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Professor Shelly Kagan:
Last time, we turned to the
00:00:04
question of what the
metaphysical key to personal
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identity might be.
What makes it be the case that
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one person, some person that
exists in the future,
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is the same person as me.
The first approach to this that
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we considered was the soul
theory of personal identity:
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the key to being the same
person is having the same soul.
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Same soul, same person.
Different soul,
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different person.
And the difficulty with that
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approach, even if we bracket the
question whether or not there
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are souls,
the difficulty with that
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approach was that it seems as
though the soul could constantly
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be changing while the
personality,
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as we might call it,
stays the same.
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I have the same beliefs,
memories, desires,
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goals, preferences and so
forth.
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But the soul underneath it all
keeps being swapped every five
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minutes.
If the soul theory of personal
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identity were right,
that would not be me.
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I would be--Every five minutes
that person would die and we'd
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have a new person,
despite having the same
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personality.
Most of us find that a rather
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difficult thing to believe,
that the person could be
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constantly changing in this way,
without having any way at all
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to tell.
And if we're not willing to
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accept that implication,
it seems as though we need to
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reject "the soul theory of
personal identity."
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Now, I use this cumbersome
phrase because,
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of course, I'm not here talking
about rejecting the existence of
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souls.
What I'm considering right now
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is the question whether sameness
of soul is the key to being the
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same person.
And this is a--There's a
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logical distinction here that's
worth drawing.
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Even if you believe in souls,
you don't have to say that
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having the very same soul is the
key to being the very same
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person.
And trivially,
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of course, if you don't believe
in souls, if you don't believe
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that souls exist,
that you certainly can't appeal
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to the existence of souls,
the continuity of soul,
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the sameness of soul,
as the key to personal
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identity.
But we might then ask,
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"Well what's the alternative?"
Now, the natural alternative is
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to say, "The key to being the
same person is not the sameness
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of the soul,
whether or not it exists,
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but rather having the very same
body."
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And again, although I'm not
going to go on and on about this
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point, it's worth noticing that
even if you do believe that
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souls exist,
nothing stops you from
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accepting the body theory of
personal identity.
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Nothing rules out the
possibility that having the very
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same body is the key to being
the very same person over time.
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Even if you believe in souls,
you can accept the body theory.
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And it certainly looks as
though if you don't believe in
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souls, you have to accept the
body theory of personal
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identity.
Now, as it turns out,
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that appearance is deceptive.
There are still other
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alternatives open to the
physicalist, but let's come to
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that other alternative later.
Let's take a few minutes and
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consider the nature of the body
theory, the body theory of
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personal identity.
On this theory,
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of course, the secret to being
the same person is having the
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same body.
So when we ask,
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well you remember last lecture
I was talking about how there'd
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be somebody here lecturing to
you, philosophy,
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on Tuesday.
Well, here somebody is.
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Is that the same person?
Is the person who's lecturing
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to you now the same person as
the person who was lecturing to
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you before?
According to the body theory,
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the answer is--turns on the
question, "Well,
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is this the same body as the
lump of flesh and bone that was
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here last week?"
If it is--and by the by it
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is--if it is,
then it's the same person.
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So am I the person who was
lecturing to you last week?
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Yes, I am, because it's the
very same body.
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That's what the body theory
says.
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And unlike souls,
where it's all rather
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mysterious how you could tell
whether soul swapping was taking
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place or not,
it's not all that mysterious
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how we check out to see whether
the same body's been around.
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Even though you didn't do it,
you could have snuck into my
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house, watched my body go to
sleep,
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get up in the morning,
followed the body around over
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the course of the day,
see it go to sleep again.
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You could have tracked that
body through space and time and
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said, "Hey look.
It's the very same body."
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In the same way that we are
able to track in principle cars,
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our earlier example,
and talk about yeah,
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it's the same hunk of metal and
wire and rubber and plastic.
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This is the same hunk,
same body.
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All right, same body,
same person.
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That's the body theory of
personal identity.
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Now, if we accept the body
theory, then of course if we
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turn to the question,
"Could I survive my death?"
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Could I survive the death of my
body?"
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at first glance,
it looks as though the answer's
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going to have to be,
"Well, of course not."
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Because when my body dies,
then, oh eventually the body
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begins to decay.
It decomposes,
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turns into molecules which get
absorbed into the soil or what
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have you.
This may take years or decades
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or even centuries,
but my body no longer exists
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after death of my body.
And so how could I survive the
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death of my body,
if for me to survive the death
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of my body,
there's got to be somebody
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who's me, and if being me
requires it being the same body,
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my body would have to still be
around, but it's not.
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That's what it looks like at
first glance.
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But at second glance we see
that there's at least a logical
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possibility of surviving the
death of my body.
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All it takes is for my body to
be put back together.
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Bodily resurrection.
Now I'm not going to here
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pursue the question of,
"Do we believe bodily
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resurrection occurs or will
occur?"
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I'll note that there have been
religious traditions that have
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taught and believed in this
possibility.
