Ontological paradox

Ontological paradox

An ontological paradox is a paradox of time travel that questions the existence and creation of information and objects that travel in time. It is very closely related to the predestination paradox and usually occurs at the same 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 was meant to happen. A time traveler attempting to alter the past in this model, intentionally or not, would only be fulfilling his role in creating history, not changing it. The Novikov self-consistency principle proposes that contradictory causal loops cannot form, but that consistent ones can.

However, a scenario can occur where items or information are passed from the future to the past, which then become the same items or information that are subsequently passed back. This not only creates a loop, but a situation where these items have no discernible origin. Physical items are even more problematic than pieces of information, since they should ordinarily age and increase in entropy according to the Second law of thermodynamics. But if they age by any nonzero amount at each cycle, they cannot be the same item to be sent back in time, creating a contradiction unless it is a reproduced item such as a seed, spore, etc.

The paradox raises the ontological questions of where, when and by whom the items were created or the information derived. Time loop logic operates on similar principles, sending the solutions to computation problems back in time to be checked for correctness without ever being computed "originally."

It is sometimes called the bootstrap paradox, in reference to its appearance in Robert A. Heinlein's story "By His Bootstraps" (see below).


* On his 30th birthday, a man who wishes to build a time machine is visited by a future version of himself. This future self explains to him that he should not worry about designing the time machine, as he has done it in the future. The man receives the schematics from his future self and starts building the time machine. Time passes until he finally completes the time machine. He then uses it to travel back in time to his 30th birthday, where he gives the schematics to his past self, closing the loop."

* A professor travels forward in time, and reads in a physics journal about a new equation that was recently derived. He travels back to his own time, and relates it to one of his students who writes it up, and the article is published in the same journal which the professor reads in the future.

* A man builds a time machine. He goes into the future and steals something. He then returns, produces his "invention" to the world, claiming it as his own. Eventually, a copy of the device ends up being the item the man originally steals.

* A man is locked outside his house because he's lost his keys. Another man approaches him with the keys. When the man enters his house five minutes later, he encounters a time machine which will transport him and his keys back in time five minutes, allowing him to close the loop. [The man would have to take the keys he left inside back in time, otherwise the keys given to him would age by a non-zero amount]

*A woman goes back in time and takes something from a drawer to use in her present time. After it has fulfilled its use she travels back again and places it in the drawer and then goes back to her own time seconds before her past self appears to take it and use it herself.

*A young physicist receives an old, tattered, disintegrating notebook containing various information about future events from his future self who has sent it back to him via a time machine; he copies it over into a new notebook before it deteriorates so badly as to be unusable. Over the years the predictions of the notebook come true, allowing him to become wealthy enough to fund his own research; which results in the development of a time machine, which he uses to send the now old, tattered, disintegrating notebook back to his former self. The notebook is not a paradox (it has an end and a beginning; the beginning where he bought it, the end where he threw it out after he copied the information), but the information is.

*A man who does not know who his father is goes back in time to find out who his father was. He goes to the bar his mother says she met him, where he meets a woman. After several drinks, he goes to her room with her. When he wakes up he discovers it is his mother he was with, becoming his own father.

Examples from fiction


* Robert A. Heinlein's stories "By His Bootstraps" and "All You Zombies—" involve the predestination paradox, but also plays with the ontological paradox. In "By His Bootstraps", the protagonist is asked to go through a time portal by a mysterious stranger, a second stranger tries to stop him, and all three get into a fight which results in the protagonist being pushed through anyway. Ultimately, it is revealed that all three are the same person: the first visitor being his future self and the second an even older future self trying to prevent the loop from occurring. The ontological paradox here is in where and how the loop started in the first place. "All You Zombies—" involves an even more convoluted time loop involving kidnapping, seduction, child abandonment and gender reassignment surgery, resulting in the protagonist creating the circumstances where he becomes his own mother, father, son, daughter, and kidnapper.

*In Jasper Fforde's novel "The Eyre Affair," a time-traveling character goes to Elizabethan times to discover who wrote Shakespeare's works. After discovering that neither Shakespeare, Marlowe, Bacon or anyone else seems to have written them, the character must give Shakespeare a copy of his own Complete Works and a rough timeline to ensure their existence in the future. (Confusing things further, however, the sequel revealed that the plays given to Shakespeare only included three comedies. The characters speculate that they proved so popular he wrote new ones himself. Fforde rather makes a point of "not" having his time travel follow any particular set of rules.)

