No End in Sight: Causal Loops in Philosophy, Physics and Fiction
Hanley (Richard)
Source: Synthese, Vol. 141, No. 1 (Jul., 2004), pp. 123-152
Paper - Abstract

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Author’s Abstract

  1. There have been many objections to the possibility of time travel. But all the truly interesting ones concern the possibility of reverse causation1. What is objectionable about reverse causation2?
  2. I diagnose that the truly interesting objections are to a further possibility: that of causal loops. I raise doubts about whether there must be causal loops if reverse causation3 obtains; but devote the majority of the paper to describing, and dispelling concerns about, various kinds of causal loop.
  3. In short, I argue that they are neither logically nor physically impossible. The only possibly objectionable feature that all causal loops share is that coincidence is required to explain them. Just how coincidental a loop will be varies: some are really quite ordinary, and some are incredibly unlikely.
  4. I end by speculating that the tendency amongst physicists to avoid discussion of causal loops involving intentional action may have been unfortunate, since intentional action is an excellent way to non-mysteriously bring about what otherwise would have been an unlikely coincidence. Hence causal loops may be more likely in a world with beings like us, than in one without.

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