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In particular,
it's probably worth mentioning
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that early Christians believed
in something like the body
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theory of personal identity and
believed in bodily resurrection
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that would happen on Judgment
Day.
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We can certainly understand the
possibility that God would
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perform a miracle,
put the molecules back
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together, turn the body back on.
Same body, same person,
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come Judgment Day.
That's the possibility.
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So it's at least worth
emphasizing the fact that even
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if we don't believe in souls,
we could still believe in the
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possibility of surviving one's
death, the death of one's body,
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if we're willing to believe in
bodily resurrection.
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Well, that's how it looks.
Now let's take a harder look.
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Talking that way assumes that
when you put the body back
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together, when God puts the body
back together on Judgment Day,
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that that's still my body.
Is that right?
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I'm inclined to think it is
right.
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If God gathers up all the
various molecules that had
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composed my body,
reassembles them in the right
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order,
putting this calcium molecule
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next to that hydrogen molecule
and so forth and so on,
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reassembles them in the right
way--obviously if what He makes
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out of my body's molecules is a
Cadillac,
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then that's not my body--but if
He puts them together in the
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right way, that seems like it
should be my body.
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So here's an analogy to give
you a sense of what's going on.
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Suppose I take my watch to the
jeweler because it stopped
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working.
And in order to clean it and
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fix it, repair it,
what the jeweler does is he
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takes it apart.
He takes the rust off of the
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gears, if there are still gears
in watches.
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Imagine it's an old stop watch.
And he cleans all the pieces
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and buffs them and polishes them
and then reassembles the whole
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thing.
And a week later,
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I come back and ask,
"Where's my watch?"
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And he hands it to me.
Well, all well and good.
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Now imagine some metaphysician
saying, "Wait a minute,
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buster.
Not so quick.
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That's not my watch.
Admittedly, it's composed of
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all the very same pieces that
made up my watch.
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Admittedly, all these pieces
are in the very same order as my
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watch, but still that's not my
watch."
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On the contrary,
it seems to me the right thing
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to say about that example is,
"No, that is my watch."
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My watch was disassembled for a
period of time.
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Perhaps we should say my watch
didn't exist during that period
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of time.
But it got put back together.
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Now that's my watch.
If that's the right thing to
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say about the watch--and it does
seem to me to be the right thing
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to say about the watch--then God
could presumably do the same
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thing on Judgment Day.
He could take our molecules,
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which had been scattered,
put them back together and say,
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"Ha!
That's your body."
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And if the body theory of
personal identity is right,
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well, that would be me.
So it seems to me.
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But there's a different example
that we have to worry about as
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well, which argues against this
proposal that the body could
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decompose and then be
recomposed.
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This is an example that's due
to Peter van Inwagen.
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He's a contemporary
metaphysician,
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teaches at Notre Dame.
Suppose that my son builds a
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tower out of wooden blocks.
We have a set of wooden blocks
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at home.
Suppose that he builds some
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elaborate tower.
It's very impressive.
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And he says,
"Please show it to mom when she
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comes home."
And he goes to bed.
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And I'm very good.
I'm cleaning up the house after
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he goes to bed and oops,
I knock over the tower.
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I say, "Oh my god,
he's going to be so angry.
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I promised him I'd be careful."
So what I do is I take the
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blocks and I put them back
together, building a tower in
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the very same shape and the very
same structure,
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the very same order as the
tower that my son had built.
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And in fact I'm so
careful--perhaps the blocks are
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numbered--I'm so careful that
every block is in exactly the
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same position as in the case
where my son built it.
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All right, I rebuild or I build
this tower and my wife comes
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home and I say,
"Look what our son built.
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This is the tower that our son
built."
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Ah, that doesn't sound right.
That's not the tower that our
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son built.
That's a tower that I built.
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This is a duplicate tower.
Sure, if my son were to wake up
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and I didn't tell him,
he wouldn't know that it was a
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duplicate.
But when you take a wooden
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block tower apart and then put
the pieces back together,
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piece for piece,
duplicate, you don't have the
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very same tower that you started
out with.
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That's what van Inwagen says
and, I've got to admit,
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sounds right to me.
If I were to point to that
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tower and say,
"Ari built that," I'd be saying
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something false.
"That's the very same tower
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that Ari built."
No, I'd be saying something
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false.
So van Inwagen concludes,
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if you have an object and you
take it apart and then put it
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all back together again,
you don't have the very same
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object that you started out
with.
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So even if Judgment Day were to
come, and God were to reassemble
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the molecules and resurrect the
body,
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it's not the very same body
that you started out with.
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And if having the very same
body is the key to personal
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identity, it's not the same
person.
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Come Judgment Day,
we've got a duplicate of me,
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but we don't have me.
That's what van Inwagen would
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say, if that's the way bodily
resurrection would work.
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I don't know,
theology aside,
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I don't know what to say about
the metaphysical questions.
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When I think about the tower
case, I do find myself inclined
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to say, with van Inwagen,
that's not the tower my son
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built.
But when I think about the
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watch case, I find myself saying
that is the very same watch.
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Now, all I can do is invite you
to think about these two cases
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and ask yourself,
what should we say here?