* In Harry Harrison's novel "The Technicolor Time Machine", Barney Hendrickson travels back in time to present his earlier self with a note explaining how to resolve a seemingly insurmountable difficulty. The younger Barney carefully folds the note and puts it in his wallet, expressing his intention to leave it there until he reaches the point in his life where he travels back in time to hand it to his younger self. This prompts some discussion of how the note actually got written, and by whom, which the older Hendrickson dismisses by saying that the note was written by "time" because it needed to exist to allow the predestination paradox to play out. At the close of the novel, Hendrickson also discovers that by traveling back in time to film the Viking settling of America, he actually caused it to occur.

* In the climax of J.K. Rowling's "Harry Potter and the Prisoner of Azkaban", a series of events leading up to the apparent execution of Buckbeak and Sirius Black's imprisonment are revealed to be the doing of Harry and Hermione, who travel back in time to prevent the deaths of both. A true paradox is created when Harry realizes that the mysterious wizard who saved his life (and who Harry mistook to be his father) was actually his future self. He is able to create the life-saving Patronus because he knew he'd "already done it."

* In Terry Pratchett's novel "Pyramids", the immortal High Priest Dios has been advising a line of kings for thousands of years. At the end of the book, Dios falls backwards in time where he becomes advisor to the first king of the line. His life is thus a closed loop.

*In the Robert Silverberg story "Absolutely Inflexible", the main character, Bureau Chief Mahler, lives in a future where time travel is possible but only to the future. It is also a society where all diseases have been eradicated and no one has been immunized in decades. Thus it is not safe for these people to be released into the general population and they are quarantined on the moon. All of the time travelers are brought to Mahler and his "absolutely inflexible" attitude towards them means they are always quarantined. However, one day a man is brought to him in the regular decontamination suit and says he has a two-way time machine which will bring a person to the future and back. The man seems to recognize Mahler and realizes that he is doomed to be sent to the moon. Mahler decides to test the new machine and goes to the past and back to his present. When he arrives, he is immediately put into a decontamination suit and is brought to the bureau office where he talks to Mahler from his past. It is revealed that the time machine is stuck in a causal loop.

* In the Marvel Comics' one shot entitled, X-Factor: Layla Miller, a paradox occurs while Layla Miller is trapped in a dystopian future. Near the conclusion of the tale, she reunites with a teammate, the X-Men's Cyclops. He had been waiting for her for to appear for years and possesses a picture of her as a reminder. When she she finally arrives, Cyclops's daughter, Ruby, ends up taking the exact same picture that Cyclops had been holding on to for all those years. Cyclops gives the Layla the newly-taken photo and instructs her to give it back to him when she eventually finds her way to her proper time, thus completing the loop.


* In the film "Bill And Ted's Excellent Adventure" The protagonists, Bill S. Preston Esq. and Ted "Theodore" Logan are met by Rufus, a figure from the future who gives them access to a time machine. To convince them he is telling the truth, older versions of Bill and Ted appear in the time machine and tell them, "Listen to this dude Rufus; he knows what he's talking about." Rufus himself never tells them his name. Ontological paradoxes are frequently used in other parts of the movie and its sequel, "Bill & Ted's Bogus Journey".
* In the film "Somewhere in Time" based on the Richard Matheson novel "Bid Time Return" , Christopher Reeve's character is given a pocket watch by an old lady. He then goes back in time and gives the pocket watch to the old lady's younger self, played by Jane Seymour, which prompts her to seek him out years in the future and give him the watch, resulting in the watch having no apparent origin.
* In "Back to the Future":
** During his first meeting with his father in the cafe in 1955, Marty McFly mentions to Goldie Wilson (a busboy in 1955) that he is going to be mayor, thus giving Wilson the idea.
** Later, Marty steps in for the guitarist at his parent's school dance and plays Chuck Berry's "Johnny B. Goode", an oldie from when Marty hails (1985), but nonexistent in 1955. Marvin Berry, the band's guitarist, calls his cousin Chuck and tells him that he found the "new sound" Chuck was looking for.
** After the dance and the Johnny B. Goode performance, Marty says goodbye to his 1950s parents who have just had their first kiss. After he leaves, his mother absentmindedly says "Marty - such a nice name..." implying that he inspired her to name her future son Marty (Oddly, he is the youngest of three children).(However, as the portrayed timeline is modifyed by some of the events in the movie, there is actually no real loop created, thus the conditions for ontological paradoxes are not fully meet.)
* In the Futurama film Bender's Big Score, the tattoo of Bender on Fry's backside, which contains the time code, is put there by Bender who took it off future Fry's backside. The question of how the tattoo was created creates an ontological paradox.
* In "":
** Scotty and McCoy attempt to find the 20th Century equivalent of "transparent aluminum." At a plastics manufacturing plant, they offer the formula for transparent aluminum to their host, a Dr. Nichols. McCoy pulls Scotty aside and says, "If we give him the formula, we're altering history," to which Scotty replies, "Why? How do we know he didn't invent the thing?" In the novelization of the film, it is explicitly revealed that Dr. Nichols "did" invent transparent aluminum.
**Kirk's sale of his antique glasses is a classic example of an ontological paradox. It is given to him by Doctor McCoy as a birthday present in Star Trek II, then sold by Kirk in the past in Star Trek IV. The glasses thus have no manufacturer or origin, and exist only because of the causal loop.
* In "", the lead character Swann travels from modern America to 1877 Baja California. There he encounters a woman named Claire Cygne. During the course of the story he tells her of his life in Los Angeles, California, and is then transported back to his origin. Before he leaves, she takes a family memento from him that has been passed down the generations. We discover that Cygne then leaves Baja, Anglicizes her name to Swann, and settles in the Los Angeles area.

