History Main / LanguageOfTruth

Compare CannotTellALie, in which the inability to lie is inherent in individual characters. Works using this trope will often discuss ThePowerOfLanguage itself.

* ''Webcomic/{{Outsider}}'': Communication done through ''sanzai'', the telepathy of the Loroi, is immediate, clear, and absolutely honest. Some Loroi prefer to use it exclusively, feeling that spoken and written language are inherently dishonest and untrustworthy. The issue is that ''sanzai'' is so absolutely truthful that it will not mask any nuance or feeling, meaning that it tact is also impossible. Loroi diplomacy thus relies on specialized diplomats, who speak to one another verbally, while everyone else holds their tongues and keeps their thoughts to themselves... literally.

A Language of Truth is a particular language or form of communication in which lies are inherently impossible or inexpressible. This is a frequent feature of {{Telepathy}},[[note]]because, as [[HighMiddleAges scholastics]] said, lying is saying one thing and thinking another, so you can't lie if you think and speak in the same act[[/note]] but it can also appear for more overt languages. A LanguageOfMagic may be this or, slightly differently, it may ''cause'' anything said in it to ''[[RewritingReality become]]'' true - this is known in RealLife as "magical notion of truth" . Beware, of course, the ConsummateLiar who is either outright immune or uses ExactWords and other forms of deception to get around this inconvenience.

A RealLife Language of Truth [[http://www.crockford.com/wrrrld/wilkins.html can't]] [[https://secure.wikimedia.org/wikipedia/en/wiki/Russell%27s_paradox possibly]] [[http://en.wikipedia.org/wiki/Gödels_incompleteness_theorem exist]] - not if you want it to be able to express ''every'' true statement. Consider:

* Telepathy functions this way in ''ComicBook/ElfQuest''. Unfortunately for them, the BigBad's mind is so malicious that it's literally painful to receive her thoughts. So most elves use vocal speech with her instead, and she can lie just fine with words.
* In ''ComicBook/TheChroniclesOfWormwood'', it is impossible to say anything untrue in the presence of Jay, who happens to be the Second Coming of Jesus Christ. It doesn't matter if you're actually trying to deceive him (if, for example, you're testing the effect with a ridiculous lie like "My parents were secretly elephants"), you just can't finish the sentence. People who ''are'' trying to deceive him, even for polite reasons, have a tendency to [[BrutalHonesty say what they really mean instead]].

* In ''FanFic/HarryPotterAndTheMethodsOfRationality'', [[spoiler:Parseltongue, the language of snakes, is revealed to have this effect as neither Harry, Professor Quirrell or Voldemort were able to express direct deception through that language. It becomes an often demanded method of communication between the parties capable of understanding it to avoid such deception. This does not, however, prevent them from telling misleading truths.]]

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* The Old Speech in the ''Literature/{{Earthsea}}'' books, except to some extent for dragons:
-->While the Old Speech binds a man to truth, this is not so with dragons. It is their own language, and they can lie in it, twisting the true words to false ends, catching the unwary hearer in a maze of mirrorwords each of which reflects the truth and none of which leads anywhere.
** The implication of the Earthsea Old Speech is that what is said in it, if it is not already true, ''becomes'' true, even if [[RealityWarper the world has to bend]] to make it so. The dragons are simply old enough and crafty enough to say false things in ways that won't change reality.
* ''Literature/InheritanceCycle'': despite stating that elves are fond of half-truths and misdirection in the ancient language, it's never much of an issue. Although it is impossible to lie directly, lies can be told by thinking to yourself that you mean something else to what you are saying. [[spoiler:The language also doesn't contain any measures to stop a speaker from being ''mistaken''.]] Which partially explains how, in ''Eldest'', Eragon is able to compose a completely fictional story in verse that tells of a battlefield romance -- because he was thinking of Arya and it ''felt'' true. It's similar to what happens when Eragon tries to demonstrate a spell to take a sort of magic photograph by using it on Arya. It was supposed to be a perfect photo, and it's supposed to be really hard to fool the spell, but it... came out different, because of the way Eragon felt about Arya.
* Telepathy works this way in Creator/UrsulaKLeGuin's ''Literature/{{Hainish}}'' novels. The only exception is an alien race named Shing (the aliens in ''City of Illusions''). Apparently, they used that ability to overthrow TheFederation and take over... until a thousand or so years later, they were defeated by a race which was capable of detecting their lies.

* Before they became LivingLieDetector[=s=] for law enforcement, the ghatti of the ''Ghatti's Tale'' series first had to learn what lying was, as like the Clan, their language is a gestural one in which successful lying is impossible.
* ''Literature/WestOfEden'': The Yilanè in Creator/HarryHarrison's trilogy have this. Learning to speak is what makes a Yilanè yilanè (capable of speech), and the thought is what causes the body motions that make up their language unless they are completely still. Humans who learn the language, however, are capable of lying in it.
* ''Literature/NineteenEightyFour'': Newspeak was a decidedly dark take on this, in that the goal was to make unsayable anything not deemed "truth" by The Party/Big Brother. ([[SubvertedTrope It's not particularly effective, and the people who developed it had to be disappeared.]])
* Obviously inspired by Orwell, the ''Literature/BookOfTheNewSun'' series features the Ascians, a people whose language is composed of a bunch of Mao-esque revolutionary slogans. However, the book explicitly shows that Ascians are capable of uttering subversive statements even when bound by this language.

