Puff of Logic



"Now it is such a bizarrely improbable coincidence that anything so mindbogglingly useful could have evolved purely by chance that some thinkers have chosen to see it as a final and clinching proof of the nonexistence of God. The argument goes something like this: "I refuse to prove that I exist," says God, "for proof denies faith, and without faith I am nothing." "But," says Man, "the Babel fish is a dead giveaway isn't it? It could not have evolved by chance. It proves that you exist, and so therefore, by your own arguments, you don't. QED." "Oh dear," says God, "I hadn't thought of that," and promptly disappears in a puff of logic. "Oh, that was easy," says Man, and for an encore goes on to prove that black is white and gets himself killed on the next zebra crossing."

- The Hitchhiker's Guide to the Galaxy

One of the nice things about reality is that a person's existence is not decided by consensual agreement, worship, or logic.

Except when it is, and then you disappear in a Puff of Logic.

Maybe the characters live in a world where Your Mind Makes It Real, or they have advanced Reality Warper powers, failing at logic can be fatal, or most likely the author likes a good laugh. Whatever the case, a convincing argument can make anyone cease to exist and simply disappear as if they never existed. However, this doesn't necessarily erase the character's prior existence up to that point; see Ret-Gone for an instance when a character's entire past gets expunged as well.

Compare The Centipede's Dilemma, Gravity Is a Harsh Mistress and Talking the Monster to Death. Contrast Self-Inflicted Hell, where a character is in Hell simply because he or she believes they are. Also contrast Clap Your Hands If You Believe, in which blind faith manages to make something work or exist where it shouldn't. See also Too Spicy for Yog-Sothoth variant where a character is too dumb to believe in what's attacking him. Can be the end result of a Logic Bomb. Super-Trope to I'm Not Afraid of You. In particularly absurd circumstances, might happen immediately after a character has proclaimed: "This Cannot Be!!"

Expect some unmarked spoilers ahead, as this can obviously be a perfect mechanism for winning, say, The Final Battle.

Advertising

 * This Skittles commercial. Three teens sit on a rainbow and enjoy their Skittles while looking down below: Teen #1: "Hey, what if this rainbow doesn't exist and it's just in our imagina-" the rainbow opens under him and falls out of the sky in mid-sentence while the other two teens look on, followed by the slogan "BELIEVE THE RAINBOW! TASTE THE RAINBOW!"

Anime and Manga

 * This is pretty much the entire premise of Noein.
 * This is more or less how the mighty Alucard met his demise.

Comic Books
"Hobbes: Another casualty of applied meta-physics."
 * A duplicator story in Calvin and Hobbes ends this way. Calvin made a "good clone" of himself to dupe into doing his work for him, and proceeded to get into an argument with him. As soon as the good clone had a bad thought, it disappeared.

"Rebis: I've come to ask the question. One of you must have the answer. Why is there something instead of nothing? Priest in Black: I am a liar and I do not know why there is something instead of nothing. Priest in White: I am an honest man and I do not know why there is something instead of nothing. Rebis: Tell me then, the Priest in Black, why is there something instead of nothing? Priest in Black: There is something instead of nothing. Rebis: Then you can't possibly exist."
 * Oliver Wendell Jones creates a math formula which explains the existence of everything everywhere...except penguins. Opus disappears, and then reappears when Oliver notices a mistake in the formula and rewrites it.
 * In Grant Morrison's Doom Patrol, the metafictional world of Orqwith disappears from reality when Rebis exposes the contradiction at its heart (based on a Raymond Smullyan puzzle):


 * One Nodwick story sees the party 'defeat' a lich by smacking it in the head with a magic club that makes you smarter (called, predictably, the "Clue-By-Four"). The lich, realizing that its status as The Undead only prolongs its own agony and causes it to lash out on others thus making the universe a slightly crappier place to live, promptly reasons itself out of existence.

Fan Works

 * Happens in the The Lord of the Rings Parody Sue fanfic The Game of the Gods.
 * Mentioned in Unfamiliar when Alex tries to dispel Louise's notion that she is incapable of magic.

