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 TerminatorEdit
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 Salvation: The Final BattleEdit