death of his body he's still
around?
00:43:05
Well, we'll say more about that
a little bit later.
00:43:09
Come back to the soul view.
It's me as long as it's the
00:43:16
same soul.
It's not me if it's a different
00:43:19
soul.
Now consider the following
00:43:23
possibility.
Suppose that over the weekend,
00:43:27
at 3:00 a.m.,
Saturday night,
00:43:30
Sunday morning,
while I'm asleep,
00:43:34
God replaces my soul with a
different soul,
00:43:39
hooks it up to the body,
gives that soul,
00:43:44
that replacement soul,
all of my memories,
00:43:49
all of my beliefs,
all of my desires,
00:43:53
all of my intentions.
Somebody wakes up Sunday
00:43:59
morning and says,
"Hey, it's a great day.
00:44:03
Wonderful to be alive.
I'm Shelly Kagan.
00:44:05
Got to get to work."
Whatever it is.
00:44:08
Says "I'm Shelly Kagan";
but he's not.
00:44:14
According to the soul view,
he's not.
00:44:17
Because according to the soul
theory of personal identity,
00:44:22
to be me that person's got to
have my soul.
00:44:25
And in this story,
he doesn't have my soul.
00:44:29
My soul got destroyed,
let's suppose,
00:44:32
3:00 a.m.
Sunday morning.
00:44:35
A new soul got created.
It's not me.
00:44:40
There's a person there,
all right.
00:44:43
It's a person that doesn't have
a very long history.
00:44:46
Maybe he'll go on to have a
long history.
00:44:49
But it's a different extended
through space and time person
00:44:53
than the one you're thinking
about right now.
00:44:57
Because, according to the soul
view, to be me it's got to have
00:45:01
the same soul and we just
stipulated, not the same soul.
00:45:05
Think about what that means.
If God were to replace my soul
00:45:13
Saturday night,
I die.
00:45:17
And the thing that wakes up
Sunday isn't me.
00:45:22
Of course, he'd think he was me.
He'd think to himself,
00:45:27
"I'm the very same person who
was lecturing about philosophy
00:45:33
last week."
But he'd be wrong.
00:45:39
It isn't the same person,
because it's not the same soul.
00:45:42
He'd be wrong and--notice
this--there'd be no way at all
00:45:49
he could tell.
He could check his beliefs.
00:45:53
He can check his desires.
He can check his memories.
00:45:56
But that's not the key to
personal identity,
00:45:59
according to the soul view.
The key to personal identity,
00:46:02
according to the soul view,
is having the very same soul.
00:46:06
You can't check that.
You can't see the soul to see
00:46:09
if it's the same one.
00:46:14
So if this were to happen to
him, he wouldn't be Shelly
00:46:19
Kagan, the person who'd been
lecturing last week.
00:46:23
But there'd be no way at all he
could know that.
00:46:28
And now the question you would
need to ask yourself is,
00:46:34
how do you know this didn't
happen to you last night?
00:46:39
You woke up this morning
thinking, I'm the very same
00:46:43
person--Joe, Linda,
Sally, whatever it is--the very
00:46:47
same person who was in class
yesterday.
00:46:50
How do you know?
How could you possibly know?
00:46:54
If God replaced your soul with
a new one, destroyed the old
00:46:57
one, gave the new one all the
old memories,
00:46:59
beliefs, desires,
goals, and so forth,
00:47:03
that person who was in class
last week,
00:47:06
yesterday, died.
The person who's here now
00:47:11
hasn't been around 10 years,
20 years, what have you.
00:47:16
You were born a few hours ago.
And there'd be no way at all
00:47:22
that you could possibly tell.
How do you know,
00:47:26
not only that it didn't happen
to you last night,
00:47:30
how do you know something like
this doesn't happen every single
00:47:36
night,
every hour on the hour,
00:47:39
every minute,
every second?
00:47:42
God whips out the old soul,
destroys it,
00:47:45
puts in a new one with--Maybe
souls only last for a minute and
00:47:50
a half.
If that was happening,
00:47:53
then people don't last very
long.
00:47:56
Bodies may last 20 years,
50 years, 80 years,
00:47:59
100 years, but people would
only last an hour or,
00:48:02
if it's every minute
substitution,
00:48:04
a minute.
And you'd never possibly be
00:48:09
able to tell.
Now these worries were raised
00:48:15
by John Locke,
the great British philosopher,
00:48:19
and he thought,
this is too big a pill to
00:48:23
swallow.
This is too big a bullet to
00:48:27
bite.
We can't take seriously the
00:48:30
suggestion that there's no way
at all to tell whether it was
00:48:35
still me from the one day to the
next,
00:48:38
from one hour to the next,
from one minute to the next,
00:48:43
just not plausible.
It's not that there's anything
00:48:46
incoherent about this view.
It doesn't say anything
00:48:49
logically contradictory about
this view.
00:48:51
You just have to ask yourself,
"Could this really be what
00:48:54
personal identity is all about?
That there'd be no way at all
00:48:58
to tell whether I've survived
from one minute to the next,
00:49:02
from one hour to the next?"
Locke thought no,
00:49:06
you couldn't possibly take this
view seriously if you thought
00:49:12
about what it meant.
Notice, this is not an argument
00:49:17
that souls don't exist.
If you find this argument
00:49:22
convincing, what it's an
argument for is the claim that
00:49:26
even if souls do exist,
they may not be the key to
00:49:30
personal identity.
And so what we have to ask
00:49:34
ourselves is,
what's the alternative?
00:49:36
What better suggestion is there
for what we could point to as
00:49:41
the metaphysical glue,
the key to personal identity?
00:49:46
And that's the question that
we'll take up next time.