Film

 * At the end of The Flight of Dragons, the main character defeats the Big Bad wizard by telling him magic is impossible. Without belief, magic doesn't work and knowledge of science is incompatible with belief in magic.
 * In The Pirates! Band of Misfits, The Pirate Captain boards a ship only to find it's a ghost ship. Once he realises the ship isn't solid, he falls right through it.
 * In the movie Cloak & Dagger, Davey has Jack Flack, an imaginary spy that helps him out throughout the movie. After Jack convinces Davey to shoot a bad guy that was trying to kill him, Davey stops believing in Jack, and Jack just fades from existance.

Literature
"Belafon sat down with his feet dangling over the edge of the rock. "Look, don't worry," he said. "If you keep thinking the rock shouldn't be flying it might hear you and become persuaded and you will turn out to be right, okay? It's obvious you aren't up to date with modern thinking"."
 * The Trope Namer is The Hitchhiker's Guide to the Galaxy, where God's existence is disproved because the Babel Fish is just too handy to have evolved naturally. Since God exists because Faith needs no proof, any proof such as the Babel Fish would cause God to vanish "in a puff of logic." The book then says that this argument has been nearly universally rejected on the basis that it is profoundly stupid.
 * It didn't stop Oolon Coluphid from making a nice bit of lunch money writing a book about it himself.
 * Fairies in Peter Pan are killed off by someone denying their existence.
 * Arguably, this is more a case of Gods Need Prayer Badly. There is no logical explanation of why fairies can't exist, just a statement of disbelief.
 * In his Meditations on First Philosophy, Descartes actually invokes this by noting that if he wasn't thinking, then perhaps he would not exist.
 * He goes on to state that, regardless of what else he may be wrong about, he must at least exist in the capacity of an entity that is capable of being wrong; if he doesn't exist in at least that capacity, then it's not his problem.
 * Discworld all over the place. e.g. with Belafon the druid with his flying rock in The Light Fantastic.

""It is a slightly arresting notion that if you were to pick yourself apart with tweezers, one atom at a time, you would produce a mound of fine atomic dust, none of which had ever been alive but all of which had once been you.""
 * The auditors believe that because mortals have a finite life and that anything finite is insignificant compared to the infinite length of the universe, to develop a personality is to become mortal is to die. Any time an auditor starts using the first person, you can bank on it evaporating in a blue flame very shortly. The narrative notes that this isn't entirely logical, but the auditors self-destruct too quickly to catch on.
 * Then there's that genie in Sourcery. The characters wish to go someplace. Cue them all sitting inside the genie's bottle for the ride. . . .while they themselves are carrying it. The entire setup was banking on the universe not noticing what they were doing, which backfired once one of the characters pointed out the conundrum. Puff of Logic ensues.
 * In The Pedant and the Shuffly by John Bellairs, persuading hapless passersby that, logically speaking, they don't exist, is the wicked magician Snodrog's favorite trick.
 * In Fight Club,
 * That's in the book. In the movie,.
 * In the Nightside novels, Tommy Oblivion, the Existential Detective, can cause things like this to happen. On one occasion, he immobilizes a couple of ambulatory statues by explaining all the reasons why it should be impossible for them to move.
 * In the Fengshen Yanyi, a certain Bi Gan was coaxed by Daji to have his heart removed. He managed to survive without his heart until he was said that no one can live without a heart. He then collapsed and died.
 * The Dresden Files: Ghost Story has a non-fatal example. Harry, who is a shade, is riding in a car. It occurs to him that, as a ghost, he is capable of moving through solid objects such as walls. This causes him to wonder what's keeping him in the car -And as soon as he starts thinking this, he immediately slides through and out of the car. Ghosts in the Dresdenverse get most of their abilities through perception; since Harry had seen other spirits move through walls it became something he associated with them being able to do. Cars, on the other hand, he thought of as solid, because he rode in them often when he was alive. As soon as he started doubting whether or not it actually was, it ceased to be (at least to his spirit form).
 * In the opening chapter of Bill Bryson's history of science A Short History Of Nearly Everything the author invites the reader to consider the molecular reality of their existence:

