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Clap Your Hands If You Believe

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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, Luke 17:5-6

An old trope, wherein enough belief in something will cause things to happen. Also known as the "Tinker Bell effect", which is itself a subcategory of what is known as "magical thinking", a belief in cause-and-effect relationships between uncorrelated events based on coincidences. This trope isn't a Magic Feather where "confidence" merely allows one to use one's own abilities to the fullest; this physically changes the Universe. Many fantasy universes include some form of this: things like love or hate may be physically manifest forces rather than only things that exist in people's minds. A 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". When turned up to a global or universal scale, this can result in a "consensus reality" — a world completely created by what people think rather than its own Ontological Inertia.

This creates a vicious cycle for non-believers, as magical events are "disproven" in a Puff of Logic in their presence because they don't believe in the first place, thus cementing their disbelief. Particularly smart characters may take advantage of this and bypass foes and other threats by simply rejecting or ignoring their existence.

A variant of this trope, 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. A Tulpa is a creature that derives its existence from this force. Compare with Willing Suspension of Disbelief. See also All Myths Are True, Psychoactive Powers, Puff of Logic, and The Treachery of Images. Might be a way of creating a Deity of Mortal Creation, or of justifying Holy Burns Evil without implying that a given religion is objectively true in the setting (especially if holy objects from multiple mutually exclusive faiths are shown to repel evil). Compare Imagination-Based Superpower, when this happens because of a character's super abilities rather than the general power of belief.


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    Anime & Manga 
  • Ayakashi in Ayakashi Triangle are Invisible to Normals, but are empowered and even created when humans believe in them and their abilities anyway. Being worshiped as a god for years made Shirogane the strongest being on Earth. Garaku's drawing-based powers are greatly strengthened by his celebrity for his artwork, even though the public think he's just a human.
  • Berserk: The entirety of the Astral Plane is actually the collective human subconscious, which is why beings that exist in human imagination (such as mythological beings) reside there, and also why they can't emerge in the physical world. It also answers why the Berserk universe is so much of a Crapsack World: humanity has always thought since ancient times that every suffering has a reason. All of their collective thoughts and prayers formed the Idea of Evil. Yep. That will do it.
  • Bleach:
  • Devils in Chainsaw Man have a variant on this trope, namely that each devil is created out of human fear of something, and the more feared that something is, the more powerful they are. The Starter Villain is the Zombie Devil, for instance, who, while being fairly threatening to normal people, pales compared to most other devils seen throughout the series because people know zombies aren't real and thus aren't too scared of them. On the other hand, everyone fears having a gun pointed at them, and to that extent, the Gun Devil is so strong, it has a kill rate of thousands of people per second simply by existing.
  • At the end of Dragon Ball Z, Goku's Spirit Bomb requires all of mankind to willingly donate their energy to defeat Majin Buu, but the Ungrateful Townsfolk refuse to hear him out and believe it's a trick. To save all of reality, the group enlists the aid of the one person they do believe in; Fake Ultimate Hero Mr. Satan.
  • In The Elusive Samurai, the strength of divine power is directly proportional to the people's faith in the gods. The power and influence of the gods is destined to wane as time goes on and humanity starts viewing miracles as natural phenomenon rather than the work of divine beings.
  • Hetalia: Axis Powers:
    • 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.
  • In 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.
  • This was bound to show up in Kamigami no Asobi, the show with a harem of gods. It's very heartwarming, though. Yui is worried about two of their friends, and Apollon tells her to just believe in him. "For centuries, us gods have relied on the belief given to us by humans. Your belief becomes our strength!"
  • 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", the setting of Magic Knight Rayearth, Esmeraude is the Pillar of the World, who sustains the world from Cessation of Existence by praying it exists. This gets deconstructed when Esmeraude begins subconsciously demanding independence so she can be with her soulmate. She doesn't want to fall in love and doom the entire world, but it happens because her feelings will it to pass. Then she summons the trio so they can retire her; with her gone, the world will be able to elect a new Land of the Will and things will generally go back to normal. Except without the ability to concretely say she wants to die, because the people don't want to believe their goddess is impure or distracted, the heroines completely misinterpret her intentions and kill her boyfriend for being an overlord. She goes completely berserk and threatens to kill the rest of the world if she isn't murdered first. This gives the heroines PTSD.
  • In The Last Saiyuki, the ability to extend the Nyoibo and bring monsters into existence depend on whether or not a person's Mou is open, basically, whether or not they believe the impossible can happen.
  • 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.
  • Inverted in Miss Kobayashi's Dragon Maid. Back when Kobayashi and Tohru first met, Tohru had been impaled by a holy sword that would break the mind of any mortal that touched it. Being from Earth, Kobayashi had never even heard of, much less believed in whatever god it belonged to, so she was able to remove the sword without being hurt. The fact that she was drunk out of her mind at the time probably helped.
  • 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). In any case, when the Gods withdrew from the world, Magic stopped being the defining essence of reality, to be replaced with the laws of physics (this is why magic has been slowly declining in power in the Nasuverse as time goes on). 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.
    • Servants are partially shaped by what people believe about them in legends.
      • Fate/Apocrypha: Vlad the Impaler says that in life he was an ordinary human warlord, but because so many people believe he was Dracula, he can become a vampire. Semiramis says that she had nothing to do with the Hanging Gardens of Babylon, but can summon and control it because so many people believe she built it.
      • Fate/Grand Order: Carmilla can summon an Iron Maiden to torture her opponents because people believe she used it to torture and kill people, even though it never actually existed. Wolfgang Amadeus Mozart and Antonio Salieri were best friends, but Salieri's personality becomes twisted into hating Mozart because people think he was jealous of Mozart and murdered him. The Dioscuri Twins, Castor and Pollux, were gods, but their inaccurate legends turned Pollux into a demigod and Castor into a mortal, and they are pissed off about this. Romulus-Quirinus' father is Mars, but due to a legend that says his father was Hercules, he's able to use a version of Hercules' Nine Lives attack as if he was raised and taught by him, and he says the Servant Hercules feels like his father even though he still remembers Mars as his father. Wandjina is an Earth-born Elemental, but since her myth says she is from outer space, she has become alien enough to become a Foreigner Servant.
    • Also in Fate/Grand Order: The Sword of Boudica started out as an ordinary weapon, but Boudica can fire a Sword Beam with it because she believes it can. Mandricardo's Noble Phantasm, Rêve de Durandal, will only activate and allow him to wield the weapons Durandal or Durindana if he truly believes he is worthy of them. Nero's skill, Imperial Privilege, allows her to copy any skill she sees as long as she believes she can do them. Zenobia's Noble Phantasm, Authentic Triumph, can only activate if she truly believes her honor has been restored and she is a worthy queen. Elizabeth Bathory (Cinderella)'s Noble Phantasm, Fairy Tale Erzsébet, powers up allies with fairy tale traits, but it turns out the people it can affect are those whom Elizabeth believes have fairy tale traits.
    • 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 imagine herself flying and thus can't fly.
    • Fate/strange Fake: Richard the Lionheart's ability to turn any object he holds into the legendary weapon Excalibur is based on his sincere belief that anything he holds is Excalibur.
  • In Negima! Magister Negi Magi, 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.
  • Late in the story of One Piece, this is the leading theory behind the Devil Fruits, according to Dr. Vegapunk, the world's leading researcher on the phenomenon. Devil Fruits represent possible evolutions for humanity, brought into existence by humanity's hopes and dreams in terms of "if only I could do that" or "I wish I could be this." So, because there are people who dream of being made of metal or having more limbs, those Devil Fruits came into existence. This is also stated to be the case for Monkey D. Luffy's Devil Fruit, which in reality isn't the simple Gum-Gum Fruit but the Human-Human Fruit, Model: Nika, which embodies the legend of the Sun God Nika who is said to be the Antropromorphic Personification of liberation and freedom. The god himself likely does not exist, but because people dream of being liberated, the legend persists and eventually became a Devil Fruit.
  • 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.
  • Pokémon 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.
  • The Destruct Code from Sands of Destruction activates whenever someone wishes hard enough that the world would be destroyed. But first, he has to be in possession of his memory storage medium and know who he is. And if the person who wanted the world destroyed loses their desire and asks him to stop mid-destruction, he will.
  • This is one of the many concepts hinted at in Serial Experiments Lain, with the Roswell Incident as its subject. It also talks about how if nobody remembers something, then it never actually happened.
  • 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.
  • The world of Gaia in The Vision of Escaflowne was 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!.
  • The Bloodline Ability of the Azazel family from Welcome to Demon School! Iruma-kun, Romantisia, functions like this. Granting them amazing battle prowess, so long as they utterly believe they are strong and will win the fight.
  • 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.
  • In Re:CREATORS, the limits to what a character can do, as well as what the author can do to them, are based on whether the audience believes it would be possible in the given character's canon or not. Simply put, it ain't working if it ain't canon. Altair, however, has a bit of a cheat: Since her personality was defined solely by fanon, all it takes is for one fan to believe she can do it and the power is hers.

