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Clap Your Hands Ifyou Believe

He replied, "If you have faith as small as a mustard seed, you can say to this mulberry tree, 'Be uprooted and planted in the sea,' and it will obey you."
Jesus addressing his disciples, The Bible: Luke 17:5-6

An old trope, wherein enough belief in something will actually cause things to happen, also known as "magical thinking". This isn't a Magic Feather where "confidence" merely allows one to use their own abilities to the fullest; this actually physically changes the universe. In particular, a somewhat post-modern take on divine pantheons posits that gods are the product of (or severely dependent upon) their believers. Take away their believers, and a god "fades away."

This creates a vicious cycle for non-believers, as magical events are "disproven" in their presence because they don't believe in the first place, thus cementing their disbelief. Particular savvy characters may take advantage of this by getting others to yell "I'm Not Afraid Of You!"

A variant of this trope crosses it with I Am Spartacus, with the hero asking the people watching the battle to lend their belief/hope/faith in order to help. A further variant, common in works aimed at children (and their parodies) involves one character turning to the audience and asking them to clap their hands/stomp their feet/whatever to accomplish whatever needs to be accomplished at the time.

The lead quote is from The Bible, making this Older Than Feudalism.

Not to be confused with Your Mind Makes It Real, which has more to do with characters getting physically hurt with The Power Of Imagination (though the two tropes do sometimes intertwine). For those who don't even need to clap, see Reality Warper. Compare with Willing Suspension of Disbelief. See also All Myths Are True, Psychoactive Powers, Puff of Logic, & The Treachery of Images. Has nothing to do with Clasp Your Hands If You Deceive.


Examples:

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    Anime and Manga 
  • Axis Powers Hetalia: Mystical ancient Shinto creatures and ghosts are disappearing and leaving Japan because not just the people of Japan but also Japan himself don't believe in them anymore. There's always England...
    • Speaking of England, a common theory about his "Imaginary Friends" is that they're all actual, real fractions of European folklore and that the reason England can see them is because he's the only one who still believes in them.
    • A popular Fanon theory has it that nations are manifestations of their respective countries' people, culture and national identity, not any political entities. They die when their culture fades away and no one identifies with them anymore.
  • Berserk: Answering the wider question as to why the world of Berserk is so full of crapsuck, humanity needed a reason as to why there was so much evil and suffering in the world so badly that all of their collective thoughts and prayers formed the Idea of Evil. Yep. That will do it.
  • In Bleach, the Masked Luchador Mask De Masculine gets stronger and heals from all damage the more people cheer for him. While he is incredibly powerful even without his fans, his fans have to be taken out first before he can be killed.
  • A Certain Magical Index: Aureolus Izzard's incredible powers are limited by what he thinks his limits are; if he loses confidence in his power and stops believing in its effectiveness, reality obliges.
    • All espers derive their powers from having radically different internal realities from the standard. The process involves little kids, experimental drugs and brainwashing. Lots of parents seem to have no problems volunteering their kids for the process. Since the process is repeatable, it's Scientific, as opposed to the methods of the magicians... Waitaminute!
  • The part where the trope crosses over with I Am Spartacus is the principle behind Goku's Genki-dama/Spirit Bomb in Dragon Ball: he draws energy from the Earth, including its people, to power it up. Addressed straight in his final battle with Buu, when Mr. Satan/Hercule asks the (remaining) people on Earth to lend their energies to him for this specific purpose.
  • The world of Gaia in Escaflowne was actually built to some extent around the trope, as it was believed to have formed from the will of the ancient people of Atlantis. More concretely, Hitomi's sense of belief is so strong that she starts reshaping events around her, even to the extent of trumping the already-daunting ability of Zeibach to invoke Winds of Destiny, Change.
  • In Fate/kaleid liner PRISMA☆ILLYA, the main character Illya, can fly because she was a fan of Magical Girls before becoming one and believes that all Magical Girls have to be able to fly. Miyu on the other hand, can't fly because she is smart and can't ignore the laws of physics.
  • Full Metal Panic!: the Lambda Driver reacts to the user's mental state. The first time Sousuke uses it, Kaname instructs him that he must believe in it for it to work.
  • In the manga, Hyde And Closer, Shunpei and his animated magical chainsaw-wielding bear toy must fight off magicians out to kill him, all while learning magic in order to defend himself. Hyde explains that the source of all magical power is belief; the point of the strange rituals is to convince the spellcaster of the spell's reality.
  • In Kanon, the comatose Ayu still believed enough in her promise to Yuuichi and the wishes that she made on a simple crane machine doll that she was able to spiritually project herself as a solid living being even seven years later.
  • In "The Land of the Will, Cephiro" in Magic Knight Rayearth, the "heart that believes" shapes the world around them.
  • In Mahou Sensei Negima!, apparently you only have a soul if you believe you have one. When Negi makes out with Chachamaru to initiate a Pactio (which requires that she has a soul to get one), despite Chachamaru all but giving up, Negi believes in her so much that she gets both a soul and a Pactio.
  • The Mermaid Melody Pichi Pichi Pitch manga has the Purple Harp, which loses its strings when Lucia fears that she'll fail, and regains them when Hanon and Rina tell her to believe in herself.
  • In the Nasuverse, the Gods of old were willed into existence because people believed they exist. This also explains their downfall, as the number of believers declined... or because their believers think they all died in some massive slugfest (like Ragnarök). Other examples from Nasu include the summoned spirits of dead heroes, who become stronger if their legend is better known, and a weapon designed by the Catholic church for defeating a reincarnating vampire by shoving their belief that reincarnation doesn't exist forcibly down his throat. Or through his liver. Whatever works.
    • Even "reality" itself is an illusion conjured by "Gaia". A Reality Marble manifests when a person with a radically different internal reality (i.e. someone with a very distorted sense of self) believes in his/her own reality so strongly that it temporarily overpowers the will of the Earth.
  • A not-so-nice version is a major plot point in Paranoia Agent. Belief in the Urban Legend of Shonen Bat led to him becoming real, and unpleasant, freaky, and completely incomprehensible things ensued.
  • Pokemon 3 crossed this trope with Reality Warping, resulting in the Unown being driven crazy by their own creation, and then being stopped by Entei when Molly Hale began believing in him.
  • In Slayers, Shinzoku are dependent on the prayers of the mortal races, to the point where their counterparts, Mazoku, tactically destroyed temples to reduce the power of Shinzoku. Mazoku have their own form, feeding off of any negative emotions the mortal races have.
    • In the Novels, Lina was once confronted by Dynast Graushera's General, a very powerful Mazoku. Realizing she couldn't fight or escape, Lina decided to try mocking said Mazoku's name. The reasoning was that because Mazoku were masses of astral energy held together by their own self image, anything that undermined their self confidence would make them weaker. The strategy works.
  • Spiral power in Tengen Toppa Gurren Lagann is given several different Techno Babble explanations, but the effective result is that if you truly believe you can win, you will win. (Possibly by virtue of a Humongous Mecha the size of a galaxy forming itself out of pure willpower.) Conversely, pilots afflicted with sudden pangs of doubt are apt to find their robots powering down, which is ruthlessly exploited by the Anti-Spirals, using tactics designed to induce fear and despair to try and shake that confidence.
    • It's also established that, due to Spiral Power, a Gunman's controls are set to how the pilot thinks it should be controlled. It's possible for someone with no prior training to get into a Gunman, move some joysticks, and get it working solely because that's what they want it to do.
  • In Umineko no Naku Koro ni, the point of Battler's game with the witch Beatrice is that, should he accept her existence and the existence of magic, magic will exist in retrospect as the cause of the murders that drive the whole mystery. Since he refuses to accept her existence, though, Beatrice must prove her existence with new unsolvable murders.
    • This is also poor Hanyuu's dilemma in Higurashi no Naku Koro ni, as lack of faith by the residents is the cause of her weakened powers.
  • In Welcome to the NHK, a large number of the episodes are spent with the protagonist Tatsuhiro Sato having hallucinations of characters, scenarios, and people are members of an organization out to ruin his life. Near the end of the series, he asks one of the other cast members to see one of these creatures, where it is revealed to her. He then imagines his cell phone is a bomb and jumps off a cliff to blow up with it in a suicide attempt.

    Comic Books 
  • In Crimson, it's apparently the vampire's religious background that counts, as one man learns when the vampire he's trying to ward off takes his cross away and beats him with it, remarking "My name is Steinman, schmuck! Why would this work on me?"
  • The DC Comics character Dr. Thirteen was a skeptic who disproved hauntings. Since he was established as existing in The DCU, and eventually encountered The Phantom Stranger, the fact he was always right in his own stories seemed strange and turned him into a Flat Earth Atheist, until Neil Gaiman's The Books of Magic explained that his complete dismissal of magic meant he lived in a personal world where there was none.
  • Excalibur member Meggan was an empathic adaptive shapeshifter — she looked like what people expected her to look like, and consequently spent a good part of her childhood turning into a monster. Eventually, she managed to develop a strong enough sense of identity that other people's expectations no longer affected her shapeshifting.
    • In one of those cosmic ironies, the current powerset of Captain Britain, Meggan's husband, depends on his own confidence, much like Gladiator below - the stronger his confidence, the stronger he becomes.
  • The living myths in Fables are made stronger by those who believe in them. This is used to explain why some lesser-known fables are killed, but Snow White can take a rifle shot to the head and survive, albeit with long-term consequences.
    • This is turned into a plot point later, when Jack Horner (of "Jack and the Beanstalk," "Jack The Giant Killer," and several other stories) decides to increase his personal power by releasing a series of Hollywood blockbusters about himself.
    • Also, not every Fable gets their power from this; Frau Totenkinder specifically gets her power from 'other' sources. (Don't ask.) Popularity equals power is a theory that's never been tested under controlled conditions.
      • Subverted by the death of Little Boy Blue in # 82. The subversion was the huge power of the character in question, as the character itself isn't neither well known nor anywhere near as popular as Snow White and her peers.
  • In the August 1966 issue of The Flash, Barry Allen starts to fade away from existence once a villain unleashes a ray that causes everyone to not believe he exists. Everyone except a little orphan girl he had helped before forgets that he really exists until he and the orphan girl start a massive letter writing campaign to force people to remember The Flash.
    • This issue is somewhat prescient considering that the DCU contains an actual comic book limbo where characters (often those who haven't appeared in books for quite some time in the real world) go to when people start to forget their stories.
  • This is central to one of Warren Ellis' stories for Hellblazer. An occult writer "acquires" a magical item called The Crib, and sets about killing people with it. The thing is, there's no such artifact, and it only works because both he and his victims believed in it. John Constantine, being more knowledgeable about the truth of the occult world, knows there's no such item, so it has no effect on him, and he's able to reveal what the person actually had — an old cereal box with a dead mouse in it. It's discussed in earlier stories that magic in general works on this principle, but this is the first one where it really takes center stage and we see just how far it goes.
  • Another example from the Marvel Universe is the Shi'ar Imperial Guard commander Gladiator: His strength is based on his own belief in his power. Shake his confidence and he can be beaten easily, rev it up and he crushes stars with his fists.
    • His son Kid Gladiator has the same basic powers and an even bigger ego, being a teenager and all. Nothing, not even temporarily being turned into a Brood, has managed to shake him up.
    • According to Marvel Adventures (and possibly main 616 canon), Dr. Strange's magic works the same way. He deliberately cultivates a Large Ham persona to boost his own confidence.
  • Yet another example from the Marvel Universe are the Cardinals, who serve as the elite shock troops/assassins for the Universal Church of Truth. The Church collects the Prayer Power of it's trillion-plus faithful worshipers, then converts that prayer power into energy and stores it in belief batteries. The Cardinals can tap into that immense power reserve, giving them the power to do anything if they believe they can. Hence the Cardinals can shoot energy beams, create force fields, and etc. because some convert on the other side of the galaxy believes they can do that.
    • It doesn't even have somebody else, it could be the Cardinal himself who believes.
  • Subverted by Walt Simonson in Orion # 24:
    You've read too much fiction, Arnicus. Gods are not dependent on their worshipers; worshipers are dependent on their gods.
    And the New Gods? We're as old as time, constantly remade, constantly reborn with each turning of the wheel.
    No worshipers? Fool!!! Look about you! Each time a mortal turns on a computer, puts a piece of bread in the toaster, opens a door, strikes a match, or wonders at the stars...
    ...he worships at the altar of the New Gods.
  • Gods and other supernatural beings in Neil Gaiman's The Sandman live off of this trope which shows up in his other writings as well.
    • In one issue there is a story that the world was once run by cats the size of men and humans were the size of cats and were just playthings and servants. Dream told a human that if enough of them dreamt that things were different they would be. After most of humanity dreams that they were in charge the universe is rewritten so that cats had never been the dominant life and nobody remembered these events (except for Dream who naturally tells a cat this story and that they can change it back with enough belief).
    • When they turn up in a Grant Morrison issue of Justice League of America, the heroes are sent into a boy's nightmare world, where a telepathic conqueror has created a world where it has already won and there are no heroes to stop it. As the boy's belief wanes, so do their powers.
  • Used in Marvel Comics in Thor # 301, where it was revealed that, while the gods themselves could exist long after they had no more worshipers, those who STILL have some had greater amounts of power. Also, a god is stronger in his home plane than gods from another.
  • In Thor Meets Captain America by David Brin, this trope is used by the hero. His actual words are "I don't believe in you".
  • When the X-Men faced off with Dracula, Kitty Pryde tries using a crucifix against Dracula and achieves nothing. Dracula then grabs her throat, and burns his hand on her Star of David necklace. No points for guessing Kitty's religion, folks!
    • Wolverine is unable to repel Dracula with a cross, but when devout Nightcrawler takes up the symbol, Drac is driven back.