Live Action TV
"Tenant Whew, that was close."
 * In the Bottom episode where Richie and Eddie are trapped on the collapsing Ferris wheel, God saves them from falling at the last moment. But then they remember that they're atheists, conclude that they must be hallucinating, and...
 * A Monty Python's Flying Circus sketch had an apartment building built using the power of hypnosis. It would only remain standing as long as the tenants believed it was the best housing available. When interviewed, one of the tenants mentions that they used to live in a villa overlooking Nice. When the interviewer comments that the villa sounds much better, the tenant realizes it's true...and the building starts to shake. Fourtunately,the man says "NO! NO! OF COURSE NOT!" Then the building changes back to normal, although some of the furniture (and the tenant) were a little shaken.

"Directed by Steven Spielberg. A crippled WW 2 bomber returning to base no longer has landing gear, and the turret gunner is trapped under the belly, facing an agonizing gory death when they land without wheels. He desperately draws cartoon tires (a la Who Framed Roger Rabbit?) but is running out of time."
 * In a Sherlock Holmes sketch, Holmes stands up to being shot with his own gun several times, then explains that he'd had Watson load the gun with blanks. However, Watson then admits he forgot to change the bullets, and Holmes notices the huge amount of blood on his chest. He dies soon afterward.
 * Another Pythonic version of this trope was a short animation by Terry Gilliam of Rodin's The Thinker coming up with Descartes' "I think therefore I am." in a thought balloon. When a hand comes from off screen and deflates the balloon with a pin, The Thinker looks up briefly in horror, then disappears.
 * The final episode of Blackadder the Third has Prince George getting shot, then rising alive and well due to a Pocket Protector. When he attempts to show it off, however, he can't find it, remarks "Damn, must have left it on the dresser this morning", and promptly dies.
 * Done in the second season of True Blood in the case of the Nigh Invulnerable ancient Maenad, Maryann Forrester. It's revealed by vampire queen Sophie-Anne that Maryann's powers are directly tied to her beliefs, stating everything in the universe imagined itself into existence. Thus by believing in her god Dionysus and becoming a maenad she was immortal. In the end Sam tricks Maryann into believing her god has returned from her sacrificial ritual by Shapeshifting into a bull and then impaling her in the chest. She is surprised when this happens, but rationalizes that if she is the final sacrifice for her god to come into the world, then she will accept it. She's shocked again when Sam morphs into his human form, questioning if there was even a god. This moment of vulnerability allows Sam to rip her heart out of her chest and crush it into the ground, finally ending her reign of hedonistic Mind Control.
 * Which raises the question, if Maryann could make herself invulnerable simply by believing in her god, then wouldn't a human be able to make himself invincible if he believed in their own religion like Christianity? And also, how did everything in the universe imagine itself into existence? Did some random thought just pop out of nowhere and everything came to be?
 * The episode "The Mission" from Amazing Stories. Here's the description:


 * The Mark Steel Lectures profile of Rene Descartes (see above) includes a spot where Mark invites the audience to stop and think about whether they actually exist for twenty seconds (with "Life is But a Dream" playing behind) ended with a buzzer and the message "Stop Thinking Now!".

Tabletop RPG
""I cast a shadow fireball." "I make a will save to disbelieve." "Good. Take 150% damage.""
 * The Dungeons & Dragons second edition Sourcebook Tome of Magic has a spell called Solipsism, which can create illusory objects that behave exactly like real ones—but only if you believe they are real. If you don't believe in it, you'll fall right through that bridge the cleric conjured. This is loosely based around the philosophy of solipsism, which posits that the only thing one can be sure exists is himself, and therefore one's perceptions define one's reality.
 * It also plays with this trope with the spell Shadow Conjuration. It summons quasi-illusory monsters that are as powerful as the real thing if you believe they're real, and one-fifth damage if you don't.
 * And, like all things D&D, it can be whored to ludicrous lengths. One prestige class specialises in shadow illusions. Layer enough "reality"-boosting effects, and you can create illusions more real than reality. Cue humorous conversations:


 * And yes, there are players who will attempt to believe the illusions they themselves created, to make them "real". "What do you mean I can't live off illusory food? I deliberately failed my save!"
 * The RPG TORG had the fantasy world of Aysle, where the local laws of reality stated that Your Mind Makes It Real to the extent that real people could cross a sufficiently convincing illusionary bridge.
 * Planescape, as a setting governed by Clap Your Hands If You Believe, has numerous examples of this. Willing yourself out of existence is one of the few non-ending methods of permanently dying.
 * The 3E Ravenloft description of Lamordia, land of mad scientists and skeptics, describes an optional phenomenon called the "Smothering of Reason", where Lamordians' prevalent disbelief in the supernatural occasionally causes spells to fail, magical creatures to weaken, etc.
 * The Illusion advantage in GURPS has an upgrade that allows it to cause small amounts of damage if the victim is convinced it's real.
 * The spell Solipsism causes you to assume you're the only thing that's real and the guy swinging a sword at your head won't really hurt you.
 * Another solipsism reference, from Scion: the Knack Solipstic Defense allows you to ignore an attack entirely by believing it isn't real - since you have Legend, an element of the divine, what you believe goes. But you can only muster that much belief once a scene.
 * Of course there is the other requirement for using the power, namely that you are unaware of the attack.
 * Aten, sole avatar of Akhetaten, The Titan of Light (having devoured all the other avatars, who were not worthy of existing compared to his glorious self) is has a version of this. He is so certain of the fact that his existence is the only one, the he is completely and utterly immune to any source of damage from anything. Your only hope of defeating him is to first debate him philosophy and theology really, really, really well. It's also heavily implied that he is the one God of monotheism. Make of this what you will.
 * Pretty much the point of Mage: The Ascension, and to a lesser extent Demon: The Fallen. You can perform amazing feats as long as you keep them believable, such as conjuring money from your wallet, or causing lightning to strike during a thunderstorm. If you strain disbelief too much, or simply don't care and go all-out, it might still work, but you have a pretty good chance of getting smacked around by the universe at large on grounds that Magic Does Not Work That Way. This is true even if there's nobody watching, although it gets worse if there is.
 * The setting explains that the main antagonists, basically The Men in Black, came into power through a centuries-spanning Gambit Roulette of convinving the world at large that no, brooms can't fly, and that yes, you can heal people by injecting them with complicated chemicals. They have actually caused mythical creatures like unicorns to go extinct by making people stop believing them, and caused places like El Dorado to cease to exist by creating maps to prove they weren't there.
 * There are some areas in the world where people still cling to their old beliefs, and thus the effect is reversed. In certain secluded spots in the Middle Eastern deserts, flying carpets and genies are considered normal, whereas airplanes are considered "vulgar magic" and a violation of common sense, and stop working as a result.
 * It's worth pointing out an additional detail of the Mage: The Ascension setting, which is that there is absolutely no difference between Science and Magic. Science is just Magic that most people believe in, and therefore everyone can use. The various "Mystic" factions are trying to reverse this trend by getting people to believe in their path instead of Science. They're not having much luck with that.
 * Also, Toon. Similar to the Wile E. Coyote example under cartoons, this RPG actually does allow your character to walk on air as long as you don't realize you're doing so. As soon as you make your spot check, you fall.
 * In Genius: The Transgression, the inventions of Geniuses are literally powered by their creator's madness. If these creations are scrutinized by Muggles, these devices will stop working. Of course, that's the best case scenario.
 * In Macho Women with Guns, the Batwinged Bimbos From Hell can learn the "Distort Reality" skill; when they are attacked, they can focus their attention on something else (their nails, a run in their stockings, a cloud, etc) and since they've forgotten the attack, it can't hit. It will instead target one of her allies, who might not appreciate the gesture.

Theatre

 * A variant happens in Gilbert and Sullivan's Ruddigore. The Baronetcy of Ruddigore is cursed - its occupant must commit a crime every day, or die, dragged off by the ghosts of those previously killed by the curse. Until, that is, the current Baronet realises that suicide itself is a crime, and since not committing a crime is tantamount to suicide, this too counts as a crime. Therefore, none of the people killed by the curse should have died; as soon as this is realised, the former Baronets simply pop back to life, just in time to Pair the Spares with the female chorus.