    Comic Books 
  • In one Astro City story, the Golden Age villain Professor Borzoi uses a Belief Ray to make a giant gorilla attack the crowd at a movie theater. A side effect of the ray brings the cartoon character Loony Leo to life. When Leo smashes the ray, he and the gorilla start to fade away, but The Gentleman convinces the crowd to believe in Leo and saves him. That's when Leo's troubles began...
  • The Red Death from Baltimore is an evil version of this trope. His offspring, the vampires, were once the dominant species on Earth, but as mankind found other gods to worship the Red Death and vampires lost their power until they eventually went dormant. That is, until the carnage of World War I reawakened them.
  • In one of those cosmic ironies, the current powerset of Captain Britain depends on his own confidence, much like Gladiator below — the stronger his confidence, the stronger he becomes.
  • In Crimson, it's 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 Department of Truth acts as a deconstruction of this trope; reality is portrayed as subjective and can retroactively change if enough people believe in a singular "fact". With conspiracy theories on the rise, the Department of Truth works to make sure that conspiracy theories don't take root because a lot of the conspiracy theories people believe in — like Reptilians or pedophilic, cannibalistic Satanists controlling the world — would be incredibly dangerous if they existed. The result is a world where modern-day society is its own Cosmic Horror Story, where human belief can literally destroy the world if left unregulated.
  • 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.
  • 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 is 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, as shown in Animal Man, 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.
  • Marvel Universe:
    • The Shi'ar Imperial Guard commander Gladiator's 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), Doctor Strange's magic works the same way. He deliberately cultivates a Large Ham persona to boost his own confidence.
    • The Cardinals serve as the elite shock troops/assassins for the Universal Church of Truth. The Church collects the Prayer Power of its 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.
    • Meggan from Excalibur (Marvel Comics) is an empathic adaptive shapeshifter — she looks like what people expect her to look like, and consequently spends a good part of her childhood turning into a monster. Eventually, she manages to develop a strong enough sense of identity that other people's expectations no longer affect her shapeshifting.
    • Used in Thor # 301, where it is 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.
  • Secret Wars (1984) featured this after Doctor Doom stole the power of the nigh-omnipotent Beyonder, as he soon realises that it requires a great deal of concentration to ensure that he only use this power to do what he wants to do, as opposed to whatever he thinks of. This is used against him after his massive attack on the heroes; while he's certain they're all dead, Klaw, being manipulated by the remaining fragments of the Beyonder's persona, is able to present a scenario where the heroes survived (Colossus and Reed Richards were Not Quite Dead as Colossus was in steel form during the blast and Reed's elastic body also helped him cope, and both managed to use healing technology to restore the others), and Doom's strained ability to control his power caused him to make that scenario real despite the odds against it happening.
    • 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 face 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! Later on, Wolverine is unable to repel Dracula with a cross, but when the devout Nightcrawler takes up the symbol, Drac is driven back.
    • To her own surprise, this is how future evil Gwenpool works in The Unbelievable Gwenpool. In her own timeline, this would not be the case, but in the past, her power or even existence depends on her past self wanting to be her.
    • Iron Man 2020 (Event): The Thirteenth Floor that the robots use as their base is a strange inversion; it's a trans-dimensional floor accessed through any elevator that is powered by people not believing there's a thirteenth floor in the building.
  • 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 The Sandman (1989) 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).
      • This story also shows the flip side of the equation when at the end one cat who's listened to it quips to another that even if all they've heard is true, nobody'll ever get enough cats to agree on what to dream of to actually turn the tables back again.
    • 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.
  • Tharg's Future Shocks: A computer technician is dumbfounded by a computer error that simply does not make sense, as he's already checked everything several times. He then starts to wonder if things only work because we believe they do, and conversely, if things stop working if we stop believing in them. Reality proceeds to fall apart as he begins to question the laws of nature, such as gravity.
  • In a comic book story based on Wacky Races, Dick Dastardly tries to figure out if he can knowingly cross a painted tunnel by convincing himself it's real.
  • Wonder Woman: The inhabitants of the Shamrock Lands (faeries and leprechauns) are susceptible to this, and as an added weakness cannot be seen by those who do not believe in them even if the other humans around are their friends and are interacting with them. They are incredibly depressed when they realize how few children can see them when they venture into the outside world in Sensation Comics.
  • The Legend of Zelda: A Link to the Past (1992): With no way to reach Ganon's floating castle, Roam goes a little nuts and surrenders to his eagle form. Back on the ground, Zelda says a prayer to the maidens, who magically float her and Link into the structure.
  • The Department of Truth is about the department of the same name, which exists to eliminate conspiracy theories. If enough people believe in a conspiracy theory, it starts to become true.
  • In Dark Nights: Death Metal: Rise of the New God, a resurrected Metron of the New Gods (he was killed by Dr. Manhattan) tells the Chronicler (a being from the Omniverse outside the DC multiverse who records the histories of dying multiverses) that the DCU is built off of belief. The mortals believe in gods and the gods believe in the Source. By becoming a believer in the DCU's stories, the Chronicler is ensuring that even if the multiverse finally falls to ruin, it will still live on in the imagination of the greater Omniverse.

    Comic Strips 

    Fan Works 
  • Crowns of the Kingdom has this in its ending. Everyone believes in Mickey and Minnie to restore them from nonexistence.
  • In Daily Equestria Life with Monster Girl, this is revealed to be the original point of the pony herd instinct. Back in the Discordant Era having the whole herd believe with single-minded fanaticism that the ground was solid and gravity pulled you down, that water was drinkable and air breathable, could often keep reality stable enough to survive in unless Discord was present "in person".
  • Dark Horse — A Five Score Tale from the Dresden Files has a rather terrifying version of this discussed by Dresden and Nemo. Nemo starts to ask Harry if it was possible to will into existence copies of Excalibur, as an example, by getting a whole lot of people to believe that the sword some joe schmoe crafted is the real thing. Harry tells him it's astronomically difficult but the theory is sound. Nemo then tells Harry that there are hundreds of millions of pony fans out there, so what if they all started to believe in the Elements of Harmony?
  • "True magic" works this way in Diaries of a Madman, which makes it far more powerful than unicorn magic, but much more difficult to master.
  • The Emancipators: Toshinori believes this is why Monoma was able to Copy One For All during his match against Izuku. Normally, it can't be passed on involuntarily, so he wasn't worried about it... and didn't think to reassure Izuku about that. Thus, Izuku went into the fight believing Monoma could copy his Quirk, and thus, it actually happened, with tragic results. What Toshinori doesn't realize is that while Izuku didn't know about his Quirk's protection, he actually wanted Monoma to take it. That's the real reason why it worked.
  • Harry notes in For Love of Magic that a fair bit of magic's actions are because people think it should act that way. For example, the reason spells travel slower underwater despite having no substance is that magic users think "I'm slower underwater so spells must be too". This gives Harry an advantage when fighting an assassin underwater as he knows his spells should travel the same speed in water or in air but his opponent doesn't so Harry's spells travel much fasternote .
    • Because most wizards believe themselves incapable of using magic without a wand, their innate magic actually gets weaker when they don't have one, leaving them more vulnerable to the magic of others.
    • Even something as simple as the color of a spell is caused by wizards expecting it to be that color.
  • Ghost of a Memory:
    Madame Pomfrey: Didn't you ever wonder how [Harry] recovered so fast after his accidents? He'd be up after just one night when you or I would have been in bed for a week. It's because he was Muggle raised. He has no idea what potions can do in terms of speed so if he's convinced he'll be healed very quickly, he will be. After finding this out on him in his first year, I've since used it with good success rates on Muggleborns. He's using his magic to heal his body - I'd never even known it was possible before!
  • In the Exalted fic Glorious Solar Saber, a Sidereal invokes this trope while teaching. He closes a student's eyes, telling her that he's going to throw her a spear. The student obediently reaches out, catching the weapon — and realizes that it was conjured by her own Essence. She expected to grasp a solid weapon, and her soul obliged.
  • In The Great Disney Adventure, part of the magic of the kingdom is believing in something enough will let it work. This also proves to be Kelsey's final challenge the first time she comes there.
  • In Harry Potter and the Weasley Seer Ron's predictions come true because other people believe that they will.
  • Intelligence Factor frequently mentions Infinity Energy as the source of Pokémon's powers. It turns out that Infinity Energy mimics everything around it in order to "improve" itself. There were no sapient Pokémon until Pokérinians evolved and Infinity Energy could "borrow" it from them. In turn, the way Pokérinians think things such as ghosts "should" be influences the way Infinity Energy manifests.
  • In The Life of Harry Potter and Hermione's Part in It a wizard's magic can become stronger through belief.
  • The Moon's Flash Princess:
    • Inverted. Kayaba's warning about players dying in Real Life if they died in the game was fundamental to prevent their deaths from happening. This is because the virus that caused SAO to become a Death Game had such a loophole.
    • The SAO survivors' capacity to use their Sword Skills in real life seems to stem from this. The fact that Asuna and Kazuto got married in SAO is enough for magic to consider them married in real life.
  • The entire premise of My Brave Pony: Starfleet Magic is based around this. The author has stated in forums that he believes in this concept.
  • In the Pony POV Series, it's eventually revealed that Discord's eldest brother D____t was the Anthropomorphic Personification of what is basically this concept, the ability by mortals to will things into existence. However, when he was erased from existence by Their Mother Entropy, his concept disappeared with him, denying mortals this ability.
  • In Radical Change Hermione states that this is true of magic to such an extent that legal cases are won not by the best arguer, but the individual who can best warp reality to support their belief.
  • In "The Third Life of Steve Rogers", Steve and Peggy's daughter Sarah speculates that this is the key to making the super-soldier serum work when she learns that, the night before Steve was given the serum, Erskine hypnotised him and asked him to describe what form he would take as a super-soldier; Steve's description of his serum-enhanced self was so exact that he even got his new height right because that's what he believed a super-soldier should be. Sarah speculates that Schmidt and Blonsky's more monstrous forms were the result of Schmidt envisioning himself as the monstrous form of Ymir, a manifestation of his full potential, while Blonsky wanted to be a more monstrous Hulk, and Steve notes that, based on what Bruce told him about his difficult childhood, he can see how Bruce would want a strong form that could never be hurt by anyone again.
  • In the Natalie Jones Marvel Cinematic Universe AU, "Stone Knight", the characters are dealing with the origin of the Philosopher's Stone myth, which can be used to bring things to life if people believe in them enough. Examples range from Clint Barton- here just a civilian- briefly being "programmed" to believe he's Robin Hood, to mythical knight Sir Stephen being brought back to life from a statue of himself. On a personal note, Natasha is shocked when the Stone creates Allen Jones, the fictional father she created for her current identity, based on her colleagues' belief in the father Natasha told them about.
  • In The Second String Harry manages to cut down a tree with a spell designed to cut only bread by convincing himself that it's a giant loaf of bread.
  • According to Xander Harris in Time and Again, belief is what makes vampires weak against holy objects rather than any innate power, making more popular religions such as Christianity, Islam, and Hinduism more effective. Furthermore, during the holiday season, a wreath on a door will prevent vampires from entering even public buildings or buildings they've been invited into because of the belief in Santa Claus by children all over the world.
  • It's eventually revealed in The Zeppo in Mind that the reason Xander took up residence in Faith's mind was because he viewed them having sex as the two of them becoming one. Combined with the unusually active Hellmouth and right at the moment of climax, Faith is sharing space in her own body.

    Films — Animation 
  • Care Bears Movie II: A New Generation, in which the audience is encouraged to say "We 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.
  • Belief in Rise of the Guardians is presented as a power that humans have that fuels spirits, with the belief that children possess being a strong motivating MacGuffin. Belief in the existence in certain spirits (Jack Frost, Pitch Black and the Guardians) and what they contribute to the world (Fun, Fear, Wonder, Hope, Dreams, etc.) is what gives them their power, the Guardians becoming ineffective and helpless after Pitch nearly snuffs the world's belief in them. Belief in that particular spirit also allows the believer to see, hear and touch the spirit in question.
  • 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 Tinker Bell on us.

