Personal Identity

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Personal Identity
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What is personal identity

• Am I the same person as I was when I was born?
  when I was a child? ten years ago? yesterday?
• Is there a single self linking all these person
  stages, or are there just a succession of
  selves?
• What kind of adventures could a person undergo
  without losing their identity? E.g. total
  amnesia, brainwashing, brain implants (remember
  the cyborg question?), brain transplant,
  teleportation?

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Numerical identity vs. qualitative identity

• Qualitative identity two objects have exactly
  the same properties. Jenny and Sue are wearing
  the same dress.
• Numerical identity A and B are one and the same.
  Clark Kent is the same person as Superman. Jenny
  and Sue are in love with the same man.
• Personal identity is about numerical identity
  not, am I the just the same as I was 10 years
  ago?, but rather am I the same person, or are
  there two people involved one that existed 10
  years ago but no longer, and me now?
• Heraclitus You cannot step into the same river
  twice. The river is constantly changing (i.e.
  qualitatively different), so it is not the same
  river (i.e. numerically different).

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Identity of objects

• Washingtons axe
• This is Washingtons axe. The handles been
  replaced three times and the heads been replaced
  twice.
• Ship of Theseus
• Ancient Greek puzzle a ship has been repaired so
  many times that there are no planks left at all
  from when the ship was first built. Is it still
  the same ship?
• Hobbess addition what if all the original
  planks were gathered up and the ship was rebuilt
  with them?
• Which ship now would be the original ship?

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Identity of persons

• What makes A at time T1 the same person as B and
  time T2? E.g. what makes me the same person as a
  little 9-year-old girl in the U.S. many years
  ago?

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The animal approach

• Adult me is a stage in the life of an animal that
  was born in Oklahoma, USA, many years ago.
  9-year-old me was another stage in the life of
  that same animal. A caterpillar is a stage in the
  life of a butterfly.
• Animals, like the Ship of Theseus, are constantly
  changing, and there may be no cells in common
  between the puppy and the adult dog it grows
  into. But the puppy and the adult dog are
  recognized as the same being.
• Animals are the same if their bodies change
  gradually and the various stages are connected
  through an underlying design (DNA) and a
  continuous life process.

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Problems with the animal approach

• Body switching
• Lockes thought experiment, a prince and a
  cobbler switch bodies/minds
• Surely, identity follows the mind. The prince is
  now in the cobblers body and vice versa.
• Brain transplant
• Identity travels with the brain?
• What about part of the brain?

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Psychological approaches

• 1) The memory criterion
• A is B if A can remember Bs experiences or
  thoughts.
• I can remember being 9, so I am the same person I
  was when I was nine

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Memory criterion paradox

• I can remember getting glasses when I was nine,
  but I cant remember what I did the day before I
  got glasses. But the day I got glasses, I could
  remember what I did the day before. So
• A Kelly today
• B the 9-year-old Kelly the day she got glasses
• C the 9-year-old Kelly the day before she got
  glasses
• According to the memory criterion
• A B
• B C
• but
• A ? C

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• Solution?
• Memory continuity criterion
• If A is connected by a chain of memories to B,
  then A is B
• Kelly today is connected by a shared memory with
  9-year-old Kelly who is connected by a shared
  memory with 3-year-old Kelly who is connected by
  a shared memory with 2-year-old Kelly. Therefore
  Kelly today is the same person as 2-year-old
  Kelly.

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• Remaining problems for the memory criteria
• Am I the same person as when I was a baby, if
  there is no chain of memory connecting me?
• If you experience a short episode of amnesia,
  were you a different person during that period of
  time?
• Are you a different person when youre asleep?
• Locke
• if the same Socrates waking and sleeping do not
  partake of the same consciousness, Socrates
  waking and sleeping is not the same person. And
  to punish Socrates waking for what sleeping
  Socrates thought, and waking Socrates was never
  conscious of, would be no more right, than to
  punish one twin for what his brother-twin did,
  whereof he knew nothing, because their outsides
  were so like, that they could not be
  distinguished for such twins have been seen.

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A B C

• 2) Psychological continuity
• Person A is person B if they are connected by
  psychological continuity. I.e. if there are a
  chain of causal psychological connections between
  A and B.
• E.g. my current psychological state depends on
  the psychological state of my brain when I was
  sleeping last night. For example, the memories
  and personality and mental capabilities that were
  part of my brain last night when I was asleep are
  still (for the most part) part of my brain right
  now. I am who I am partly because of what I was
  last night, last year, and when I was two.

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• Problem
• Psychological continuity may exist beyond the
  relationship between ones past self and ones
  present self. E.g. I am what I am partly because
  of my parents psychological states when I was
  growing up. Thoughts and ideas were transferred
  from their minds to my mind, causing my mind to
  develop a certain way.
• Solution? The causal connection must be of the
  right kind the normal causal connection between
  psychological states in a mind.
• Is that a cop-out?

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Problem cases

• Brainwashing and total amnesia
• If you had total amnesia (could remember nothing
  of your previous life) and were brainwashed so
  that you were psychologically radically different
  than before,
• would you be the same person?
• On the animal approach yes
• On the psychological approach no

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• Fission
• Hemispherectomy and half brain transplants
• Toms brain is divided into two halves and
  transplanted into two different bodies. The right
  hemisphere is transplanted into a new body and
  called Righty. The left hemisphere is
  transplanted into a new body, called Lefty.
  According to the psychological criterion, they
  both should be the same person as Tom. But lefty
  is not righty.
• Teleportation
• John is on Planet Zorgon and wants to go back to
  his spaceship. He steps into a teleporter. The
  teleporter makes an exact duplicate of Johns
  body (and brain), destroys Johns body on Zorgon
  and rebuilds his body on the spaceship. The
  duplicate of John on the spaceship remembers
  everything that John did up until the time John
  stepped into the teleporter. He is also
  psychologically identical to John. He thinks he
  is John. Is he right?
• What if Johns original body is not destroyed?

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• Brain implants
• If your brain was implanted gradually with
  artificial parts that retained the same function
  as your brain, would you retain your identity?
  What if your entire brain was replaced gradually
  in that way? On the animal approach or the
  psychological approach? What if your brain was
  replaced suddenly rather than gradually?

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Skepticism about personal identity

• There is no personal identity. You are not the
  same person you were when you were a child, as
  you were last year, or yesterday, or when you
  walked into the lecture room. Any change makes us
  a different person.
• Problems
• Moral responsibility how can we blame anyone (or
  praise anyone) for anything they did, when it
  was not them, but their predecessor. I am not
  the person who stole the money yesterday, so
  dont punish me.
• Concern for our future selves Why should I go to
  class? It wont be me who graduates, but a
  different person. Why buy food, if it wont be me
  who eats it?
• Perhaps the relationship between A at T1 and A
  at T2 is not one of identity, but it is still a
  special relationship. Special enough that A can
  be punished for the actions of A and A cares
  deeply about the welfare of A.

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Suggested Readings

• Derek Parfit, What we believe ourselves to be
  in Reasons and Persons, pgs. 199-217, on reserve
  in the Philosophy Department office
• Adam Morton, Identity through Time in Problems
  in Philosophy, pgs. 407-415, on reserve in the
  Philosophy Department office