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Of course, for those people who
think it really is the same
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tower, no problem.
Then we say,
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the watch and the tower,
in both cases,
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it's the very same object when
it's reassembled.
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Reassemble the body,
that'll be the very same body
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as well.
For those people who say,
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"Yeah, van Inwagen was right
about the tower,
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and the same thing would be
true about the watch.
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The reassembled watch isn't the
very same watch," then we have
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to say bodily resurrection would
not be the very same
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body.
So that wouldn't be me waking
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up on Judgment Day.
The alternative is to try to
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find some relevant difference
between the watch case and the
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tower case.
Something that allows us to say
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that "well, when you reassemble
the watch it is the same watch.
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When you reassemble the tower,
it's not the same tower.
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Here's the explanation of why
those two things work
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differently in the reassembly
cases."
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And then of course,
we'd have to further
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investigate whether when you
reassemble a body,
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is it more like the watch case
or is it more like the tower
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case?
I just have to confess,
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I don't know what the best
thing to say about these cases
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is.
I find myself inclined to think
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reassembled watch,
same watch.
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Reassembled tower,
not same tower.
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Maybe there's a difference
there.
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I don't have a good theory as
to what the difference is.
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Since I don't have a good
theory as to what the difference
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is, I'm not in a good position
to decide whether a reassembled
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body would be the same body or a
different body.
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I don't know.
So there's metaphysical work to
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be done here by anybody who's at
least interested in getting this
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theory of identity worked out
properly.
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Still, at least the possibility
that we could work this out is
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still there.
So I suppose there's still at
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least the possibility that
bodily resurrection would be
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coherent in such a way that it
would still be the same body.
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So if we accept the body
theory, could there be life
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after death?
Could there be survival of the
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death of my body?
Seems like, as far as I can
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tell, it's still a possibility,
although there's some puzzles
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here that I don't know how to
see my way through.
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Mind you, that's not to say
that I myself do believe that
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there will be a Judgment Day,
and on that day God will
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reassemble the bodies.
But it at least seems like a
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coherent possibility.
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Let's refine the body view.
I've been suggesting that the
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key here, the idea of whether
it's the same person or not,
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is whether it's the same body.
But of course as we know in
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thinking about familiar objects,
we don't need to have every
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single piece of an object,
of an entity,
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stay the same to have the same
thing.
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So I think I previously talked
about the steering wheel in my
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car.
Every time I drive the steering
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wheel in my car,
I rub off some atoms.
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But that's okay.
It's still the very same
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physical object.
The steering wheel is--Having
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the same steering wheel is
compatible with changing of a
00:17:21
few pieces.
The same thing is true for
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bodies, right?
You get sunburned,
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your skin peels,
you've lost some atoms in your
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body.
It doesn't really matter.
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It's still the very same body.
So if body is the key to
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personal identity,
we don't have to worry about
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the fact that we're constantly
gaining and losing atoms.
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Yes, question?
Student: What about
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someone who loses a huge amount
of weight?
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Professor Shelly Kagan:
Good.
00:17:53
The question was,
"What about somebody who loses
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a huge amount of weight?"
They feel different.
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People treat them different.
What about that case?
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Well, I think if we're doing
metaphysics, as opposed to
00:18:06
psychology--Psychologically,
we understand why losing weight
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might make a real difference as
to how you feel about yourself.
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And we might even say,
loosely, it's as though she's a
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whole new person.
But strictly speaking,
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we don't think it is literally
a whole new person.
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It's not as though we say,
"Poor Linda died when she
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entered the spa.
Or a week into the spa when she
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dropped those 50 pounds.
Somebody else who remembers all
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of Linda's childhood,
some imitator came along."
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We don't say "different person."
We say "same person,
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lost a lot of weight."
Now that's not a problem for
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the body view,
because on the body view,
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the question is,
is it the same body?
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And what we want to say is,
of course, look,
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just like it's still your body
even if you break your arm.
00:19:04
Even though--It's still your
body after you've eaten dinner,
00:19:08
and so now some molecules have
been absorbed into your body
00:19:11
that weren't there before.
It's still your body after you
00:19:16
lose some molecules,
even a lot of molecules.
00:19:21
There can be changes in your
body that are compatible with it
00:19:27
still being the same body.
Now, we might worry about
00:19:33
the--Which changes?
Are all the changes,
00:19:36
it's certainly not as though
any change will do.
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I mean, suppose what happens is
Linda goes to bed and what we do
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in the middle of the night is we
take away that body and put some
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new body there.
Well that 100% change,
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that's clearly too much.
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Change of some small
percentage, from eating,
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not a problem.
Change from a somewhat larger
00:20:03
percentage of losing a fair bit
of weight doesn't seem to be a
00:20:07
problem.
So which changes in bodies make
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for a different body and which
changes in body make for the
00:20:17
same body?
And in particular,
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how should we run that if we're
thinking about the body as the
00:20:23
key to personal identity?
I think if we have that
00:20:26
question in front of our minds,
we're going to want to say not
00:20:31
all parts of the body are
equally important.