* In "The Terminator" movies:"
** The Terminator cyborg sent back in time to kill Sarah Connor is destroyed, but its components are salvaged to form the basis of the artificially intelligent computer network Skynet that will, in the future, send it back in time on its murderous mission. The knowledge of how to create an artificially intelligent machine therefore has no ultimate source.
** Kyle Reese, having traveled forty-five years into the past, gives Sarah a message from his commander John Connor. In "", John says that his mother made him memorize the message — which, ironically, says that the future can be changed — in order to give it to his father, so that his father might then pass it on to her. At no point do we learn when or how the message was originally composed. Similarly, Kyle shows Sarah how to fight Terminators. Sarah teaches the same methods to John, who trains Kyle in the future. In "Terminator 2" a plot hole is when the "good" Terminator and his future memory chip are destroyed at the end; in fact the ontological paradox of changing the future would have already taken place when John Connor destroyes the "evil" terminator components; with these components no longer existing and thus no basis for an artifical intelligence "Skynet" of the future, logically both the terminators and John Conner would "never exist"!
** In the movie "Terminator 3: Rise of the machines", the Terminator tells John Connor and Katherin Brewster than he was sent by Katherin herself after she reprogrammed him, turning him to be one of the good guys. Later in the movie, he takes the couple to Sarah Connor's grave and tells them that Sarah buried her weapons there. Since Katherin knew about the weapons location because the Terminator told her and then she told this same information to the Terminator before sending him to the past, the origin of the information about the weapons location remains a complete mystery, thus causing a ontological paradox.


* In the beginning of the "Dexter's Laboratory" made-for-TV movie Ego Trip, a group of robots who came from the future from Dexter's time machine tell him they are there to "destroy the one who saved the future". After he easily destroys them all he goes into the future to see how he saved the future. In the end of the film during the showdown against his arch-enemy Mandark, Dee Dee saves the world by wandering in from the open time gate and pressing the button to reverse the waves of the "Neurotomic Protocore", thus turning the dystopian world into a utopian world. Dexter, overcome with rage, create a group of robots and tell them to "destroy the one who saved the future", and send them back through the time machine to take care of Dee Dee, creating an ontological paradox. When Dexter notices that this paradox is too confusing, he decides to ignore it and goes to eat lunch.

* In the "" episode , Miles O'Brien is sent forward in time periodically, seeing himself die several times. Even though he tries to stop events by telling Quark to not allow any Klingons into his Bar, the events happen because of Quark's greed for the Klingons' money. When the reason for his time travel his discovered, radiation intensified by a singularity, he travels forward in time once more and finds the Deep Space Nine being evacuated, his future self telling him there was an explosion. When he returns to his own time, armed with the knowledge he is forced to have the radiation intensified, which sends him into the future. He tells his future self the station will be destroyed, and they head to Operations, seeing the cause of the attack: a Romulan Bird of Prey which was in orbit of the station being cloaked, their cloaking device being powered by a singularity, the explosion being after the Bird of Prey decloaking and attacking. O'Brien is too weak to return, the radiation killing him, and he gives the device which allowed his future travel to his self, who returns and reveals the events. In comical and ontological fashion, he finds himself having experienced a day or so before everyone else, and feels that "somehow this was the other O'Brien's life"; when Quark proposes him a business deal whereby O'Brien reveals the results he saw in the gambling games at Quark because of his knowledge, he refuses, but when walking out the bar tells Quark "Dabo", which is in sychronisation of the result of a game of Dabo at the bar. The episode is rather unique because of the amount of loops created by the events, and their effect on the history of the show.