    Fanfics 

    Films — Animated 
  • Care Bears Movie II: A New Generation, in which the audience is encouraged to say "I care!" to save a dying little girl, which not only succeeds, but acts as Love Redeems for the Big Bad.
  • Inverted in The Flight of Dragons where the protagonist Peter defeats the evil wizard Omadon by 'denying' that he exists, and since magic relies on human belief to exist Omadon crumbles away to nothing. A list of hard, proven sciences to counter Omadon's list of magic creatures hurts too, fighting dark dreams with the proven and repeatable.
  • In Yogi Bear and the Magical Flight of the Spruce Goose Yogi gets his friends out of the cargo hold of the eponymous airplane by having them believe a set of doors into existence.
    Booboo: This is the part where he goes Tinkerbell on us.

    Films — Live-Action 
  • In A Country Christmas Santa's powers, and then his very existence, depends on people believing on him.
  • In Candyman, the eponymous character was actually created by the people's belief. Interestingly enough, after Candyman dies in the climax of the film, the people's belief shifts to Helen: as a result, she becomes a murderous spirit like Candyman. The sequels, though, are a different story.
  • Parodied again in Dracula 2000. One of Team Good Guy brandishes a crucifix at one of the vamps, who remarks "Sorry, sport. I'm an Atheist." The good guy wittily remarks "God loves you anyway." before stabbing the vamp in the eye with the knife hidden inside the crucifix.
  • In Elf, Santa's sleigh won't fly without the proper amount of Christmas spirit from people believing in him. Or engines, which he's used since the 70s to keep his sleigh aloft as Christmas spirit has gone down.
  • In Erik the Viking, Harald the Missionary who accompanies the Vikings on their quest staunchly refuses to believe in Ragnarok and any of the Viking myths. Eventually, the Vikings make their way to Valhalla, where they triumphantly demand that the missionary accept that they were right all along - only to discover that because he doesn't believe in it, he can't actually see it, and causing a certain amount of frustration. This actually saves them in the end, as because Harald doesn't believe in the Aesir they have no power over him. He can walk through the walls of Valhalla, make it back to the ship, and use the MacGuffin to bring them all back home while the other Vikings are trapped.
  • In The Fearless Vampire Killers (or Pardon Me But Your Teeth are in My Neck), a cross fails to work on a Jewish vampire. In the mock documentary at the end of the film, an expert on vampires notes that the effectiveness of the religious symbol depends not on the human wielding it, but the vampire itself. Crosses work on Christians, Stars of Davids work on Jews - but the expert warns that using a Star of David on an Arab vampire will only make it angry.
  • A woman in Feast II: Sloppy Seconds tries to believe her way out of terrible situation after terrible situation.
  • In Freddy vs. Jason, Freddy Krueger's weakness is that he only has power so long as people believe in him, so he has to bring Jason back to remind them. This hearkens back to the original ending for A Nightmare on Elm Street (1984), where he's defeated by Nancy refusing to believe in and fear him any longer, robbing him of his powers - in the theatrical release, this only appears to work.
  • Fright Night.
    Peter Vincent: [brandishing a crucifix] Back, spawn of Satan!
    Jerry Dandrige: [chuckles] Oh, really? [grabs the cross, crushes it, and throws it aside] You have to have faith for this to work on me.
    • Later they face off again, and Jerry (now fully vamped out) laughs and taunts Peter with the same words... only to stop and recoil as Peter, smiling, demonstrates that he does now.
    • The Fright Night (2011) remake did this too, except with Charley holding the cross instead of Peter. The vampire simply feigns weakness before grabbing the cross with one hand and pinning Charley to a car with the other. The cross catches fire as he touches it, but he blows it out without even flinching.
  • The Haunting Hour presents a rather twisted version of this by having The Evil Thing only exist as long as at least one person thinks about it, but making it almost impossible not to do so (if you'd read about a monster that vicious in a book, you'd think about it too.)
  • In Hook, the grown Peter Panning says he doesn't believe in fairies. Tink 'faints', awakes, and tells him that fairies die when not believed in. The way she yells at him to clap harder seems to indicate that she's feeling just fine. (But then, she has a pack of Lost Boys believing in her.)
    • Despite being the trope namer, this is actually something of a subversion. Tinker Bell says that a fairy dies every time someone says they don't believe in fairies; the statement seems to be all that is necessary regardless of actual belief. Similarly, Tinker Bell never mentions needing to believe to save her, just clapping appears to be enough.
  • In John Carpenter's In the Mouth of Madness, which pays homage to both Stephen King and H.P. Lovecraft, we see just how terrible the consequences of this trope can really be.
  • In The Matrix the red pill humans are able to perform seemingly superhuman feats by believing that they can do it, since they're in a virtual reality. As Spoon Boy elaborates: "There is no spoon." There are limits to even their abilities, though, which is what makes Neo, whose belief can transcend those limits as well, so important (at least, that's how it seems at first).
  • Used at the end of the first Power Rangers movie to repair their decimated hidden base and restore Zordon to full health.
  • Parodied in the first film of The Mummy Trilogy - Imhotep's soon-to-be servant tries to fend him off with a cross and a murmured Lord's Prayer, which is utterly useless. He then runs through a keychain of similar holy symbols and their matching incantations, none of which have any effect until he yanks out a Star of David and starts babbling in Hebrew - which the undead priest recognizes as "the language of the slaves," which makes Beni useful to him as a translator. Discussion of the actual use of Hebrew slaves in ancient Egypt and the language they spoke at time is reserved for other places...
  • In the Jim Carrey vehicle Once Bitten, The Countess shrugs off the religious symbol ("Put down the cross, Robin. It only works in movies. Besides, I'm an atheist.") Then Mark shows up with a torch, and the Countess recoils, declaring, "Fire, on the other hand..."
  • In the horror movie The Skeleton Key, it is claimed the African witchcraft of Hoodoo can only be used on those who believe it. The plot plays with the notion that this means it's only psychology and suggestion (if you believe you were witchcrafted, you'll just act as if you did). However, the scientific approach is eventually abandoned. Once the antagonists finally manage to get the protagonist convinced that it's real, they can perform supernatural witchcraft on her. They then proclaim it's getting tougher for them to use witchcraft on new victims, as it's getting harder and harder to convince modern people that it's real.
  • In Star Wars, a Jedi's adeptness at manipulating the Force is closely linked to self confidence and belief in their abilities; sheer willpower and determination is not enough, and the Jedi must "unlearn" everything they think they know about how the universe works. In The Empire Strikes Back, Yoda blames Luke's failure to levitate his X-wing out of the swamp on his not believing that such a feat is possible.
  • In Wes Craven's New Nightmare, a real supernatural entity tries to use the belief in and popularity of Freddy Krueger to manifest in the real world, adopting Freddy's identity. Wes Craven (playing himself) explains that stories, and people's belief in them, have always been the bridge between the real world and the supernatural.
  • Parodied in Woody Allen's What's Up, Tiger Lily?.
    Phil Moskowitz: No bullets? Ah, but if all of you in the audience who believe in fairies will clap your hands, then my gun will be magically filled with bullets.
  • Andrei Tarkovsky is fond of this one: Stalker (not Stalker), Solaris (not Solaris).

