Time Travel & the Predestination Paradox Explained

Time Travel & the Predestination Paradox Explained

A Predestination Paradox refers to a phenomenon in which a person traveling back in time become part of past events, and may even have caused the initial event that caused that person to travel back in time in the first place. In this theoretical paradox of time travel, history is presented as being unalterable and predestined, with any attempts to change past events merely resulting in that event being fulfilled. Science-fiction provides fertile ground for exploring this “Effect before Cause” concept, and over the years has provided much entertainment in the form of countless books and movies on the subject.

Etymology of Predestination Paradox

– Predestination: The word ‘predestination’ derives from the Greek word “proorizo” with pro meaning “before” and the verb “orizo” meaning to “determine”. It has been in use since classical times, with the Greek physician Hippocrates (460-370 BC) using it to describe an intended result following the administration of medication. It is mentioned four times in the Bible, or more specifically in the Epistles of Paul, and over time in theology has come to represent God having immutably determined all event throughout eternity that will come to pass.

– Predestination Paradox: Although the concept of a predestination paradox has been explored by scientific writers in the past, most notably by Robert A. Heinlein in his short stories entitled “By His Bootstraps” (1941) and “All You Zombies” (1959), it was the Star Trek franchise that coined the phrase “Predestination Paradox” in a 1996 episode of Star Trek: Deep Space Nine episode titled “Trials and Tribble-ations“. The show was a homage to The Original Series, and involves agents from Starfleet’s Department of Temporal Investigations visiting DS-9 in order to determine whether the timeline had been corrupted after Captain Sisko took the USS Defiant 105 years back in time to save Captain James T. Kirk from being assassinated. The expression is used twice throughout the show, the first time by two time agents who are trying to establish Captain Sisko’s motive for traveling back in time:

LUCSLY: “So you’re not contending it was a predestination paradox?”
DULMUR: “A time loop. That you were meant to go back into the past?”

In the second instance, Doctor Bashir worries that after being invited on a date by a woman bearing his great grandmother’s name, Watley, he could be destined to fall in love with her and become his own great-grandfather, who no one ever met, stating: “If I don’t meet with her tomorrow, I may never be born.”

The Paradoxes of Time Travel

Time travel paradoxes can generally be categorized into either:

1) Closed Causal Loops (Bootstrap Paradox, Predestination Paradox) in which an action resulting from time travel to the past ensures the fulfillment of a cause.

2) Consistency Paradoxes (Grandfather Paradox, Hitler Paradox, Polchinski’s Paradox) in which an action resulting from time travel to the past stops the cause from ever happening.

To highlight their differences further, Consistency Paradoxes such as the Grandfather Paradox create timeline inconsistencies caused by actually being able to change the past, including killing your own grandfather, thereby preventing your own existence, and resulting in an inconsistent and altered version of a past event. A Predestination Paradox, on the other hand, results in an internally consistent version of history, albeit involving an event which appears to predate the time traveler’s initial decision to travel to the past. This is because the paradox creates a closed casual loop in space-time with cause and effect running in a continous circle.

For example, someone visiting the past to prevent someone from being killed will still ultimately be unable to prevent their death, after which they can still use their time machine to return to their own present and continue living their lives in a linear manner. This is to be differentiated from one of the favorite themes of time travel movie’s, namely time loops, in which the sequence of events within a loop reset after a certain point in time is reached, and whoever is trapped within the loop must then repeat the same period of time endlessly.

Predestination Paradox Examples

Physical Time Travel

In Predestination (2014), an intersex temporal agent who has undergone sexual reassignment surgery travels back in time to save his younger female self from falling in love and becoming pregnant by a mysterious male lover, who then disappears, completely ruining her life. Upon meeting his younger, female self, the time traveller subsequently falls in love and impregnates her, thus becoming the very stranger who caused all the heartache he traveled back in time to prevent. As well as an example of a predestination paradox, the act of self-creation in which the time traveler is his own mother and father is an example of a bootstrap paradox, or a self-created entity (object, data, person) with no discernible point of origin.

A simpler predestination example involves a person traveling back in time to prevent a fire that broke out at a famous museum a century earlier resulting in the destruction of many valuable pieces of art, only to accidentally cause a kerosene lamp to fall, therefore creating the very fire that later motivated them to travel back in the first place. Likewise, a person traveling back in time to save a loved one from suffering a tragic death will be unable to save them from their fate as the event has already been determined. In the 2002 remake of the The Time Machine, for instance, the scientist Alex Hartdegen witnesses his girlfriend Emma being killed by a mugger looking to steal her engagement ring, after which Hartdegen devotes his life to building a time machine in order to change the past. Once completed, subsequent attempts to interfere with time sees Emma die under different circumstances, including being trampled by a horse, leading him to conclude that “I could come back a thousand times… and see her die a thousand ways.” He then travels to the future to see whether scientists have discovered a solution on how to change the past, and during a conversation with the Über-Morlock in the distant future is told:

“You built your time machine because of Emma’s death. If she had lived, it would never have existed, so how could you use your machine to go back and save her? You are the inescapable result of your tragedy, just as I am the inescapable result of you.”