00:20:35
You lose a fair bit of weight,
some fat from your gut,
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not a problem.
Here's one of my favorite
00:20:40
examples.
In the Star Wars movies,
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Darth Vader whips out his light
saber and slashes off the hand
00:20:52
of Luke Skywalker.
"Luke, I am your father."
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"No!"
Then the hand goes, right?
00:21:00
The very next scene--this has
always amazed me--the very next
00:21:03
scene, Luke's got an artificial
hand that's been attached to his
00:21:07
body and they never even mention
it again.
00:21:10
No one says, "Oh, poor Luke.
He died when Darth Vader cut
00:21:16
off the hand."
It seems pretty clear that not
00:21:21
all parts of the body matter.
You can lose a hand and still
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survive.
Same body, except now without a
00:21:31
hand.
Suppose Darth Vader had aimed a
00:21:34
little higher and cut off Luke's
entire arm.
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It would still be Luke.
It would still be Luke's body.
00:21:41
Suppose, even worse,
Darth Vader slices off both
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arms and both legs.
It would still be Luke.
00:21:50
It would still be Luke's body,
though now without arms and
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legs.
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What part of the body,
if any, is essential?
00:22:00
Well here's a proposal.
It seems to me we'd say
00:22:04
something rather different if
what happened was that what got
00:22:09
destroyed was Luke's brain.
Suppose that Darth Vader uses
00:22:13
the force--the dark side of the
force of course--Darth Vader
00:22:17
uses the dark side of the force
to destroy,
00:22:20
to turn into pea soup,
Luke Skywalker's brain.
00:22:26
Now I think we might want to
say, "Well look,
00:22:28
no more Luke."
And if what happens is they
00:22:32
drag out some replacement brain,
it's still not Luke.
00:22:39
At least, that's a possible
version of the body view.
00:22:45
According to this version,
which I take to be the most
00:22:48
promising, the best version of
the body view,
00:22:51
the crucial question in
thinking about personal identity
00:22:54
is whether it's the same
body--but not all parts of the
00:22:57
body matter equally.
The most important part of the
00:23:00
body is the brain.
Well, why the brain?
00:23:03
No surprise there,
because of course the brain is
00:23:07
the part, we now know,
the brain is the part of the
00:23:11
body that is the house of your
personality,
00:23:15
your beliefs,
your desires,
00:23:17
your fears, your ambitions,
your goals, your memories.
00:23:21
That's all housed in the brain.
And so that's the part of the
00:23:27
brain that's the key part of the
body for the purpose of personal
00:23:34
identity.
That's what I'm inclined to
00:23:37
think is the best version of the
body view.
00:23:45
We find examples of this
thought, that the brain is the
00:23:51
key, in odd places.
So let me actually share one
00:23:55
with you.
This was something from the
00:23:58
Internet that my brother sent to
me some years ago.
00:24:01
It purports to be from a
transcript from an actual trial
00:24:06
in which a lawyer's cross
examining the doctor.
00:24:11
And you'll see.
I don't actually know whether
00:24:14
it's true or not,
whether it's just somebody made
00:24:16
it up.
But it purports to be true.
00:24:18
Q: Doctor,
before you performed the
00:24:22
autopsy, did you check for a
pulse?
00:24:24
A: No.
Q: Did you check for
00:24:28
blood pressure?
A: No.
00:24:31
Q: Did you check for
breathing?
00:24:34
A: No.
Q: So then it is
00:24:38
possible that the patient was
alive when you began the
00:24:43
autopsy?
A: No.
00:24:46
Q: How can you be so
sure, doctor?
00:24:51
A: Because his brain was
sitting on my desk in a jar.
00:24:58
Q: But could the patient
have still been alive
00:25:02
nevertheless?
A: It is possible that
00:25:06
he could have been alive and
practicing law somewhere.
00:25:12
The point--The reason that this
is funny, other than of course
00:25:17
the obvious moral,
which is that lawyers are
00:25:21
morons, is that of course.
Why is it so clear the lawyer's
00:25:25
got to be a moron?
Because of course we think,
00:25:27
look, lose a hand,
the guy could still be alive.
00:25:31
Lose an arm, lose a leg.
Lose the brain,
00:25:35
he's not alive.
So again this is,
00:25:38
this is hardly philosophical
proof, but it shows that we're
00:25:42
drawn to the thought that the
key part of the body is the
00:25:47
brain.
Now, think about what the
00:25:49
implication of holding that
view.
00:25:50
Suppose we adopt that version
of the body view.
00:25:56
If I get a liver transplant,
so here I am and we take out my
00:26:04
liver and we put Jones' liver
inside.
00:26:09
I've gotten a liver transplant.
It's still me.
00:26:14
Suppose we rip out my heart and
put Jones' heart in here.
00:26:20
I've gotten a heart transplant.
It's still me.
00:26:25
Suppose we rip out my lungs and
put in Jones' lungs.
00:26:31
I've gotten a lung transplant.
It's still me.
00:26:35
Suppose we rip out my brain,
put in Jones' brain.