    Literature 
  • Subverted in F. Paul Wilson's The Keep, in which a "vampire" pretends to be affected by a Christian cross, but not a Star of David in order to cause a Jewish professor to question his faith. Later it's revealed that the vampire is actually affected by the symbol of a magical sword, and the Christian cross just happens to be very similar to this sword symbol.
  • In Neil Gaiman's American Gods, gods and supernatural creatures are made real and powerful by worship and belief, and fade away and die when people stop believing in them.
  • Laurel K. Hamilton's Anita Blake novels also has this; if the person does not believe in the religious symbol, it will not work. To do with the beliefs of the person against the vampire.
  • The page quote isn't the only example from The Bible: e.g., in the Gospels, Simon Peter walks on water until he starts to doubt.
    • Stephen Colbert (apparently sincerely) believes this to be an instance of comic relief in the Bible, saying Jesus wouldn't be truly human if he could witness that without laughing.
  • Subverted in Blindsight; the vampires and crosses thing is not because of anything religious or mystical but because their brains go into seizure when exposed to straight vertical and horizontal objects in their visual field forming a 90 degree angle (not as dumb as it sounds: there are people who have similar types of problems due to head trauma). That sort of thing is not that common in nature, and it wasn't much of a problem until their food source went and invented architecture and drove them into extinction.
  • An early example: In A.E. van Vogt's Book of Pthah gods and goddesses are ordinary humans who have immortality and supernatural powers by the virtue of being worshiped by great numbers of the opposite sex.
  • Fred Saberhagen's Book of Swords series had this as a plot development. The gods, including such familiar names as the war god Mars and Vulcan the smith, are bored. To entertain themselves, they play a game with humanity: 12 highly powerful magic swords are created, and spread throughout the lands purely to incite wars amongst the various nations. The plan backfires when, thanks to the highly visible power of the various swords, mankind's belief in the gods wane and is replaced by belief in the swords. Consequently, the gods rapidly weaken and die.
    • In the interquel novel Ardneh's Sword, which was written years later and is widely regarded as Fanon Discontinuity, it is explained that the Gods Are really humans who put on some Sufficiently Advanced Technology suits that turned them INTO gods. It seems likely that their apparent dependance on belief was psychosomatic at first, but became this trope over time.
  • In John C. Wright's Chronicles of Chaos, this is one technique of Functional Magic, where the character can make true what he wants to be true. Its weakness is that he really has to want it; if you do not actually feel the malice necessary, you can not curse someone, for instance.
  • C. S. Friedman's Coldfire Trilogy features a substance called fae which responds to brain activity and can do anything. This is used as a justification for Functional Magic as well as Clap Your Hands If You Believe. A clever fae hack involved spreading a made-up religion in order to change the natural laws.
    • Fae is also nasty. It doesn't just make for "proactive" magic; things based entirely on natural laws DON'T work if their user has any fear they might malfunction. Hear a bump in the night, and the fae will play on your instinctive fear to fill in what might have made it... The vicious cycle goes straight down into scenarios that approach Cosmic Horror Story. Furthermore, even the slightest belief that a device such as a gun could backfire will make it backfire; the fae makes Murphy's Law even worse. This is why the setting has been stuck in Medieval Stasis for 1000 years at the series's start.
  • In Christopher Moore's Coyote Blue, this will happen to Coyote, and did happen to his brother Anubis, if people stop believing in him and telling his stories. Coyote fears this so much that he allows Sam's girlfriend Calliope to die so that people will still talk about him.
  • The Christopher Durang play Dentity Crisis references Peter Pan and the ensuing subversion from the fed-up actress playing Peter Pan who decides to sabotage it in the worst way possible:
    That wasn't enough. You didn't clap hard enough. Tinkerbell's dead.
  • The gods in the Discworld series work like this.
    • The climax of Monstrous Regiment involved a beloved leader who had died and was being tormented by the prayers of those who put her on a godlike pedestal.
    • In Hogfather, when the Big Bad was magically preventing people from believing in the local equivalent of Santa Claus, the extra, unused belief-energy made any imaginary creature that was even slightly plausible (like a creature that eats odd socks, and a bird that eats pencil stubs) come into existence.
    • Small Gods describes in detail how gods come into existence and become powerful -and what happens when their followers lose genuine faith.
    • "Belief" is stated as a very powerful force on the Discworld - if enough people believe something to be true, it will become true, however there are limits. The rules have never been fully stated, but it appears there needs to be a "space" that makes it somewhat reasonable such a thing could be true (hence the non-existence of the Give-The-Dean-A-Big-Bag-Of-Money goblin). In Pyramids the mess of multiple combined mythologies that made up the religion of Djelibeybi, much of which was self-contradictory, and a lot of which could be contradicted by simple observation, only became true when the kingdom was pushed into an alternate reality with an even lower reality threshold than the Disc.
    • Mistress Weatherwax does this on many occasions, usually boxing the ears of said fairies. She doesn't believe in DEATH, because it's like believing in the postman.
      • Witches and Wizards generally take the same attitude about Gods. They know the Gods are there, so there's no call to go believing in them.
    • An evil witch set herself up as secret ruler of the Magic Kingdom of Genua in Witches Abroad by manipulating the lives of people, and reality itself, by bending fairy tales around herself.
    • In Carpe Jugulum, one family of vampires have developed the ability to resist religious symbols (as well as most things that vampires are traditionally vulnerable to) through extensive psychological conditioning. This later backfires when their conditioning wears off under the influence of a witch, but the study that went into it leads to them being able to recognize - and as a result be affected by - "hundreds of the damned holy things! They're everywhere! Every religion has a different one!"
      • Later expanded into the Black Ribbon Society, which provided a better integration with a multicultural modern city
    • The New Discworld Companion has as Watch standard gear, "One holy symbol of recruit's choice, vampires, for the discouragement of. One Critique of Pure Reason, vampires, for the discouragement of (Freethinker's option)." This was before a vampire joined the Watch...
    • What happens to people on the Discworld after they die is determined by what they believe. Not necessarily what they want, but what they believe. In Small Gods, there is a character who believes in Om, but after he dies he thinks about what he believes and it's implied that he has a slightly different outcome than other Om believers. He has a different outlook on life than other Om believers, and therefore, something different would happen to him.
      "What happens to people after they die is what they believe will happen. The people who go to hell are the ones who believe, deep down in their hearts, that they deserve it. However, if you've never heard of hell before, it's impossible to believe in it. That is why it is important to kill missionaries on sight."
      • A group of people (the entire crew of a ship) who are assumed to be Omnians (as they live in Omnia) but know full well that it's all rubbish get a completely different afterlife from all the other Omnians. They decide to go looking for the afterlifes of those foreign gods they've heard of, where you get food, wine, and women for all eternity.
  • By the time Dracula was written, vampire lore included an aversion to a cross. This, in different series, can be either the product of the vampire's belief in the cross, or the product of the wielder's belief in the cross. Often, it also works with another strong symbol of belief - for example, a rabbi using a Star of David to hold a vampire at bay. See: Our Vampires Are Different.
  • The title character of The Dresden Files has little or no faith in the Almighty, so crosses don't ward off vampires for him. However, he has loads of faith in magic, and so his silver pentacle charm (a symbol of magic) works very well in putting aforementioned fang-faces in their place.
    • His sometime ally Michael is a devout believer however, so the Cross works just fine, as does his named sword and since Michael is a Knight of the Cross his bare hands work equally well. (He's not called the Fist of God as a pet name, folks!) When a Red Court vampire (who are not as vulnerable to faith as the Black Court) mocks the idea that Michael's faith in the cross will defend him, she lightly places a finger on one of the crosses stitched into his cloak, and she instantly bursts into white flames.
    • Faith in God himself is not necessary for a Knight of the Cross. Of the three knights presented so far, only Michael is particularly religious. Shiro was confused when he was being converted (though he tries his best to be a good Baptist regardless), Sanya is Agnostic and Butters, the most recent Knight of the Cross as of Skin Game, is Jewish. It's their belief in defending the common man against evil that gives the knights their powers. It just happens that in Michael's case, this belief manifest itself as Christian Faith.
    • Dresden, being the First-Person Smartass he is, goes on to mock this trope during the climax of the fourth book, Summer Knight, by charging into a Fae battle screaming "I don't believe in faeries!!" Doesn't help him kill any Fae any better, but certainly is good for the adrenaline.
    • However, this apparently does work when fairies gain confidence in their own abilities: the more Toot-toot accomplishes on Harry's behalf, the bigger he gets. In the first book he is only six inches tall; by the 12th book, he is more than 15 inches tall and described as "ridiculously tall." Or alternatively, it was the result of him becoming the leader of the "Za Lords" and gaining followers.
    • Magic in the Dresdenverse requires belief in whatever the caster is doing. A caster cannot produce a spell if they do not, deep down, believe in the reasons behind why they are casting the spell. This is actually a small but critical plot point in Turn Coat, where LaFortier's murder involved no magic being slung. It is eventually revealed that the killer was being mind-controlled, but deep down she understood that she shouldn't be doing it, so she couldn't use magic against LaFortier. Meanwhile LaFortier knew she was being mind controlled and wasn't responsible for what she was doing, so he couldn't target her either.
    • In the Novella Backup, Thomas and Lara Raith are members of a secret society which fights against creatures who take their power from other people believing in them. The only way to assure victory is to limit as much as possible the number of people who know about the enemy (optimally: zero), making for some of the most severe "need-to-know" requirements ever faced by any army. (Being vampires, the Raiths aren't in it for the good of humanity, but rather to protect their food supply.)
    • This trope is conversed in Skin Game. Harry and a member of his crew come across the real shroud of Turin. When someone asks why the fake in the real world works like it does, Harry replies that if enough people believe the fake is real, it gains some power through said belief.
  • In the Eisenhorn novel Malleus, the title character is able to severely weaken a Chaos-corrupted stone by recording himself reciting one of the (many) Imperial declarations of faith and continually transmitting the recording into the stone.
