Introduction to
Personal Identity
Lecture 7
Dan Turton
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Personal Identity Essay
Question
• What is the best theory of personal
identity and why?
• Explain and evaluate at least two
common philosophical theories about
personal identity, including
‘psychological continuity theory’.
• Apply these theories to at least one
‘whacky’ thought experiment and the
real-life split-brain experiments as
part of your evaluation.
Personal Identity
• Who am I?
• What makes me the same
person through time?
• What happens to me if
I’m copied?
• What about people who
have their brains
chopped in half!?!
• Hard questions, even if
we have all of the facts
Terminology
• Numerical Identity
– A (literally) unique thing
• Qualitative identity
– Looks, feels, tastes (etc) identical
• Essential properties
– Required for numerical identity
• Accidental properties
– Can change without affecting
numerical identity
Personal Identity & the
Afterlife
• It can comfort us to think that
our loved ones live on somehow
after death
• But what would that really entail?
Reincarnation
• You are reborn into a new body
after death
• PROBLEM: Reincarnations don’t
seem to be the same person
Resurrection
• You (and your body)
come back to life
after you die
• PROBLEM:
– Need an earth-like
place to go to
– If we’re recreated
exactly the same,
we’ll just die again
Soul Liberation
• When we die, our soul leaves our
body to live on somewhere else
• PROBLEMS:
– What, exactly, is a soul?
– If the soul is just the mental, then
how can it live on?
– Is my soul (without my
body) human enough to
be me?
Cryogenics
• Being frozen until medical
advances can fix all your
ailments
• PROBLEMS:
– Technological risk
– The brain may be
too damaged
Cyborgs
• Use technology
to keep us
alive!
• PROBLEMS:
– Will it ever
work?
– How will we
know?
Personal Identity & the
Accident Victim
• Brain damage and
amnesia could
drastically
change what a
person is like
• But, would it
change who they
are?
COMINS
• Continuity of
the Mental Is
Necessary for
Survival
• VERDICT: Mr Edward’s son has not
survived the accident
• PROBLEM:
– How much and what type of ‘the
mental’ has to continue and how must
it continue?
CEBINS
• Continued Existence of
the Body Is Necessary
for Survival
• VERDICT: Mr Edward’s
son has survived the
accident
• PROBLEM:
– This may be necessary,
but is it sufficient for a
person to survive?
CESINS
• Continued Existence of
the Soul Is Necessary for
Survival
• VERDICT: Mr Edward’s son
has survived the accident
• PROBLEM:
– If it’s not the body or the
mental… what, exactly, is
the soul again?
Take Home Lessons
• Please don’t do any
life-after-death
experiments when you
get home!
• He’s our best bet for
life after death, so
start saving now!
• The beauty of youth is
fleeting – enjoy it
while you can!
For Next Time
• Read:
– Baggini, Julian: The Elusive I (p8)
– Law, Stephen: Brain Transplants,
‘Teleportation’ and the Puzzle of
Personal Identity (pp9-14)
• Get ready to discuss:
– Two promising theories and the
‘whacky’ thought experiments that
seem to refute them
Bodily
Continuity
vs
Psychological
Continuity
Lecture 8
Personal Identity Essay
Question
• MAIN QUESTION: What is the best theory
of personal identity and why?
• INSTRUCTIONS: Explain and evaluate at
least two common philosophical
theories about personal identity,
including ‘psychological continuity
theory’.
• INSTRUCTIONS: Apply these theories to
at least one ‘whacky’ thought
experiment and the real-life splitbrain experiments as part of your
evaluation.
Personal Identity
• We want our theory to be
able to provide answers
to questions like these:
• What makes me me?
• What makes me the same
person through time?
• What happens to me if
I’m copied?
• What about people who
have their brains
chopped in half!?!
The elusive ‘I’
• Who here thinks
they exist?
• Cogito ergo sum
• Meditation time
• Lets ‘find
ourselves’
• Where am ‘I’ ?!?!
Sci-Fi Disclaimer
• The following ‘whacky’
thought experiments may
never be possible in real
life
– But, then again, they might!