00:26:42
Have I gotten a brain
transplant?
00:26:45
No.
What's happened is that
00:26:50
Jones has gotten a
body transplant.
00:26:55
Or, as we might put it,
a torso transplant.
00:27:00
If we accept this version of
the body theory,
00:27:04
we say the crucial part of the
body for personal identity is
00:27:10
not sameness of torso.
The crucial part of the body is
00:27:17
sameness of brain.
Just like "follow the soul" was
00:27:21
the answer if we believe in the
soul theory of personal
00:27:24
identity,
if we believe in the brain
00:27:27
version of the body theory of
personal identity,
00:27:32
same person or not?
Follow the brain.
00:27:37
Same brain, same person.
Different brain,
00:27:42
different person.
As I've now been saying several
00:27:46
times, I think that's the best
version of the body view,
00:27:49
although not all body theorists
believe that.
00:27:52
As you know from reading your
Perry, the assigned reading,
00:27:56
his Dialogue on Personal
Identity and Immortality,
00:27:59
the heroine of that story,
Gertrude--Gertrude actually
00:28:04
thinks the key part of the body
is the torso.
00:28:08
Follow the torso,
follow the person.
00:28:12
That's what she thinks.
I'm inclined to say, no.
00:28:15
In those moods,
when I accept the body theory,
00:28:18
I'm inclined to think,
no, follow the brain.
00:28:25
Gertrude would presumably say
you get a brain transplant,
00:28:29
you got a brain transplant,
because it's the same torso.
00:28:33
I want to say,
as a fan of the brain theory,
00:28:36
you get a brain transplant,
what's really happened is
00:28:40
somebody else has gotten a torso
transplant.
00:28:43
Follow the brain.
How much of the brain?
00:28:47
Do we need all of the brain?
Well, just like we didn't have
00:28:53
to follow the parts of the body
that aren't essential for
00:28:58
housing the personality,
we might ask ourselves,
00:29:03
"Do we need all of the brain to
house the personality?"
00:29:09
Research suggests that there's
a fair bit of redundancy in the
00:29:14
brain.
You can lose portions of the
00:29:18
brain and still have a perfectly
functioning, P-functioning
00:29:25
person.
Some of you may know that there
00:29:29
have been experiments in which,
for one reason or the other,
00:29:33
the two halves of the brain
have been separated.
00:29:37
And you often end up there
with, well, something closer to
00:29:42
two persons being housed within
one skull,
00:29:46
because they can often still
communicate in various ways.
00:29:49
We don't quite get that.
I gather that the best research
00:29:53
suggests we don't really have
complete redundancy with
00:29:56
hemispheres.
But suppose that we did.
00:29:59
Let's be science-fictiony.
Suppose that,
00:30:03
as a kind of backup security,
what evolution has done is
00:30:08
produced so much redundancy in
the brain that either half of
00:30:13
the brain would suffice.
All right, so think about our
00:30:17
brain transplant example.
So there's an accident with
00:30:21
Jones and Smith.
Jones' torso gets destroyed.
00:30:29
His brain is fine.
Smith's brain has gotten
00:30:34
destroyed.
His torso is fine.
00:30:37
We take Jones' brain;
we put it in Smith's torso.
00:30:42
We hook up all the wires,
as it were.
00:30:45
The thing wakes up.
Who is that?
00:30:48
Jones' brain, Smith's torso.
Follow the brain.
00:30:52
That's Jones that woke up.
Version two.
00:30:57
Horrible accident.
Jones' torso has been destroyed
00:31:01
and the left half of his brain
has been destroyed.
00:31:05
But the right half of his brain
is still there.
00:31:09
Smith's torso is fine,
but his entire brain has been
00:31:13
destroyed.
We take the right half of
00:31:17
Jones' brain,
put it into Smith's torso,
00:31:20
hook up all the wires the right
way, the thing wakes up.
00:31:26
Who is it?
It's Jones.
00:31:29
Follow the brain,
and more particularly,
00:31:33
follow however much of the
brain it takes to have enough of
00:31:39
the brain there to still give
you the memories,
00:31:44
beliefs, desires,
and so forth and so on.
00:31:47
If it were true--it probably
isn't true, but if it were
00:31:50
true--that half of the brain was
enough, then half the brain
00:31:53
would be enough.
That would be Jones that woke
00:31:56
up.
Question?
00:31:58
Student: [inaudible]
Professor Shelly Kagan:
00:32:03
Great.
The question was,
00:32:04
"On this theory,
what do we say about the case
00:32:07
where we take the two halves of
Jones' brain,
00:32:10
split them, put them in two
different torsos.
00:32:13
They both wake up.
Would they both be Jones?"
00:32:17
That's a wonderful question.
It's a wonderful case to think
00:32:21
about and, indeed,
I am going to come back to it.
00:32:24
But I just want to bracket it
for the time being.
00:32:28
But it's a great question to
keep in mind as you think about
00:32:33
the plausibility of the body
theory.
00:32:36
All right, so I'm inclined to
think that the best version of
00:32:41
the body theory has to do with
following the brain.