    • In the third book Hereticus, after Eisenhorn is forced to release the bound daemon Cherubael in order to defeat a Chaos Battle Titan, he then tries to weaken him by reciting The Benediction of Terra. However by that point Eisenhorn has been both physically and mentally drained and couldn't force his will enough for the prayer to actually have effect. On the other hand, a crazed Imperial priest who witnesses all of this manages to scare off Cherubael by mistaking him for a manifestation of the Emperor's power and running at him at full speed, chanting praises for the Emperor and holding a holy Imperial Aquilla, hurting the daemon with the sheer force of his belief in the Emperor.
  • In David Eddings's Elenium and Tamuli series, gods' powers are derived from their worshippers' belief. The Elene God is thus very powerful; the Younger Styric Gods have less individual power but together are considered comparable to the Elene God. Meanwhile, the Elder Styric Gods were severely weakened as a result of being forgotten to the point that all but one (Azash, who found new believers in the Zemochs) were bound and sealed away. The Tamul gods, who are worshipped only superficially, end up manifesting as simple, childlike deities. Then there are the Forgotten Ones—gods without worshippers who are reduced to shapeless wisps with barely even a voice. Someone actually tries to depower a goddess by ordering the slaughter of her worshippers (Zalasta, after he's been outed as a Mole), so the other Styric Gods each chip in some of their belief until the crisis is averted.
  • The Faction Paradox beings known as the Celestis are actually ascended beings that are tethered in reality by nothing more than the power of others' belief in them; therefore, they appear as gods or demons wherever they choose to manifest.
  • Goes horribly, horribly wrong in regard to the "Stuff" in The Gone-Away World by Nick Harkaway. It becomes not what you believe, but what you're thinking of—and if you're thinking of ten things at once, it'll become a splice of all 10 things. This gets even worse if you get covered in Stuff.
  • Good Omens not only explicitly uses this concept as the core of its magic system, but actually introduces a system which measures the intensity of belief in one of its footnotes.
  • A variant occurs in the Harold Shea stories by L. Sprague de Camp and Fletcher Pratt, in which it's possible to travel to another world by believing in the logical principles that govern that world. The place you're going was real to begin with (even though they're all based on mythology or literature), but believing the right things makes it accessible to your senses.
  • In The Haunting of Alaizabel Cray, there's an interesting case: when humanity believed that disaster was God's anger, everything was fine. Then came the beginning of the Age of Reason, and we outgrew such silly superstitions... or so we thought. Because we had no-one left to blame, but lacked the emotional maturity to take responsibility for our actions, our subconscious minds started to blame every fairy-tale-style monster ever, at which point they appeared and began to terrorise the world's cities.
  • In I Am Legend, vampires fear the holy symbol of what they believed in before they became vampires. The Protagonist's archenemy is terrified by the Star of David.
  • In the Iron Druid Chronicles, all gods and supernatural entities are created by human belief and thought, including Jesus, the Celtic gods, the Norse gods, Elvis Presley and the comic book version of Thor.
  • In Stephen King's IT, the eponymous shapeshifting monster takes the form of a werewolf, making it vulnerable to silver simply because the child heroes of the book firmly believe that werewolves have to be vulnerable to silver. Also, believing that his inhaler was full of poison allowed a protagonist to harm It with the contents.
    • Established in King's writing much earlier in his short story The Boogeyman, which is in many ways a precursor to IT.
    • A cross does not work on a vampire in 'Salem's Lot because its owner has lost his faith. When that character faces vampires again in a later King book, he has recovered his faith and is able to (briefly) drive them off, even after he puts the cross aside - it's only a symbol, after all.
    • It should be noted that disbelief in the supernatural generally doesn't protect against it in King's works. For example, in Literature/It, the eponymous reality-warping shape-shifting monster devours victims regardless of whether or not they believe in the supernatural, but strong enough belief in supernatural things (like, the fact that silver bullets can be used against It when It takes the form of a werewolf) allows the protagonists to fight back. Also, in the short story 1408, the hotel manager urges Mike Enslin, a writer of books that chronicle his sojourns in supposedly haunted locales, not to stay in room 1408 specifically because he doesn't believe in the supernatural, and things will go worse for him because of it.
  • Deconstructed in Kingdom Keepers. Enough people believing in them is what causes several Disney characters to come to life...including the villains, who are putting the world in danger.
  • This appears to be the driving force behind mythological beings in the Logical Magician series of books by Robert Weinberg. In the second book, an Amazon (naturally, exceedingly beautiful) serving as a weapons instructor is explicitly confronted by the main character with theories regarding the rather hideous appearance of historical amazon women; he's rebuffed with "Maybe the real ones were. We aren't." Applies to myths both old and new; one of the most feared mythological beings around is 'The Man'. Also given an interesting inversion; Nergal, the Babylonian god of disease, has been hauled into the modern world. With no believers to get rid of, he seems invincible, until the main character gets an article about him published in several supermarket tabloids. Since people automatically disbelieve what they read in those, this does Nergal in.
  • All Myths Are True in Douglas Adams's The Long Dark Tea-Time of the Soul because of this effect. The old gods, like Odin, are languishing but a new God of Guilt is created, possibly from society as a whole, but also possibly from the eccentricities of Dirk Gently alone.
    • The Hitchhiker's Guide to the Galaxy has a theory on God's non-existence as a guide entry. Shortly, it goes like this: Since nothing as useful as the Babelfish can be born through coincidence, this proves God's existence, but with knowledge, there isn't faith, and without faith, God is nothing. This seems to follow the same logic.
  • Lord Dunsany uses this. To say where would spoil an excellent short story.
  • Some gods in Steven Erikson's Malazan Book of the Fallen are formed from the belief of their adherents and die if they are forgotten. Others are independently existing beings whose divine powers are powered by worship.
  • In Monster Hunter International holy symbols have power over undead monsters by virtue of the belief placed in them. However, the biggest act of faith-based ass kicking comes from Milo, who shares the author's Mormon beliefs.
  • Skeeve from Myth Adventures is struggling to teach his apprentice Massha to light a candle via magic when he realizes she doesn't actually believe she's capable of such a thing. When he encourages her to visualize a magical trinket (a form of magic she does believe in) inducing the same effect, she succeeds in setting the candle alight.
  • A rare inversion with a short story ("Obstinate Uncle Otis") about an obstinate Vermonter (and as such, the most obstinate man in the world) whose power of disbelief was legendary, to the point where he could almost convince others that their eyes were tricking them. And then he got struck by lightning, and got a dose of Your Mind Makes It Reality. The statue in the town square to the man he hated? Gone after he commented about how "No one would build a statue to a nincompoop like that!" The barn that was obstructing a nice view? Also gone when he commented how "No barn there, boy! Nothing but th' view - finest view in Vermont." His nephew realizes the danger this poses (e.g. his hatred of Franklin D. Roosevelt, his recent disbelief in stars, etc.). It comes back to bite the elderly man on the ass, though, as he got a bit of Easy Amnesia and believed himself to be a traveling salesman with a different name. "Humph - ain't no such person as Otis Morks."
    • And before Fridge Horror enters into it, the narrator was also named Otis Morks, yet didn't disappear - unlike his hapless, obstinate Uncle.
    Narrator: The ancient prophets may have had faith strong enough to move mountains. But Uncle Otis was possessed of something far more remarkable, it seemed - a lack of faith which could unmove them.
  • Tom Holt spoofed this scene in Open Sesame; a fairy provides medical care by shouting "I do believe in humans!" And again in Paint Your Dragon:
    There's an urban folk-myth that every time a human says he doesn't believe in dragons, a dragon dies. This is unlikely, because if it were true, we'd spend half our lives shovelling thirty-foot corpses out of the highways with dumper trucks and the smell would be intolerable.
    There's an old saying among dragons that every time a human says he doesn't believe in dragons, a human dies, and serve the cheeky bugger right.
  • Trope namer comes from a famous scene from Peter Pan. In this verse, a fairy is mortally wounded any time a child says "I don't believe in fairies;" in the scene in question, Peter uses the effect in reverse to save the fairy Tinker Bell's life by calling on children everywhere to indicate that they do believe in fairies. (In the original stage version - which predates the novel and the various film and television adaptations - this was an audience participation bit...and, in case you're wondering, if the audience is a bunch of heartless bastards who won't clap, the orchestra is instructed to begin the applause.)
  • Subverted in Christopher Golden's Shadow Saga in that the effects of the cross on vampires is purely psychosomatic because the Roman Catholic Church captured a bunch of vampires during the dark ages and brainwashed them into believing in a number of myths.
  • The basis of all magic in the Shannara series.
  • In Ssalia and the Dragons of Avienot, the only way to reach the upper shelves in the jade tower's (physics-defying) library is to walk on thin air, which can only be done if one believes such a feat is possible.
  • In Sergey Lukyanenko's Star Shadow, it is eventually revealed that the human jump drives work because the pilots believe them to work. This is also why humans are the only ones who retain their sanity when using it - because this should not be possible. The protagonist even recalls that the jumper was invented by a bunch of underfunded Russian researchers, and the scientific basis for the device was added as an afterthought and seems tacked-on. Also, every jumper works exactly the same, no matter the design or power. Kinda makes sense since astronauts have to believe they'll succeed in order not to die.
  • In Christopher Stasheff's Warlock of Gramarye series, the planet Gramarye has a native fungus known as "witch-moss" which can assume animated forms based on the thoughts of those with latent Psychic Powers. Since five centuries of inbreeding has spread those genes to half the population, a lot of fairy tale creatures have since become real; if they become too real, and there's some of both genders, they can even mate and have fixed-form offspring, essentially creating a whole new species. The Wee Folk were born this way and can somehow interbreed with humans, producing fully fertile offspring.
  • Interestingly used in Jeri Smith-Ready's Wicked Game; Ciara Griffin's blood heals her vampire boyfriend of holy water scars, which are supposed to be permanent, and Ciara postulates that it's because of her complete lack of religious faith.
  • In explaining the history of money Dave Barry specifically uses the Tinker Bell scene as an analogy for how money works these days (i.e. no longer tied to gold or another precious metal). We all believe currency has value, so it does.
  • There is a short story in which a demon has the job of dragging humans to Hell, and can only be defeated by holy words. The specific religion doesn't matter so much as the strength of the person's belief. His first intended victim is a Christian who prays and forces him to let go. The second is an atheist, and her holy words are the laws of physics. Hilarity Ensues.