Other examples of predestination paradoxes involving physical time travel in the movies includes the Terminator franchise (1984-2015), Back to the Future (1985), Bill and Ted’s Excellent Adventure (1989), Kate and Leopold (2001), Harry Potter and the Prisoner of Azkaban (2004), Timecrimes (2007), Looper (2012), and Interstellar (2014). The movie 12 Monkeys (1995) also presents a worthy example, with the main protagonist James Cole traveling back thirty years in time to investigate a deadly plague that decimated humanity in 1996. During his investigation, he experiences flashbacks to when he was a boy and witnessed a man being shot at an airport, only at the end of the film becoming the very same man he witnessed being killed, while a younger version of himself in 1996 watches on from the airport.


In addition to a person traveling backwards in time and fulfilling his role in a past event, another type of predestination paradox involves information sent from the future causing a person to fulfil his part in an event yet to happen. In either case, any attempts to change either the past or future are doomed to ultimately fail.

For example, a person who receives information from the future that they were fated to die from a heart attack resolves to get fit and avoid his fate. The man then takes up an active exercise regime, but ends up overexerting himself and dying from the very heart attack he set out to prevent. In another example, a person receives future information that they will die by drowning in the future, and so decides to never step foot off dry land. A decade later, his car falls off a collapsing bridge and he drowns in the river, having never learned to swim. In both these stories, information from the future interacts with past events to form a causality loop with both cause and effect running in a continuous circle, thus resulting in a chicken or egg type dilemma. It is the fact that the information received from the future was truly known to occur that makes them examples of predestination paradoxes, rather than just being a question of past events causing future actions.

The next example based upon the classic Greek tragedy called ‘Oedipus Rex‘ (429 BC) is another such case, albeit with a force beyond science element included, as even the god Apollo warned King Laius about the supernatural curse placed on his family by King Pelops of Pisa. The story centres around King Laius, Queen Jocasta and their son Oedipus, whom the oracle at Delphi prophecies will grow up to kill his father and marry his mother, thus bringing disaster on the city of Thebes. King Laius then leaves the infant on a mountainside side to die, which is subsequently found and raised by King Polybus and Queen Merope. After growing up, Oedipus learns of the prophecy and so leaves home to protect his adopted parents, but on his journey quarrels and kills a stranger (Laius), and after later saving the kingless Thebes from a monstrous Sphinx marries the king’s widow, Jocasta, thereby inadvertently fulfilling the prophecy.

An example of a predestination paradox involving information from the future can be seen in Star Wars Episode III: Revenge of the Sith (2005). In the movie, Anakin Skywalker sees a premonition of the death of his wife Padmé Amidala while giving birth to Luke and Leia, leading him to turn to the Dark Side in an attempt to save his wife, ultimately causing her to lose the will to live, and die in childbirth.

You Can’t Change the Past

In predestination paradox themed movies, the protagonist is usually depicted as helpless to change their fate either through a lack of free will, ignorance, or an external force seemingly controlling their actions and circumstances. This tallies with Novikov’s self-consistency principle, which asserts that a time traveler is constrained to only creating a consistent version of history, and that there can be zero probability of creating a time paradox. The force which interferes with attempts to alter past events may involve physical laws, fate, or even an improbable event, which according to another solution called the ‘timeline-protection hypothesis’ would result in a probability distortion that occurs to protect the timeline, with a highly improbable event occuring in order to prevent a paradoxical, impossible event from happening.

Another possibility that has also been explored in science-fiction stories is that the time traveler may actually be a willing participant in ensuring a paradox is maintained, such as in Predestination (2014) and the book which inspired it called All You Zombies (1959), as the alternative to the time traveler not impregnating his younger transgender self would have resulted in him never having been born at all, and therefore ceasing to exist.

In any case, a person interacting with past events will usually only be able to act in a consistent way that enables the already established past events to be preserved. For instance, say you built (effect) a time machine to stop a loved one from dying in a hit and run car accident (cause) a year ago. After travelling to the past, you are driving on your way to the scene of the crime, but instead of preventing the accident you accidentally run over your loved one and cause it to happen. You then flee the scene of the crime and return to your present and continue with your life in a linear way, but your self in the past upon learning of his loved one’s accident then sets about building a time machine only to once again travel back in time and cause the accident. In this predestination paradox example, your action in creating a time machine caused the accident to happen, and any time travel attempts to change the past event will invariably still result in the accident occurring, and history being preserved. You then go on and live your life in linear time knowing that history is pre-written, and that you cannot change an event in the past which has already taken place.

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