I. The problem of personal identity
- Remember that the founders of analytic philosophy wanted to
get away without doing metaphysics; they wanted only to do science
- But it turned out that this was impossible. They needed to
account for a lot of things that traditional metaphysics did.
- Remember the notion of a substance from Descartes. The
wax itself—the substance—is what remains throughout the changes.
- Even modern scientists need something like that. They need
to be able to explain what makes the butterfly "the same thing" or
"the same organism" as the catterpillar—as opposed to saying
that the caterpillar died and a new organism was born. They don’t
necessarily have to explain this in terms of substances, but they
have to have some account of identity over time.
- To say that things are identical is to say that they are the
same. But there are two meanings of same. (1) being one and the
same thing, or (2) being exactly similar, i.e., having all properties
- This is the difference between numerical and qualitative
identity. Identical twins are qualitatively identical; they
are exactly alike. But they are not one and the same thing. On the
other hand, I am numerically identical to the person I was when I
was four. This means that I am one and the same person. But notice
that I'm not qualitatively identical to who I was then.
- The notion of identity of time is thus a notion of numerical
identity. A lot of interesting questions are raised when we apply
this to people.
- The question of personal identity is a question of the
conditions of the numerical identity of persons, i.e. it is about
what makes this time-slice of me the same as earlier and later time
slices of me.
- PERSONAL IDENTITY IS NOT ABOUT QUALITATIVE IDENTITY.
- PERSONAL IDENTITY IS NOT ABOUT A PERSON’S "SELF-IMAGE"
OR "IDENTITY" IN THE SENSE IN WHICH IT'S OFTEN TALKED ABOUT IN ORDINARY
II. The Set-up to the Dialogues
- Three characters: Gretchen Weirob, philosophy professor, Dave
Cohen, one of her students, and Sam Miller, college chaplain and
- Gretchen has been badly hurt in motorcycle accident. Only has
a few days to live.
- Sam seems relatively unconcerned about Gretchen’s imminent
death. This is because he, unlike her, has a strong belief in life
- They decide to engage in a discussion about the possibility
of life after death. They admit from the outset that Sam
will never convince Gretchen that it's probable that there is life after
death, but she says she'll accept an argument to the effect
that it's even possible—that is, imaginable—that there
could be life after death, given the inevitable facts.
- It should be easy to see how this relates to the problem of
personal identity. The question of my life after death is the question
of whether there could be a being numerically identical to
me, who lives after my death.
- So you can see why she dismisses the "merger with being" hypothesis.
Survival after death means survival of the self. I don't survive
death unless there is a being which is uniquely me after
III. The Kleenex box
- Sam says its easy to imagine the two of them meeting sometime
in the future in a very different place
- Gretchen uses the analogy of the kleenex box to call this into
question: but I will rot in a few days. How can, after I rot,
the same person suddenly exist somewhere else. It's as if I burned
this kleenex box to ashes and you told me the very same one was sitting
at home on the self! Wouldn’t that be absurd?
- Sam says there could be an exactly similar box, but Gretchen
says this is not relevant. It needs to be one and the same box. I
can't anticipate having the experiences of someone just because
she's exactly like me.
- Focus on key concept of anticipation--I must be able
to anticipate the experiences of future temporal parts of myself.
I need to be able to remember and be able to feel proud of what past
temporal parts of myself have done.
IV. Sam's first theory: Personal identity is based on the sameness of
- Refers to the work of Descartes: the soul is not the same as
the body. It is an invisible, intangible, inaudible and immaterial
substance that in principle can exist separate from the body. It's
true that her body will rot, but not her soul, and that's what's
- Gretchen asks about how he can then make personal identity
judgements. How does he know she is the same person he ate lunch
week last week? He has to be able to know that her body is
inhabited by the same immaterial soul.
- But how does he know he’s not talking to Barbara Walters or
Mark Spitz? Perhaps by some strange turn of events, one of their
souls came to inhabit her body.
- Sam: I use the principle "same body, same self (same soul)".
V. Problems with "Same body, same self"
- The problem that is if you also apply this principle to heaven,
it becomes impossible for someone to survive after death of the body.
- Sam responds that "same body, same self" is a rule of thumb
only applicable on this earth, where it is a well-confirmed regularity.
- But then it cannot be known a priori, because it's not a necessary
- But how can it come to be known through experience? We don't
experience other people’s souls. How can we confirm this regularity?
- Box of chocolates example.
- Gretchen: Therefore, since we have no way of knowing "same
body, same self", our personal identity judgments would be groundless
and silly. But they obviously are not groundless or silly, so there
must be something wrong with your theory.
VI. Knowledge via Psychology
- Sam: Although I can't see your soul, I do have a way of "biting
into the chocolate" so to speak. When I talk to you, I recognize
your psychological traits. The way you think, reason and choose to
behave are all properties of your soul, not of your body, and I
do have access to them. If you acted very differently, I would
conclude you were someone else. But since you act like you, I know
it's still you with your body.