    Live Action TV 
  • In Being Human, vampires recoil from George's Star of David pendant. But George's affection for his best friend Mitchell (who is a vampire) makes Mitchell immune to its deleterious effects. Mitchell even keeps the necklace safe when George transforms.
  • In one episode of Bottom, Richie and Eddie are saved from a Ferris Wheel by the hand of God. When they remember that they don't believe in God, the hand vanishes and they fall to their doom.
  • In the Buffy the Vampire Slayer episode "Out of Sight, Out of Mind," a girl is actually rendered invisible because no one ever noticed her (an effect heightened by the school she attends being built over a hellmouth).
  • Possibly occurs in The Stinger of an episode of Caroline In The City. During the episode's plot, Caroline and others make references to Caroline's made up boyfriend. In the stinger a man claiming to be her boyfriend appears; the episode leaves it the audience to decide if it was Richard playing a joke on her, or if she accidentally talked him into existence.
  • In Community episode "Epidemiology" it was brought up and then thoroughly subverted.
  • Toyed with in Dead Like Me. The recently deceased will cross-over with the gateways to the next world taking a form that appeals to them. In the pilot, a little girl sees a huge spectral carnival; in a later episode, the soul of an old yet feisty man of indeterminate UK clearly Irish origin leaps from the precipice of a chalk cliff the Cliffs of Dover.
  • Doctor Who:
    • The finale of the Doctor Who new series third season came under some fire for relying on this, albeit with a Hand Wave involving a Phlebotinum-assisted telepathic field that focused the belief, causing what fans call TinkerBell Jesus or Fairy Doctor.
    • In the fifth season finale the Doctor was erased from existence, but Amy remembered him and somehow magically brought him back. It... sort of makes sense in context.
    • The Doctor once cobbled together a temporary working TARDIS out of spare parts, lampshaded by a companion that he accomplished this feat partly because he refused to even entertain the possibility that he couldn't.
    • Earlier, in "The Curse of Fenric", a cross works only if the bearer has faith in it, and other objects of faith work equally well: a WWII Russian soldier fends off vampires with a soviet badge, and both the Doctor and Ace are able to hold them at bay with no physical object, through their faith in each other. The priest who doubts his meets sticky end.
  • One episode of Fraggle Rock introduced a one-off character named Skinfred, a small monster whose transformations were based upon this Trope. His physical appearance depended on what other people thought about him (it's impressive how upbeat his personality was given how very definitely Blessed with Suck he was). Red and Wembly like him, think he's very cute and friendly... and that he sports goofy pigtails. Ma Gorge does not like him, thinks he's creepy and scary for living in her flooded basement, and wonders if he's actually a giant, fanged, two-headed monster. Guess what happens next. (Skinfred: "Aw, I hate having to be a monster!")
    • A similar creature appeared in the Fraggle Rock comic book. The cast had to deal with a considerably less friendly monster who was also exactly as tough as an opponent believed it to be, resulting into hilarious scenes of our heroes making things worse and worse.
      "I don't care if you're fifty feet tall..."
      Poof!
      (Monster is now fifty feet tall.)
  • In the TV miniseries Merlin, Merlin finally defeats the evil Queen Mab by encouraging everyone to forget about her. This is the culmination of the fading belief in her and led to her vanishing. The novelizations went as far as noting that Merlin omitted her from his stories about the events and misattributed them to Mordred or Morgan le Fay.
  • On BBC Merlin, when Arthur is trying to draw Excalibur, Merlin says that he needs to truly believe he can in order to do it. Subverted since Merlin was just trying to boost Arthur's confidence: once Arthur is sold on Merlin's story, Merlin covertly uses magic to make the task extremely easy for Arthur, thus reinforcing the idea he was trying to instill.
  • Discussed in The Office (US): Nellie tells the office that she can't make their wishes come true (i.e. give them all raises) unless they believe in her (i.e. accept her as the manager just because she walked in and asserted that she was now the manager). This ends with her comparing herself to Tinkerbell and making everyone clap for her.
  • Power Rangers Mystic Force: The key component to being able to use magic is, it seems, believing in magic. In the premiere, Nick is unable to use magic because he doesn't believe - even after he's seen others using it (and despite considerable effort 'trying' to believe). He gains the ability to cast spells only after announcing that he really does, after all, believe in magic. In the finale, the entire city's belief is used as a Combined Energy Attack.
  • The Stargate SG-1 Big Bad of seasons 9 and 10, the Ori, are ascended beings who thrive on worship. And they also ''lose'' their powers when not worshiped, hence how The Ark Of Truth beats Adria, forcing the Priors to realize that the Ori, and by extension, Adria herself, were not gods. A fitting end.
    • The Big Bads of the previous eight seasons, the Goa'uld, are a more figurative example. Once a significant number of people stop believing that a particular Goa'uld is a god, it's usually a sign that said Goa'uld is about to lose out.
  • An episode of Star Trek: The Original Series has the crew find a pulled-from-myth planet of Ancient Greece, presided over by Apollo, who laments that the rest of the gods perished, more or less, from a lack of followers.
    • The Star Trek Expanded Universe has "the Beings" in Peter David's Star Trek: New Frontier series, who gained power from worship and fear, and inverted when it turned out the most powerful among them was so because he gained power from peoples' belief in themselves. In the novel Gods Above, the only way for the crew to defeat them is to be truly fearless.
  • An early Star Trek: The Next Generation episode had a Sufficiently Advanced Alien known as The Traveler strengthened by the entire Enterprise crew concentrating on making him better. (Granted, they were in an area of the universe where thoughts become reality, but it still fits the trope).
  • The early Star Trek: Deep Space Nine episode "If Wishes Were Horses" had the contents of people's imaginations becoming real, starting with Rumpelstiltskin, courtesy of Miles O'Brien reading the book to his four-year-old. The low point was Julian Bashir's fantasies of Jadzia Dax resulting in a copy of the latter that kept throwing herself at him. Meanwhile Odo manages to wish Quark into a holding cell. After they imagine a spatial anomaly nearly destroying the station they figure it out and Sisko orders everyone to stop speculating and focus on the hard data. Turns out there were Sufficiently Advanced Aliens experimenting on them to find out what imagination was.
  • An episode of Supernatural focused on a spirit that was created (and maintained) by people's belief in it. Unfortunately, getting people to stop believing was not an option.
    • Leading Sam to wonder how many of the things they hunt only exist because people believe in them.
    • One episode had a kid who made things he was afraid of real because he believed in them. He turned out to be The Antichrist, which made him a Reality Warper.
  • Lettie Mae, Tara's mother, in True Blood gets rid of a "demon" that makes her an alcoholic via exorcism. It turns out to be a scam, but that doesn't faze Lettie Mae.
    • This also works on Tara as well, for a while, at least. Then she finds out it was all a scam and becomes her old "friendly" self. Then a maenad shows up and tells Tara it was her belief that called her to Bon Temps.
  • One episode of Wire in the Blood dealt with this trope. The murderer of the story was thought by some people to be using magic. Tony Hill, however, knew that it was all in the victims' heads and when the murderer was finally caught, she thought Tony was a powerful wizard because he'd been able to see through her "invisibility".
  • Nickelodeon's Kids Choice Awards 2008 has a character called the Rocktopus (a rock and roll octopus who wears shades) and during the end where Jack Black and Orlando Bloom are doing the final slime stunt - there's no slime coming out at first because the machine requires someone with 8 arms to operate it, and the Rocktopus happens to be the one that fits that - the only problem is that he needs encouragement from the audience - so the audience give him encouragement by shouting... "Slime! Slime! Slime! Slime! Slime! Slime!"
  • Stephen Colbert fully believes in this trope, naming it Wikiality, wherein if enough people believe something to be fact, it is; and the best method for altering the public's belief in something? Change its Wikipedia page.
    • To demonstrate this, he single-handedly tripled the African Elephants' numbers via Wikipedia. Quite a feat.