* In an episode of the Twilight Zone, a man builds a time machine in order to travel to the time of Lincoln’s assassination and prevent the murder. He finds the President’s security in a tavern and begs them to stand guard directly at the entrance to the theatre box as an assassin could easily harm the President with the planned security setup. The guards laugh off the notion and ignore the man’s pleas. Unbeknownst to the time traveler John Wilkes Booth is in the tavern and overhears him. Armed with this new knowledge Booth is inspired to shoot the President feeling that he could kill Lincoln successfully.

* In the "Red Dwarf" episode "Stasis Leak", Rimmer encounters the future holographic version of himself who tells him that the future crew had traveled back in time through a stasis leak found on one of the lower levels of the ship. He writes this in his diary. In the future, Lister reads Rimmer's diary and looks for the leak, which the crew finds and uses to travel back in time, where future Rimmer tells past Rimmer about the leak. The paradox not only involves the knowledge of the leak, but also the fact that the phenomenon itself is called a "stasis leak".

* In the animated TV series "Gargoyles" the wealth of billionaire David Xanatos is based on an ontological paradox. On his twenty-first birthday, Xanatos receives a letter containing an ancient coin, which is the seed of his entire fortune. Many years later, he follows the instructions in the letter: he travels back in time a thousand years, acquires a small coin, and makes arrangements for it to be delivered to his past self a millennium later. While the letter itself is not an ontological paradox, the written text of the letter, and the information it contains, is.

* In the "Futurama" episode "Roswell That Ends Well", Fry (and the others) are transported to the past, where he inadvertently impregnates his grandmother, thus becoming his own grandfather. This is further complicated by the events of "The Why of Fry", which reveals that Fry is in the future because of the events of "Roswell That Ends Well", and the events of the former episode meant he could defeat the Brains in "The Day the Earth Stood Stupid", although (if the episodes are taken to be in a chronological order) this is because of events in the later episode "Roswell That Ends Well". In "The Why of Fry", the loop is revealed, and complicated by Fry who, armed with knowledge from the future, sends his past self into the future; it is not a pre-destination paradox, as the inconspicuous shadow of Nibbler from Space Pilot 3000 is now joined by Fry's shadow. He breaks the loop by telling Nibbler of the inadequacy of the vehicle he used in the events of "The Why of Fry", and this was how he was able to escape the loop with the superior vehicle not forcing him back into the loop.

* In "Quantum Leap":
**The time traveler Sam Beckett performs the Heimlich Maneuver on a choking man who is addressed as Dr Heimlich; no one else present recognizes the technique as it had not yet been invented.
**Sam gets a TV host, Captain Galaxy, to share his theories of time travel to a young Sam watching the program, which in turn greatly influences Sam in his own theories of time travel.

* In "Doctor Who":
**The 2007 "Doctor Who" episode "The Shakespeare Code", set in 1599, has a running joke where the Doctor, in the presence of William Shakespeare, quotes lines from plays that Shakespeare has not yet written. In each instance, Shakespeare comments that he "likes that" and might use the line in a future work. The true origin of these lines form an ontological paradox (with the exception of the word "Sycorax," which the Doctor did not use as an intentional reference to Shakespeare, but to an alien species that appeared in "The Christmas Invasion.")
**In the 2007 "Doctor Who" episode "Blink", the Doctor records a message on film in 1969 in the form of half a conversation. The other half is filled in when Sally Sparrow views the film on DVD in 2007, which her friend Lawrence Nightingale transcribes. The full transcript, including the Doctor's portion, is eventually handed to the Doctor in 2008, but before he is sent back to 1969 from his subjective viewpoint, so he can use it in creating the message later. The contents of the conversation form an ontological paradox.
**In the Children in Need "Doctor Who" mini-episode "Time Crash" the Tenth Doctor meets the Fifth Doctor which causes an extremely powerful paradox strong enough to tear a hole the size of Belgium in the fabric of space and time. The Tenth Doctor saves the day by firing an artificially created supernova into a black hole caused by the paradox thus cancelling out the implosion of the black hole. The Tenth Doctor knows how to do this because he remembers seeing himself do this when he was still the Fifth Doctor.
**In the two-part episode Silence in the Library/Forest of the Dead, Professor River Song tells the Doctor about how in his future, he could open the doors of the TARDIS by simply clicking his fingers, which he dismisses as impossible. At the end of the episode he does open the doors exactly as she described, allowing him to show this River in his future, her past.

