Predestination paradox

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"Causal loop" redirects here. For the diagram, see Causal loop diagram.
For the science fiction plot device, see time loop.

A causal loop[1] is a paradox of time travel that occurs when a later (future) event is the cause of an earlier (past) event, through some sort of time travel. The past event is then partly or entirely the cause of the future event, which is the past event's cause.

Bootstrap paradox[edit]

A causal loop is an ontological paradox in the sense that an independent origin of the events that caused each other cannot be determined, they simply exist by themselves,[1] thus they were predestined to occur. Predestination does not necessarily involve a metaphysical power, and could be the result of other "infallible foreknowledge" mechanisms.[2] The predestination paradox allows time travel to be self-consistent, similar to the Novikov self-consistency principle.

Self-fulfilling prophecy[edit]

A self-fulfilling prophecy is a form of causality loop, only when the prophecy can be said to be truly known to occur, since only then events in the future will be causing effects in the past.[2] Otherwise, it would be a simple case of events in the past causing events in the future. A notable fictional example of a self-fulfilling prophecy occurs in classical play Oedipus Rex, in which Oedipus becomes the king of Thebes, whilst in the process unwittingly fulfills a prophecy that he would kill his father and marry his mother. The prophecy itself serves as the impetus for his actions, and thus it is self-fulfilling.[3][4]

See also[edit]


  1. ^ a b Nicholas J.J. Smith (2013). "Time Travel". Stanford Encyclopedia of Philosophy. Retrieved June 13, 2015. 
  2. ^ a b Craig (1987). "Divine Foreknowledge and Newcomb's Paradox". Philosophia 17 (3): 331–350. doi:10.1007/BF02455055. 
  3. ^ E.R. Dodds, Greece & Rome, 2nd Ser., Vol. 13, No. 1 (Apr., 1966), pp. 37–49
  4. ^ Popper, Karl (1976). Unended Quest: An Intellectual Autobiography. LaSalle, Illinois: Open Court. ISBN 978-0-87548-343-6. OCLC 2927208.