A fantasy world where all prophecies are [[AllMythsAreTrue mandated]] by the Universal Laws to be [[BecauseDestinySaysSo 100% accurate]] easily lends itself to reveal-the-plot prophecies, particularly when the author isn't skilled in the fine art of obfuscation and ProphecyTwist. However, laying out the plot beforehand is a good way to kill any plot tension. All but the most incompetent of authors realize that something has to be done.

As its name implies, an Either-Or Prophecy specifies two possibilities. '''Either''' the good will triumph over evil '''or''' the BigBad will mop the floor with the pesky heroes and reign unconquered forevermore. The point is that there is no middle ground.

It is implied that each of the possibilities has a 50% chance of coming true, but in practice, the good will always triumph and the evil option is [[EvilOnlyHasToWinOnce just there to motivate the characters]] (and distract the audience). Occasionally, through a ProphecyTwist, ''both'' halves come true.
And it's always possible that the heroes might say "ScrewDestiny" and TakeAThirdOption.

A little thought reveals that the [[InvertedTrope inverse]] of this trope, when applicable, falls under NoManOfWomanBorn. The latter trope requires that two or more conditions be met that are supposed to be contradictory (and thus interpretable as Neither-Nor)[[note]]For instance, "No man of women born shall kill you" can be read as "The one who kill you will neither be a man, nor will that one be born of a woman".[[/note]][[note]]This can be proven in general terms through formal logic: as the other trope's description puts it, it is "If X, then Y" where X is seemingly impossible, and formal logic clearly states that "If X, then Y" is equivalent to "Either Y or not X". Trust me.[[/note]], but in reality aren't, leading to the inevitable ProphecyTwist.

When the Either-Or Prophecy is split into two opposing prophecies, it forms a ProphecyPileup.

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!Examples:

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[[folder:Anime and Manga]]
* {{Naruto}} has the head frog sage of Myobokuzan foretell [[spoiler:that one of Jiraiya's pupils will either change the world for the better or bring the world to ruin. The possible candidates are Naruto and Pain/Nagato. Nagato ends up endorsing Naruto as he performs his DeathEqualsRedemption in order to resurrect all the victims of his attack on the Leaf Village]]
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[[folder:Comicbooks]]
* A ''SpiderMan'' annual, "Night of the Bend-Sinister", begins with a prophecy from the Book of the Vishanti, stating that once every 60,000 years a mystical conjunction called the Bend-Sinister is possible, and at that time demons will succeed in invading the Earth unless "a mighty sorcerer'' joins forces with "one who both spider and man". Fortunately, Spider-Man and Comicbook/DoctorStrange are old friends...
* In the ''ComicBook/TomStrong'' story with the interdimensional Aztech Empire, the computer-god Quetzocoatl-9 tells the High Priest that if he invades the world with superhero Tom Strong on it "there will be a great victory". The victory in question was Tom Strong destroying the hardwired controls that left Quetzocoatl-9 enslaved by his priesthood. Thus the computer-god destroyed the priest and took direct control of his empire.
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[[folder:Fairy Tales]]
* Parodied in a fairy tale in which a woman asks a wizard about the sex of her unborn child. She is told: "The child will be either a boy or a girl."
** But in fiction it's sort of [[AmbiguousGender good news already]].
* One Norweigan folktale has a village idiot make his way to fame and fortune via well-timed ambiguous statements. The last test set before him by the king is to predict the sex of the queen's unborn child; he has her walk towards and away from him before declaring, "When she walks towards me it looks like a boy, but when she walks away it looks like a girl." She gives birth to twins.
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[[folder:Films -- Animated]]
* In Disney's ''Disney/{{Hercules}}'', the Fates prophesize that Hades will overthrow Zeus at a time when the planets align perfectly unless Hercules fights to stop him. Hades spends most of the rest of the movie doing his darnedest to kill Hercules before the deadline.
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[[folder:Films -- Live-Action]]
* In the film ''TheDarkCrystal'':
-->When single shines the triple sun
-->What once was sundered and undone
-->Shall be made whole; the two made one
-->By Gelfling hand, or else by none.
** The Skeksis massacred the Gelflings to prevent the healing of the Crystal, following the logic that so long as no Gelfling was alive at the conjunction nobody could repair it. Sadly, they missed two.
* In ''Film/TheMatrix'', the Oracle examines Neo and says, "But you know what I'm going to say, don't you?" "I'm not the [[ChosenOne One]], he says." The Oracle tells him that he has [[RealityWarper the gift]] but that he seems to be waiting for something--"Your next life, maybe." She then tells him that, soon, Neo's life or that of Morpheus's will hang in the balance, and that he can save himself or Morpheus. Because Neo believes (but the Oracle did ''not'' confirm) that he is not the One, Neo chooses to save Morpheus. Neo dies and arrives [[EnlightenmentSuperpowers in his next life]] once he disbelieves the reality of the Matrix.
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[[folder:Literature]]
* In ''ChroniclesOfThomasCovenant'', Thomas Covenant is prophesied to "save or damn" the world.
* DavidEddings loves this. The ''{{Belgariad}}'' has two competing prophecies which, combined, amount to one big Either-Or Prophecy. In the sequel series, the same continues in a slightly tweaked form, so that the winning future is determined by one person who is supposed to be totally impartial. [[spoiler: The dark prophecy tries to cheat at the last second... and it backfires, as they send the person making the choice into such a meltdown that she throws herself at the light prophecy.]]
* The prophecy at the heart of the ''Literature/HarryPotter'' novels does not describe the eventual triumph of good over evil, but instead simply declares that Harry and Voldemort are destined to battle each other to the death. The ''aftermath'' of that battle is not something the prophecy is concerned with.
** When the prophecy was made it specified a child who could be either Harry Potter or Neville Longbottom, and only Voldemort's actions settled it on Harry.
--->"Neither can live while the other survives."
* Almost all important prophecies in TerryGoodkind's ''SwordOfTruth'' series of novels are of this type. The fourth book puts a twist on this, as both possible fates seem to require the hero's death...
** The very same prophecy also mentions his beloved will betray him. It's never explained completely, but I assume it meant that they both thought she was betraying him, while later they both realised she had not been betraying him. Or something.
*** His beloved ''has to'' betray him (and it is foretold that she will do so [[spoiler: "in her blood"]]) in order for him to [[spoiler: enter the Temple of the Winds through [[ExactlyWhatItSaysOnTheTin the Path of the Betrayed]]]]. And she does. Once [[MyGodWhatHaveIDone she realizes]], she begs the only witness not to tell Richard. The witness's response: [[spoiler: "I think 'Richard' already knows."]]
** It's also worth noting that [[spoiler: the final equation prophecies for both good and evil prove true by the end of the series. Magic is saved and destroyed when Richard spits the world in two and creates a new "no magic" world for the communists to live in.]]
* In ''Literature/TheLastRune'' series people are trying to save or kill Travis since he's fated to both save and destroy the world (usually based on how optimistic they are). Turns out he destroyes the world then rebuilds it exactly the same only without the BigBad.
* Depending on what happens to the Lightstone in the ''EaCycle'', either an Age of Darkness would start and a monster would destroy most of the universe or TheChosenOne would bring about an Age of Light and lift everyone to a higher state of existence.
* ''Literature/TheWheelOfTime'' has one of these among a hundred. For the most part, Min's viewings are unavoidable, thus making them useless as prophecies; whether she tells them or not makes no difference. But there are a couple that are conditional. Interestingly, from a certain point of view both options could be seen to come true:
** Gawain will either kneel to his unofficial girlfriend Egwene, or kill her. [[spoiler: He kneels, though he is also largely responsible for her death]]
** Min's viewing of Siuan Sanche and Gareth Bryne said that "You must stay close to each other or you will both die." [[spoiler: They end up saving each others lives after an assassin carrying a poisoned needle attacks them (Gareth kills the assassin and Siuan heals him from the poison). Later, during Tarmon Gai'don, they are separated, and just after Min reveals that the viewing is still in effect, Siuan is killed in an attack. The effect of the warder bond makes Gareth go berserk and get killed.]]
** The various viewings of the future beyond the Last Battle, including Min's, qualify as well. They're accurate readings of The Pattern that shapes the past and future. However if the Big Bad wins The Pattern itself will be destroyed, rendering the viewings false.
** Also used in one of the prophecies regarding Mat Cauthon, who was told "You will go to Rhuidean." He asked the prophet "Why do I have to go," and was told "If you do not, you will die." Mat could theoretically tell his destiny to screw off, if he was willing to die for it and possibly doom the world.
* This is seen somewhat in ''{{Dune}}'', where Paul and later Leto II can see possible futures and must choose the best one to carry out.
* In ''PercyJacksonAndTheOlympians'', there is a prophecy that a half-blood child of one of the big three will either save the Olympian gods or damn them... [[spoiler: or so we believe for the whole freaking series. what it actually says is that ''when'' the next child of the big three turns 16, ''a'' hero will make a choice to save or damn he Olympian gods...this hero and the halfblood aren't the same person.]]
* In ''Literature/WarriorCats'', a prophecy says, "Fire alone can save our clan". It doesn't specify if it will or not.
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[[folder:Live-Action TV]]
* The key prophecy in ''Series/FirstWave'' from the Lost Quatrains of Nostradamus:
--> On the seventh dawn of the seventh day;