    Films — Live-Action 
  • In The Angel Levine, Levine says that in order for him to perform a miracle, Morris must have faith in him. Morris says that he won't have faith until Levine performs a miracle. Morris's sick wife's health does seem to improve dramatically whenever Levine is around and decline again when he's gone, but that's not enough for Morris, who wants something more obvious.
  • In Artemis Fowl, the "giant dwarf" Mulch Diggums spends most of the film narrating the events of it to an MI6 interrogator, who refuses to believe any of it. Just before being broken out, Diggums reveals his Pointy Ears to the interrogator and mocks him by stating "Clap your hands if you believe in fairies."
  • 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.
  • The Disney Channel Made-for-TV Movie Don't Look Under the Bed invokes this trope by name as part of a key plot point. Boogeymen are actually imaginary friends who are unwillingly turned into what they are when the children who created them stop believing in them too soon. The only way to reverse the transformation is by reaffirming belief in them... which is exactly how the movie's Big Bad is dealt with.
  • 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 The Empty Man, the titular Empty Man is what allows The Pontifex Society to experiment with this, up to and including the creation of thoughtforms, essentially giving them The Power of Creation.
  • 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 the Jewish vampire Shagal. 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 (1985):
    • Vampires are vulnerable to crucifixes, but it's not so easy that simply grabbing one will do the trick.
    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.
  • 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.)
  • Hook
    • The grown Peter Banning 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 based on 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.
    • The Lost Boys' feast of imaginary food doesn't become real for Peter until he begins to believe in it. Or at least use his imagination in general.
  • 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. Sutter Cane, a diabolical horror writer, eventually has so many people believing in his stories that the Town with a Dark Secret in his novels becomes a real place and unleashes a plague of Lovecraftian monsters that ultimately destroy the world. As one character states: "A reality is just what we tell each other it is."
  • In Jingle Jangle: A Christmas Journey, the Buddy 3000 has an energy core consisting of several parts (as shown in Jessica's notes), but he is powered by people's belief that he could exist. If there is too little belief in the room he is in, he will power down.
  • 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. Technically it was the "Great Power" they retrieved from a distant planet to restore their morphing ability, but it was their belief that guided the working of it.
  • 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..."
  • Ordet: Johannes had a mental breakdown in which he believes he is Jesus. He reappears after going wandering, back in possession of his wits, but still acting as if he is on a Mission from God. He tells everyone that if any of them actually truly believes in God and asks God to resurrect Inger, He will. Finally Mikkel and Inger's little daughter takes Johannes's hand and asks him to bring her mother back. And Johannes does.
  • Santa Hunters: Santa's sled, sans reindeer, only flew because the children believed it would do so. This was after things started to disappear due to the lack of belief, but of reliance of physical evidence of Santa's existence. Even gets invoked by Zoey.
  • 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 Violent Night, Santa explains to Trudy that most of his powers come from "Christmas magic", which even he doesn't fully understand, although it seems to depend on the level of belief others have in Santa. When the Lightstone house is initially attacked, Santa is unable to escape up the chimney, but later on one of Trudy's traps gets some of the attacking mercenaries credulous enough that Santa is able to escape. After Santa is killed in the final battle, Trudy is able to rally the rest of her family to declare their belief in Santa and bring him back to life.
  • War God have this happening in the Darkest Hour; all of humanity's best weapons, including the prototype Death Ray from Chao's labs, has failed against the Martians. Mr. Chao, still insisting on believing his faith in his precious statue of Guan Yu, starts kneeling to the War God while the city is being destroyed all around him while his daughter Li-Yu pleads him to leave the statue and run. But his faith isn't in vain, as the Guan Yu statue suddenly comes to life, enlarges to kaiju size, and battles the invaders.
  • Wendy: A version of this happens at the end, when after Mother is killed, at Wendy's urging both the children and Olds sing, inspiring them. This makes the volcano erupt, signaling she is revived.
  • 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.
    • Followed by a dubbed exchange between a henchman and the crime boss:
    Henchman: But, boss, I don't believe in fairies.
    Crime Boss: Then don't clap, stupid!

  • 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.
    • A children's tale from the Red Scare '50s has a teacher in Russia convincing her students that God doesn't exist by having them close their eyes to pray for candy. She quietly goes around putting candies on each desk. When the children go "Aw, you put that there," she says "Exactly. God doesn't give you things. People do." (Jews see right through this one, because the principle of tikkun olam (world healing) means that kindness and love are God acting through us.)

  • 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").
  • 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.

