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Personal Identity
- How we identify someone over time
- Questions
- What makes a person the same person from one moment to the next?
- What makes us ourselves?
- We care about numerical identity not qualitative identity
Theories
The Soul Theory
- You are your soul
- Two objections:
- Asserts numerical identity over time but doesn't explain it
- No clear identity conditions even at a given time
- Do we really understand what makes one soul different from other souls?
Spatiotemporal Continuity Theory
- An object is identified in terms of a continuous series of locations in space and time
- You are something that inhabits a continuous series of locations in space and time
- Does it really give us a philosophical account of personal identity?
- Objection: Prince and Cobbler thought experiment
- Brain transfer swap
- Prince commits a crime then gets a mad scientist to swap his brain with the Cobbler's
- Prince is now in the Cobbler's body
- Cobbler (inside the Prince's body) is punished
- No transfer swap
- Same as above but the scientist just alters the existing brain's
- John Locke concludes that personal identity follows psychological continuity, not spatiotemporal continuity
- Brain transfer swap
- John Locke on personal identity
- Personal identity consists in sameness of consciousness
- Consciousness is inseparable from thinking
- One distinguishes between oneself and other thinking beings via thought
- A person's identity stretches back in time as far as one's thought extends
- Personal identity consists in sameness of consciousness
Brain-Based Psychological Continuity Theory
- A past person is the same as a future person if and only if:
- The two persons are psychologically continuous with each other
- The brains of the two people are spatiotemporally continuous with each other
Split Brain Cases
- *X*'s brain is split into two halves
- Two spatiotemporally distinct individuals, *Y* and *Z*, are formed
- Is *X* the same individual as *Y*, *Z*, both, or neither?
- [Derek Parfit](/second-brain/derek-parfit)'s response
- Something wrong with the question
- All that really matters for personal identity is psychological continuity
David Hume on personal identity
- Human mind is composed of a bundle of impressions in rapid succession
- The mind is not identical over time
- We ascribe a unified personal identity to ourselves over time as follows:
- We form ideas of identity and diversity via actions of the imagination
- We slide from one idea to the other, because the corresponding actions resemble each other
- We invent the fiction of a persisting self to mask our mistake