    Music 
  • The song Kingdom of Heaven of the Dutch symphonic metal band Epica has a chorus that is this trope (see Real Life below too): Quantum physics lead us to. Answers to the great taboos. We create the world around us. God is every living soul.

    Newspaper Comics 

    Professional Wrestling 
  • During one storyline in the early-to-mid-nineties Kama stole The Undertaker's urn of power. The Undertaker said that he now had to rely on his Creatures of the Night (his special nickname for his fans) to provide him with the power he needed to win the match.
  • According to "American Made", Hulk Hogan's theme song in WCW pre-Face-Heel Turn (1994-1996), you are what makes Hulkamania possible: "He wears the heart of his country on his sleeve / He'll fight for your freedom if you really believe."

    Tabletop Games 
  • Beyond the Supernatural features a reversal of sorts with the nega-psychic class. Most character classes in this game have psychic and/or magical abilities. The nega-psychic has psychic powers, but is so convinced that supernatural phenomena are bunk that his power is used unconsciously to suppress all psychic and magical phenomena in his area. For example, a character who can normally lift things with telekinesis will find it difficult or impossible to do so around the nega-psychic, thus bolstering the nega-psychic's belief that there is no such thing as telekinesis.
  • In Deadlands, this device works in both short and long term. When visiting the Spirit World of the setting, exactly what one sees is colored by exactly what one expects. A Protestant might see Mount Zion, with Heaven at the top and Hell at its base. A Native American might instead see a World Tree, again with pleasant things at the top and bad things at the bottom. And most of the "Abominations" in the game world are drawn straight from people's worst fears; sometimes, a house is haunted not because someone died horrifically there, but because people believe it is haunted.
  • The Defictionalization of Dresden Codak's Dungeons and Discourse takes place In a World like this filled with philosophers. The upshot is that they can do things like use their belief in Cartesian duality to do two moves in one round.
  • The Dungeons & Dragons campaign setting Planescape revolves around the idea that belief shapes the planes. It can also move mountains, as the beliefs of the inhabitants of an area determines it's actual geographic location.
    • Exploited several times in the video game Planescape: Torment; for example, the player at one point unlocks a memory of a previous incarnation who had just debated a man into the conclusion that he did not exist, which caused him to vanish.
    • The concept was added to the Forgotten Realms setting in the "Avatar trilogy" of novels. As of Third Edition, this is actually considered the default handling of gods in the default setting (Greyhawk, though they don't call it that) and Forgotten Realms; in Dragonlance, suiting the role of its gods, although belief is important to them, it's not directly necessary for their existence.
    • In Eberron, the gods exist independent of mortals entirely, but their power in the material world seems to be dependent on their worshipers - as in, the stronger churches are better able to carry out what they divine as the will of their god... though different religions don't even agree on whether or not that is even necessary. It isn't even strictly made clear that the gods actually exist, or whether the manifestations and abilities of priests and so forth are just a (local) result of their faith. And some of the things that are worshiped as gods (such as the Dreaming Dark) don't really fit any conventional use of the term.
    • The book Faiths of Eberron makes this trope even more evident. Followers of the Lord of Blades (A warforged of considerable might, but who is mortal) have access to divine magic from their belief/faith in his divinity and his cause.
    • In the 3.5 core rules, clerics were able to gain power by revering a cause. Eberron actually had attempts to train clerics of nationalism (although it failed... except in Riedra).
    • The 2E supplement Shaman used this trope extensively, with the twist that any spirits generated by such power of belief weren't considered "real" by deities, or at least, not as "real" as the deities themselves.
    • Ravenloft, like Eberron, prefers to keep its gods' legitimacy subject to doubt. At least one of the major deities of the Land of Mists, Zhakata, is expressly stated to be the figment of a crazy darklord's twisted imagination. This doesn't prevent clerics of Zhakata from receiving divine spells when they pray. (However, it is also stated that their spells are granted by Ravenloft itself, rather than what they believe.)
    • Inverted with two spells of the Illusion school, phantasmal killer and the even more powerful weird. These spells create incredibly convincing illusions in the mind of a victim of his greatest fear that can literally cause him to die of fright. The only way to fight it is to realize it isn't real and have enough willpower to "disbelieve" it (whether a victim can succeed or not depends on a lot of factors, including his Wisdom score and how powerful the wizard casting it is).
  • In Exalted, gods, ghosts, demons, and most supernatural beings (including the Exalted) regain Essence and Willpower faster if enough people pray to them. In Yu-Shan (Heaven) these prayers coalesce into Quintessence and Ambrosia, substances that are the most delicious food and drink in the history of every and are easily transmuted into... anything else, making anyone who has even small amounts fabulously wealthy.
  • Genius The Transgression features something of an inversion with Bardos. When enough people believe in something, and then suddenly stop believing (like, say, if it's publicly disproven), the energy of all those minds changing their opinion releases Mania into the world. This has created, among other things, an underground world full of dinosaurs, an army of Martian invaders, and a race of Aryan "Übermenschen" of genuinely superhuman ability.
  • Similar to the Doctor Thirteen example mentioned above, one power available to players in GURPS IOU is the advantage Mundanity. Magic and super-science fails to work in a Mundane's presence, and at the higher levels monsters, aliens and assorted other non-normal entities actually change to have mundane explanations (a monster turns into someone wearing a monster costume, the alien invasion turns into a movie set) until the character leaves the area.
    • A lesser version of this is available in the 4th edition as the perk (one-point advantage) Skeptic. Any supernatural powers the character doesn't believe in get a penalty to use, and the effect is cumulative when there are multiple skeptics present.
  • In In Nomine, the Marches, the land of dreams separating the corporeal realm (Earth and the rest of the physical universe) from the celestial realm {Heaven and Hell) is populated by the power of human imagination with pagan gods and creatures of myth.
  • The card game Munchkin Bites has an item The Yarmulke of Religious Obfuscation which gives the wearer an extra bonus against The Vampire Hunter and The Meddling Cleric.
  • In the New World of Darkness:
    • In Mage: The Awakening, the disbelief of normal humans can unravel magic, but only because their souls bear a fragment of the nothingness which stands between the sources of magic and reality.
    • In Changeling: The Lost a magical effect preys on the beliefs and psychological expectations of mortals and other supernaturals to make Changelings and Fae Tokens appear as mundane people and objects, rather than the (sometimes flagrantly) magical things they are.
    • Elsewhere in the New World of Darkness, spirits of things reflect what people believe that thing should be — a dog spirit, for instance, is nearly the platonic ideal of a dog — but it's left deliberately unclear whether this is because human belief shapes spirits, or spirits shape human belief. Is a spider spirit the way it is because we believe a spider should be this way... or do we think spiders should be this way because this is how spider spirits are?
  • In the Old World of Darkness:
    • In Mage: The Ascension, reality is the result of consensus belief; normal humans who haven't pierced the Masquerade can disrupt magic through disbelief. "That can't happen," they think, and their belief is strong enough to make it unhappen, make them forget it ever happened, and punish the mage for his attempt. Conversely, mages have carefully-constructed belief systems that allow them to impose their wills upon reality and reshape it as they see fit. For example, the Earth never used to orbit the Sun, steam power never used to be possible, until the Technocracy managed to make most of humanity believe in it.
    • In Hunter The Reckoning the collective force of human belief makes supernatural phenomena simply invisible to most people.
    • Changeling The Dreaming had this as a central element of the story; since humanity considers fairy tales to be, well, fairy tales, changelings consider themselves to be an endangered species, and the discouragement of freedom and the imagination (known as Banality) is actually toxic to them.
    • Vampire: The Masquerade, vampires aren't averted by crosses or other holy symbols unless the wielder's faith is particularly strong. In addition, a vampire character may purchase a number of supernatural flaws that are common to vampire lore: be it being repulsed by crosses, being unable to cross running water, being unable to enter a house uninvited... Depending on the DM and player's interpretation, those flaws are either factual problems caused by the character's particular bloodline (after all, someone must have given rise to those myths, and that someone probably sired other vampires) or this trope: the vampire fears garlic, because he's convinced vampires do.
    • The demons in Demon The Fallen power their abilities through the harvesting of faith from humans. This can be done quickly, through "reaping" (kind or cruel as the demon wishes), or on a long-term basis by making a pact with a human.
  • In Over the Edge, one NPC mentioned is a fairly obvious Expy of James Randi, who makes all the rampant weirdness of the setting shut down around him due to sheer power of disbelief.
  • In Scion, the various deities (and their progeny, including the player characters) derive power from the number of people who are aware of their exploits. This is known as Legend. However, while the Gods make sure stories about them maintain circulation, they discourage outright worship, because Fate is a bastard when it comes to such strong connections. It's a dangerous balancing act.
  • In Shadowrun (fourth edition, at least), there are numerous magical traditions based on assorted religious and philosophical beliefs, but all are equally capable paths to studying magic. In addition, spirits take on the shape of whatever the caster believes they should take the shape of; a spirit of fire can look like everything from a triumphant archangel to a happy little puff of flame depending on who summons it.
  • In Toon, things like gravity will only work on you if you remember that it should. As a result, you can take a Smarts test hoping to fail, and if you do, you can cheerfully row across the sea with a boat that's still tied up at the dock, or make a call from a phone in the middle of the Wild West...
  • This is the basic principle in which magic in Unknown Armies works. An Adept's obsession warps their view of the world so much that he can bend reality with his will simply because he is absolutely sure that what he does is possible.
  • Da Orks in Warhammer 40,000 subconsciously generate a mild psychic field, its strength directly proportional to the amount of "boyz" present, so if enough Orks believe in something then reality is given a swift kick in the balls and told to follow the proper, Orky way of doing things. While it won't cause a stick to be able to shoot bullets if an Ork believes it will, Ork belief in "da red wuns go fasta" really does make vehicles painted red move slightly faster, and because Orks believe that the biggest Ork is in charge an Ork will actually grow in response to other Orks following him.
    • While Orks can't make a stick fire bullets, their powers are able to make a lot of things that shouldn't work shoot bullets. Most of their "shooterz" are little more than boxes filled with gears and bullets that are in the general shapes of guns, and Orks have been known to make ships without fuel fly across solar systems.
      • The power of the Ork gestalt field varies Depending on the Author. In one book, an Ork with a huge BFG took on an entire Imperial Guard platoon. When the Ork was killed by a sniper and the gun was recovered, it was found to have no trigger or firing mechanism, making it little more than a metal pipe with a gun belt fed through it. In another, Ork weapons and vehicles can be used by human forces fairly effectively, but they are still prone to misfires and jams. Ork Mekboyz have a very good instinctive understanding of mechanics, but for the most part, Ork technology requires the gestalt field to work.
      • In one of the Gaunt's Ghosts novels, the eponymous commissar has no problems commandeering an ork buggy beyond the fact that it was designed for a significantly stronger being and as such lacks power steering. Another example is that of a unit of Ork-hunter Imperial Guard who will often loot Ork guns and use them, again with no problems. The general idea is that Ork technology does work, and the Orks' psychic power simply makes it work better.
      • This sometimes even works against the Orks. Their mortal enemy Sebastion Yarrick, despite being as badass as a human could possibly be in the horrifying 40K universe, REALLY should be dead just by weight of age and everything he's endured making his body give out, even with advanced future medicine. But he's accomplished so much against the Orks that they believe he's an unkillable monster, ergo...
    • Tech-priests of the Adeptus Mechanicus are taught genuine mechanical skills, just in an odd and highly-ritualised way involving lots of chanting and application of holy oils in order to please the "machine spirits". Machine spirits are quite real, with many examples of a vehicle functioning long after its crew are dead, or even "going feral" and rampaging across the battlefield. It isn't certain how much of Imperial technology is this trope and how much is genuine engineering.
      • The holy oils could just be lubrication for various components and the chanting is in binary, it might be some sort of voice activated diagnostic program.
    • There are also the faith-based powers of the Adeptus Sororitas (aka Sisters of Battle), particularly in Dark Heresy, where their Faith renders them immune to the negative effects of Daemonic Presence, and provides many other useful abilities at higher character ranks.

    Video Games 
  • Specifically referenced in A Fine Day For Reaping, as an explanation for why you can't simply walk past an armed soldier. As The Grim Reaper, you'd normally be Immune to Bullets... but you only exist because of this principle, and combined with the soldier's firm belief that there's no problem he can't solve by shooting it, he might actually be able to kill you.
  • In Age of Mythology and the Titans expansion, all four civilizations need their followers to do something for them before they'll grant units and upgrades. However, simply advancing your civilization gives you one free God Power to use at your discretion, so advance today!
  • The science-magic dichotomy in Arcanum: Of Steamworks and Magic Obscura is partially based on this; an extremely science-oriented character is immune to magic because s/he does not believe such foolishness could have any tangible effect.
  • How deities in Asura's Wrath gain the power of mantra. Or they can just kill you and take your soul, that works too.
  • In the PC game Black & White, the various deities gain "faith points" when humans witness them doing things; one can convert villages by building up enough faith points. Also, godly powers are driven by belief, which is gained from getting villagers to worship at your temple.
  • In City of Heroes, the Clockwork King's robots shouldn't work at all, but because he believes they do— thus subconsciously animating them with his telekinetic powers— they do.
  • Final Fantasy Tactics uses this as an actual game mechanic, where characters have a numeric stat called Faith between 0 and 100, and this is directly applied to damage amounts and success rates of magic that the character uses or is hit by. A character with a Faith stat of 0 is utterly immune to magic. Characters' Faith stat can be raised or lowered with certain abilities, though if you raise faith high enough, a character will become too pious to put up with your obsession over mundane trivia like trying to stop demons from taking over the world, and will wander off to worship God in peace.
  • The Eidolon Wall in Final Fantasy IX reveals that the Eidolons are in fact created by the belief of humans. The creatures of myth and legend in effect become real by people believing them, and serve as guardians of the planet.
  • Many magical items in The Game Of The Ages turn out to contain no intrinsic power, but your initial belief in them imbue them with actual magic.
  • Glory of Heracles does this to Iphicles who was given a fragment of Heracles's soul to be revived from the dead. He gets amnesia from the experience and believes himself to be Heracles. When Iphicles learns the truth, that he's actually dead, he fades into ether.
  • In Kingdom of Loathing, the description of "Trusty", the axe wielded by the Avatar of Boris, uses this trope to explain how certain legendary weapons become legendary.
    Not every magical weapon is forged of meteorite iron under an unusual planetary conjunction, inscribed with gilded runes of ancient power, and imbued with supernatural strength and sharpness through mystical rites and sorcerous incantations. In truth, many of the most powerful weapons of lore are possessed of far humbler beginnings — common metal, torn from an enemy's grasp in a dire emergency. If the warrior survives the day, the weapon will likely be kept. Polished, sharpened, and re-sharpened, it will be carried from battle to battle, becoming as much a part of the man as his own arm, and as his name rises from warrior to hero to legend, so too will an aura of reverence and awe begin to surround the blade. Legend and belief are powerful forces, and it should be no surprise that a powerful artifact might have become powerful simply by dint of everyone believing it to be powerful. That is, after all, where the gods came from.
  • Mother
    • In MOTHER, Giegue is defeated by the use of the Sing command, singing Queen Mary's lullaby that Ninten and friends learned over the course of their adventure.
    • In the fangame midquel Mother: Cognitive Dissonance, Alinivar has to use PK Harmony to defeat Giegue/Giygas. It puts your party into "Harmony" status, until Niiue goes into "Giygas" status, showing he's finally returning to Giegue to normal... For awhile. Niiue thanks you for using it at the end of the game.
    • In Earthbound, the only way to beat the Big Bad Giygas is the liberal use of the "Pray" command... and the prayers of everyone who you met on your quest, culminating in the player. These prayers actually do physical damage to him.
  • The main character of Ōkami is a severely weakened god reincarnated as a wolf. She gains experience points in the form of "faith" and grows stronger as she helps people and performs miracles. The final battle actually sees her stripped of all her powers a second time, and it's only because of her left-behind ally spreading her name and leading the people of Nippon to pray to her that she's able to regain them all and save the day.
  • The Ouendan and Elite Beat Agents series run entirely off this, in which members of a Japanese cheerleading squad (or secret government agency, in the case of EBA) show up and miraculously resolve random peoples' issues through, well, cheering and/or interpretive dance. This is taken to its logical extreme in each of their final story missions, where everyone's fighting spirit takes on a more, uh, tangible form.
  • Subverted in Phantom Dust. It's explained in a small codex entry that Faith skills are, confusingly enough, not powered by faith, but a lack of faith. The NPC who uses the most faith skills is appropriately suicidal and self-loathing, having no faith in herself or her comrades.
  • The law of physics upon which all of reality is ordered in Planescape: Torment. The game is set in the outer planes, a multiverse created from the accumulated belief of the people living in the real world (the "Prime Material Plane"), so this operates both on a grand scale (every version of Hell believed in by all of the world's cultures exists somewhere) and a smaller one (in the Planes, one can will a plant to grow or create a person by telling enough people he exists).
  • A key point in the Shin Megami Tensei series, where entities from virtually every mythology ever exist, specifically because people believe in them.
  • The is the general fandom consensus towards how Silent Hill works; the Dark World and the monsters therein are manifestations of a character's fears, memories, et cetera; the Malevolent Architecture is someone willing the player character not to succeed, and the player character receives weapons and ammunition from their desire to live and achieve whatever goal they're working towards. As the game continues and all people concerned become more desperate and determined, the difficulty level and the potency of available weapons increases. This also explains why the mysterious "power" is limited to the eponymous town, as only a small cult there believes in it... until the more recent games, that is.
    • The film makes this somewhat canon. The little girl's hatred, combined with that of a spirit of vengeance, transforms the town into a hell. In turn, the cult it was created to punish is protected by their faith; more precisely, it's their blind ignorance of their own fate which prevents the spirit from killing them all (until it finds a loophole).
  • Space Channel 5 Part 2. The game has people you save helping you stop evil by singing and dancing along. But the trope really comes into play in the final level, where Ulala falls unconscious and defeated, but the entirety of the cast starts to clap for her and bring her back, before they all sing in unison to stop the bad guy. Even though just moments before she was zapped close to dead.
  • Tears to Tiara 2: Hamil raises the battle cry of Ashtarte, and all Canaanites at the Ba'al Festival follows suit. This empowers Tarte, which prevents both her and Hamil from being burnt alive.
  • Touhou Fuujinroku ~ Mountain of Faith works around this concept, as the Big Bad is forced to flee to Gensoukyou after the normal world loses faith in her, making her powerless.
    • While only gods need faith, belief is hugely important to the setting. Youkai (most of the cast) are created from humans ascribing the mysterious to unknown forces, and will fade away if people stop believing in them. Since this has mostly happened, the setting is behind a barrier that causes it to be sort of the opposite of the rest of the world, pulling in things that people don't believe in.
  • Used during the final boss battle of Viewtiful Joe 2. Joe and Silvia go into the real world to fight the Big Bad, but find out their powers don't work, yet his do. After getting thoroughly beaten, the crowd starts to chant their support, at which point, the two of them transform, and hand out a royal beating of their own.
  • In World of Warcraft, the ability to use the Light comes from the belief of the individual—for this reason, non-sentients who lack free will are unable to use it the conventional way, crises of faith such as disasters can often have the side effect of cutting off individual contact, and people who commit atrocities can still access the Light if they believe they are acting for the greater good.