--> A twice-blessed man will roam the fields.
--> Doomed to shadows with his brethren;
--> Or savior to all who walk the ground.
** Basically, it's up to Cade (the "twice-blessed man") whether Earth will be conquered by aliens or not.
* The Shanshu prophecy in ''Series/{{Angel}}'' says that the vampire with a soul will either save the world or destroy it during the Apocalypse.
* ''{{Lexx}}'' has the Time Prophet basically state that a Brunene-G will destroy His Divine Shadow. So, of course, HDS kills all of the Brunen-G... Only to turn the last one into a BrainwashedAndCrazy undead assassin. It was a specific case of His Shadow trying to ScrewDestiny, since He never thought that Kai would recover from being brainwashed (not so much the undead bit), nor that Kai would just so happen to have a brain-eating Cluster Lizard handy when His Shadow transferred back into the body of a [[GiantSpaceFleaFromNowhere planet-sized Insect]]. Although the prophecy ITSELF is cut and dry, it falls into this trope because the Time Prophet specifically makes her predictions by looking "more or less into the [[HistoryRepeats cycles of Future-Past]]", which basically means "Since all this happened this way before under different names, it will happen again, probably, unless it doesn't".
* On ''Series/{{Vikings}}'' the Seer is fond of those and will rarely give anyone a straight answer to their questions. He tells Ragnar that if he defeats Jarl Haraldson it will be a sign that the gods favor him and thus his rebellion is not a crime. If Haralsdon wins then it means that Ragnar was obviously not favored by the gods and had to be punished for his crime. Since it is highly unlikely that the two men will reach a peaceful resolution, one of those two outcomes is inevitable and thus the Seer will be proven correct.
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[[folder:Newspaper Comics]]
* ''{{Candorville}}'' parodies this during TheReveal. [[spoiler:If a vampiress can produce a {{Dhampyr}}, which Roxanne managed to do thanks to modern fertilization techniques, she'll lose all the standard weaknesses and the need for blood while retaining all the assets. It's prophesied that she'll someday rule over mankind--unless she gives into her still-existing ''[[HorrorHunger desire]]'' for blood, in which case she'll be returned to normal having gained nothing. "[[ArsonMurderAndJaywalking And her APR would shoot up to 29.97%.]]"]]
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[[folder:Tabletop Games]]
* SJ Games' ''TabletopGame/InNomine'' {{RPG}} features the Archangel of Destiny, who knows with divine certainty that ultimately everything will turn out all right... and the Prince of Fate, who has an equal certainty that Hell and the forces of evil will triumph. Fate and Destiny hang in a sort of metaphysical eigenstate over any sort of prophecy in this setting, and as angels and demons, the player characters themselves are often the 'spooky action at a distance' that resolves them.
* The Usurpation of the Solar Deliberative in ''{{Exalted}}'' was triggered when the Sidereals read the Loom of Fate and noticed a gigantic celestial clusterfuck would ensue if the Solars kept doing things as they were. They could either tell the Solars about this and hope that they'd yield to the advice, or overthrow the Solars and ensure that the crisis did not come to pass. They chose the latter, which had its own string of nasty side effects. The best part? Due to the manifestation of the Great Curse upon the Sidereals, the choice to kill them all did ''not'' avert the dark and miserable future that would come if they failed to persuade the Solars -- it only delayed it, and if not for the careless arrogance of the forces of Evil, there wouldn't have been any Solars to stand in the way.
* The Draconic Prophecy in the DungeonsAndDragons setting {{Eberron}} can be said to follow this trope; it describes the inevitable results of certain events, while remaining silent as to whether these events will ever happen. This works out perfectly for adventures: If event X happens, event Y will happen. If you want to prevent or cause event Y, you've got to worry about event X.
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[[folder:Theater]]
* In ''Theatre/TheWomenOfTrachis'' Deianira reveals the prophecy that after finishing his current task Herakles would either die or live a happy life. She is appropriately [[DownerEnding concerned]] about this.
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[[folder:Webcomics]]
* "In Webcomic/TheOrderOfTheStick, Belkar asks the question from the Oracle:
--> "Do I get to cause the death of any of the following: Miko, Miko's stupid horse, Roy, Vaarsuvius or you?"
** The answer is of course [[MathematiciansAnswer "yes"]].
** [[spoiler:When Belkar complains that the prophecy didn't come true, the Oracle tries to convince him that he [[HalfTruth caused all of their deaths already]]. Belkar doesn't buy the ProphecyTwist so well and goes for the last one. Except that it turns out that the Oracle was CrazyPrepared, engineered circumstances that resulted in the murder backfiring on Belkar, and arranged for clerics to resurrect him after Belkar left.]]
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[[folder:Videogames]]
* The game ''VideoGame/SuperPaperMario'' revolves around a prophecy of multiversal destruction written in a book called the Dark Prognosticus, rivaled by a prophecy that the multiverse will be saved by a band of heroes written the book's Good Counterpart, the Light Prognosticus.
** This one gets a bit [[MindScrew confusing]]: both books predict almost exactly the same set of events coming to pass; the Dark Prognosticus mentions a band of heroes fighting for the multiverse's survival as well. Eventually it is revealed that [[spoiler:the Light Prognosticus isn't prophetic at all, but was written "to counter the Dark Prognosticus", suggesting that it simply contains the same prophecy but with a rewritten outcome. Or instructions on how to make the favorable outcome of the Dark Prognosticus's either or prophecy (which is never mentioned that it has) come to pass. Since the Light outcome happens in the end anyway, the suggestion is that even if the Dark was truly prophetic, ThePowerOfLove can ScrewDestiny. One prominent EpilepticTree is that the Dark Prognosticus was written by the DragonWithAnAgenda as part of an elaborate {{plan}}, rather than actually predicting the future. The writers have not commented on this.]]
* One of the plot points in ''VideoGame/MetalGearSolidPortableOps'' revolves around a pair ([[JekyllAndHyde well...]]) of twin psychics, one of whom sees the main character destroying [[HumongousMecha Metal Gear]], the other of whom sees the main character starting a terrible war. Of course, the ProphecyTwist is that the girls later realise that they were both right. (Since the game is a prequel this surprises no-one - we've already seen the main character try to start a war, twice, in the latter timeline.)
* ''BaldursGate II: Throne of Bhaal'' reveals that the prophecy about the Bhaalspawn bringing great destruction was actually an either-or condition: Either the PlayerCharacter will succeed, ''or'' the destruction will take place. (That is to say, even more destruction. Apparently the prophet specified some high level of destruction that would be even worse than what did happen in the games and potentially could happen because of what the PlayerCharacter could do after them.)
* LegacyofKain, Raziel sees murals depicting two champions that will battle each other to decide the fate of Nosgoth, but the victory is undetermined as the murals show both champions slaying the other. Then in a serious ProphecyTwist, we find out [[spoiler:Raziel is ''both'' champions at once. He ultimately allows himself to die because this is the only way he can "win," effectively meaning ''both'' outcomes of the prophecy are fulfilled - because the two champions are the same person, they both win, and they both lose.]]
* In ''BrutalLegend'', the prophecy foretelling Eddie's arrival from the Modern World to the Age of Metal says that he will either destroy the world or deliver the humanity from the demons' evil. [[spoiler:It is an early foreshadowing of the fact that he is half-human, half-demon.]]
** Actually, the dialogue between the characters when they are discussing the prophecy shows that there is disagreement about the translation, making this an EitherWorldDominationOrSomethingAboutBananas kind of thing.
* In ''{{Vindictus}}'', the main plot is that the goddess will appear when all the fomors are dead. It turns out that the fomors have their own prophesy with a similar outcome. [[spoiler: By the end of Chapter 10, they both start coming true.]]
[[/folder]]