* In the "Stargate SG-1" episode "1969", SG-1 accidentally travels back in time to the year 1969, where they are aided by Lt. Hammond because of a note his future self gave to Carter before they left, spurred by a familiar cut on Carter's hand. Recalling the memory of the future SG-1 visiting him early in his career, Gen. Hammond had ordered research into using the Stargate for time-travel and was subsequently able to provide them with the information they needed to get home — before they left.

* In the "Heroes" episode "Out of Time", Hiro Nakamura spreads the stories of 'Takezo Kensei' in the past, only to learn them as a young boy and eventually go back in time to spread them again in the first place.

* In the TV show Mr. Meaty a new game system comes out and Josh & Parker are first in line, but their brothers cut in front of them. So they decide to go forward in time to when the game system is cheaper. When they get there, they discover that the world is controlled by baboons. Eventually they become the alphamales and go back in time with the baboons. When the baboons are brought back, they realize that the baboons will eventually take over the world.

* In the two-part episode "War Without End" of the TV show Babylon 5, two characters (Jeffrey Sinclair and Zathras) take the space-station Babylon 4 back in time 1000 years, to be used by the Minbari in their war against the Shadows. During the trip back Sinclair transforms into Valen, a Minbari holy leader long known to be "Minbari not born of Minbari", who was roughly equivalent in status to Gautama Buddha, Christ or Mohammed. The paradox is contained in three letters written by Valen for Sinclair, Delenn and Draal; these letters were sealed in a sanctuary on Minbar, with orders that the sanctuary be opened on specific dates and times and the letters then given to the appropriate persons. These letters contained the information about how to send Babylon 4 back in time, as well as identifying Sinclair as the historical Valen. In addition to the letters, the Minbari's religious and historical texts, as well as much of their culture, political structures and religious beliefs, are also an integral part of the paradox. Sinclair had studied these at length before he learned he was Valen, and so when he went back into the past he intentionally created the Minbari history he remembered from the future. There is also a predestination paradox here: Delenn is a human-Minbari hybrid, having transformed at the beginning of season two, however to change she needed human DNA - which the Minbari gained through Valen, himself still partly human. Had Sinclair not gone back, Delenn could not have undergone the transformation - in fact she would not even have been born.

* In the anime series The Melancholy of Haruhi Suzumiya, the time-traveling character Mikuru Asahina comes from the future to observe the reality-bending Haruhi Suzumiya. At one point in the series, an older version of Mikuru comes to the past to pass some important information to Kyon. The older Mikuru went to great lengths to ensure that her younger self did not discover her presence, but, despite all these precautions, she accidentally let slip a small bit regarding the star-shaped mole on her chest. Mikuru herself was not aware of the mole until Kyon had pointed it out to her. However, Kyon "himself" was not aware of the mole until the older Mikuru pointed it out to him.

* In the 2008 television miniseries The Andromeda Strain, the aforementioned disease is sent back in time via a wormhole by the citizens of future Earth, who cannot stop the disease because a required bacterium has gone extinct and only exists in the past. Scientists in the past manage to utilize this bacteria and kill the virus, but a single sample is saved and stored in the International Space Station at the series' end. It is implied that this sample is the cause of a viral outbreak on the future Earth, causing its citizens to once again send the virus back and hope that it can be destroyed in the past. This creates a further paradox due to the fact that Andromeda seems to have no origin and only exists in the past because it was sent from the future, whose citizens kept a sample from the past and then sent it back again, creating a never-ending loop.

* In the episode "Lost and Founded" of the TV series "Aladdin", Iago brings the blueprints for Agrabah almost 700 years into the past and gives them to Jasmine's ancestor, Hamed, who founded Agrabah using them. We never learn how or when the blueprints were originally drawn up.

* In British television play The Flipside of Dominick Hide, a time traveller from Earth's future, who illegally visits the London of 1980 to search for an ancestor, falls in love with a local woman. He gets her pregnant, and discovers that he was/is the ancestor he was looking for. It is explained that the character is a victim of something called a "genetic time-slip".

* In the Supernatural episode "In The Beginning" Dean Winchester is sent back in time and meets his mother, and learns that he may be able to kill the Yellow-Eyed Demon, preventing him from killing Mary Winchester, but unwittingly puts the Demon on Mary's scent, allowing him to kill her as shown in the Pilot episode.