Examples by author:
  • Douglas Adams:
    • 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. It's also noted that most theologians consider the whole thing "a load of Dingo's kidneys".
    • All Myths Are True in 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.
  • 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.
  • 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.
  • Stephen King:
    • In 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", from Night Shift, 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 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.
    • This is a recurring theme for King. In Needful Things, the Sheriff is able to assault the demonic Gaunt with a bunch of sleight of hand tricks made into real sorcery by simply willing himself to believe it'll work. Conversely, in The Stand, sociology professor Glen Bateman understands the nature of Flagg's powers and is so focused on believing that Flagg's magic only works if one believes in it, that Flagg really couldn't cast anything on Bateman and had to order a lackey to shoot him. A little later against a rebellious cultist, Flagg is able to roast him alive with magic because of the man's fear and belief.
    • Taken to its most ridiculous degree in the Four Past Midnight story "The Library Policeman", in which the hero attacks the villain with a ball of red vine licorice. Because the licorice has a special significance to him, it works.
Examples by work:
  • The Adversary Cycle: Subverted in 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. It's later 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 Amagi Brilliant Park, the fairies from Maple Land need people to like and believe in them or else they will cease to exist. After settling down on Earth, they opened up a theme park with them as the star attractions. The story starts with the park declining in popularity and threatened with foreclosure, so they bring in intelligent human Seiya Kanie to bring the park back in shape and save them. They comment that some of them could probably survive by turning into begging street performers, but that isn't really an option for the less talented and less attractive among them.
  • In 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. In addition to this, changes in what people believe about a certain deity cause a new version of that deity to come into existance as an entirely seperate entity from the original.
  • Anita Blake: Religious symbols will only harm vampires if the person wielding it actually believes in it.
  • 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.
  • In one book of the Blood War Trilogy, the protagonists have to hold off a demonic invasion in the Beastlands that will shortly arrive through a portal near a river. When one of the heroes asks a native what the river is called, they respond by saying they haven't named it because it's holy to them, leading to another of the heroes abruptly telling everyone to put up fortifications on the other shore without explaining why, later when the demon army shows up it turns out that the natives' belief has turned the river into holy water.
  • An early example: In A.E. van Vogt's Book Of Ptath, 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.
  • Book of Swords:
    • The 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 dependance on belief was psychosomatic at first, but became this trope over time.
  • The Broken Empire Trilogy takes place in what seems to be a horrific fantasy world with magic and undead monsters, but is actually a post-apocalyptic hellscape brought on by the "Builders" (us) messing with quantum physics and ripping he fabric of reality. The result is that, because people believe in things like heaven, hell, angels, demons, the undead, and magic, all of those things exist, feeding off people's expectations. This also holds true for the sequel series, The Red Queen's War.
  • Catch-22: This sums up Yossarian's feelings on the titular Catch-22.
    Catch-22 did not exist, he was positive of that, but it made no difference. What did matter was that everyone thought it existed, and that was much worse...
  • Celestial Wars:
    • While celestials have certain innate powers, if a mortal believes in them, they also gain whatever additional powers the mortal thinks they have (i.e., if a celestial's worshippers believe he has the power to control the weather, he can control the weather. If the worshippers believe the celestial can raise the dead, she can raise the dead). This is referred to as the "powerbase".
    • The powerbase is counterbalanced by the "thrall": a celestial also gains whatever flaws, vulnerabilities, and beliefs her worshippers think she has. Hephaestus's worshippers believe that he is crippled after being thrown off Mount Olympus, and so he is crippled. The Norse pantheon's worshippers believe that they will die if they don't get Idun's apples once a year, and so it becomes true. If a god's followers were convinced that he was a womanizing asshole, he would become a womanizing asshole.
    • In addition, an established celestial is immutably convinced that their current powerbase and thrall is right and proper and the way things should be, and will fight tooth and nail to preserve it, even if it is objectively horrible.
    • For a further complication, unless a celestial is attuned to the realm they are in (a process that can take centuries), then he must be within fifteen feet of a mortal for the mortal's belief to have any effect. If attuned, the worshipper need only be in the same realm. In case of contradictory beliefs, the belief with the most backers becomes true.
    • As one final twist, a celestial cannot permanently die (by any means) so long as they have an active powerbase somewhere, even if they are currently out of range of that powerbase.
  • 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.
    • Word of God is that Level 5 (the highest level) espers are as powerful as they are simply because it never occurred to them that they would be anything else.
    • A mysterious entity seems to be the legendary figure St Germain. It is eventually revealed that St Germain never actually existed in this universe, but this entity was manifested to play the part due to a lot of people believing in his story.
  • In 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 cannot curse someone, for instance.
  • The 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 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.
  • Cruel Illusions: The stage magicians' power is literally tied to the belief of their audiences. Their power is fed by the audiences believing that they can do their magic for real, and that gives the magicians a boost in power allowing them to do it for real.
  • In Dad, Are You the Tooth Fairy?, fairies apparently existed centuries ago but then had to leave "because of technology" and can still communicate with children's parents, but only if the kid believes in them.
  • "Selecting Afterimages of the Fading", a short story by John Chu published in the anthology Defying Doomsday, depicts a world where anything that is not sufficiently perceived eventually fades from existence. People known as "super-perceivers" are regularly employed to keep things like farmland or buildings from fading, and most everything is a little blurry at least, but people can keep themselves workably intact with moderate self-attention. The protagonist is a high-capacity super-perceiver, but his muscle dysmorphia keeps him from properly perceiving himself so he needs help from others to keep from fading.
  • This happens a lot in the Discworld series.
    • For one thing, it applies to the gods and their power. If you look at sources that go into more detail about the background, like the Discworld Roleplaying Game or especially The Science of Discworld, you'll see that the Discworld is set in a universe different from ours, with the powerful added combined element of magic/narrative causality/power of belief. Narrative Causality especially ties to Clap Your Hands If You Believe and overlaps with it. On the Discworld, most people's beliefs about how the world works are as naïve and unrealistic and prone to forming neat narratives as in our world, but belief distorts reality so that they become sort of true in retrospect. So you might falsely believe your god is great and powerful, but when enough people believe the god is great, they will become powerful. Good luck trying to make the god good and wise, though — that's not what you get by worshipping someone and giving them power. (Anyway, it's been remarked that people don't really believe that's what their gods are like in the first place, even though of course they'll say that. Really what you expect is more like your father after a long day at work.)
    • Similarly, it's remarked (in The Science of Discworld) that the Fifth Elephant that is supposed to have crashed onto the Disc may be just a myth, and the deposits of fat and whatnot found underground at the supposed crash site may be from lots of ordinary megafauna having got buried in some lesser disaster. On Roundworld, you could test this by seeing whether the deposits are in the shape of one big elephant. On the Discworld, there's no point because they will have that shape regardless, since that's the story people are now telling.
    • 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. Om, the main god in the story, despite his massive religion, was down to one sincere believer and one atheist who was almost as good because he very specifically didn't believe in Om.
    • "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.
    • This is the reason why the arguably most powerful goddess in the Discworld pantheon is "The Lady With Green Eyes", implied to be Lady Luck. Because no matter what faith you belong to, if you find yourself in deadly peril she's the one you ultimately prays to, and believe in.
    • 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!". This concept is later expanded on by the Black Ribbon Society of Vegetarian Vampires, which provided a better integration within 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.
    • Draco nobilis, the noble dragon, is a species so dependent on magic for survival that when the Discworld's magical ambiance declined to its present level, they were forced to retreat to a new habitat: the human imagination. At present they can only become real in a magic-saturated locale where an imaginative human visualizes them, as Twoflower and the Wyrmberg's ruling family do in The Colour of Magic, and the Elucidated Brothers do in Guards! Guards!, with the resulting dragons "feeding" off of the powerful magic fields of Wyrmberg and the Unseen University, respectively.
    • Things and places may gain a magic, life or attitude of their own due to belief and people's dedication to them — like a historical artifact of great value (even when it's not the real one), the opera, or a steam engine.
  • 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. In Dracula itself it only really works for the Catholic Van Helsing; the others, mostly Church of England members, just can't take the idea seriously. 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 Dresden Files:
    • This is a universal trope for supernatural beings. Magical beings don't necessarily require belief, but they do require knowledge of their existence in order to exist in the mortal world at all. Human perception can also shift their nature, sometimes even creating multiple distinct personalities for the same being. For example, Odin is technically the same person as Santa Claus, although there are some differences. This has even been stated to be able to capable of cosmic scale Retcons. For example, if enough people believe that the Abrahamic God created the universe, then things will change such that God will have always created the universe.
    • Symbols of faith also harm vampires, although the user has to believe in the symbol. A cross won't work for Dresden but will be incredibly effective for his friend and divine Knight of the Cross Michael. Conversely Harry's pentacle charm (a symbol of magic) will work for him, but not for Michael. Michael's faith in particular is strong enough that it's even able to cause a Red Court vampire (who is not particularly weak to symbols of faith) to instantly burst into flames on contact.
    • Interestingly, the above-mentioned Knights of the Cross don't actually require Faith in God, with only one of them being particularly religious. Shiro was converted without understanding (but he tries his best to be a good Baptist regardless), Sanya is Agnostic (despite having received a magic sword from an archangel), and Butters, the most recent Knight of the Cross is Jewish and not particularly religious. Uriel makes it clear that the important factor is faith in doing good and helping people in general, including defending others against evil as well as redeeming those who have made mistakes in the past. In Michael's case, this does come along with his Christian Faith, but Butters belief in Star Wars as a story of people fighting for good and triumphing over evil is a large part of his Faith, and Sanya simply seems to believe in doing good and helping people.
    • 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!". It doesn't actually do anything , but certainly is good for the adrenaline. Knowledge of fairies does matter just like everything else, though, as Mab made sure the Brother Grimm published books of Fairy tales to ensure that humans continued to know about them. And on a smaller scale, the more authority Harry has give Toot-toot and the more he accomplishes, 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. Him becoming the leader of the "'Za Lord's Guard" and gaining followers actually results in him personally becoming more powerful.
    • Magic 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, in which Senior Council LaFortier's murder involves no magic being slung. It is eventually revealed that the killer was being mind-controlled, but understood that they shouldn't be attacking LaFortier. Meanwhile, LaFortier was too confused and shocked at the sight of someone they knew attacking them to magically defend themself.
    • This is also why breaking the laws of magic is such an irredeemable taboo. The more a mage uses their magic to commit these crimes, the more it reinforces in their minds that doing them is right. Harry recounts witnessing the execution of a teenage wizard who spent weeks mind controlling his family, and by the end he was a lunatic with a god complex. Combined with Dark Magic being generally addictive and the result is that those breaking the laws of magic are almost always summarily executed. Even Harry, who killed with magic purely in self defense, is only saved when a Senior Wizard agrees to take him on as an apprentice, and is still on very thin ice with the Council decades later.
    • In the Side Jobs story "Backup", Thomas and Lara Raith are members of a secret society which uses this to banish creatures by making humans forget about them. The only way to truly win is to eliminate all knowledge of a particular being from humanity, 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 eliminate their competition. Word of God confirms that this is also the purpose of the Archive. Once everyone else has forgotten about a particular being, they wait for a few years, keeping an eye out for any mentions of the being until ultimately erasing their own memory of it as well, ensuring it is well and truly gone forever.
    • This trope is discussed in Skin Game. Harry and a member of his crew come across the real Shroud of Turin. Someone asks why the fake has magic powers and Harry replies that if enough people believe the fake is real, it gains some power through belief. That being said, it's still pretty clear that the fake is not as powerful as the real deal.
  • Eisenhorn:
    • In Malleus, Eisenhorn 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 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 The 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.
  • In Epithet Erased: Prison of Plastic, we're introduced to Rick Shades, who has the epithet "Soulmates", giving him the abilities of all of his friends. It's later revealed that this isn't limited to copying what his friends can do, but rather what Rick believes they can do. One of his friends, Trixie, likes to make "potions", but Rick, unaware that these potions are really just gross combinations of various substances, can copy this and create real, working Magic Potions.
  • 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.
  • In "The Forbidden", the original version of the Candyman worked this way as much as his film counterpart. He needs people to believe in him to exist. Should someone doubt him or damage his reputation he will be obliged to show himself to them and take some innocent blood for good measure.
  • In the Freya series, this is the foundation of divinity. Belief defines all of the book's gods, physically and mentally, and this is discussed, played with, and even used - particularly by the villains - as a tool.
  • 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 Golgotha Series, Jim sees that Mormon religious artifacts have magical power and asks if that means the Mormon religion is the correct one. The Angel Biqa responds that enough of any form of belief will grant power.
  • Goes horribly, horribly wrong in regard to the "Stuff" in The Gone-Away World. 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, 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. The inverse also works: the scientist in the team doesn't believe in any of this and thus makes a fine Anti-Magic weapon.
  • 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 Hell's Kitchen Sink, the collective minds of humanity have formed entire pantheons. This is not the only source of magic, however.
  • 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.
  • Incarnations of Immortality: In For Love of Evil, Jehovah (the Jewish God) says the number of believers in an Office determine the strength of the Office. Therefore, Satan's Office is extremely powerful because many people believe in Hell, but the powers of other deities wax and wane with the number of their believers.
  • 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 Jago, a town is afflicted with a force that causes people's beliefs and obsessions to become real. A small boy is able to defeat the Evil Dwarf that lurks in his room after the lights go out by ceasing to believe in it; he finds that it's a lot less plausible when it appears in clearly visible physical form than it was as a vague possibility lurking in the dark. The manifestations that successfully do in the people who feared them tend to fade away afterward unless they've been witnessed by somebody else and a new belief created. The horrifically deformed revenant Badmouth Ben manages to survive for quite a while after taking his revenge on his murderer because he finds a Nightmare Fetishist who wants him to stick around. The manifestation of Danny Keough's terrors tries to get someone else to believe in her, but nobody else can because Danny's fears were so personal and idiosyncratic that nobody else can understand what she is, let alone believe that she exists.
  • In the Joel Suzuki novel Ballad of the Bluerock, Joel, who is stranded on Earth without a wavebow or a loudstone, tries to manipulate the Aura using an ordinary guitar. He succeeds in getting the headstock to light up a little, but he finds that his ability only works in front of some people. He eventually realizes that his powers only work around people who want to believe in Spectraland.
  • Discussed in John Dies at the End. The various monsters/demons are repelled by holy symbols like crosses, and Dave wonders at one point if this is because the people wielding the symbols believe that should happen, or because the monsters do, or because the symbols simply are genuinely divine.
  • 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.
  • In The Machineries of Empire, enough people following a calendar will cause o it manifest Reality Warping properties, enabling the setting's Functional Magic. The easiest way to do Anti-Magic is to introduce a new calendar, as exotics work differently under different time and date systems.
  • An entire universe follows something very like this rule in The Magician's Nephew. As a screw-you to her sister when she tried to overthrow her, Jadis cast a Fantastic Nuke that killed every living thing in her world except herself. Once Jadis leaves that world with Digory and Polly, it immediately ends, as no one is left to believe in it.
  • Some gods in 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.
  • The Misfit of Demon King Academy:
    • Spirits essentially exist due to this, as they are based on the rumors, myths, legends and traditions that people believe in. For instance, a strong fear of fire will create fire spirits while if people have faith in water, water spirits will be produced. Spirits can even survive having their source destroyed as long as enough people maintain a belief in their tradition. However, spirits are highly dependent of their tradition and if that fades, the spirit will cease to exist and if there are traditions that contradicts each other in regard to a particular spirit, their lifespan will be shortened. In addition, if a spirit itself deviates for its established lore, their source will be crushed and they will die.
    • The most interesting case is Misa Ilioroagu, who is a half-demon/half-spirit, and the biological daughter of Reno, the mother of all spirits. As the Top God; Nousgalia, wanted to create a being to destroy Anos Voldigoad; The Demon King of Tyranny, who constantly opposed the gods, he set about to use Misa as a tool to do so. By taking advantage of Hero Kanon's False Flag Operation to save Anos by creating a fictional Demon King to be The Scapegoat for human hate, Nousgalia exploited the plan by syncing Misa's source to the tradition of Avos Dilhevia, the fictional Demon King, thus giving her power equal to that of Anos and the ability to usurp control over anything that was associated in tradition with the Demon King of Tyranny, such as his subordinates; Seven Elder Demon Emperors and his castle; Delsgade.
  • 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.
  • Necrotic Apocalypse: Even though they can't make use of it consciously, all living things naturally have a mana system, and can sometimes unconsciously create powerful magical effects when enough people believe something strongly enough. This has been going on for all of human history, but these effects are universally either subtle or completely irrelevant to daily life. Churches have a sanctuary effect that changes the local mana balance and keeps certain monsters out, but since no one can access their mana and monsters didn't exist until recently, no one noticed. Digby loots the Cloak of the Goblin King from a display for Labyrinth and finds that it provides a passive mana buff, which again is irrelevant to anyone who doesn't have their mana enhanced already.
  • In a nutshell, what the Inner Party representative explains to Winston at the end of Nineteen Eighty-Four: that as long as the people believe it happened and there is no written evidence to the contrary, it actually happened, and screw the laws of nature if BB says so. In fact, the ideal citizen is one who can subconsciously alter his perception, memory, and experiences to meet whatever the Party says in order to make it true. Of course, the mind doesn't change any independent physical things, but that's not the point, since the Party doesn't really believe in those anyway, or at least doesn't care about them. Basically, they're saying that this trope applies even though it doesn't apply.
  • A rare inversion appears in the short story "Obstinate Uncle Otis" by the great horror writer Robert A. Arthur, Jr. — it's in Ghosts and More Ghosts — about an obstinate Vermonter (and as such, the most obstinate man in the world) whose power of disbelief is legendary, to the point that he can almost convince others that their eyes are tricking them. Then he's struck by lightning and gets a dose of Your Mind Makes It Reality. The statue in the town square to the man he hated? Gone after he comments 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 comments 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 gets a bit of Easy Amnesia and believes himself to be a traveling salesman with a different name. "Humph — ain't no such person as Otis Morks." Before Fridge Horror enters into it, the narrator is also named Otis Morks, yet doesn'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.
  • In Pact, this effect is justified by the animist nature of the setting. Small, barely perceptible spirits are everywhere, and as a result of years of tradition, have been convinced to enforce the various laws that bind practitioners, such as that they Cannot Tell a Lie, by removing power from those that break the laws. The spirits like a good show, and if you can look good while doing something and are as showy as you can be and convince them that you can manage something, then it's more likely that you'll pull it off.
  • Past Doctor Adventures:
    • Salvation features a race of beings who gain power based on the belief others have in them, to the extent that they have been shaped into modern-day gods due to the prayers for salvation from the general population. Recognising the danger of these beings, at one point the First Doctor deliberately provokes the head of this pantheon into attacking him after inspiring doubt in the gods in their worshippers, with the result that he survives being hit by a fireball in front of a crowd of believers because his belief that he can’t be hurt outweighs the crowd’s belief in his attacker. The Doctor later drives these beings away by dropping a dud bomb on the park where their congregation has gathered and making everyone present think it can hurt their ‘gods’.
    • In Deep Blue, after determining that the nature of the Xaranthi infection is psychic, the Fifth Doctor is able to use ordinary tap water and his own willpower to "convince" the Xaranthi that he has a cure for their transformation and force them to withdraw from Earth.
  • The Trope Name comes from a famous scene from Peter Pan. 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.)
  • Riddle of the Seven Realms: In one world, when the locals lose their belief in luck (the world's form of magic) after it's defeated by someone who calculates odds, the world begins to disintegrate.
  • Mundanes are largely immune to being attacked by maleficaria in The Scholomance, because if they spot them at all, they don't believe they're seeing a dangerous magical beast, and the mal loses both its magic and its danger. El's gym teacher once spotted a creature that was trying to get the jump on El, thought it was a rat, and killed it with a cricket bat. El, who is prophesied to destroy wizard society with her apocalyptic magic, says that she could not kill even a small mal with a piece of wood.
  • In Shadow Police, Occult London is made up of what London believes about itself. The intensity and nature of Londoners' beliefs is purposefully manipulated in the series.
  • 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.
  • 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 is once confronted by Dynast Graushera's General, a very powerful Mazoku. Realizing she can't fight or escape, Lina decides to try mocking the Mazoku's name. The reasoning is that because Mazoku are masses of astral energy held together by their own self image, anything that undermined their self confidence will make them weaker. The strategy works.
  • 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.
  • The Stars Are Cold Toys: In 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.
  • "The Beings" in Star Trek: New Frontier gain power from worship and fear; it turns out that the most powerful among them is so because he gains 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.
  • Summer of Night: This is vaguely and strangely alluded to when one of the Big Bad's minions explains that it is vulnerable to holy water due to a habit acquired from hanging around in the Vatican in the past. Of course, this leaves the details very unclear. Is it about the monster's unwilling Catholic beliefs? Is it just an excuse, and does the holiness itself really have an effect?
  • The mythical Tlön culture in "Tlön, Uqbar, Orbis Tertius" is capable of this; they don't believe in a mind-independent reality, so reality becomes dependent on their minds.
  • In Warlock of Gramarye, 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.
  • Wild Cards: Characters theorize that the Wild Card virus works this way, causing the acquired powers to follow rules that their owners believe in. Unfortunately, the characters are not generally capable of consciously controlling their own beliefs, so trying to use this information to alter one's powers risks unpredictable results.

