Logical and Nomological Obstacles to Foreknowledge of the Future


  • Erdinç Sayan Middle East Technical University
  • Hasan Cagatay Social Sciences University of Ankara




A famous puzzle called “Grandmother Paradox” is used to argue against the feasibility of traveling backward in time because of the logical and nomological problems such travel involves, and not only because we don’t have the technology to make it reality.  The same kind of problems would be encountered in leaping forward in time and then returning to the time of departure.  We argue that a similar family of problems also arise in our having foreknowledge of the future without making any time travel.  We point to the mysterious consequences of having access to a being, say a machine or a psychic, that can have infallible knowledge of the future and conveys this foreknowledge to human beings truthfully, without any lies or distortions.  The cause of these mysterious consequences is the fact that such machines or psychics will raise logical and nomological complications reminiscent of the ones we encounter in time travel scenarios, and that is a strong reason why infallible foretellers cannot exist.  We conclude that we can have foreknowledge of the future, in principle, only within certain narrow limits, if at all.

Author Biographies

Erdinç Sayan, Middle East Technical University

Visiting Professor, Bilkent University, Department of Philosophy, Ankara, TURKEY

Hasan Cagatay, Social Sciences University of Ankara

Department of Philosophy, Ankara, TURKEY


BEM, Daryl J. (2011). “Feeling the Future: Experimental Evidence for Anomalous Retroactive Influences on Cognition and Affect,” Journal of Personality and Social Psychology, 100, pp.407-25.

DAVIES, Paul (2002). “How to Build a Time Machine,” Scientific American, 287 (3), pp.50–55.

EARMAN, John (1986). A Primer on Determinism. Dordrecht: D. Reidel.

KENNEDY, J. B. (2003). Space, Time and Einstein: An Introduction. Montreal, Kingston, Ithaca: McGill-Queen’s University Press.

LEWIS, David (1976). “The Paradoxes of Time Travel,” American Philosophical Quarterly, 13, pp.145–52.

SMEDES, Taeda A. (2003). “Is Our Universe Deterministic? Some Philosophical and Theological Reflections on an Elusive Topic,” Zygon, 38, pp.955-979.

SMITH, Nicholas J. J. (2018). “Time Travel,” The Stanford Encyclopedia of Philosophy (Summer 2018 Edition), Edward N. Zalta (ed.), URL = https://plato.stanford.edu/archives/sum2018/entries/time-travel/.