• Regardless, a good theory of
personal identity should be
able to answer theoretically
possible as well as actually
possible problem cases
Animal Theory
• In essence, each
person is a living
animal
• What essentially
makes me me
through time is that
I am the very same
living creature as
the one in the
photos
Brain
Transplant
Case
• A brother and
sister have
their brains
swapped while
they slept one
night
• Problem for the
Animal Theory
Brain Theory
• In essence, each
person is their
unique living brain
• What essentially
makes me me
through time is
that I have the
very same brain as
the ‘me’s in the
photos
Brain
Recorder Case
• This device resplices the existing
brain bits so that a
pre-recorded
personality (etc) can
be downloaded into
the (same) old brain
• Problem for the Brain
Theory
Stream Theory
• AKA: Psychological Continuity Theory
• In essence, each person is (the right
kind of) continuation of psychological
properties
• E.g. What MIGHT essentially makes me me
through time is that my memories are
psychologically continuous
The Reduplication Case
• This device makes perfect copies of
anything put in cubicle A (in c. B)
but the original is vaporized
• A new model also makes a duplicate
in cubicle C
• Problem for the Stream Theory?
Modified Stream Theory
• In essence, each person is (the right
kind of) continuation of psychological
properties
• Except when two or more people are
psychologically continuous (in the
right kind of way) from one person
– In which case, none of those later people are
the same person as the original person
The Duplicator Gun Case
• This device makes a perfect copy of
anything shot with it but it doesn’t
destroy the primary target
• Problem for the Modified Stream
Theory
They All Seem Wrong!
• The Animal Theory
– Gets the brain transplant and
recorder cases wrong
• The Brain theory
– Gets the brain recorder case wrong
• The Stream Theory (AKA the
Psychological Continuity Theory)
– Gets the reduplication and
duplicator gun cases wrong
• The Modified Stream Theory
– Gets the duplicator gun cases wrong
The Teletransporter Case
• You have been ‘teletransporting’ to work
(on a very distant planet) for 3 years
• You are at work when you are informed that
the ‘teletransporter’ really works like the
reduplicator (it copies & kills you)
• Do you get in and ‘teletransport’ home?
Why? Why not?
Take Home
Lessons
• This course is about
tackling the big
questions, not
necessarily the
relevant ones
• If you do something
stupid quickly get soo
drunk you lose your
memory of it – then it
wasn’t you who did it
• With a duplicator gun we
could win the world cup
For Next Time
• Read:
– Nozick, Robert: Personal Identity
through Time (pp15-26)
• Get ready to discuss:
– Nozick’s more complex views on this
topic
The Closest
Continuer Theory
Lecture 9
Some Theories of P.I.
• CEBINS: Continued Existence of the Body
Is Necessary for Survival
– E.g. The Brain Theory
• CESINS: Continued Existence of the Soul
Is Necessary for Survival
– E.g. The Soul-Pellet Theory
• COMINS: Continuity of the Mental Is
Necessary for Survival
– E.g. Psychological Continuity/Stream Theory
• E.g. You have to remember being your previous self
(and that previous self has to remember being a
more-previous self and so on)
Nozick: Personal
Identity through Time
• Bernard Williams’ main
Principle for P.I.:
• The numerical identity of
something cannot depend
on facts about other things
• Because what makes you
uniquely you is not
dictated by facts about
things other than you
The Vienna Circle (TVC)
• 3 of the 20 original members
continued meeting in Istanbul
• Later, they hear that all of the
other TVC members are dead and
considered themselves as ‘TVC’
• Later still, they hear that 9
other members have been meeting
in New York the whole time and
realised that they were just an
offshoot of the real TVC in NY
• Thus Williams’ principle is false
Closest Continuer Theory (CCT)
• What essentially makes me me
through time is that I am
always the (one) closest
continuer of the previous me
• And that the closest continuer
(CC) is close enough
– I.e. too dramatic a change of an
essential property (even) in the
cc will mean that the cc is not
numerically identical with the
original
The Vienna Circle (TVC)
• Later, the 3 hear that all of the
other TVC members are dead and
considered themselves as ‘TVC’
– Because they are the closest
continuer of TVC
• Later still, they hear that 9
other members have been meeting
in New York the whole time and
realised that they were just an
offshoot of the real TVC in NY
– Because they are not the closest
continuer of TVC
The Ship Theseus
• A repaired ship is the CC of the
original
• Until the old parts are all put
together in ship B
More Specific on the CCT
• Being the closest continuer needn’t
involve being qualitatively similar
– Although it often will
• More important is that the CC is
causally dependant (in the right kind
of way) on the original
– E.g. The CC has grown or developed out of
the original (or maybe) was caused by it
• There can be many factors that are
relevant to being the CC, but they
needn’t all be necessary (essential)
How Do We Discover the
Dimensions of Closeness?