    Live-Action TV 
  • In the Amazing Stories episode "The Mission", a gunner trapped in a B-17's belly turret uses this to save himself when the plane is forced to make a belly landing, with battle damage preventing them from extending the landing gear or retracting the turret. He quickly sketches the plane with a pair of big cartoony tires and concentrates on the drawing... and it works. Twenty-odd tons of bomber, held up (for a few crucial minutes) by nothing but imagination and belief.
  • Barney & Friends: In the beginning of the show Barney Live in New York City, it is suggested by the announcer that all the audience members use their imagination to make Barney appear on stage.
  • In Being Human (UK), 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 Mind, Out of Sight", 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.
  • The Colbert Report: Stephen Colbert fully believes in this trope, naming it Wikiality, wherein if enough people believe something to be fact, it is. The best method for altering the public's belief in something? Change its Wikipedia page. To demonstrate this, he single-handedly triples the African Elephants' numbers via Wikipedia. Quite a feat.
  • Parodied in Community; at the end of one episode Abed plays a prank on Troy by painting a cartoon version of himself on a wall, claiming that it's the doorway to a cartoon land, and insisting Troy can cross over if he just runs at the wall and believes hard enough. He's not prepared for Troy to genuinely believe this, however:
    Abed: All you have have to do is believe!
    [Troy gears up to run into the "cartoon world"; Abed pops out of a dumpster seconds before he does]
    Abed: [Alarmed] Wait! You don't have to believe.
    Troy: I didn't! [clearly disappointed] I didn't...
    [clearly broken, Troy slinks away]
    Abed: ...I may have done some damage there.
  • 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:
    • In "The Curse of Fenric", a cross works on Haemovores only if the bearer has faith in it, and other objects of faith work equally well: a WWII Soviet soldier fends them off with a red star cap badge, and the Doctor is able to hold them at bay with no physical object, simply by invoking his faith in his companions. The priest who doubts his faith meets a sticky end.
    • "Last of the Time Lords" came under some fire for relying on this, albeit with a Hand Wave involving an Applied Phlebotinum-assisted telepathic field that focused the belief, causing what fans call Tinker Bell Jesus or Fairy Doctor.
    • In "The Big Bang", the Doctor is erased from existence, but Amy remembers him and somehow magically brings him back. It... sort of makes sense in context.
    • In "The Doctor's Wife", the Doctor cobbles together a temporary working TARDIS out of spare parts. A companion lampshades that he accomplished this feat partly because he refused to even entertain the possibility that he couldn't.
  • Forever Knight: In one episode, a woman whom Nick Knight had dismissed as being a vampire because she'd been seen in daylight turns out to have a Split Personality, one of which was vampire and the other human. Dr. Natalie Lambert sees this as a good sign, and in an Amnesia Episode she's hopeful that if he doesn't remember he's a vampire he'll be cured, but it doesn't work out that way; he can eat solid food but is still scalded by sunlight and she has to tell him the truth.
  • In Good Omens (2019), when London is surrounded by a ring of hellfire along the M25, Crowley decides to drive right through it. Hastur is burned to ash almost instantly, but Crowley just keeps on driving, and the car manages to survive without melting to burst out of the wall of fire on the other side. Crowley just keeps telling the car that it can handle it. God's voiceover explains that, unlike every other demon, Crowley has developed an imagination over the 6000 years of living on Earth. So, as long as he's convinced that neither his body nor the car have been burned to a crisp by the hellfire, that is indeed what's happening. Plus, he's hurrying to save the world and, most importantly, his best friend, the angel Aziraphale.
  • In one episode of Haven, this trope mixes with Your Mind Makes It Real when a Conspiracy Theorist who believes in aliens causes Alien Invasion signs (i.e., Crop Circles, abductions, UFO sightings) to occur throughout the town.
  • In Lucifer (2016), angels all have a specific unique power that is based on who they are as individuals, such as the titular character able to draw out peoples' desires while his sociopathic twin brother Michael can identify peoples' fears.
  • Kaizoku Sentai Gokaiger has a mid-season upgrade unlocked this way:
    Gai: I don't really understand, but... when I imagined it, it came true! The first debut of this historic form! Go-on Silver and Go-on Gold! These two are a single Go-on Wings!
  • 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!"
  • In the TV miniseries Merlin (1998), 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.
  • In Merlin (2008), 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 Tinker Bell and making everyone clap for her.
  • Once Upon a Time in Wonderland: Referenced. Alice and Will clap in order to summon the fairy Silvermist to help them out when they need a ferry.
  • 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.
  • Quark: Parodied in "May the Source Be with You". To stop a Gorgon invasion, Quark is trusted with the Source, which can make anything possible as long as you believe in it. But as it's such a powerful weapon, the Source has been sealed up for 200 years and is now suffering from confidence issues.
  • It turns out that this is the case in Ressha Sentai ToQger. The Toqgers are children, given adult bodies to able to get the best of both worlds when fighting the Shadow Line: able to handle the darkness better and able to handle combat better of an adult while still possessing strong imagination of a child. This becomes somewhat of a minor plot point as it commented that if the Toqgers are continuously exposed to darkness the chances of being able to be successfully returned to their true ages will decrease.
  • The Sandman (2022): In "A Dream of a Thousand Cats", the Prophet's message is that the nature of reality can be changed more easily than people realize — if enough people, perhaps as few as a thousand, all dream the same thing at once, that will become reality. It's already happened once, creating the damaged and strife-torn world we inhabit, and the Prophet is trying to gather believers to make it happen again and create a better world (that is, one that's better for the Prophet and her followers).
  • Spoofed twice on Saturday Night Live
    • A season 2 sketch features John Beliushi as Tinker-Bee, who not only demands the audience clap to save him from dying... but also a standing ovation!
    • A Weekend Update segment in which Tina Fey and Amy Poehler receive a serenade from the little people who live under the desk. When the woman falls to the ground, the man declares that she has become seriously injured. He implores the reporters and viewers to help her, by chanting, "I believe in magic! I believe in love!" The little man then attempts to lead everyone in a series of gestures, which become progressively naughtier. Fey and Poehler become so disgusted with his motions, that they push him off the desk.
  • Shaun Micallef's Mad as Hell discusses this in a sketch where Peter Pan and Tinker Bell show up in the studio audience and explain this rule to Shaun (in reference to a slightly bizarre statement from Prime Minister Scott Morrison about believing in miracles). While most of the audience claim to believe in fairies, Shaun can't suspend his disbelief that far and apparently kills Tink by pointing out that she's obviously just Christie being filmed in front of a bluescreen and badly superimposed. And indeed, when Tink collapses in pain, Peter runs down onto the set and reveals that Christie and the bluescreen in question had been in plain view the whole time.
  • Stargate SG-1:
    • The 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 (such as when a man noted that his "god" was actually surprised at something), it's usually a sign that the Goa'uld is about to lose out.
  • Star Trek:
  • Supernatural:
    • One episode focuses on a spirit that was created (and maintained) by people's belief in it. Unfortunately, getting people to stop believing is not an option, as it had been posted online. The Winchesters are eventually able to stop it by creating a myth of its weakness, but Sam is left to wonder how many of the things they hunt only exist because people believe in them.
    • One episode has a kid who makes things he's afraid of real because he believes in them. He turns out to be The Antichrist, which makes him a Reality Warper.
  • True Blood:
    • Lettie Mae, Tara's mother, 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.
  • The Twilight Zone (1959): In "Ninety Years Without Slumbering", Sam Forstmann is convinced that he will die if his grandfather clock, which was given to his parents on the day that he was born, ever winds down as his father and grandfather had always told him as much. He becomes so obsessed with winding the clock that his granddaughter Marnie Kirk and her husband Doug send him to a psychiatrist named Dr. Mel Avery. Shortly afterwards, Sam collapses when the pendulum briefly stops swinging. Several weeks later, Sam's spirit appears to leave his body after the clock winds down. However, he has come to realize that Marnie, Doug and Dr. Avery were right all along. He tells his "spirit" that he doesn't believe in him and therefore he doesn't exist. Sam then tells Marnie that when the old clock wound down for the last time, he was born again.
  • The Twilight Zone (1985): In "Room 2426", Dr. Martin Decker is extremely skeptical of his cellmate Joseph's claim to be able to teletransport. Joseph assures him that he has been specifically trained and has done so many times. He explains that a person must believe that they are capable of teletransportation in order to do it. Subverted in that Joseph is a mole who tricks Martin into believing that they have teletransported to a safehouse. Double Subverted in that, after realizing the truth, Martin uses the power of his mind to transport himself to safety.
  • One episode of Wire in the Blood deals with this trope. The murderer of the story is thought by some people to be using magic. Tony Hill, however, knows that it's all in the victims' heads, and when the murderer is finally caught, she thinks that Tony is a powerful wizard because he'd been able to see through her "invisibility".

  • This is the entire theme in the music video for "Bury It" by CHVRCHES. Lauren's belief (with the support of her friends) enables her to gain telekinetic powers. Haley showing the other characters that she can fly enables them to do it. When Martin has a moment of doubt, he has a Die or Fly moment. He doesn't die.
  • Christian rock band Daniel Amos mocked the "prosperity theology" incarnation of this thinking (see "Other", below) in their song "New Car!" (from the album Doppelgänger). Televangelists preached that God would shower his followers with material wealth if they'd just believe hard enough; DA put this same message into the mouth of a crazed-sounding game show host, to make it sound ridiculous.
  • 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.
  • Nautilus Pompilius: In the song "Air", faith helps the lyrical hero walk in the sky.
  • Deconstructed in "Jabberwocky" by RedHook, which is about vocalist Emmy Mack's experience being sexually assaulted on tour in 2019. The song references the Jabberwock in Alice in Wonderland, which Alice defeats by convincing herself it doesn't exist, but unlike the Jabberwock, the trauma from her sexual assault is real, and attempting to convince herself it didn't happen doesn't help.
    Wake me up, 'cause this isn't real
    It's just a bad dream
    A cave in my chest,
    Hell freezes in my bloodstream
    But it's all in my mind
    'cause I don't believe
    In this Jabberwocky, Jabberwocky

    Myths & Religion 
  • Many, if not all, religions rely on this in their preachings to strengthen the faith of their followers. One of the more famous examples is the water walk scene in the New Testament.
  • 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 (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.
  • 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.
  • 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.
  • "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, based closely on Wattles' original text) and What the Bleep Do We Know by J.Z. Knight. Both films feature followers of J.Z. Knight's 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".
  • Somewhat related: Santa Claus is often depicted as "real for those who believe."
  • This is a common feature of New Age beliefs in general: visualization of mental images can be powerful enough to manifest desired outcomes. "Decrees and affirmations" are not just declarations of faith but recitations of things you want to have happen, as if they were already true. A cancer patient might decree, "I am free of cancer and perfectly healthy." 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 the core principle behind Christian Science. Diseases like cancer are an illusion and if you pray and believe in God enough you’ll be healed. Believers in this will sometimes refuse to be treated by doctors because of this belief — this generally doesn't end well for the believer. James Hetfield's mother was one such believer, and when she died after refusing to be treated for her cancer due to the belief that God would heal her, his anger about this would lead him to write "The God That Failed."

