10. Personal identity, Part I: Identity across space and time and the soul theory

10. Personal identity, Part I: Identity across space and time and the soul theory


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

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