• Nozick: Introspect
• We have intuitions about
whether something is
numerically identical with
something else
• We must analyse these intuitions
to discover what makes
something ‘closest’ to the
original in each particular case
• PROBLEM: Intuitions might track
accidental properties
The Duplicator Gun Case
• This device makes a perfect copy of
anything shot with it but it doesn’t
destroy the primary target
• CCT seems to work in this case
Modified Brain Transplant
Case
• You’re dying of a heart
attack, but your brain is
transplanted into a
healthy clone of your body
• The old body dies as the
new one comes to life
• CCT says that the clone
with your brain is now the
real you
Conflicting Judgements
• What if our intuitions are
different?
• What if we disagree about what
the dimensions of closeness (the
important properties) are?
• Nozick thinks we can eliminate
most disagreement by comparing
cases and going for consistency
• But maybe the CCT is too flexible
Brain Splitting Case
• You have ½ of your brain
transplanted into a
clone of yourself
• Both you and the clone
live on with full
psychological
continuity
• CCT says that you are
still you and the clone
is a different person
Random Cosmic Occurrence
Case
• A random chemical reaction on a
distant planet creates a perfect
copy of you exactly as you die
– But not caused by you in any way
• CCT says it’s not you because it
isn’t caused by you
Teletransporter Case Revisited
• You’ve been teletransporting to work (on a
very distant planet) for 3 years
• Nozick: teletransporting probably
destroys you because if Person A was not
destroyed then Person B would not be the
Closest Continuer
– So on the CCT, Person B is probably not close
enough to Person A to be numerically identical
to them
Mono-Relatedness & Jumping
• More specifically, CCT entails that
numerical identity can only pass
between pairs of closest continuer
and closest predecessor
• Strangely, this allows ‘jumping’ if
being temporally connected is not
set as a dimension of closeness
Overlap Brain Splitting Case
• You have ½ of your brain
transplanted into a clone of
yourself
• Both you (A) and the clone (B)
have full psychological
continuity
• But you slowly die
• Nozick/CCT says that A is you
until A dies, then you jump
to B – depending on how long
it takes A to die!
Overlap Brain Splitting Case 2
Nozick on the Overlap Problem
• The CCT is a good theory, but cases of
overlap seem to show that it’s wrong
• The problem is that we want to claim
that D is a later A, but we can’t when they
overlap
– Because D is closest to C, A is closest to B,
and B and C exist simultaneously so they
cannot be numerically identical
3 Different Types of Theory
of Personal Identity
1) Intrinsic Abstract Structural
* E.g. Soul-Pellet Theory
2) Relational
* E.g. Psychological Continuity Theory
3) Closest relative
* E.g. Local Closest Continuer Theory
and Global Closest Continuer Theory
The Soul-Pellet Theory
• What essentially makes me
me through time is that all
of the ‘me’s have my one
unique soul
• PROBLEMS:
– What is a soul?
– How does it know where to go
in the reduplicator case?
– What if it didn’t pay attention
and lost your body?
Nozick’s Parting Shots
• CCT is the best, but it has major
problems:
– Overlap
– weighting/lexicaltiy of dimensions of
closeness
• There are no fixed facts to construct
dimensions of closeness for people
because:
– The essential properties of unique
individuals will vary through time and
across individuals
– And, the essential properties of unique
individuals are “partially determined” by
our own conceptions of what it means to be
ourselves
For Next Time
• Read:
– Parfit, Derek: Divided Minds and the
Nature of Persons (pp27-31)
• Get ready to discuss:
– An introduction to the scientific
findings in split-brain cases and a
discussion of what Derek Parfit thinks
this means for personal identity
How Many People
Am I?
