Abstract
There have been many objections to the possibility oftime travel. But all the truly interesting ones concern the possibility of reversecausation. What is objectionable about reverse causation? I diagnose that the trulyinteresting objections are to a further possibility: that of causal loops. I raisedoubts about whether there must be causal loops if reverse causation obtains; but devote themajority of the paper to describing, and dispelling concerns about, various kinds ofcausal loop. In short, I argue that they are neither logically nor physically impossible.The only possibly objectionable feature that all causal loops share is that coincidenceis required to explain them. Just how coincidental a loop will be varies: some arereally quite ordinary, and some are incredibly unlikely. I end by speculating thatthe tendency amongst physicists to avoid discussion of causal loops involving intentionalaction may have been unfortunate, since intentional action is an excellent way tonon-mysteriously bring about what otherwise would have been an unlikely coincidence. Hencecausal loops may be more likely in a world with beings like us, than in one without.
Similar content being viewed by others
REFERENCES
Berkovich, J.: 2001, 'On Chance in Causal Loops', Mind 437, 1–23.
Clarke, C. J. S.: 1977, 'Time in General Relativity', in J. Earman, C. Glymour, and J. Stachel (eds.), Minnesota Studies in the Philosophy of Science, Volume VIII: Foundations of Space-Time Theories, University of Minnesota Press, Minneapolis, pp. 94–108.
Deutsch, D.: 1991, 'Quantum Mechanics near Closed Timelike Lines', Physical Review D 44, 3197–3217.
Dowe, P.: 2001, 'Causal Loops and the Independence of Causal Facts', Philosophy of Science 68, 89–97.
Faye, J.: 2001 'Backward Causation', in N. Zalta (ed.), The Stanford Encyclopedia of Philosophy(Winter 2001 Edition), URL = <http://plato.stanford.edu/archives/win2001/entries/causation-backwards/>.
Godfrey-Smith, W.: 1980, 'Traveling in Time', Analysis 40, 72–73.
Grey [formerly Godfrey-Smith], W.: 1999, 'Troubles with Time Travel', Philosophy55–70.
Hall, N.: 2000, 'Causation and the Price of Transitivity', Journal of Philosophy 97, 198–222.
Harrison, J.: 1980, 'Report on AnalysisProblem No. 18', Analysis 40, 65–69.
Levin, M.: 1980, 'Swords' Points', Analysis 40, 69–70.
Lewis, D.: 1986, in D. Lewis, Philosophical Papers, Vol. II, Oxford University Press, Oxford, pp. 67–80. (Reprint of Lewis, D.: 1976, 'The Paradoxes of Time Travel', American Philosophical Quarterly vn13, 145–152.)
Lewis, D.: 1976, 'Survival and Identity', in A. Rorty (ed.), The Identities of Persons, University of California Press, Berkeley, pp. 17–40.
Lossev, A. and I. Novikov: 1992, 'The Jinn of the Time Machine: Nontrivial Self-Consistent Solutions', Classical and Quantum Gravity 9, 2309–2321.
Mellor, H.: 1981, Real Time, Cambridge University Press, New York.
Mellor, H.: 1995, The Facts of Causation, Routledge, London.
MacBeath, M.: 1982, 'Who was Dr Who's Father?', Synthese 51, 397–430.
Moravec, H.: 1991, 'Time Travel and Computing', URL: http://www.frc.ri.cmu.edu/hpm/project.archive/general.articles/1991/TempComp.html
Nahin, P.: 1999, Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction, 2nd edn, Springer-Verlag, New York.
Nerlich, G.: 1981, 'Can Time Be Finite?', Pacific Philosophical Quarterly 62, 227–239.
Niven, L.: 1971, 'The Theory and Practice of Time Travel', in All the Myriad Ways, Del Rey, New York, pp. 110–123.
Parfit, D.: 1984, Reasons and Persons, Clarendon Press, Oxford.
Price, H.: 1996, Time's Arrow and Archimedes' Point, Oxford University Press, New York.
Riggs, P.: 1997, 'The Principal Paradox of Time Travel', Ratio 10, 48–64.
Riggs, P.: 1991, 'A Critique of Mellor's Argument against 'Backwards' Causation', British Journal for the Philosophy of Science 42, 75–86.
Smith, N. J. J.: 1997, 'Bananas Enough for Time Travel?', British Journal for the Philosophy of Science 48, 363–389.
Townsend, Aubrey, 'Time Travel, Freedom and Deliberation', inA. Townsend (ed.), Time, Self and Freedom, Monash University, Melbourne.
Wheeler, J. and R. Feynman: 1949, 'Classical Electro-Dynamics in Terms of Direct Interparticle Action', Reviews of Modern Physics 21, 425–433.
Rights and permissions
About this article
Cite this article
Hanley, R. No End in Sight: Causal Loops in Philosophy, Physics and Fiction. Synthese 141, 123–152 (2004). https://doi.org/10.1023/B:SYNT.0000035847.28833.4f
Issue Date:
DOI: https://doi.org/10.1023/B:SYNT.0000035847.28833.4f