Video games

* In the computer game "Escape from Monkey Island", Guybrush travels through a marsh where time flows differently and encounters his future self on the other side of a gate, who gives him the gate's key and several other items. Unconvinced, the present Guybrush asks what number he's thinking of, and opens the gate when his future self gives the correct answer. Later in the marsh, Guybrush must go through the gate from the other side, and so has to give his past self the key and the miscellaneous items, then pass the number-guessing test by recalling what his future self told him. The question of where the key and items originally came from is thus never resolved. True to the game's humor, failure to repeat everything precisely will cause a "temporal anomaly" that sends Threepwood back to the start.

* In the interactive fiction game "Sorcerer", the player is given the combination to a safe by his future self. He then has to give the combination to his past self to prevent a temporal paradox.

* In ', the protagonist Link visits a windmill in Kakariko Village as an adult and a musician tells him a young boy played a mysterious song there seven years earlier which caused the windmill to spin much faster than normal; the musician then teaches Link that song as he couldn't forget it. Link then travels seven years back in time, becoming a young boy again, and plays the song before the same musician in the windmill, causing the windmill to spin faster than usual. A paradox is created as the earlier event of Link's playing the song would not have occurred had Link not heard of it in the future. Likewise, the musician had learned the song from Link in the past while Link had learned it from the musician in the future, thus the mysterious song seems to have no actual composer (although the song reappears in the sequel ', this time with a ghost composer).

* The game "" makes frequent use of this paradox. Incidents include the player receiving a key from his future self and handing it later on to his past self (with no clear origin of the key), learning a password in the same manner and on more than one occasion saving his own life (which often entails playing through the same section of the game more than once).
* In Jak II, the protagonists accidentally use a Rift Rider to travel centuries into the future. During the course of the story, one of them, Keira, builds another Rift Rider based on the first one (which gets destroyed after the time travel). At the end of the game, they are forced to send younger versions of Jak and Samos into the past so that they can become old enough to play their parts in defeating Kor and the Metal Heads, which means the Rift Rider Keira build is evidently the same Rift Rider she based it on.
* In Jak 3, Jak discovers pieces of armour that were once used by the ancient hero Mar. Near the end of the game, Jak discovers that Mar is actually an older version of himself, who went far into the past, and apparently spread the armour throughout the world. This causes the paradox that the armour was never actually made, and is of infinite age.
* The computer game series "Sam & Max Season Two" uses this paradox frequently. One instance is when the main characters look out their window and a unknown person calls out to them to ask if he can have the item they are holding. After they give it to him, he gives them an egg in return. They use the egg to later solve a puzzle. In a later episode, the main characters yell at their office window and ask their past selves for the item they are holding, which you use to solve a puzzle. In return you give them the egg that helps them solve the puzzle in the past. Thus revealing that they were the people that helped them in the past and also creating a paradox. The paradox is joked about in normal Sam & Max fashion when, after receiving the egg Sam comments, "Thanks. Be you later." A scene in the second to last episode creates paradox when the main characters go back in time to Episode 2 of Season 1. Their doubles from that episode then steal the time machine and come into the present time. The main characters reappear in the present angry at their past selves for having to relive the last two years over. Afterward, the main characters trick their past selves to go back to their original time and trap them there by recalling the time machine. This means that two sets of Sam and Max lived through those two years to get to the current time. This plot hole is written off by a computer who declares "Time stream repaired."
* In Final Fantasy I, Garland's pact with the four fiends sends him into the past where he can re-activate them in the future to send him back again, creating a loop.

Possible solutions for the Ontological paradox

* For a material object that travels through time repeatedly (for example, the keys to the house the man locked himself out of, only to have the keys delivered by his future self) without being recycled (as opposed to the physicist's notebook), it is possible that the recycled item ages in real time, despite going through time. Similar to the fact that, if one were to go back in time to his or her first birthday, the time traveler would not become a year old, but would rather age normally. Likewise, a recycled item may break, corrode, become overused, etc., destroying the loop when the item becomes unusable.
* In all ontological paradoxes, including the one above, it is possible that, by going through time, the time traveler actually causes a "bona fide" change in history. For example, when an aspiring inventor goes back in time and steals an invention, then returns to his present and claims the invention as his own, it may be that the invention was originally created by someone else, but by stealing it, he becomes the acknowledged inventor, effectively changing history.

ee also

*Newcomb's paradox
*Time travel in fiction
*Grandfather paradox
*Predestination paradox
*Self-fulfilling prophecy
*The chicken or the egg


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