Predestination paradox

A predestination paradox, also called either a causal loop, or a causality loop, and (less frequently) either a closed loop or closed time loop, is a paradox of time travel. It exists when a time traveler is caught in a loop of events that "predestines" his or her journey back in time. Because of the possibility of influencing the past while time traveling, one way of explaining why history does not change is by saying that whatever has happened must happen. A time traveler attempting to alter the course of history in this model would only be playing their part in shaping history as we already know it, rather than changing any aspects of the past. This is regardless of the time traveler's intentions or efforts to preserve their personal experience, or knowledge, of events.

Predestination paradox in Terminator

The Terminator

Terminator 1984 - Deleted scene 7 - The Factory

The predestination paradox was an integral part of The Terminator, the first movie in the Terminator franchise. There are two main examples where a future time traveler goes back in time and fulfills their role in history (rather than changing it):

• Kyle Reese fathering John - Kyle Reese goes back in time and fathers John Connor, whom he later works under in the Resistance.
• The T-800 wreckage left in the Cyberdyne factory - The T-800 wreckage left in the Cyberdyne factory triggers the AI research via reverse engineering, which eventually results in the creation of Skynet and even Terminators. (The actual scene showing that the factory in The Terminator is a Cyberdyne facility is in a deleted scene, but these facts are restated in Terminator 2: Judgment Day.)

The predestination paradox is heavily tied to the concept of fate. The photograph of Sarah Connor by the Mexican boy is an example of this: the photo that Kyle had in the future is exactly the same as the one taken of Sarah at the end of The Terminator. This heavily suggests that the events of The Terminator fulfilled the predestination paradox: The T-800 and Kyle Reese traveled back in time to fulfill their roles in history, not to change it.

Additionally, the novelization by Randall Frakes makes use of the film script's unused concept of Sarah having a metal pin in her leg, with the Terminator mutilating its victims in order to find this identifying pin and confirm the termination of the correct Sarah Connor. Where the original script attributed it to a skating injury, the Frakes novel alters the origin of the pin so that Sarah receives it as the result of shrapnel damage from destroying the Terminator, further cementing the predestination paradox of the first film.

Terminator 3: Rise of the Machines

A controversial theory is that the T-X used her nanomachines to give Skynet its sentience. Due to her almost infinite connection to the computer databases, it is feasible to assume that the reprogramming extended from the vehicles into the computer networks, as seen in the worldwide blackout that prompted Skynet's dominion and self-awareness. If so, then the franchise hinges on not one but two predestination paradoxes, the first being the necessity of Judgment Day. Otherwise, Kyle Reese would have no reason to travel back in time to sire John in the first place if there was no Judgment Day. John Connor's very existence is tied to Judgment Day happening.

Terminator Salvation: The Final Battle

The message sent by Dr. Serena Kogan to her past self and the development of living tissue with the aide of the Teenaged Terminator are both predestination paradox.

The Terminator: Future Shock

Skynet in 2015 used the Temporal Data Transmitting System to reprogram its 1995 self, essentially giving itself self-awareness.

See also

• Alpha timeline
• Single timeline
• Fate