- Gretchen responds with the Blue River example: Sameness is
characteristics does not require sameness of substance. It could
be the same substance "flowing through the same spot" or through
the same body, in her case.
VII. Abstracting from one's own case.
- Sam says he knows from his own case that his body goes with
his soul. It may be kind of an inductive leap, but since there is
no reason to think otherwise, he assumes the same is true of everyone
- Gretchen: but you don't really know about your own case. Perhaps
exactly 5 years ago the soul in your body then vanished unnoticeably
and a new one took over with all the same memories and psychological
traits as before. It remembers being the old one. It does not know
that it is not the same soul.
- Suppose that happens every five years, or every five minutes,
or continually. The Blue River example also applies to you.
- Gretchen is very skeptical about the very idea of souls, because
she thinks it's impossible to say what "soul identity" consists in.
But the real problem is that if personal identity is based on identity
of souls, then our personal identity judgments are completely
VIII. Objections to Gretchen's theory
- At the end of the first dialogue, Gretchen claims that her
own belief is that a person is just a live human body. Personal identity
is therefore based on sameness of the physical body.
- Sam doesn't quite know how to keep arguing for the idea that
sameness of self is based on sameness of an immaterial substance,
but he does think Gretchen's positions works either.
- His counter-example is that of waking up in the morning. A
person could tell who she was without looking around. This means
that a person does not need to look to see if she has the same body
to tell if she is the same person.
- You can even imagine yourself waking up with a different body--the
body of someone else, or even a cockroach. So obviously the theory
that personal identity is based on sameness of body is not true,
or else we couldn't imagine this.
- Where does this leave us? Sam has given arguments for why personal
identity can't be based on the sameness of physical substance. Gretchen
has argued that it isn't based on the sameness of immaterial substance.
The conclusion? Personal identity is not based on the sameness
of a substance at all!
- When we make personality identity judgments, we are not claiming
that there is any thing that is the same. We are only judging
that the person is the same, but the survival of a person over time
does not mean survival of any thing.
- Leads into memory theory.
IX. The Memory Theory
- Sam again talks about the Blue River. He asks us to imagine
seeing two different parts of the same river. What makes the two
parts parts of the same river? It's not because we are seeing
the same substance at all. Rather, we are seeing certain substances
that are connected in some way. Specifically, in this case, they
are connected by stretches of water.
- Another analogy: doubleheader. Stupid to ask "Is this game
the same game as itself?" But it makes sense to ask "Is this the
same game as it was before I went for hotdogs?" But what is "the
same game"? Again, it's not some substance, but about how
what you're seeing now is connected by what was before.
- A person is a "stream of consciousness"--a collection of different
states. To say that I am the same person I was when I was four is
to say that Kevin here and little Kevin are two parts of the same
stream of consciousness.
- But what is the relationship between these person-stages that
unite them into a stream of consciousness?
- We can extend our consciousness forward and backward in time.
- Locke: extending backward in time. That we exist in the same
stream of consciousness as we did is why we can remember having certain
- This theory basically states that person-stage X and person-stage
Y are part of the same stream of consciousness, and thus the same
person, iff X can remember being Y or Y can remember being X.
- So here we can see how survival after death is possible, for
there may be being who remember being us, whose consciousness is
continuous with our own.
X. Actually remembering and seeming to remember
- Gretchen's response: There are such things as false memories.
Some people claim to remember being Napoleon. Surely, such people
are not the same person as Napoleon.
- Therefore, there must be a distinction between actually remembering
and only seeming to remember, and the memory theory must state that
X and Y are the same only if one of them actually remembers being
- The question is: how do we explain the difference?
- Hypnotist example.
- Sam's response: the person actually remembering is the person
who actually had the experience.
- Problem: that involves a personal identity judgment... you
need to say that the person actually remembering is the same
person as the person who actually had the experience, but the
person who is only seeming to remember is a different person
- But then we need personal identity to explain actually remembering,
but we also need actually remembering to explain personal identity.
This is circular in a bad way.
XI. The Caused-in-the-right-way Hypothesis
- In order to avoid the problem of circularity, Dave (who has
been silent so far), suggests that instead of explaining the difference
between actually remembering and seeming to remember in terms of
whether or not that same person performed the thing remembered (and
thus involving personal identity), Dave suggests that the difference
between real memory and apparent memory should be explained
in terms of the memory being caused the right way.
- When the causation is all internal to the brain, it's probably
the right sort of causation, but if it involved other people--like
the hypnotist, then obviously we don't have the right sort of causation.
- "a person is a sort of causal process"
- The question then becomes how to describe "the right sort of
causation". Does it necessarily have to be all internal to the brain?
If so, then this theory doesn't allow for life after death.
- But if we allow causation via God to count, then there are
other problems. God could conceivably create 2 or 4 or 6 people who
remember having my experiences. But these people can't all be identical
to me, because they're not identical to each other.
- Dave points out that God could create just one. It's only a
problem if God create mores than one, and all we're looking for here
is the possibility of survival.
- Gretchen: but this really amounts to a change in your view.
