Bananas Enough for Time Travel?
Smith (Nicholas J.J.)
Source: The British Journal for the Philosophy of Science, Vol. 48, No. 3 (Sep., 1997), pp. 363-389
Paper - Abstract

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Author’s Abstract

  1. This paper argues that the most famous objection to backward time travel1 can carry no weight. In its classic form, the objection is that backward time travel2 entails the occurrence of impossible things, such as auto-infanticide – and hence is itself impossible.
  2. David Lewis has rebutted the classic version of the objection: auto-infanticide is prevented by coincidences, such as time travellers3 slipping on banana peels as they attempt to murder their younger selves.
  3. I focus on Paul Horwich's more recent version of the objection, according to which backward time travel4 entails not impossible things, but improbable ones – such as the string of slips on banana peels that would be required to stop a determined auto-infanticidal maniac from murdering her younger self – and hence is itself highly improbable.
  4. I argue that backward time travel5 does not entail unusual numbers of coincidences; and that, even if it did, that would not render its occurrence unlikely.

  1. Introduction
  2. Backward causation6 and changing the past
  3. Lewis and Horwich
  4. How often do coincidences occur?
  5. Coincidences and backward time travel7 I
  6. Coincidences and backward time travel8 II
    • 6.1 Curiosity
    • 6.2 Memory failure
    • 6.3 Forcing coincidences
    • 6.4 Backward time travel9 without trying?
  7. Conclusion

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