    Professional Wrestling 
  • In a general sense, all wrestlers run on this in the same way celebrities do - if people don't respond to their work, they're effectively useless to the company.
  • An angle in the early-to-mid-nineties where 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."

    Puppet Shows 
  • One episode of Fraggle Rock introduced a one-off character named Skenfrith, a small fuzzy creature 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 Wembley like him, think he's very cute and friendly... and that he loves to swim and sports goofy pigtails. When he starts swimming in the Gorgs' flooded basement, Ma hears something down there and thinks it's a giant, fanged, googly-eyed, two-headed monster. Guess what happens next.
    Skenfrith: [transforming] No, no! Don't turn me into a monster! I can't stand googly eyes and fangs! I hate being 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..."
      [Monster is now fifty feet tall.]

  • In Apotheosis: Aedificatoris In Absentia, miracles run on this. If a god's followers believe something, then (assuming the god is strong enough) he will gain it as a new miracle.
  • Vivian from Dawn of a New Age: Oldport Blues can warp reality, but it's directly dependant on her belief. If she believes enough that something is real, then it will be real. For example, believing that she could be as strong as Raven from Teen Titans ended up giving her Raven's stoic personality and magic powers.
  • This is the source of the supernatural in A Geek's Guide: DeathWorld Earth. Which has had bad results when monsters became fact.
  • The Murderverse: A Game Of Mafia takes place within the 'Ideaverse', a place where fictional beings gain power by being thought of, known and remembered. The whole game exists for Timeline Master Awe to be remembered... by traumatizing the participants of the game. This sends ripples throughout the entire 'verse — at the end of EXE 2, the Virus reveals that its primary motivation is to find the Ideaverse themself and usurp TM Awe, which is why they're hosting their own game—the remembrance would already be there by the time they would find it, and the Headmistress of Murder U has a similar motivation.
  • 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.

    Tabletop Games 
  • Ars Magica: Faeries are born from human legend and imagination, though they don't need human belief to survive. There are dark, dangerous forest faeries because people warn each other about the perils of the woods; a large mining community could give rise to a realm of underground dwarves; and so on.
  • 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.
  • Chronicles of Darkness:
    • 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.
      • Domains in the Temenos — the Dream Land of humanity's collective subconscious — are populated with "extras" that suit the local theme, such as generic nameless passers-by in an urban landscape. They usually have no real personality and minimal interactivity, but if visitors treat one like it's real, it slowly becomes more unique and free-willed, possibly reaching a point where it becomes a person in its own right.
    • 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.
    • 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?
    • Slashers are human serial killers who often end up developing supernatural abilties. One type is the Legend: a killer who's stories have become so believed in that they find themselves gaining the abilities and weaknesses from those stories, even if they never had them before.
  • 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.
  • Dungeons & Dragons:
    • Planescape revolves around the idea that belief shapes the planes. It can also quite literally move mountains, as the beliefs of the inhabitants of an area determine its 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.)
      • Most Mad Scientist characters in Ravenloft believe that their ability to craft golems, surgically sculpt Broken Ones, and so forth comes from their own scientific genius. Out-of-character materials for the setting suggest that they're actually tapping into the Land of Mists' supernatural tendency to grant villains whatever their obsessions drive them towards, which explains why such creations have so often Turned Against Their Masters: they're manifestations of their makers' failed Powers checks, hence always come at a price.
    • 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).
    • The insane Fish People known as Kuo-Toa have this as a racial ability, according to the 5th Edition Monster Manual. They make up their own bizarre deities based on random objects they find, and if enough Kuo-Toa believe in that god, it becomes a real being that grants their clerics genuine divine powers.
  • Fabula Ultima: Demons are born of human thoughts and beliefs. Even the dark thoughts of a single person are enough to spawn a lowly imp, and the Fabula Ultima Atlas: High Fantasy sourcebook suggests that the very gods of your group's campaign setting may be powerful demons born of widespread belief in a religion or state propaganda.
  • 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 "Übermensch" of genuinely superhuman ability.
  • GURPS:
    • Similar to the Doctor Thirteen example mentioned in the Comic Books folder above, one power available to players in GURPS Illuminati University 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 Nomine: Zig-zaggd.
    • 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), are populated by the power of human imagination with pagan gods and creatures of myth. Since the begins of the Marches are thoughts, archetypes, tropes and stories made manifest, they rely heavily on continued human attention for their continue existence, and the details of how they're perceived or described can significantly affect how they think, live, and act.
    • The Celestial realm, by contrast, is not affected by human belief — angels, demons, and their Superiors exist entirely independently of human ideas about or knowledge of them. This extends to human souls: spirits may anchor themselves in the material world or the Marches for a while, but ultimately everyone goes to the same Heaven or Hell regardless of where they think they are going to go.
  • Interstitial: Our Hearts Intertwined: The Memory playbook relies on this to survive — if it loses all its Links, which represent one's memories of another character — then everyone forgets about them and they cease to exist.
  • 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.
  • Little Fears: Your characters are children who have access to Belief magic, which gives power to childish fancy and superstition. For example, if a child honestly believes that their toy gun can shoot monster-melting lasers or that stepping on a crack can in fact break their mother's back, then that's exactly what will happen does. The older your character is, the less Belief you have.
  • 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.
      • This actually extends to when the normal people aren't directly observing a spell, too, the immediate impact just isn't as acute. The laws of nature aren't actually natural, they're a carefully constructed paradigm that the Technocracy taught to the Masses to create a unified Consensus on what is real and what isn't. For instance, there wasn't actually any such thing as gravity before Newton "discovered" and codified it: you accelerate at 9.8 meters per second per second toward the earth's surface because that idea is engraved on the Sleepers' minds by a Technocrat-run orthodoxy.
    • 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 fairy tales, changelings consider themselves to be an endangered species, and the discouragement of freedom and the imagination (known as Banality) is 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.
  • Warhammer 40,000:
    • All Orks subconsciously generate a mild psychic field, its strength proportional to the amount of Orks present. 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. The Ork belief that "da red ones 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 this ability 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 "shootas" 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 (although a Tech Priest in the group is still mystified that half of it works at all). 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 Guardsmen who will often loot Ork guns and use them, again with no problems. (These examples all feature the weapons being used against or at least in the presence of Orks, raising the possibility that they wouldn't work if the greenskins weren't there). The general idea is that Ork technology does work, and the Orks' psychic power simply makes it work better. The RPG systems went with this as well; in the hands of an Ork everything works fine, but if a human tries to use it the guns will be unreliable and more advanced or esoteric technology won't work at all.
      • This sometimes even works against the Orks. Their mortal enemy Sebastian 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...
      • It's gotten to the point where a common fandom joke revolves around both the Orks and their enemies exploiting this trope in hilarious ways - a squad of guardsmen are defending a point against a large wave of Orks, only to run out of ammo. Their commander decides to resort to Saying Sound Effects Out Loud by pointing his guns at the Orks and saying noises like "bang!" His men follow suit, and the Orks start falling over dead. And then suddenly a small squad of Orks suddenly comes running towards the group, and they seem to be immune to the "gunshots", only for the guardsmen to hear the Orks repeatedly chanting "I'm a tank! I'm a tank! I'm a tank!" note 
    • 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. And it's not always clear that the machine spirit isn't an on-board AI system. Maybe Magic, Maybe Mundane is a trope that a large part of the background runs on.
      • The machine spirits seen in some advanced Imperial technologies, like Land Raider tanks, Titans, and some of the older Legio Cybernetica robots, are described as complex computer systems, akin to an artificial intelligence (although they get around the Imperium's AI ban by not being fully sentient, and/or not being entirely mechanical). In simpler cases, it's hard to say if the machine has a literal spirit, or if that's just the Mechanicus' way of handwaving quirks that could be attributed to manufacturing variations, like a gun jamming slightly more often than others of its type.
    • 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.
    • Several Ecclesiarchal artifacts (usually the bones or personal effects of a dead saint) can bestow this upon its bearer provided that the bearer is faithful enough. Whether this is a direct result of the bearer's beliefs or if it's just some hidden piece of tech that the bearer is unaware of varies depending on the author. Unsurprisingly, the Adepta Sororitas are deeply tied to the Ecclesiarchy, which sometimes accounts for the "miracles" that happen. In one case the belief was strong enough that it rendered anything within the artifact's range of influence to be completely immune to plasma and fusion guns.
    • This is essentially the only hope of anything that's not a Daemon surviving for any length of time in the Warp. Since the Warp is literally a place powered by strong emotions, the only way to avoid being torn apart by its energies or the Daemons inhabiting it is to believe, without an absolute shadow of a doubt, that you can survive a place where Everything Is Trying to Kill You. The trick is the fact you need to keep believing this or else the protection goes away. It helps if you're also an extremely powerful psyker too, which gives you a better way of controlling your surroundings.
    • Daemons, on the other hand, require this to enter realspace, as otherwise they're stuck as formless masses in the Warp (although there is the rare time they find a powerful but weak-willed psyker to possess). However, once they enter realspace, they no longer need further belief to keep them going (and sometimes will happily murder those who just summoned them). This is why the Imperium and the Inquisition bans any knowledge on daemonic matter, even ones that would theoretically help in a daemonic invasion; the mere knowledge that Daemons exist can sometimes be enough to bring them into realspace.
    • It's implied that the universal belief in the Emperor's divinity within the Imperium is practically allowing him to ascend to godhood.
  • In RuneQuest, gods always exist in some form, because they're manifestations of universal laws like Heat, Truth and Plant(s) (the eponymous runes)...but their personalities change. And this effect is localized, as well as retroactive. So if your character gets stuck in a heroquest bubble where they-as-Chalana-Arroy fail to heal Orlanth's madness, the fact that the 'real', canonical version of Orlanth is a sane, kind person will not help.

  • 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. Tinker Bell's dead.
  • Peter Pan (1904) is the Trope Namer. Tinker Bell intentionally drinks a poison meant for Peter, and Peter appeals to children everywhere to invoke this trope. Naturally, 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 On the play's opening night, Nina Boucicault as Peter cried out "Clap your hands!" and the applause was so immediate and overwhelming that she burst into tears.
  • Peter Pan Goes Wrong plays with this. When the time comes for Tinker Bell to drink the poisoned medicine, the actress experiences an unscripted electrocution. Even though it doesn't look like she'll wake up, Tootles' actress attempts to pick up the script where Peter's actor left off, overcoming her own stage fright. As everyone either onstage or in the audience joins her in clapping while chanting, "I believe in fairies!", the noise surprisingly helps Tinker Bell regain consciousness.