[[folder:Real Life]]
* Historical example: King Croesus of Lydia asked the Oracle of Delphi what the result would be if he took his troops across the Halys River and attacked the Persians. Her answer was, "If you do, a great empire will be destroyed." The seer didn't specify ''which'' great empire. In the end, it was Croesus' kingdom, not Persia, that was destroyed, but the seer would have been "right" either way--but note that there was no way the seer could have known that Lydia or Persia would be utterly crushed (rather than a stalemate or minor gains for one side or another). That makes this a classic example of the trope, eliminating all possible middle ground.
* Prince Siddharta Gautama was foretold at birth to be either a great king or a great sage. His father, preferring the former, tried to shelter him from the world's pain and sorrow. When he did catch a glimpse, he ran away to meditate and became [[OlderThanFeudalism Buddha]].
* Creator/DerrenBrown claimed in an interview to have heard a psychic tell the person they were "reading," [[CaptainObvious "You either live alone, or with other people."]]
** A basic trick for mentalists and phony psychics is to throw these out so fast you only notice the correct sides.
** Just having [[CrazyCatLady pets]] is [[TakeAThirdOption neither]].
* Not exactly a prophecy, but more of a prediction: AdolfHitler supposedly was so fond of this kind of platitude ("there are two possibilities: Either x will happen, or y will") that even his secretary started japing about it ("there are two possibilities: Either there will be rain tomorrow, or there won't").
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