Lecture 10
How to Argue that a Theory is
the Best Theory in the Essay
• Explain at least 2 different theories
• Apply the theories to examples
1st) Use a real-life example
2nd/3rd) Use 1+ whacky thought experiments
2nd/3rd) Use the split-brain case
• A good theory will give an answer in each case
(who is the same person?)
• The best theory will give the right answer in
most of the cases
• Right answers are generally consistent with
our reflected-upon intuitions
• But you can also explain why some particular
intuitions are wrong (and your theory is right)
Closest Continuer Theory (CCT)
• What essentially makes me me
through time is that I am
always the (one) closest
continuer of the previous me
• And that the closest continuer
(CC) is close enough
– I.e. too dramatic a change of an
essential property (even) in the
CC will mean that the CC is not
numerically identical with the
original
More Specific on the CCT
• Being the closest continuer needn’t
involve being qualitatively similar
– Although it often will
• More important is that the CC is
causally dependant (in the right kind
of way) on the original
– E.g. The CC has grown or developed out of
the original (or maybe) was caused by it
• There can be many factors that are
relevant to being the CC, but they
needn’t all be necessary (essential)
How Do We Discover the
Dimensions of Closeness?
• Nozick: Introspect
• We have intuitions about
whether something is
numerically identical with
something else
• We must analyse these intuitions
to discover what makes
something ‘closest’ to the
original in each particular case
• PROBLEM: Intuitions might track
accidental properties
The Duplicator Gun Case
• This device makes a perfect copy of
anything shot with it but it doesn’t
destroy the primary target
• CCT seems to work in this case
Divided Minds and the Nature
of Persons
• Derek Parfit
• Split-brain cases tell us
something interesting
about personal identity
• There are no ‘persons’ in
a split-brain case
• But there were no
‘persons’ before the
brain was split either
Why Chop Your Brain in Half?
• Suffers of severe epilepsy had
their corpus callosum chopped
in half to prevent seizures
spreading across hemispheres
• This means that the two halfs
of the brain cannot
communicate directly with
each other
• The resulting body acts as
normal in most cases and
suffers from less debilitating
seizures
The Experiments
• Left hemisphere
controls right eye &
hand (& speech in
right-handers)
• Using a partition,
each hemisphere
was exposed to a
different stimuli
• Each hand
responded as though
there is a separate
stream of
consciousness in
each hemisphere
The Ego Theory
• What essentially makes me
me through time is that all
of the ‘me’s are the same
subject of experiences (ego)
• What unites the many
experiences I have had in
my life is that I was the one
having them all
• The Cartesian View is an
example of this (my ego is
my soul)
The Bundle Theory
• We cannot explain our survival
through time by referring to a
‘person’
– Because no ‘person’ (subject of our
experiences) exists!
• There are just bundles of mental
states (experiences) tied together
by the causal relation of memory
(experiencing remembering
previous experiences)
• We call these bundles ‘lives’
The No Self View
• Buddha was the first
bundle theorist
• His No Self View is a
type of bundle theory
• People have ‘nominal
existence’ (we
sometimes talk as if
they exist), but only the
parts that make them up
really exist
Parfit: What We Believe
Ourselves to Be
• Science tells us that:
– There is no evidence for the Ego
Theory
– There is evidence for the Bundle
Theory
• Most of us believe something like
the Ego Theory to be true
• Unfortunately, most of us hold
false beliefs about who we are!
• Me: But does science tell us that?
Replacing Your Cells Case
• A high-tech alien is going to
replace some of your cells
with identical replicas (all at
once)
• If it changes 1% of your cells,
are you the same person?
• What if it changes 100% of your
cells?
• There are answers to these qns
How We are Not What We
Believe
• How could we even know if 49% or
50% (or whatever) replaced cells is
the right place for the line?
• It is implausible that a few cells
will make the difference in the
Replacing Your Cells Case
• But that is what our natural
beliefs/intuitions force us to say!