00:32:46
So one thing that a
physicalist, who does not
00:32:48
believe in souls,
one thing that a physicalist
00:32:51
could say is,
"What's the key to personal
00:32:54
identity?
The body.
00:32:56
Sameness of body."
And then I'm inclined to think
00:33:01
the best version of the body
view is the brain view.
00:33:05
So that's something that a
physicalist can say.
00:33:08
And for that matter,
it's something that a soul,
00:33:11
somebody who believes in souls,
could say as well:
00:33:13
even though there are souls,
that may not be the key to
00:33:16
personal identity.
Maybe sameness of body is the
00:33:20
key to personal identity.
That's something a physicalist
00:33:25
or dualist can say.
But, and this is not--to make
00:33:28
good on a promissory note I
offered earlier,
00:33:31
it's not the only view
available to physicalists or,
00:33:34
for that matter, dualists.
Even if there are no souls,
00:33:40
we don't have to say that the
key to personal identity is the
00:33:45
sameness of the body.
We could instead say the key to
00:33:51
personal identity is the
sameness of the personality.
00:33:58
After all, go back to the
Lockean worries about the soul
00:34:03
theory of personal identity.
It seemed very hard to believe
00:34:08
that it isn't the same person
when the memories and beliefs
00:34:13
and desires and goals and
ambitions and fears are all the
00:34:18
same,
even if a soul is constantly
00:34:21
changing.
It seems as though we wanted to
00:34:23
say same person.
Why?
00:34:25
Roughly speaking,
because it's the same
00:34:28
personality.
And with the body view,
00:34:31
when I started arguing a few
moments ago that the best
00:34:35
version of the body view was the
brain view,
00:34:38
why did that seem plausible?
Why didn't we say that Luke
00:34:42
died when he lost his wrist?
Because the brain,
00:34:46
after all, was the part of the
body that houses the
00:34:50
personality.
Enough of the brain was good
00:34:53
enough, I said.
What counts as good enough?
00:34:56
Enough to keep the personality.
Well, if what we think is
00:35:01
really important here is the
personality, why don't we just
00:35:05
say the key to personal identity
is the personality?
00:35:10
Let's just say it's me,
provided that there's somebody
00:35:17
who's got the same set of
beliefs, desires,
00:35:23
goals, memories,
ambitions, fears.
00:35:28
To coin a word,
the same "personality."
00:35:34
So the secret to personal
identity on this new proposal
00:35:40
isn't sameness of body,
it's sameness of personality.
00:35:53
Now, it's important to bear in
mind that this view is perfectly
00:35:59
compatible with being a
physicalist.
00:36:02
After all, we're not saying
that in order to have
00:36:07
personalities you need to have
something nonphysical.
00:36:12
As physicalists,
we can still say that the basis
00:36:16
of personality is that there are
bodies that are functioning in
00:36:22
certain ways.
But for all that,
00:36:25
the key to the same person
could have to do with the
00:36:30
personality rather than the
sameness of bodies.
00:36:34
Of course, normally the way you
get the same personality is by
00:36:40
having the same body.
Still, if we ask,
00:36:43
"What's doing the metaphysical
work here?
00:36:47
What's the key to being the
same person?"
00:36:52
we can say sameness of body
gave us the same personality,
00:36:56
but it was sameness of
personality that made it be the
00:37:00
very same person.
00:37:05
Could there be some way to get
sameness of personality while
00:37:09
not having sameness of body?
Maybe.
00:37:12
Suppose that we had some
disease.
00:37:16
The doctor tells me the
horrible news that I'm going to
00:37:19
have some disease that's going
to eventually turn my brain into
00:37:23
pea soup.
But luckily,
00:37:25
just before it does it,
they can take all of my
00:37:28
personality and put it into an
artificial replacement brain.
00:37:34
So there'll be --just like you
can have artificial hearts,
00:37:36
artificial livers,
you can have artificial brains,
00:37:38
which will get imprinted with
the same personality.
00:37:42
Same memory,
same beliefs,
00:37:44
same desires,
same fears, same goals.
00:37:47
We obviously can't do that.
This is a science fiction story.
00:37:51
But at least it allows you to
see how the body and the
00:37:54
personality could come apart.
And so we could have same
00:37:58
personality without literally
the same brain.
00:38:01
If personality is the key to
personal identity,
00:38:05
that would still be me.
Hold off again for a few
00:38:08
minutes, at least,
on the question,
00:38:10
"So what should we believe
here, the body,
00:38:12
the personality view?"
Let's try to refine the
00:38:16
personality theory.
So again, the point I was just
00:38:21
emphasizing was even if we
accept the personality theory,
00:38:25
this doesn't threaten our being
physicalists.
00:38:29
We can still say the reason
that we've got the same
00:38:31
personality in the normal case,
is there's some physical
00:38:34
explanation of what houses the
personality.
00:38:37
But for all that,
the key to personal identity is
00:38:41
same personality.
Notice, by the way,
00:38:44
that somebody who believes in
souls could also accept the
00:38:48
personality theory of personal
identity.