    Web Comics 
  • The Fae kingdom in Dan and Mab's Furry Adventures works on belief, while the laws of physics take a day off. Scientist-by-heart Jyrras, then proceeds to step right through a floating platform.
  • In Digger, this can have some disturbing results. In particular, street children put a new spin on a Crystal Dragon Jesus, making his mother evil. This creates a goddess so horrible that just seeing her drives a priestess insane, and apparently leaves the priestess covered in "shadows" that are not her own. The evil goddess is based on myths created and believed by street children in Miami.
    • Gods cannot die while their followers believe in them, even if they want to.
  • Dream Catcher does it for laughes as a bonus page FAN SUPPORT POWER BOOST!
  • In Elf Life, magic is portrayed as only having an effect on those who believe. Knowing this doesn't seem to help.
  • In Fans!!, the "crosses are only effective in the hands of those who believe" rule is used as an indication that a particular character's faith is wavering. In desperation, one of the fans (Rikk, a Christian whose faith had been weakening at the time) instead tries a symbol he does believe in: the Vulcan salute. It works, but not really; the vampire was faking it.
  • Gunnerkrigg Court: Coyote is of the opinion that human belief created every supernatural entity, and is even capable of re-writing reality.
  • Played with in this Mac Hall strip.
  • In The Order of the Stick, Elan creates his own god, Banjo the puppet (so called because he has a banjo) for when he multi-classes to Cleric. When Roy tells him his opinion, Elan calls for Banjo to smite Roy. A tiny storm appears and throws a tiny lightning on Roy, which has no effect. Elan comments that maybe Banjo needs more believers.
  • This is the entire plot of Parallel Dementia.
  • Roommates never outright tells us, but heavily implies that fan belief and human memory keeps fiction alive and has a cast of self-aware fictional characters. The examples include things like characters, who fans would rather forget, being Deader than Dead, or a Dangerously Genre Savvy character telling his son to fight for his love/happiness, beacause then someone will believe and even if he fails or even dies he will be remembered and so live and get new chances.
  • Art from Sequential Art loses the ability to use any piece of technology, once he's told that "artists radiate an anti-technology energy... and the effect gets 100 times worse when the artist knows of the energy's existence."
    • Eventually, he has surgery to correct it, which involves hypnotic therapy, a computer chip, and a large drill. It's a placebo, but that doesn't stop it from working.
      • Later, he tells Pip to whack him on the back of the head to disable the chip, bringing back his imaginary powers temporarily.
  • In Sluggy Freelance, the following exchange takes place during the first clash with vampires:
    "You'll also need a holy symbol to drive him back in case he's too strong for you!"
    "Will this can of beer work?"
    "Is it light beer?"
    "Nope."
    "That should do the trick."
  • Legotech in Troops Of Doom runs on this. If you can make an agglomeration of Legotech vaguely resembling the device you want, it will function perfectly as such.
  • Unwinder's Tall Comics. Here:
    Howard: Excuse me. All of the women at that table would like to meet you.
    Dr. Minivan: A-Are you sure? How do you know?
    Howard: You must speak with them! Your doubt is causing them to fade away!
  • Wonderella once used "Peter Pan fairy logic", as she called it, to get people to bring Christmas strength back to The Krampus. It worked, and he was able to return to his job of... throwing naughty children in a sack and taking them to hell.
  • In Zebra Girl, magic works along these lines. As one character explains, Magic fundamentally doesn't work, but as long as you don't believe that it does. For example the main magic user tells a character to close his eyes as the magician heals him because as long as his eyes were open he wouldn't be able to accept the spell working. This same wizard then starts on a one man (but occasionally one werewolf) mission to bring back magic into the world through teaching people (mainly kids) to believe in it again. He does this as a really, really, really, good street magician.
  • Weirdly used in 8-Bit Theater #490. Fighter manages to defy gravity because he thinks the team broke physics, causing Red Mage's brain to crash.
    Fighter: Don't you understand? With gravity slain, now we can fly! (floats off the top of the panel)
    Thief: Huh.
    Red Mage: But he. You can't. Love, hate, clouds. (faints)

    Web Original 
  • Most of the monsters of The Fear Hole are created by human fears in an alternate dimension. This is mostly Played for Laughs.
  • Gaia Online's ill-named "Demonbusters" event in 2009 ends with the titular gods depowered and turned into humans. The following Christmas event had them getting Gaians to believe and pray to them so they could become divine again. It didn't work.
  • I'm a Marvel... And I'm a DC. When Deadpool runs out of bullets he asks the audience to do this to make new bullets appear in his guns. When this doesn't work he calls the audience a bunch of amputees.
  • In Kickassia, the That Guy with the Glasses team note  attempted an amazing one of these to ressurrect Santa Christ, complete with appealing to every member and many lapsed members of the site, and eventually asking the audience to join them in wishing Santa Christ back to life. At the end of this, Santa Christ proceeds to... lie there dead. But he comes back after three days anyway.
  • Protectors of the Plot Continuum: The Substance Menu has this to say about Bleeprin, a medication made of bleach and aspirin: "Please refrain from reminding the PPCers that this is chemically impossible. They already know that. They don't care. However, if you remind them, it may no longer work; then they will probably kill you."
  • SCP Foundation: this is how SCP-239's power works. If she believes something to be true, then reality instantly reshapes itself so that her beliefs are true. The fact that she's an 8-year-old who's aware of her power, but not how it works, makes things... problematic for the rest of humanity.The Foundation tried to convince her that she is a witch and can only cast spells out of "spellbooks", and although this failed to limit her power, it made her much easier to enroll in "magic school". She's in a coma now thanks to her powers backfiring. She was so afraid of Doctor Clef that she believed he was planning to kill her. The belief became reality, which was bad since Doctor Clef also happens to specialize in killing Reality Warpers like 239.
  • One fan theory states that this is how Slender Man exists; the reason he scares people and gets them to keep records of him in pictures and videos is so he will exist forever.
  • In docfuture's hilarious "Let's Play Sonic 2: Special Edition," in Mystic Cave Zone, he points out that the game engine is belief-based, and consequently the graphics looked bad because not enough of the viewers believe that this game exists.
  • The inverse occurs in Spoony and Linkara's review of Warrior #4, when they realize that the comics' ability to break hypertime and merge the universes is powered by their desperate attempts to believe in or discern any sort of meaning from the comics. They then call for all the critics to help them defeat the Warrior by declaring how much they…don't care.
  • Tech Infantry borrows the explanation of the magic of Mages from the Old World of Darkness, so it follows this trope. One of the characters even tries to weaponize this fact of life, using a Mind-Control Device to change what everyone believes about how the universe works, and thus change the way the universe actually works.
  • We Are Our Avatars: To a limited extent, Luna's technology works like Orc Tech, if she believes the red car will go faster the red car will go faster. This does not however give her the ability to make a stick work like a gun just because she thinks it is one.
  • Discussed by Worst Muse: "If the rights to your favorite character haven't entered the public domain, it's because you didn't believe hard enough."
  • In the Whateley Universe, there are two different kinds of Mad Scientist. The first are Gadgeteers, who operate based on the laws of reality, obey them, and just have a strong enough understanding of sane science that they can leap years ahead of everyone else. The second are Devisers, who simply believe strongly enough in their inventions that, somehow, those inventions work. A particularly strong Gadgeteer is a threat. A particularly strong Deviser is one shade away from a full-fledged Reality Warper.