    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 & Magick 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.
  • Word of God for Darkest Dungeon is that the Light, the main religion, is "Humanity's faith in delusions of its own making" - which is kind of fitting, given that Darkest Dungeon is a Cosmic Horror Story. In this case, it appears that humanity's faith in delusions of its own making is potent enough that the Vestal can heal wounds and call down the lightning on your enemies (even indoors), the Crusader is able to accuse people to death with a giant list and light up the area by producing a battle standard from nowhere, and the Flagellant's dedication to redemption through pain allows him to summon giant ethereal whips, transfer injuries from his teammates, and heal self-inflicted ones by constantly whipping himself.
  • Miracles in the Dark Souls series seemingly work this way, being tales of miracles and accomplishments performed by the gods, which grant their effects when recited by one with sufficiently high Faith. This implies that the strength of the miracle comes from how firmly the caster believes the events of the story actually happened.
  • In Digimon Survive, the Digital World is dependent on humanity believing that Digimon exist, and the Big Bad is an Eldritch Abomination created by the waning belief in the modern age. After Takuma temporarily returns to the real world with Agumon and Piedmon, pictures of them start going viral on social media, weakening The Master and giving the group the power to destroy him.
  • In Disco Elysium, this is one of the main principles of Nilsen's theory of infra-materialism, a form of communism. It states that the success or failure of a communist society is dependent largely on belief in communism—not just in a sense of patriotism and esprit de corps, but in a sense that communism literally warps reality to make its believers more successful. For instance, all things equal, a farmer who truly believes in communism will see greater crop yields than a farmer who does not. Because of this, communist societies that crumble invariably do so because their inhabitants just don't believe in communism enough. The main character can point out all the issues in this, naturally, causing its believers to admit that it's bordering on religious belief rather than socioeconomics. Yet despite the absurdity of the theory, the success of one event, involving getting an impossibly unstable structure to stay up, is dependent on how communistic your character has been acting.
  • Disgaea 4: A Promise Unforgotten offers a variation. The Netherworld is powered up by humans being afraid of demons but due to the constant wars in the human world, humans stopped fearing demons and became afraid of each other. This wreaked havoc in the Netherworld, with most demons losing their powers. Likewise, Celestia, realm of the angels, is powered by love and is also in dire straights as humans no longer pray to angels for protection and guidance.
  • 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.
  • Final Fantasy XIV: Similar to the FFIX situation above, this is what the Primals are. At first it's believed that the Primals are creatures of aether that are summoned (each beast tribe has its own Primal). But later, a bunch of moogles summon a fictional character from one of their stories, and everyone notices that it behaves just like a Primal. Still later, Ysayle turns herself into a figure from the past who united humans and dragons, Saint Shiva, and everyone once again notices that it behaves just like a Primal. And at one point, Gilgamesh simply reminisces about his friend Enkidu while in the presence of a cartload of crystals, which ends up summoning a version of Enkidu who behaves just like a Primal. Much later in the story, you meet Hraesvalgyr, a dragon who lived back when Shiva was alive, and Ysayle shows him her summon, at which he reveals that all primals are this: belief and faith given aetheric form by basically making a wish near a bunch of crystals. Primals will always be exactly what the summoner believes them to be. The Final Boss of the Heavensward expansion takes advantage of this to turn himself and his knights into Primals who are based on a Historical Hero Upgrade of Ishgard's founders, empowering themselves in part through a thousand years' worth of faith.
  • Fire Emblem: The Blazing Blade: Despite Religion is Magic apparently being the rule (your playable light magic user is also a priest in the setting's church), the existence of generic enemy monks, who presumably have no such affiliation, suggests this trope. It's clarified with Kenneth, a Bishop boss who has explicitly renounced the gods in favor of worshipping the main villain but is still perfectly capable of using light magic on you.
  • 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 (DS) 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 Granblue Fantasy, Zooey mentions that Primal Beasts are born from the people's desires or wishes. During the Fate Episodes of her permanent version, she has to "be one with the world" in order to prevent an oncoming threat that could end all life. Days past and Zooey never returned. Then Vyrn motivates the crew to wish and think for Zooey to come back, and she does.
  • 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 EarthBound Beginnings, 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 (1994), 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, 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.
    • Ouendan's destroys an asteroid about to collide with Earth.
    • EBA's crushes an alien invasion. Bonus points for featuring the cast actually clapping their hands because they believe. "I WAS BOOOOOOOOOOORN IN A CROSSFIAH HURRICAAAAAAAAAAAAANE"
    • Ouendan 2's reignites the dying sun.
  • 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 second installment of the spinoff Persona series takes this to far greater extremes, where rumors you start actually become true.
    • Persona 5 also uses this as a game mechanic - the main dungeons are based on how the villains see the world. Therefore, whatever they believe is true. This causes you to have to change what they believe in order to progress, such as entering a locked room in the real world so that the villain will see the corresponding door open in their Palace. How much ordinary people believe in the main cast is also important: when their belief rating hits 0%, the main characters stop existing; when it hits 100% belief, the protagonist is capable of summoning a Persona that's bigger than a skyscraper and powerful enough to headshot a god.
    • Shin Megami Tensei IV: Apocalypse specifies that only humans have this ability, which is why all those galaxy-suplexing gods are so fixated on a single blue speck with a bunch of bacteria-like shit-throwing apes running around.
      • Which directly contradicts Shin Megami Tensei II where the faith of the archangels running the town somehow managed to create a fantom YHVH who sanctified their actions.
  • 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).
  • SoulBlazer has the protagonist using the Dream Rod to travel into someone's dream, which take place in nearby real locations. Often, he'l be led to step on a floor panel that will open a nearby pathway. When he returns to reality and visits the same location of the dream, it will have changed in the same way.
  • This seems to be happening in the South Park videogames South Park: The Stick of Truth and South Park: The Fractured but Whole. In both games the premise is that the kids are engaging in LARP (fantasy themed in the first game and superhero themed in the second game). However, their attacks even seem to work against those who aren't part of the LARP, including aliens and eldritch gods.
  • 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.
  • Psychic Powers from Stellaris are implied to work that way in the Flavor Text of psionic technology. Spiritualist empires have an easier time researching these technologies... But the Flavor Text of technologies tend to be written from the perspective of ethics most associated with it (slavery related technologies' Flavor Text being written from the perspective of an Authoritarian). Materialists can only research psionics if they have a researcher with Psionic Expertise leading research, or have large populations with psychic powers living within their borders, the proverbial "extraordinary evidence" required to prove the "extraordinary claim" of psionics, and then they can use psionics just as freely as anyone else. In short, Spiritualists see Psychic Powers as faith made material, while Materialists see it as Sufficiently Analyzed Magic. We never learn whom is right on that subject, and even the devs will just give a Shrug of God about it when asked.
  • 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.
    • In some cases, even the inhabitants of Gensoukyou have stopped clapping their hands. E.g., things from the outside world sometimes slip through the barrier, and one of the things that slipped through in the past was a scientific magazine that explained how echoes are actually just sound waves bouncing off surfaces. As a result of people learning this, the Yamabiko, mountain-dwelling spirits born from humans ascribing echoes to the Yamabiko shouting people's words back at them, are currently facing extinction via Puff of Logic.
  • In Tyranny, the oldest Fatebinder theorizes that this is what turns people into Archons. She knew Graven Ashe before he became an Archon, and he didn't have the power to keep his men from dying. But he was a great leader who could inspire confidence and bolster his troops morale, and they would in turn fight harder than they would despite the odds against them. As his legend grew with his victory, more and more people believed in Graven Ashe's powers until his leadership literally turned into the Aegis. This may be why the two oldest Archons, Tunon and the Voices of Nerat, barely seem human anymore.
  • A cutscene in the first case of Unsolved: Mystery Adventure Detective Games states that the Slavic folklore creatures need human belief in order to exist.
  • In Yuletide Legends: The Brothers Claus Mrs. Claus states that if children stop believing in Santa then Christmas will never come.
  • 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.
  • Wintermoor Tactics Club: The Tactics Club members are not actually warriors and mages, but by using their imagination, they can channel their fantasy selves and treat the Snowball Fight competition like one of their games. This actually leads to them reaching the final rounds of the competition!
  • 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 (which often makes the crisis of faith worse), and people who commit atrocities can still access the Light if they believe they are acting for the greater good.

    Visual Novels 
  • When They Cry:
    • This is poor Hanyuu's dilemma in Higurashi: When They Cry, as lack of faith by the residents is the cause of her weakened powers.
    • In Umineko: When They Cry, 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.
    Web Animation 
  • Bung Chronicles: The entire universe runs on the Tinkerbell effect, to the point that even mythological characters can be seen alongside aliens.
  • Aurora: It's generally thought that when the Paladin Order was founded, the Light Dragon they worshipped wasn't real, but as the order grew, she came into existence as the embodiment of their beliefs. Erin, being a very scientifically-minded person, gets quite annoyed that the paladins cheated by making a theory that was definitely not true (the Light Dragon) true via insisting it was until they made their own proof. This is false. The Light Dragon is and always was real, people just thought she wasn't because she tended to be non-interventionist.
  • Dan and Mab's Furry Adventures:
    • The Fae kingdom 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.
    • This turns out to be the source of Biggs' true power: His Fae boon from Mab makes him as powerful as others think he is. If enough people think he can take on a dragon and win, he can. It also means he can simultaneously get smacked around by his sister, Wildy, who just sees him as her annoying sibling and herself as his equal.
  • 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 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.
  • In Fweeeeetopia, this trope is discovered early on to be a fundamental law of the universe.
  • Gunnerkrigg Court: Coyote is of the opinion that human belief created every supernatural entity, and is even capable of re-writing reality retroactively (allowing Coyote to exist long before his first believers). It is noted, however, that this is just Coyote's opinion: god or not, even he does not know for sure.
  • In Homestuck, Jake's Hope powers allow him to make things real by believing in them. In one case this results in the creation of Tulpa made of a Living Memory.
  • Played with in this Mac Hall strip.
  • The Order of the Stick:
    • Elan creates his own god, Banjo the puppet (so called because he has a banjo) for when he considers multi-classing to Cleric. When Roy tells him his opinion, Elan calls for Banjo to smite Roy. A tiny storm cloud appears and strikes Roy with a spark of electricity, which has no effect. Elan comments that maybe Banjo needs more believers. In a later story, Banjo actually did gain some more followers briefly, although they ended up worshiping another puppet instead.
    • This is also why Roy doesn't have the Greenhilt family sword in the afterlife. As his grandfather explains; "To me, it's my sword, so I have it. But to you, it's still my sword, so I still have it."
    • The goblinoid god The Dark One became a god after death from the devotion his followers had to his memory. The murderous rampage in his name against the nations that betrayed and murdered him that acted as a gigantic blood sacrifice to him also helped.
    • The nature of the setting's afterlives and how the gods operate in general is largely shaped by belief, even down to how the gods themselves look and what they're capable of. For instance, Thor claims that he used to have red hair before the the comic books popularised the idea of him being blond. As well as this, because he has a planetful of worshippers who see him as a Trickster God, Loki is physically unable to come clean and tell Hel that he's only acting against her plot to get all the dwarven souls in this world because there's a once-in-forever chance to stop the Snarl for good, no matter bad he feels to keep lying about it. He is allowed to be honest with Thor as long as it takes the form of rubbing things in his face.
      Loki: Half a billion people down there believe I'm incapable of honesty. Do you think I can just go against that when it's inconvenient?
      Thor: You're explaining it to me just fine.
      Loki: There seems to be some doctrinal flexibility when it comes to rubbing things in your face, specifically.
  • In Rhapsodies Peaseblossom, a pixie, claims it's all nonsense, but then she's trying to convince a human she didn't just break The Masquerade.
  • 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 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.
  • 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?"
    "That should do the trick."
    • There's also the dreamlike realm Gwynn is trapped in in "The Bug, the Witch, and the Robot" and the magical space within the Book of E-Ville shown in "The Immortal King", which are probably at least partly the same thing. In these, the environment keeps shifting based on the thoughts, mental state and deliberate manipulation of the characters within, and so do the characters themselves while there.
  • 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.
  • Subverted in 8-Bit Theater #490. It seems that Fighter manages to defy gravity because he thinks the team broke physics, causing Red Mage's brain to crash, only for it to turn out to instead be Sarda the Sage screwing with them.
    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)
    • Played a bit straighter with Red Mage's ways of avoiding damage, which appear to be fuelled solely by his belief that they make sense.
    Black Mage: We heard you die. was wonderful.
    Red Mage: Oh, that. I lost my pencil in the monster goo, so I never got to write down what the damage was.
    Black Mage: It removed your entire skeleton, RM.
    Red Mage: Bah. Skeletons are wholly vestigial, everyone knows that.
  • The first story in The Adventures of Dr. McNinja has the Doctor face off with Donald McBonald, an evil clown that turns out to be a mime. They fight by miming imaginary things that have real effects. The last story has them fight again, and this time it's said to work because they're in "mime magic zone". The Doctor foils McBonald's plan to blow him up by making him doubt whether it's possible to mime a bomb; the doubt of its creator causes the invisible mime stuff to vanish.
  • In Bruno the Bandit, a professional sceptic makes magical stuff stop working by questioning its possibility. He himself later figures out that the magic is real but depends on belief.
  • A core metaphysical law in the world of Kill Six Billion Demons. One specific example are the Magus Gates: The Universe is believed to be a story told by a very good liar known as YISUN, while individuals can alter YISUN's story on their own using The Art; The Keys are fragments of Their voice, and with them one's capacity for the The Art can grow to extraordinary heights.
  • xkcd: Beret Guy seems to somehow change the world around him to the way he naively believes it should work (as with his "business").