• Therefore, we should embrace the
Bundle Theory
Bundle Theory Applied
• When applied to all of the cases, the
Bundle theory rejects the question, ‘what
happens to you?’
• The Bundle Theory can explain what
happens, but it doesn't refer to persons
(because they don’t really exist)
• If ‘50% of your cells are replaced,’ then
50% of that bodies cells are replaced
• You don’t end or survive because you
were never there in the first place!
• These cases only raise worries because
we don’t properly understand the nature
of persons
PARFIT: Split-Brain Cases
and the Ego Theory
• The Ego Theory says that all of
the experiences in the splitbrain case are being had by the
one ego/person (but in 2
streams)
• The Ego Theory is wrong
because it ignores the disunity
between the two streams of
consciousness
• The ego can’t just split in two
– Because it is supposed to be the
one unique persisting essential
element of a person
PARFIT: Split-Brain Cases
and the Bundle Theory
• On the Bundle Theory, bodies
normally have an awareness of
having several different
experiences at any one time
– There is no ‘I’ (an independently
existing & persisting thing)
required for the explanation
• In the split-brain case, there
are two separate states of
awareness of experiences
– But neither of those states is a
unique, independently existing &
persisting ‘I’ (they don’t exist)
Parfit: Split-Brain Cases 1
• While both the Ego Theory and
the Bundle Theory can explain
our normal awareness of
experiences…
• Only the Bundle Theory
provides a good explanation
for the split-brain cases
• Combined with the lack of
scientific evidence for the Ego
Theory, we should accept the
Bundle Theory
• Which means that our belief in
our persisting ego/self/I is
false!
Parfit: Split-Brain Cases 2
• When someone’s brain is divided,
two streams of consciousness are
created
• Neither of the streams is the same
person as the original
• But, this is just like ordinary
survival!
– We are just bundles of mental states
tied together by remembering what the
previous experiences were like
– So, with every new experience, who we
are changes (our old numerical
identity dies!)
For Next Time
• Read:
– Puccetti, Roland: Brain Bisection and
Personal Identity (pp32-40)
– Gillet, Grant: Brain Bisection and
Personal Identity (pp41-43)
• Get ready to discuss:
– More views on what the split-brain
cases mean for personal identity
How Many People
Am I?
Lecture 11
Why Whacky Thought
Experiments & Unusual Real
Cases are Important
• Why not focus on just real & normal cases?
• All of the theories that we discuss give
plausible answers to the real & normal cases
• So, all of these theories seem pretty good, but
some contradict each other! They can’t all be
right (or best) – so which is the best?
• To find out, we use more unusual and even
currently impossible thought experiments
• If a theory is truly correct, then it will have
the right answer even in theoretical cases
(cases that might never happen but could
happen in the future or on other planets etc.)
How Many People in SplitBrain Cases?
• PARFIT: none
– Bundle Theorist / No Self View
– In fact, there was always none!
• PUCCETTI: two
– Dual Persons Theory
– In fact, there was always two!
• GILLETT: one
– A mixture of theories
– Obviously, there was only 1 before too!
The Actual Experiments
Brain Bisection and
Personal Identity
Roland Puccetti
More Info on the Actual
Split-Brain Experiments
• A picture is flashed in the
left visual field (for a
right-hander) so fast that
the right eye can’t see it,
but the left eye can.
• When asked, the person says
they couldn’t see the
picture
• But the ‘locked-in’ right
hemisphere did see it!
Puccetti vs. Eccles
• Eccles: The sub-dominant hemisphere
(SDH) is not conscious,
– The SDH processes but doesn’t communicate –
so it’s like a dumb animal
• Puccetti: The SDH is conscious
– When the whole of dominant hemisphere is
removed, people still consciously live on
– The sub-dominant hemisphere does have
rudimentary language capacity, but it can’t
control speech and often not writing
– E.g. Abstract concepts can be recognised
• E.g. Being instructed to retrieve objects that ‘go
with’ pictures – see hammer, retrieve nail etc.
What ‘Goes With’ What?
• When asked to
point to the
picture that
‘goes with’
what they
see…
• Each hand goes
for a different
picture!
Hemispheric
Conflicts
• Surely the two consciousnesses will
argue all the time like siblings?