    Western Animation 
  • In Aaahh!!! Real Monsters, it was the fear and belief of monsters in the minds of humans that caused them to come into existence in the first place, and they can only exist if humans continue believing in monsters, which is why they scare. In one episode the entire cast begins to disappear because they hadn't been scaring enough humans, and reform themselves after going on a scare rampage.
  • In Barbie & The Diamond Castle, while a song is the key to the castle, the lyrics indicate that it's belief in the song that actually makes the castle appear. "Believe/Your song will hold the key"
  • In the Christmas Episode of Buzz Lightyear of Star Command, it's the power of belief that allows Santa's sleigh to work (naturally, the final dose of necessary belief-power comes from Team Lightyear's most skeptical member, XR).
  • Ember, a ghostly rocker from Danny Phantom, gets more powerful the more her fans chant her name.
  • Parodied in an episode of Earthworm Jim where, after his super-suit gets stolen, Jim tries various generic ways of gaining super powers (including space radiation and radioactive arachnid bites). One of his attempts is to plead to the audience where he tells the viewer he will get powers if the audience were to "Believe! Believe and clap very hard!" prompting:
    Jim: ...Well? Are they clapping?
  • Inverted in one episode of The Grim Adventures of Billy & Mandy. Mandy is unharmed by the Tooth Fairy's wand (which can turn people into Anthropomorphic Food) because she doesn't believe in the Tooth Fairy. (Or course, this was not only a Dream Sequence, it was Billy's dream sequence; He has weird dreams.)
  • Mocked in Futurama:
    Bender: If you don't believe in him, he can't hurt you!
    Santa: (smack)
    Bender: Oh GOD, the pain!
  • One episode of Freakazoid!! spoofs the Peter Pan example above, with Cosgrove asking the viewers to revive a defeated Freakazoid with their applause.
    Cosgrove: ...And throw in some "Huggbees" while you're at it.
    Crowd: HUGGBEES!
  • In the Justice League series from the early 2000's: Wonder Woman, despite being super strong, sometimes exclaims "Hera give me strength!" Which maxes her strength out to the point where it rivals Superman's She even states that there were times that without her belief in Hera, she would not have been successful.
  • In an episode of The Real Ghostbusters, the city was visited by two benign ghosts who appeared to be Sherlock Holmes and John Watson, and a very nasty one who appeared to be Professor Moriarty (who eventually conjures up a demonic version of the Hound of Baskervilles). Egon at first thought this didn't make sense; as fictional characters, these people were never alive to begin with, and thus could not be ghosts. When it became clear that they were indeed the real deal, he brought up a theory he had read about called "belief made manifest". What this meant was, if enough humans believe that a fictitious character is real and he has enough fans, it can give the character a pseudo-life, which seems to be what happened. Once they figured this out... The game was afoot!
  • In South Park, the Imaginationland storyline revealed this to be the case (technically Doing in the Wizard in doing so). Everything and everyone ever imagined by someone on Earth is real in Imaginationland, including all religious figures (even including real people believed to be gods and prophets, such as Joseph Smith, founder of the Mormon faith). This is made hilarious if one remembers that Jesus has a public access television show in the real world.
  • Inverted in Teen Titans: Recently-deceased villain Slade has returned to beat the living crap out of Robin... or so Robin thinks. Turns out he'd been exposed to a drug that makes him see Slade, and his body to react as if struck. He is able to disbelieve in his opponent just in time to save himself from the killing blow.
  • An episode of Tiny Toon Adventures revealed that laughter (or, perhaps more correctly, the Power Of Fandom) helped cartoon characters stay young.
  • In Winx Club the Believix transformation's powers are amplified when humans believe in the Winx.

    Other 
  • A classic joke has a beautiful woman trying to drive a vampire away by brandishing her crucifix; the vampire's response is an amused, "Sorry, lady, 'svet gornisht helfen" (Yiddish for "It won't help a bit").
  • In Apotheosis, miracles run on this. If a god's followers believe something, then (assuming the god is strong enough) said god will gain it as a new miracle.
  • The Indian deity Hanuman, the "monkey god," is so caught up in his devotion to Lord Rama that he needs his followers to remind him of his own divinity for his powers not to dwindle.
  • "The Law of Attraction" and "Universal Magnetism" and "Like Attracts Like" are concepts explored in at least two books, The Science of Getting Rich by Wallace Wattles and Excuse Me, Your Life is Waiting by Lynn Grabhorn, as well as at least two films: The Secret by Rhonda Byrne (also a book) and What the Bleep by J.Z. Knight. Both films feature followers of Ramtha's School of Enlightenment in Washington State, which also teaches this concept.
    • A lot of megachurches have co-opted this by calling it "prosperity theology".
  • The Logical Fallacy known as argumentum ad populum implies this. For some reason that doesn't stop people from using it, even though the implications should be obvious.
  • Somewhat related: Santa Claus is often depicted as "real for those who believe."
  • There is a joke about some Jews coming to a rabbi and asking him if he can pray for a rain. He says it won't work since they have no faith. How does he know they have no faith? They didn't bring umbrellas.
  • There's a number of urban legends about Christian college students and their Atheist professors, who try to convince their students that God isn't real. One variation has the professor hold up a piece of chalk saying that if God was real, he'd stop the chalk from breaking on the ground if he dropped it. The student prays that he will have the courage to tell the professor he believes in God. When he tells the professor this, the chalk slips out of the professor's hand, rolls down his pant leg, bounces off his shoe, and lands on the ground unharmed.
    • The professor's retort, if someone is around to say it to the original storyteller, goes something like "I've been doing this for twenty years. Either we have a coincidence, or 1/20 of a god."
    • Countered with 'God doesn't do cheap tricks for show'. Which means it was dumb luck the chalk didn't break.
    • Another version has the professor standing on a chair declaring that if God exists, he should knock him from the chair. Followed by a student bodily tackling him and claiming he was sent because God was busy. Obviously, trying that in real life easily leads to legal and academic problems.
  • This is a common feature of New Age beliefs in general. In Wicca and some other Neo-Pagan religions, a variant is taught: you can perform magic(k) by visualizing the desired results and focusing your will upon them, but doubts in the efficacy of the technique will rob you of the necessary focus and prevent it from working.
    • Some practitioners of magic(k) claim that any symbol has the power the magic(k)ian invests in it. This can lead to two conclusions: One, the whole subjectivist interpretation (the idea of all persons living in a reality of their own making (thus not the same as the one everyone else lives in), or two, that humans actually innately possess some huge magic power, but have developed mental blocks to prevent the world's destruction by a toddler Eldritch Abomination, and such symbols are ways around these psychic walls.
  • This is generally how the occult practice of chaos magic works — if someone believes in it, you, too, can believe in it, and channel it for power. Grant Morrison, being delightfully wacky, has written articles on channeling the occult significance of everything from the Greek pantheon to the New Gods to James Bond.
  • WE'RE GONNA YES SO HARD, WE'RE GONNA BRINK KIKI BACK TO LIFE. BELIEVE IN THE YES.
  • Generally invoked by psychics, fortune-tellers and such chalartans when they fail to perform during controlled experiments. Many of them would argue that the general atmosphere of skepticism around them is suppressing their powers.

    Real Life 
  • Celebrities. If you don't put faith in a celebrity... if you don't "clap your hands"... the celebrity will disappear!
  • For that matter, most superstitions work this way too; believing something may encourage someone to try things and do things they might not otherwise. Like athletes who tend to have the most unusual and personalized superstitions.
    • Confirmation Bias also plays into it. If you do a superstitious ritual or action, and something "good" comes of it (or at least nothing "bad"), you attribute it to the superstition. Likewise, if you forget to do the superstition, and something "bad" happens, even if it was probably a coincidence, you'll still attribute it to the lack of the superstition.
  • G.E. Moore's eponymous Paradox asserting that something is true demonstrates one's belief that it is true. It's kinda like screaming in a rage ("I'M NOT ANGRY!").
  • An argument in Not Always Right involves this trope when a customer seeks a blue camera and no such item exists in stock, so the manager plays along in order to get the customer to buy a red one.
  • Pat Robertson claims that the credulous will get more miracles than the skeptical.
  • The placebo effect is the real life equivalent of this, though it is far more effective in fiction than in real life. This is generally attributed to the nervous system and the immune system being interconnected, and the idea that the immune system can be activated in a specific part of the body. The effect is strongest when treating symptoms with a strong mental component, like pain and nausea.
    • It's pretty strong in real life too. There is one instance of rats apparently being tricked into curing themselves of a certain type of cancer by a placebo. (They were given normal water, then the real stuff in flavored water long enough to cause remission, then normal water again long enough for the cancer to cease going into remission, then flavored water without the chemo.)
    • And it's getting stronger. More recent drug trials have been seeing larger and larger parts of the placebo control group actually having positive reactions. This is mostly chalked up to people having a much stronger belief in modern medical pharmacology, and hence are more likely to believe the placebo is really a new miracle drug.
    • There's also the related nocebo effect which has been claimed as powerful enough to kill people.
    • And then things get really interesting and weird: The placebo effect can happen even when people are TOLD it's a placebo!
      • That, in itself, may be a placebo effect, as the people were told that the pills they were taking were indeed placebos...that have shown to have markedly improved their health anyway. The people believe that despite the pill being a fake, maybe there's something in it that really isn't fake!
      • It likely has more to do with the fact that people know placebos work. If it works it works, it doesn't matter if it's fake.
  • Quantum Mechanics (or a misinterpretation of it, especially the part which indicates that mere observance changes the outcome of an event), is often used as a Hand Wave for any and all of the above. However, this is not a mainstream or even accepted interpretation for quantum mechanics except for a tiny minority, and the entire point of Quantum Mechanics in the first place is that subatomic particles behave completely differently to larger matter.
    • Incidentally the reason why observation changes objects on the quantum level is that the only way to observe any subatomic particle is to collide it with another subatomic particle. It has nothing to do with consciousness changing the reality, as subatomic particles collide anyway all the time.
  • The stock market. Expectations of the future are one of the most powerful forces, as evidenced by how stocks consistently rise/fall after optimistic/dour speeches, reports and addresses. So if the market tanks, it will come back to life if everyone just believes in it.
    • Bank runs, where people believe that their bank is failing and rush to take their money out of it, which causes more people to believe that the bank is failing, which causes more people to take their money out of it, which eventually causes the bank to actually fail, even if the original reason for thinking that that the bank was failing was completely false.
    • Really, money itself depends on this trope. Money gains or loses its worth only based upon widespread belief in it (specifically, the faith the holder has in his ability to exchange it for something he really wants like food, which is dependent on the other guy with the food having enough faith that he can in turn use that money to trade for something else like clothes, and so on). Currency that could be used to buy quite a lot one day can be next to worthless the next, in the right circumstances. The money itself hasn't changed, the little squiggly world leader imprinted on it hasn't changed; its value derives entirely from how widely it is believed to have value.
  • This is how hypnotism works. You have to believe that you can be hypnotized in order for it to work, and it is impossible to be hypnotized against your will. The fact that the word "hypnotism" is applied to a half-dozen or so completely unrelated ideas, some well-understood and some utterly absurd, doesn't help.
    • In addition, even if you believe you can be hypnotized, you cannot be commanded to do things you are unwilling to do consciously. A man might be able to be hypnotized into thinking an orange is a apple, but if he believes stealing is wrong, there is no way you can force him to take money out of a wallet without permission.
      • Theoretically he can be made to believe that the wallet is his own, but this depends on the skills of the hypnotist and the susceptibility of the subject.
  • This is the most likely explanation of the Midnight Game. The environment and the setup mean the player(s) will spend three and a half hours stressing, worrying, and freaking themselves out.
  • Some more modern branches of the occult (In particular, Chaos Magic)follow this line of belief. The idea is that while the magic itself might not be real, the belief in it is very real and may be able to 'trick' your mind into believing that it is real (For example, curses only working if the victim feels like they've been cursed, and therefore would begin to associate every little misfortune with the curse so that, in their mind at least, they have been cursed).
  • Invoking this trope is an advised method of avoiding The Centipede's Dilemma: If you believe you will be successful in a task you already know how to do, you are not likely to overthink the actual process and goof yourself up.

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alternative title(s): The Power Of Imagination; Tinkerbell Jesus; Clap If You Believe
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