The Problem of Personal Identity

The Problem of Personal Identity

Introduction

  • A murder case is presented, where the defense argues the client has changed so much they are not the same person who committed the crime.

  • This raises the question of what it means to be the "same" person over time.

  • The problem of personal identity focuses on what makes persons numerically the same over time.

Qualitative vs. Numerical Identity

  • Qualitative Identity: Being the same in terms of qualities or characteristics.

    • People do not maintain qualitative identity over time due to changes in appearance, experiences, etc.

    • Example: Clark Kent before and after meeting Lois Lane.

  • Numerical Identity: Being one and the same person or thing.

    • Despite changes, you are numerically the same person you were five years ago.

    • Example: Superman and Clark Kent are numerically identical; they are the same entity under different presentations.

The Murderer's Paradox

  • A defense attorney argues that their client isn't the same person who committed the crime because of personal changes.

  • The argument fails because it confuses qualitative and numerical identity.

  • Being numerically identical means being one and the same thing, not just qualitatively similar.

Relevance of Personal Identity

  • Understanding numerical continuity is important for:

    • The hope of an afterlife (being numerically identical to your former self).

    • Avoiding punishment for crimes committed by someone numerically different.

    • Making practical decisions, such as those involving relatives in persistent vegetative states.

The Ship of Theseus Paradox

  • Introduces the broader problem of identity: When are two things the same thing?

  • The Ship of Theseus is an example of a philosophical paradox revolving around the persistence of identity. How can every single part of something be replaced, yet it still remains the same thing?

  • The original tale involves a ship whose parts are gradually replaced over time.

  • A twist is introduced: The replaced parts are used to rebuild the original ship.

  • This results in two ships, raising the question of which one is the "real" Ship of Theseus.

  • The paradox highlights how identity is complex and involves constantly changing parts.

Logic of Identity

  • Identity in logic implies that if A = B, then B = A.

  • Also, If A = B and B = C, then A = C (transitivity of identity).

  • In the Ship of Theseus example, if both the renovated ship (X) and the rebuilt ship (Y) are claimed to be the Ship of Theseus, it violates the transitivity of identity because X and Y are different.

  • Logically, only three options exist; Ship of Theseus is equal to X, Ship of Theseus is equal to Y, or neither is the Ship of Theseus.

Personal Identity vs. General Identity

  • When it comes to personal identity, there is a stronger sense that there is a fact of that matter. For example, either a picture of an infant is you or it isn't.

  • The problem of personal identity is harder than the problem of identity because you have properties that you can in principle rely on to establish identity of persons that are not available for identity of ships or cars. For example, psychological properties.

Thought Experiment: Memory Erasure and Transfer

  • Scenario: Memories erased, new memories (Anthony Steele's) implanted, followed by waterboarding.

  • Question: Who is being waterboarded? You? Anthony Steele? Someone else?

  • Second Scenario: Memories transferred to Sandy Jones, and original body waterboarded.

  • Question: Who is being waterboarded now? You? Sandy Jones? Someone else?

  • The intuitions in the thought experiments attract two things: continuity in your body and continuity in your psychological properties. For example, memory is an example of a psychological property.

Theories of Personal Identity

  • Same Soul Theory: Sameness of souls determines sameness of persons.

  • Physical Continuity Theory: Sameness of bodies determines sameness of persons. Sometimes called the biological theory.

  • Psychological Continuity Theory: Sameness of psychological properties determines sameness of persons.

Memento and Personal Identity

  • The movie Memento raises interesting questions about personal identity due to the main character's (Leonard Shelby) amnesia.

  • Leonard has trouble remembering events, so it raises the following question: is he the same person over time? Based on the three theories of personal identity:

    • The Same Soul Theory: You're gonna have a serious problem because the concept of soul is fairly mysterious.

    • The Physical Continuity Theory (Biological Theory)
      *Is Leonard Shelby the same person before and after his accident according to this theory?
      *Yes, there is continuity of the body. If you take a video of Leonard's life from the beginning of the present moment, there is continuity of bodies, even though there isn't continuity in the memory

      • Problems with the Theory:

        • Brain Swapping - Suppose we change the brain of a prince with the brain of a cobbler in such a way that the two psychologist are swapping their entirety. Meaning, whatever memories of the prince are are now in the body of the cobbler and vice versa. The theory would say that the prince’s body still contains the prince because the body itself hasn’t changed. But a lot of us, when presented with this sort of case, would not be too happy with the view and would say that the prince is now in the cobbler body and the cobbler is now in the prince’s body because the memories are what determines who is one and who is the other because the memories have been swapped.

        • After Life - it is conceptually impossible for you to get to the afterlife because once your body expires, and it will once you die, there is no spatial-temporal continuity between you on this Earth and you in the afterlife.

    • The Psychological Continuity Theory - dominant theory of personal identity
      *Persons are identical over time if and and only if they preserve over time a common cluster of psychological properties.
      *These properties can be high levels such as, your personality traits, stream of consciousness, memories, moral sense.
      *The most popular was developed by John Locke, it's a memory based criterion for personal identity, which says basically the following:
      *A past person is identical to the future person, if any, who has that past person's memories, whether or not the future and the past persons are physically continuous with each other
      *Problem with the Theory
      *Is Leonard the same person?
      *No, a future Leonard is not connected to Leonard previous to the incident by any chain of memory.
      *Advantages of the Theory
      *Conceptual possibility to get to the afterlife
      *As long as your memories transition to something that is in the afterlife on this criterion, it is you who are in the afterlife despite the discontinuities at the physical level.