Video Games

 * Divine Divinity had two skeleton Mooks discussing the scientific impossibility of their very existence. One of them remarks that realizing the truth would be quite unpleasant and the other agrees to drop the issue. Still, the seeds have been planted and they both collapse immediately after.
 * Planescape: Torment. Being set in Planescape (mentioned above), everything works this way. Several notable examples include:
 * The Nameless One recovering a memory in which an earlier incarnation manages to prove to a Sign of One devotee (a sect of solipsists) that he does not actually exist... Said man then disappears, much to the delight of the crowd who has gathered to watch the debate.
 * If the Nameless One gives his name as 'Adahn' frequently enough, a man named Adahn actually appears in-game. He only exists because the Nameless One's been claiming to be him, after a fashion, and if you point out as much to him... poof.
 * At one point, the current incarnation is able to do this to if your WIS score is high enough.
 * In Flight of the Amazon Queen, you encounter a gorilla blocking your way. How do you get rid of it? By telling it that gorillas only live in Africa.
 * In the first third-season episode of Sam and Max, if Sam looks at a readout on one of Mama Bosco's computers, he will say that according this they should not exist, at which point both characters disappear for a few seconds before coming back. Given that they are a talking dog and a rabbit-like thing, the readout is partially true. On the other hand, their entire world runs on the Rule of Funny.
 * In Silent Hill 1,  disappears in a puff of blood when she realizes that she is the same as the other monsters around her. And Then John Was a Zombie.
 * Super Scribblenauts allows the player to summon various deities. It also allows you to summon an atheist who upon seeing a god will immediately start displaying the "thinking" icon and run towards it, causing the god to die on contact.

Visual Novels

 * Almost happens twice in Umineko no Naku Koro ni episode 4. The first near-Puff of Logic is actually suicidal in nature. The second is not, but it's quite a bit more brutal than a simple "puff".

Web Comics
"Wonderella: You are blue. WHITE SPACE Oh dear. *pop*"
 * This 8-Bit Theater strip. (Incidentally, Red Mage tried this much earlier on a giant, and failed miserably.)
 * Red Mage also uses similar reasoning in a later strip to deny the existence of 'Megahedron', his supposed avatar of the gods, claiming that it is really just a figment of his own imagination. His reasoning was that, if Megahedron was a figment of Red Mage's own mind, then he'd be smart enough able to convince him of his existence, a task at which he had so far failed (Megahedron's own suggestion). And when Red Mage conceded that point, he went on to say that since Megahedron had convinced him with that argument, then that means that Megahedron is a figment. The only problem with that (which RM is too busy ignoring Megahedron to listen to) is that by that logic, Megahedron did not convince him. So that should convince him, which should not convince him, which should and oh dear, I've gone all cross-eyed.
 * He encounters a similar situation during his trial for class promotion. He encounters a monster who keeps outwitting him. He "defeats" it by admitting that he has failed and cannot beat it; the whole purpose of the conflict was to teach him humility. As soon as the monster leaves, however, he assumes that he subconsciously outsmarted the ordeal and learns absolutely nothing.
 * Captain SNES attempted this three times... twice in canon and once as a side-story. The first In-Canon attempt failed miserably, while the side-story one succeeded. The second time in canon, the victims did it to themselves accidentally.
 * Stickman and Cube did this in the early "Cube Disappears" arc, which ended up creating the comic's first recurring villain.
 * Sluggy Freelance: This is how Bun-Bun exorcised the ghost of Ayn Rand from Kiki here.
 * No surprise here: the guest comic is courtesy of Bruno the Bandit creator Ian McDonald, who loves this trope.
 * The Order of the Stick #585: Vaarsuvius attempted to use his Common Sense to aid in the Banishment of an enormous devil which was in clear violation of the Square-Cube Law. Didn't work.
 * Another comic (#321) has the team's horses and riding dog disappear when Elan points out that they shouldn't be there. Only Durkon's pony, who had every right to be there, remained.
 * Wonderella beats WHITE SPACE this way:


 * PvP has Scratch Fury succeeding exactly where Red Mage failed in this strip. To be fair to RM, he didn't think to write up the equation beforehand.
 * And he does it again, to a chimera this time, in this strip. This time, however, it doesn't go off until he corrects an error in his equation.
 * It occurs in this Sverd Shelgr strip, though it's more of story mechanics than true logic.
 * El Goonish Shive: Melissa attempts to deny a portly dragon its ability to fly, only to find that "'The Flight of Dragons' rules don't apply" in her Verse.
 * In Goblins, one of the alternate universe Minmaxes (nicknamed Psimax) tries this on the Universe using some Insane Troll Logic.
 * In The Adventures of Dr. McNinja, the good Doctor is knocked out at his parents' house, and his family is kidnapped. When he awakens, Doc discovers that the (cooked) turkey they were going to have for dinner is now walking around and talking. He correctly surmises that this is a hallucination brought on by his injuries and guilt over endangering his family. After he leaves to go save them, the turkey continues to move and speak for a few seconds, before realizing that it can't do so when no one is around to hallucinate it. It promptly falls over, inert.
 * Happens here in Scenes From A Multiverse.

Web Original
"Please refrain from reminding the agents that this is chemically impossible. They already know that, and they don't care. However, if you remind them of this, it may stop working. Then they would have to kill you."
 * Protectors of the Plot Continuum take Bleeprin, a mixture of aspirin and bleach, to ease the pain of working with bad fanfic. The Board Constitution contains a clause which reads thus:


 * In this parody of Kingdom Hearts known as Kingdumb Hearts, Goofy asks if The Heartless have no hearts, how can they live..
 * In his review of Azumanga Daioh, The Banjo Kid muses over whether or not it's possible to expect to be disappointed, promptly causing the world to explode.
 * In Eddsworld, the three main characters get a car and get it to fly by "using the Z-Gear of course". It goes up to very trippy music in which Edd and Tom start dancing in the car. Matt then shouts "how can a car fly?" It then falls down to land on top of a plane. This trope is then inverted when the pilot wonders whether his plane can fly. Then this continues and when the car gets there, several planes are now below them (each having doubted their flying capability).
 * 5-Second Films gives us an example in the form of a mailman working on the wrong day.

Western Animation
"Foghorn: ...No, I'd better not look - I just might be in there."
 * Looney Tunes:
 * Averted, or at least avoided, in Foghorn Leghorn cartoon "Little Boy Boo". While playing hide-and-seek with Junior, Foghorn Leghorn hides in a feed box, claiming the kid would need a slide rule to find him. Junior writes out some equations, using a slide rule no less, then marks a spot before somehow digging Foghorn up from it. This leaves Foghorn irate, at which point the child shows him the equations; forced to admit that "figures don't lie", Foghorn is nevertheless curious and makes to open the lid, but stops himself midway through.

"Tennessee: No, you just think I'm dead. Abe: No, you're dead. I was your biggest fan. Look, I clipped your obituary. Tennessee gasps and turns to dust."
 * SpongeBob SquarePants:
 * In "Life of Crime", as Spongebob and Patrick are keeping warm with a fire, Patrick questions how they have a fire when they're underwater, and it immediately goes out.
 * An episode of Histeria! had the kids annoying Rene Descartes ("I Think, therefore I Am") so much that he couldn't think. As soon as he realizes this, *poof* ! This is a riff on a summary of Decartes's argument for existence: "I can doubt everything except that I am doubting. Doubting is a type of thought. I am thinking, therefore, I must be existing."
 * In The Simpsons, Grandpa sees Tennessee Ernie Ford, an old celebrity whom he believes to be dead:

"Franklin: Wait a minute... penguins can't fly... PENGUINS CAN'T FLY! *the plane immediately nosedives*"
 * An episode of Chowder. "No. You're not in this episode."
 * In the final episode, Chowder becomes so smart that he realizes that he is in fact in a cartoon. The show is promptly canceled.
 * The Phineas and Ferb episode "Phineas and Ferb's Quantum Boogaloo" has the Bad Future version of Candace disappearing in one of these after Phineas points out she'd be gone after the two Candaces undid that future. Also earlier in the episode (...or, alternately, twenty years later), Candace climbed a holographic tree and stayed in the air until she remembered it was holographic, at which point it turns static and she suddenly fell.
 * In the Powerpuff Girls musical episode, a gnome takes their powers to take the evil out of the city. Later, they regained them after learning that the gnome was being a communist by feeding off the wants of the people to thank him from that point on and forcing them to worship him. When they fought him later, they win by singing about how everything needs its opposites and chasing him off the edge of a giant vine. He then went into a non-singing speech saying "As I fall towards the earth, seeing the universe above me, I learn that life evolves, revolves, and dissolves completely around its opposites. Therefore, I conclude that I cannot exist in my utopian mind." When he hit the ground, all the lines became white and the colors became black, and he became a silent explosion.
 * An episode of El Tigre had Frida defeat a skeleton by pointing out there was noting holding it up, causing it to collapse.
 * During the intro to an Arthur episode, Arthur is talking about the upcoming story while Francine is flying around in the background. At the end of the intro Arthur turns around and yells to Francine that flying around like that is impossible. She immediately crashes to the ground.
 * Bender attempts to invoke this in Futurama with the Robot Santa. "Come on, everybody! He can't hurt us if we don't believe in him!" It doesn't work.
 * The Critic episode in which Jay and Margo send their parents on a vacation for their 50th anniversary and they wind up on a dilapidated airplane flown by an alcoholic penguin.


 * In the Super Secret Secret Squirrel episode "Quark", a sub-microscopic supervillain named Quark plans to flatten North America by "pulling out the bottom atom" of everything to make it all collapse, to make room for his own amphitheater (Canada) and a parking lot for it (the US). Secret Squirrel shrinks to subatomic size and lures him onto a dictionary, then points out the dictionary defines a quark as "a hypothetical subatomic particle". Secret manages to make the villain doubt his own existence enough that he vanishes into thin air.

Jokes
"Two men are standing on a skyscraper. Suddenly, the first one jumps down. The other one expects him to die horribly, but to his surprise, the first guy just bounces off the pavement, bounces a few more times, until he comes to rest. The second guy inquires how this is possible. The first guy explains: "It's all in your mind. You just have to think you're a rubber ball, and you will bounce just like a ball." "And everyone can do that?" "Yes, everyone, it's the easiest thing. Try it." The second man is curious and really makes the jump. All the time while he's falling, he thinks "I'm a rubber ball, I'm a rubber ball". Then, shortly before hitting the pavement: "But if I was a tomato?" SMASH!"
 * Old joke:


 * Inversion Punchline: "You're such an asshole, Superman."
 * Descartes walks into a bar, the bartender asks him what he wants, and he orders a beer. He drinks it, and the bartender asks him if he wants another beer. Descartes says "I think not", and disappears in a puff of logic.

Real Life

 * Logical positivism asserts that only statements about empirical observations are meaningful, effectively asserting that all metaphysical statements are meaningless. Unfortunately, this fundamental tenet of logical positivism belongs to the family of statements that it asserts to be meaningless. As a result, the entire edifice of logical positivism vanishes in a puff of logic.
 * Likewise, a true nihilist must believe that nihilism itself is as meaningless as all other supposed truths.
 * As evidenced here.
 * Eh, doesn't matter.
 * Several other belief systems have this characteristic.
 * According to the Jargon File, Schroedinbugs are bugs in which a program works fine until someone looking at the source code realizes it shouldn't work, at which point it stops working.
 * This actually does occasionally happen, mostly because it only works because of some strange bit of junk data lodged in the memory it references. When the program is edited, it references something else, which means that the little bit of randomness that made it work isn't there anymore.
 * It's common to wake up from a dream when you realize that you're dreaming.
 * If you manage to stay in the dream however, you can take over the place.