    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.
  • 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.
    • The tale Theology of a Snake features a dark deconstruction of this trope. The Ambassador could make the King of Alagadda divine by convincing the people of Alagadda to believe in the stories he told of the King's divinity. Unfortunately, this also meant that the Ambassador could manipulate the King however he wanted, simply by telling stories. The King lost interest in resurrecting his wife (the reason he wanted to be a god) because a god needs no wife, and he even killed his son because a god needs no heir. This ultimately became the King's doom, as the Ambassador had told a story that the God-King's journey to immortality would end when he hang from the highest tower, and placed on his spiked throne, leaving the Ambassador to be his herald to the people. And that's the story of the Hanged King.
  • A very oft-mentioned and popular theory by both characters and viewers of The Slender Man Mythos is that the man himself exists due to humanity knowing about him and the reason people are compelled to document him in blogs, journals, videos, art, etc. is to spread his influence. At one point, a bunch of blogs worked together to write stories in which they injured him believing that people would take these stories to be true and it would help bring him down. It didn't work. Some theorize that the mythos' popularity could lead to such a phenomenon occurring in real life.
  • The worldbuilding notes for Tall Tales explain that the metaphysical realm operates according to the thoughts and will of humans. It is therefore a consensus reality that can interact with the physical world to some limited degree.
  • 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.
  • 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.
  • Abandoned by Disney: The final story in the series interprets Disney's entire "when you wish upon a star" imagery and their works in general to be a way to experiment with, and harness this. They're convinced that, when people believe in something intensely enough, and in big enough amounts, it may just come to be. Problem is, Humans Are Flawed, and negativity tends to seep into these attempts and corrode them, or even create them in their entirety out of terrible thoughts. This is why their every attempt has failed: Things do come into being through belief, but so far, all those things have been flawed, negative, and entirely wrong.
  • The player character of Choice of the Vampire is only repelled by crosses and hallowed ground if they believe they will be — or, perhaps, if they don't believe they won't be.

    Web Videos 
  • 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 Channel Awesome 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.
  • In docfuture's hilarious "Let's Play Sonic The Hedge Hog 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.

    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 "Where Have All The Monsters Gone?", 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 Batman: The Brave and the Bold episode "Cry Freedom Fighters!", Plastic Man leads a group sing-along of (a mangled version of) "Yankee Doodle", invoking the spirit of freedom to revive Uncle Sam and turn the tide in the heroes' favor.
  • 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).
  • Danny Phantom: Ember, a ghostly rocker, gets more powerful the more her fans chant her name.
  • Earthworm Jim: Parodied in an episode 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?
    Peter: A few of 'em, most of them are just changing the channel.
    • And then there’s this lyric from the theme song:
    Jim can be a winner if we all just sing along!

  • An episode of The Fairly OddParents! had Timmy dealing with Mr. Crocker once and for all by getting him committed, his obsession with proving the existence of fairies cured. Unfortunately, it turns out that Fairy World powers all its magic on belief in fairies, specifically the belief of crazy people disbelieved by those around them, and Mr. Crocker was so crazy that they decided to power everything with him. Now Fairy World is without magic and slowly plummetting into Giant Bucket of Acid World, giving a time limit to Timmy trying to relapse Crocker into his fairy obsession without any help from magic. Once power is restored, they go back to drawing power from multiple nutjobs.
  • Mocked in Futurama:
    Bender: If you don't believe in him, he can't hurt you!
    Santa: (smack)
    Bender: Oh GOD, the pain!
  • Freakazoid!: One episode 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!

  • The Grim Adventures of Billy & Mandy: Inverted in one episode. 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.)
  • In He-Man and the Masters of the Universe (2021), it's eventually revealed by Orko the Great that anyone can use magic on Eternia. The trick is that you have to believe not only in magic, but that you can use magic.
  • Justice League: Wonder Woman, despite being super strong, sometimes exclaims "Hera give me strength!", at which point she shows off even greater strength that occasionally rivals Superman's. She even states that there were times that without her belief in Hera, she would not have been successful. Note that Hera is real in this universe, though actual divine intervention is left up to interpretation.
  • My Little Pony 'n Friends: In "Woe Is Me", Woebegone's curse is ultimately fueled by his belief in it. As long as he's convinced that he's unlucky, unlucky he shall be.
  • Phineas and Ferb: Parodied in the special "Summer Belongs To You" as everyone is preparing to jump an unfinished road on their bikes; when Candace doubts it, Phineas encourages her to not give up and believe in herself, and has everyone shout "I BELIEVE!", including Candace, and they safely jump the road and land back home.
  • The Real Ghostbusters: In one episode, 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.
  • Tiny Toon Adventures
    • An episode of revealed that laughter (or, perhaps more correctly, the Power Of Fandom) helped cartoon characters stay young.
    • It is revealed the classic gag of running onto air and not falling is because of this trope. The character believes they are on safe "ground" but looking down causes them to disprove it and gravity takes effect.
  • Total Drama: In World Tour, DJ accidentally destroys a mummified dog in Egypt and after a few incidents where he hurts animals, he starts to believe he's cursed. However, he only hurts animals when he believes in the curse, which is proved in "Jamaica Me Sweat". When he thinks he broke the curse (courtesy of Alejandro's trick), he doesn't hurt any more animals. When he overhears what Alejandro did, he starts to believe in the curse again and his bad luck comes back.
  • In Winx Club the Believix transformation's powers are amplified when humans believe in the Winx.

    Real Life 
  • Generally invoked by phony mediums, psychics, fortune-tellers and such charlatans 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. (In Modern Spiritualism, disbelief or skepticism won't stop real spirits from communicating, although they may get a little snarky.)
  • Most superstitions work this way. 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.
  • 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.
  • 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 the 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. 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.
    • There is one instance of rats 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.
    • More 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 the related nocebo effect which has been claimed as powerful enough to kill people.
    • This effect can get really interesting and weird: The placebo effect can happen even when people are TOLD it's a placebo!
  • 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 from 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.
  • Money itselfnote  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.
    • 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 truly fail, even if the original reason for thinking that that the bank was failing was completely false.
    • 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.
  • 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, muddies the waters.
    • 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). Scientists who study belief in magic have found the same thing to be true of people such as Australian Aboriginals-when cursed (at least in the past) they would worry themselves to death over it, or sometimes even die of heart attacks. It still only worked if they knew they'd been cursed, though that was enough. However, it failed to work on Europeans when they arrived due to their disbelief, much to the horror of the Aboriginals.
  • 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.
  • There are many, many things that are true because they are widely believed or felt to be true, or because people have widely accepted certain conventions. If the consensus or conventions changed, the statements would no longer be true. The example of money is above. Further examples: The correct adjectival term in Standard American English in 2016 for things related to France is French. The Nobel Prize is highly prestigious. Tickets to the NBA Finals are widely desired by many people. Aardvark comes before zoology in alphabetical order in English.
  • Fiction works like this too. Break the Willing Suspension of Disbelief and a lot of the magic drains away.
  • Technically speaking, colors like pink or white or even yellow don't exist. Human eyes have color receptors called cones in their eyes which detect the relative intensity of red, blue, or green in a given image. (This is why almost every modern display monitor, including what you're likely reading this on, is an RGB display; it's the same visual system your eyes use to denote colors.) Every other color is just the result of your brain mixing together the strength of each hue your eyes receive into a composite, like three separate snapshots of the red, green, and blue hues in an image superimposed on top of each other.
    • Color is a property that is difficult to describe in language without referencing examples of objects of that color. Describing the color "blue" often constitutes naming objects that are blue like the sky or blueberries; the color "orange" is named after the fruit, not vice versa, and many other names for colors are named after objects which match the color's shade and hue in the same way. This leaves a conundrum as to if any given color is the same visually for all humans, since language is limited in its ability to describe color without inadvertently referencing visual examples of that color.
    • This is to say nothing of the fact that colors are just parts of a narrow band of the light spectrum which humans see in, and thus x-rays and radio waves are as much of a "color" as green or purple is. The only difference is that they lie outside the visual spectrum, and thus appear invisible.
  • The fact that people's beliefs influence how they act, and by acting people can create things, means that in a very real way the belief in something can cause in to come into existence. The effect is generally much more subtle than it is portrayed in fiction however. And the opposite is almost as likely: there are many many cases of people inventing something in the process of trying to prove that thing wouldn't work. It is also true that people do not necessarily act on their beliefs, but are in fact very susceptible to social pressures: so it's relatively rare for this trope to occur even in its subtle form in real life. However, many modern technologies were first conceptualized in science fiction and then became reality almost solely because someone read the story and decided they were going to figure out how to make that cool thing a reality.


Video Example(s):

Alternative Title(s): The Power Of Imagination, Tinkerbell Jesus, Clap If You Believe


We Care

The Care Bears, John, Dawn, and even the villain Dark Heart put all their love and caring together to save Christy.

How well does it match the trope?

5 (9 votes)

Example of:

Main / ClapYourHandsIfYouBelieve

Media sources: