Will's summary/hot take(s):

  • Reasons and Persons is a surprisingly readable book. It appears to cater to both the professional academic philosopher and the inquisitive non-professional, a rare feat.
  • Parfit concludes that the question of personal identity is an empty one
    • One's original identity neither survives nor dies during teletransportation, according to Parfit.
  • He concludes that what matters instead is psychological continuation.
    • I actually have a hard time pinning down exactly what Parfit means by this. To me, it almost feels like the answer, psychological continuation, is as mysterious as the question of personal identity. See "Mysterious Answers to Mysterious Questions".
      • My best stab at a non-mysterious answer is "correlation in neuronal mapping between oneself at time x and oneself at time y."
    • My interpretation of Parfit's solution:
      • What matters is correlation with one's replica (i.e., correlation between version x of yourself and version y).
        • Imagining a scenario in which many replicas of one's original identity exist, all strongly correlated with each other and with the original, it doesn't make sense to ask which is "you".
        • Observation: we all become less correlated with our past selves as we age (e.g., I'm not that correlated with baby me, but strongly correlated with me from a week ago).
          • This is interesting because it provides a legitimate basis for discounting the future, on account of our future selves becoming progressively less correlated with our present self.
            • How this discounting effect interacts with longtermist views seems open to interpretation, but I think my solution - assuming Parfit's psychological continuation conclusion is true - would be that correlation between people (and between people existing at different times) is just as real as correlation between versions of a single person.
            • (I've not yet read part 4 of Reasons and Persons. Though it's titled "Future Generations", so probably Parfit addresses this interaction between personal identity and concern for the future. It'll be interesting to see how closely my solution above aligns with Parfit's.)

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fyi, newcomers to Parfit might find my short book, Parfit's Ethics (Cambridge University Press), to be a helpful guide.  Overview here:

https://rychappell.substack.com/p/parfit-in-seven-parts

And excerpts on personal identity in particular:

https://rychappell.substack.com/p/do-you-really-exist-over-time