00:38:51
Locke believed in souls.
He just didn't think they were
00:38:56
the key to personal identity.
So you might think, "Oh no.
00:39:00
The physicalist is wrong when
the physicalist says that
00:39:03
personality--memory,
belief, consciousness,
00:39:05
what have you--is housed or
based in the body.
00:39:08
It's based in an immaterial
soul."
00:39:11
Dualists could say that.
And yet, for all that,
00:39:16
the dualist could consistently
say, "Still, same soul is not
00:39:21
the key to personal identity.
Same personality is the key to
00:39:26
personal identity.
If God replaces my soul every
00:39:30
10 minutes, as long as He does
it in such a way as to imprint
00:39:34
the very same personality on the
soul,
00:39:37
it doesn't matter any more than
it didn't matter whether or not
00:39:40
some of my body parts were
changing."
00:39:42
So the personality theory of
personal identity can be
00:39:46
accepted by physicalists and it
can be accepted by dualists.
00:39:57
So, just to keep score,
right now we've got three basic
00:40:02
theories of personal identity on
the table.
00:40:06
The soul theory,
the key to personal identity is
00:40:09
the same soul.
The body theory,
00:40:11
the key to personal identity is
the same body.
00:40:14
Where the best version,
I think, is the brain version
00:40:17
of the body theory.
And the personality theory,
00:40:20
the key to personal identity is
having the very same
00:40:24
personality.
00:40:30
Well again, we've got to be
careful about refining this.
00:40:33
Just like we all agreed,
I suppose, that you can have
00:40:37
the very same body,
even though some of the parts
00:40:40
come and go,
atoms get added,
00:40:43
other atoms get knocked off.
We can say, we'd better say,
00:40:48
that you can have the very same
personality even if some of the
00:40:54
elements in your personality
change.
00:40:58
After all, we defined the
personality in terms of it being
00:41:03
a set of beliefs and memories
and desires and goals and fears
00:41:08
and so forth.
But those things are constantly
00:41:12
changing.
I have all sorts of memories
00:41:15
now that I didn't have when I
was 10.
00:41:18
I have memories of getting
married, for example.
00:41:20
I wasn't married when I was 10.
So does the personality
00:41:25
theorist have to say,
"Uh-oh, different personality.
00:41:30
That kid no longer exists.
That person died,
00:41:35
got married and the memories
died."
00:41:38
If we say that,
we have very,
00:41:40
very short lives.
Because after all,
00:41:43
right now I've got some
memories that I didn't have two
00:41:47
hours ago.
I have some memories I didn't
00:41:51
have 20 minutes ago.
If every time you got a new
00:41:56
memory you had a new personality
and the personality theory said
00:42:02
having the very same personality
was the key to survival,
00:42:07
then none of us survive more
than a few seconds.
00:42:11
Well, the answer presumably is
going to be that the best
00:42:16
version of the personality
theory doesn't require item for
00:42:21
item having the very same
beliefs,
00:42:25
memories, desires, and so forth.
But instead requires enough
00:42:32
gradual overlap.
Your personality can change and
00:42:37
evolve over time.
So here I am as a 10 year old
00:42:41
child.
I've got certain desires,
00:42:44
certain memories.
As the year goes by,
00:42:46
I get some new memories.
I lose some of my goals.
00:42:50
I no longer--When I was 10,
when I grew up I wanted to be a
00:42:54
trash collector.
That was my first chosen
00:42:57
profession.
At some point I gave up that
00:43:00
desire.
I didn't want to be a trash
00:43:02
collector anymore.
I wanted to be,
00:43:04
I kid you not,
I wanted to be a logician when
00:43:07
I was a teenager.
I wanted to study symbolic
00:43:10
logic.
So at a certain point I gave
00:43:12
that up.
So my memories,
00:43:15
my desires were changing,
but they all changed gradually.
00:43:21
I lost some old memories.
I don't remember everything I
00:43:24
knew or remembered when I was
10.
00:43:26
When I was 10,
I had pretty vivid memories of
00:43:29
kindergarten.
Now I have very sketchy
00:43:32
memories of kindergarten.
Still, it wasn't abrupt.
00:43:37
It was gradual.
There was this slow evolution
00:43:41
of the personality.
And so when the personality
00:43:44
theorist says the key to
personal identity is the same
00:43:48
personality,
they don't' mean literally the
00:43:52
very same set of beliefs and
desires.
00:43:55
They mean, rather,
the same slowly evolving
00:43:59
personality.
00:44:04
Here's an analogy.
Suppose I had a rope that
00:44:08
stretched from that end of the
room all the way across to this
00:44:16
end of the room.
Very same rope at that end as
00:44:23
this end.
What makes up a rope?
00:44:25
Well as you know,
ropes are basically bundles of
00:44:28
fibers, very thin fibers that
have been woven together in a
00:44:32
certain way.
But the interesting thing is
00:44:35
the fibers themselves aren't
actually all that long.
00:44:39
They might be a couple of
inches or at most a foot or so.
00:44:42
And so no single fiber
stretches all the way across the
00:44:49
room.