• Sperry: they experience very similar
things, so will have similar tastes
• We perform lots of activities
unconsciously (walking home etc)
• Bodily status often dictates primary
drives like being hungry and both
hemispheres have access to this info
• But conflicts can occur
– e.g. wife beckoning and pushing away
Does Each Hemisphere Know
about the Other One?
• They seem to ignore or be unaware of
each other
• Before the op. patients can name objects
on both sides, but only on one side after
the op.
• Interestingly, they
don’t complain about
the loss
– Probably because the
dominant hemisphere
doesn’t remember seeing
the plant before
Hemispheric SelfCenteredness
• When asked how they managed to
point out the key, participants
(left brain) claim not to know or
make up some story
• They do not admit to the presence
of another self in their body!
• If either hemisphere knows, then
it is definitely the SDH because it
hears words come from it’s body
that are not from itself
Two Minds in One Person!?
• Bogen: each of us “has two minds
in one person”
• Puccetti: one person can’t have
two minds unless we change our
notion of ‘person’
• If we allow for two minds in one
person then a person can
simultaneously believe that he is
seeing red and seeing blue, while
also believing that he is not
seeing red and seeing blue!
Two People from One Person!?
• How can chopping my Lefty:
brain in half create ‘Pleased
2 people, when there to meet
you’
was just one?
– How do I know which
is the new one?
• Puccetti: Easy, there
have always been two
people in each of our
bodies!
Righty:
‘Please
d to
meet
you’
Dual Persons Theory
• In essence a person is a mind
– Add in some kind of COMINS theory here
– E.g. Psychological Continuity
• From the time of birth, each of our
hemispheres start to specialise in
certain tasks and develop distinct
proficiencies, but…
• Because they are stuck in the same body,
these two people have very similar
personalities.
– They have had very similar experiences and
have made very similar memories
Who am I?
• OK, two people in one body… but
which one am I !?
• Puccetti: To even consider such
a complicated question, you
must be your dominant (verbally
proficient) brain hemisphere
• Who will write your essay?
– Hopefully your dominant hand &
brain!
• But who painted my paintings?
– Your SDH (right). So say thank you!
Brain Bisection and
Personal Identity
Grant Gillett
Gillett on the Experiments
• The resulting behaviour would
normally be thought of as 1
stream of consciousness per
hemisphere
• But, in real life situations, the
patients are pretty much
normal
– Probably because the hemispheres
do find ways to communicate
– E.g. In real life, they would look
at things with both visual fields
Gillett on the Experiments 2
• What we should focus on is the one
person who realises that they have
performed strangely in the tests
• They don’t think that another
person inside their body is messing
things up for them!
• It’s important to note that we can’t
tell what (or even if!) the right
brain is consciously thinking
• We do lots of things without really
consciously thinking about it
– e.g. recognising colours
Gillett on the Experiments 3
• A mind is a conscious rational thinker
– This involves self-ascribing thoughts which
involves “complex conceptual connections”
• The right brain by itself doesn’t have
the language capacity to do this
• The best explanation is that one
mind/person is having more trouble than
it used to integrate all of the
information its sensory organs gather
How Many People in SplitBrain Cases?
• PARFIT: none
– We are a constantly changing bundle of
mental states so there are no ‘people’
• PUCCETTI: two
– Each hemisphere has its own stream of
consciousness (before and after brainbisection)
• GILLETT: one
– One mind is conceptually aware of
compiling our complex functioning
(before and after brain-bisection)
Does Each Hemisphere Have
Its Own Sense of Self?
• Michael Gazzaniga
• Forty-five years of split-brain
research and still going strong
– In Nature Reviews Neuroscience
• Each certainly can be
independently aware of things
• But, no “clear-cut” evidence that
each has a “full sense of self”
• But, the left hemisphere is more
important in self-recognition
Recognising Yourself
Test on Friday!!
• See qn on Blackboard
– It’s on David’s section: Consciousness
& the Mind/Body problem
• Do a practice run!
• Any questions?
• Next week is Jay Shaw
– Topic: Nature of Human Beings, Law of
Karma and Concepts of Harmony