Now memory alone isn't enough for personal identity, but rather memory
plus "lack of competition"
- And this is an absurd theory. Why would I be able to anticipate
having a being's experiences only until God creates another one?
The being in heaven wouldn't even know who she was unless she knows
what God has done. Finally, God could create another Gretchen in
Albuquerque, thus killing her right then.
- She's not saying that God would do such things, but that their
theory is absurd for saying that if God did, she would cease to exist.
XII. Introduction to the Third Night
- They agree to talk about personal identity without necessarily
in conjunction of seeing how it relates to the question of life after
- Why? What's really going here is that Dave was attracted to
the theory that personal identity is based upon a certain sort of
causal process internal to the brain.
- Gretchen never actually did anything to shoot down this theory.
All she said was that it wouldn't allow for immortality, which shut
Sam up. Dave, however, is not religious and doesn't mind the consequence.
- He thinks this theory has advantages over hers, which makes
personal identity based on sameness of the body as a whole
. Therefore, he gives the Julia North case as an example.
XIII. The Julia North Case (Not an actual event, but the characters pretend
- Julia North was a person who was hit by a train saving the
life of child. The child's mother, Mary Frances Beaudine, had a stroke
watching the scene.
- Julia's brain remained unscathed, but her body was destroyed.
The opposite was true for Mary Frances, so they put Julia's brain
in Mary Frances's body.
- The resulting person looked just like Mary Frances and had
her body, but had the memories and psychological traits of Julia.
- Most people--including Sam and Dave--clearly think that the
new person is the same person as Julia North, not Mary Frances.
- They think this proves Gretchen wrong. Personal identity cannot
be based on sameness of body, or the survivor would be Mary Frances
and not Julia.
- But this is exactly what Gretchen believes. Are they at an
XIV. The Supreme Court and Convention
- At this point, Dave appeals to the supreme court, which allegedly
ruled that the new person is Julia North
- He points out that we normally assume personal identity goes
along with both bodily identity and psychological continuity. But
when these normal cases don't apply, we need to appeal to things
like the Supreme Court to resolve questions of how old concepts apply
to new cases.
- Gretchen's response: No, personal identity cannot be about
how to apply words or the conventions adopted by any legal body.
- Aspirin example: It's only appropriate for me to anticipate
the experiences of someone who is identical with me. But the supreme
court can't decide whether I ought to take the aspirin. It's not
a matter of convention.
XV. Supposed Advantages of Memory/Brain Theory
- They are at an impasse. But Dave says that there are two advantages
to their theory
- The first is that it explains how we can know who we are without
opening our eyes--it's because personal identity is based on memory
and psychological continuity rather than on the body.
- Secondly, it stresses on what we take to be important about
people: their psychological traits and life histories. It does not
focus on the body, which we take to be less important.
XVI. Brain Rejuvenation
- Their current theory focuses on causation internal to the same
- Gretchen asks if it is crucial if the same brain be involved
- Suppose a new brain could be built--for likely stroke victims--in
which all the memories, etc., of the old brain are duplicated, but
the potential health risks avoided
- Will the person with this new brain be the same as the person
whose brain it replaced?
- Problem with saying yes: Then one could create 10 such brains,
and you get the same absurdity as before.
- But Gretchen also isn't happy with them saying no. Now, the
very same brain is requried. But suppose they did create
a new Gretchen brain, and put her current brain in another's body.
Now we have Gretchen-A and Gretchen-B.
- Which is the real Gretchen? Dave has to say that's it's whichever
one got the old brain, Gretchen-A.
- But can Gretchen-A and Gretchen-B know who's the real Gretchen
just by thinking about it? They both remember being Gretchen. So
it's not actually true on their theory that a person can tell who
she is before she opens her eyes.
- It's also not true that their view tracks psychological traits--Gretchen-A
and Gretchen-B have the same psychological traits. Both seem to preserve
what is important about Gretchen.
- The conclusion: so much for the supposed advantages of your
weird theory. Why not accept my theory--it's much simpler?
XVII. Are we even interested in personal identity?
- At the very end, before Gretchen dies, Dave very quickly suggests
a different sort of theory. He never gets to elaborate but it's very
- He asks suppose you went through the procedure. Perhaps for
theoretical reasons we can't say that the new person is identical
to you, but the person would be happy, and we'd be happy
having someone around like you.
- Maybe what we're interested in is not identity at all--where
that is taken to be a transitive, symmetric, reflexive relationship--but
merely survival. Perhaps it's possible for us to anticipate the experiences
of beings who are not identical to us.
- Derek Parfit talks about a race of birfurcating creatures.
Every few months, the race of aliens splits into two beings, each
of which remembers being the old being. We can't say that either
of the new beings is identical with the old one, or else they'd have
to be identical with each other, but that's impossible. But
perhaps it would not have been improper for the old to anticipate
the experiences of the experiences of both of the new creatures.
So identity is not a necessary condition for anticipation.
- Perhaps what we're interested in is survival--which needs not
be transitive, reflexive and symmetric--not identity at all.
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