Or even if some fibers did,
00:44:52
most of the fibers don't.
Does that force us to say,
00:44:56
"Ah, so it's not the very same
rope at the end as at the
00:44:58
beginning"?
No.
00:44:59
We don't have to say that at
all.
00:45:01
What we want to say is,
"It's the same rope as long as
00:45:06
there's this pattern of
overlapping fibers."
00:45:10
Certain fibers end,
but most of the fibers are
00:45:13
continuing.
Some new fibers get introduced.
00:45:15
They continue for a while.
Eventually maybe those fibers
00:45:19
end, but some new fibers have
been introduced in the meantime.
00:45:22
As long as it's not abrupt.
Imagine I take my scissors and
00:45:27
cut out a foot in the middle.
Then we'd say there isn't the
00:45:31
right kind of pattern of overlap
and continuity.
00:45:34
Now we really do have two
ropes--one rope here,
00:45:37
one rope there.
But if, in contrast,
00:45:39
there is the right kind of
pattern of overlap and
00:45:43
continuity,
same rope, even though,
00:45:46
even if no single fiber makes
it all the way across.
00:45:50
Something analogous needs to be
said by the personality
00:45:56
theorist.
Even if I have few or no
00:45:59
memories identical to the ones
that I had when I was 10,
00:46:05
that's okay.
We can still say it's the same
00:46:09
personality, the same evolving
personality, so long as there's
00:46:15
a pattern of overlap and
continuity.
00:46:19
New memories get added,
some memories get lost.
00:46:22
New goals get added,
some goals get lost.
00:46:26
New beliefs get added,
some beliefs get lost.
00:46:29
There might be few beliefs,
desires, goals that made it all
00:46:33
the way through.
But as long as there's the
00:46:36
right kind of overlap and
continuity, same personality.
00:46:40
All right, so what have we got?
Three views--soul view,
00:46:45
body view, personality view.
Three rival theories about the
00:46:50
key to personal identity.
Now, which of these is right?
00:46:56
Well, I don't myself believe in
souls, it's hardly going to
00:46:59
surprise you to learn that I
don't think the soul theory of
00:47:02
personal identity is right.
For me, the choice boils down
00:47:06
to the choice between the body
theory of personal identity and
00:47:11
the personality theory of
personal identity.
00:47:15
Of course, in real life,
they go hand in hand.
00:47:19
In ordinary cases at least,
same body, same personality.
00:47:24
Both theories are going to say
it's the very same person.
00:47:27
And if you believe in souls,
you are likely to think,
00:47:29
same soul as well.
In ordinary cases,
00:47:32
you have the same soul,
same body, same personality,
00:47:35
same person.
To think about which one of
00:47:39
these is the key to personal
identity, we need to think about
00:47:43
cases,
maybe somewhat fantastical,
00:47:46
science-fictiony,
in which they come apart.
00:47:49
Cases in which bodies and
personalities go their own ways,
00:47:56
as it were.
So that's what I'm going to do.
00:48:00
I'm going to tell you a story
in which your body ends up one
00:48:10
place and your personality ends
up someplace else.
00:48:18
And I'm going to invite you to
think about which of these two
00:48:24
resulting end products is me.
If you could figure out which
00:48:30
one's you, that would tell you
whether you think the body
00:48:34
theory is the right theory or
the personality theory is the
00:48:39
right theory.
Now, what's going to be our
00:48:44
guide?
I'm going to,
00:48:46
rather gruesomely--not in real
life, a science fiction
00:48:51
story--I'm going to torture one
of the two end products.
00:48:57
I'm going to ask you,
"Which one do you want to be
00:49:03
tortured?"
Or to put the point more
00:49:06
properly, which one do you want
to not be tortured?
00:49:11
Because I'm going to assume,
I'm going to take it,
00:49:16
that it's important to you that
you not be tortured.
00:49:21
So by seeing who you want to
keep safe, this will help you
00:49:26
see which one you think is you.
00:49:33
Of course, I've got to be sure
that you're thinking about this
00:49:35
in the right way.
Like some of you are probably
00:49:38
good, moral individuals and you
don't want anybody to be
00:49:42
tortured.
I say, "Ah, I'm about to
00:49:43
torture Linda over there."
You say, "No, no.
00:49:45
Don't torture Linda."
Still, if I were to say to you,
00:49:50
"I'm about to torture you."
You'd say, "No, no!
00:49:53
Don't torture me!"
and there'd be some extra
00:49:56
little something when you said
that, right?
00:49:58
So I want to invite you to keep
that extra little something in
00:50:04
mind when we tell the stories,
which we won't get to until
00:50:08
next time, when we tell the
stories next time,
00:50:10
and I say,
"Okay, who do you want to be
00:50:12
tortured, this person or that
person?"
00:50:14
The question is,
from that special egoistic
00:50:17
perspective that we're all
familiar with,
00:50:20
which is the one you really
care about?
00:50:23
That's going to be our guide to
deciding what's the key to
00:50:28
personal identity.
But to hear the stories,
00:50:31
you've got to come back next
lecture.