* In ''Literature/SectorGeneral'', the Kelgian speech and telepathic communication technically qualify. Kelgian languages are perfectly ordinary: the fun part is that their vocal speech is inextricably linked with the involuntary expression of emotions in the movements of their fur. The species developed no concept of lies. Or tact. They're not so hot on bedside manner, either. Telepathic contact is full awareness of the partner's psyche, making lies exceptionally pointless.
* In Neal Stephenson's ''[[Literature/TheBaroqueCycle Quicksilver]]'', philosophers are attempting to make a truly logical language which, when used correctly, makes it impossible to say things which are false. The idea is that it would work like algebra: valid algebraic transformations on correct equations always lead to other correct equations. This is a little bit different from some of the other examples, since it protects not only against the speaker lying, but also against the speaker mistakenly saying something wrong.
* In Creator/EEDocSmith's ''Literature/{{Lensman}}'' series, it is absolutely impossible to make an untrue state telepathically, and the recipient knows this, with absolute certainty. It is possible, however, to make a correct but uninformative statement, such as "I cannot divulge that."

* In the ''Literature/YoungWizards'' series, the Speech is the language that defines the fabric of the universe. Even the [[BigBad Lone Power]] can't lie in it. Although as the Speech can express every concept, it includes both words and grammar which are inaudible, incomprehensible, or guaranteed to be predictably misunderstood by any non-omniscient listener. Beings on the order of the Lone Power have a lot of potential wiggle room, though the book series only exploits this to the extent of allowing the Lone Power conversational freedom in the Speech. When used in spells as the LanguageOfMagic, saying or writing something in the Speech is what ''makes'' something true, which makes truthful descriptions of things especially important.
* Creator/NancyKress's ''Literature/ProbabilitySpace'' series has a race that experiences a consensual, shared reality, and can't say things that disagree with the consensus. It's not so much that they can't lie -- but they can't lie unless they all believe the lie.
* In Creator/ChinaMieville's ''Literature/{{Embassytown}}'', the Ariekei speak a very unusual language -- in fact, the oddness of the language is a central part of the whole book--but one of its features is that they can't really lie. Some of them are trying to learn, however, by starting a statement, and then saying the second half too quietly to be heard.
* In Creator/DavidEddings' ''Literature/{{Belgariad}}'' and ''Literature/{{Malloreon}}'' series, it is impossible to tell a lie in the language of wolves. At one point a wolf wants Ce'nedra to stop talking. Garion tells her the wolf wants to sleep. When he tells the wolf to close her eyes to pretend to sleep, the wolf is amazed that is possible to say things that aren't true in the human language. (Interestingly, while the wolf's dialogue wasn't false, it ultimately turns out to been an expression of deception regardless.)
* In several of Creator/MarionZimmerBradley's works, being under the effect of a truthspell makes any language work like this. However, while you can't ''lie'', you certainly can say things that are not true provided that you believe them to be true. It's also specifically noted that in situations where an objective "truth" is ambiguous or nonexistent (for example, most political disputes), truthspells are next to useless.
* In Creator/RobertAHeinlein's ''Literature/BetweenPlanets'' the language of the [[VenusIsWet Venerian]] "dragons" is called "true speech" and as one (human) character points out, doesn't even have a word for the concept of deliberate falsehood, meaning that Venerians (at least when they're speaking their own language) [[LanguageEqualsThought are unable to lie]].
* Downplayed in ''Literature/{{Transpecial}}''. It's possible for a good actor to lie in the ky'iin languages, but it's much harder than it is in any human language because ky'iin communication is so dependent on body language.

* ''Franchise/StarTrek'':
** This is played with and ultimately subverted in ''Series/StarTrekDeepSpaceNine''. For a long time, Odo [[BlatantLies insists]] that [[MentalFusion linking]] with other [[VoluntaryShapeshifter Changelings]] "isn't about information exchange." Then they accidentally reveal the identity of a Changeling infiltrator to him, and the entire cast assumes this trope is in effect. [[spoiler: It isn't. The Changelings deliberately misled Odo.]]
** Played straight with most other forms of telepathy in the Star Trek universe.

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* ''TabletopGame/InNomine'' has the divine language, which is impossible to lie in. The demons don't like that, so after the initial fall they create a butchered version, called Dark Celestial.

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* ''Webcomic/GeneCatlow'': The "Sight of the Soul" telepathic communication works like this - since it's direct communication between souls, it doesn't allow for lies, falsehood, or even withholding the truth. However, at least at one point, there existed a type of etherical being with a mind so insane and fractured that it was capable of lying through the Sight of the Soul...

* In ''Webcomic/{{Roommates}}'' things said in double lined letters (the Voice of Truth & Magic) are true and not even subjectively true as it even makes mistakes and the like impossible. The only one who ever uses it is Jareth the fae roommate, mostly to magically bind himself to his given word. Considering that nobody tends to trust him and he has a SuperpoweredEvilSide this is a wise precaution. The one time when he was trying but not able to promise something in it that was actually a plot point.

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* ''Literature/NineteenEightyFour'': Newspeak was a decidedly dark take on this, in that the goal was to make unsayable anything not deemed "truth" by The Party/Big Brother.

* Creator/NancyKress's ''Probability: Space'' series has a race that experiences a consensual, shared reality, and can't say things that disagree with the consensus. It's not so much that they can't lie -- but they can't lie unless they all believe the lie.

* Telepathy works this way in Creator/UrsulaKLeGuin's Literature/{{Hainish}} novels. The only exception is an alien race named Shing (the aliens in ''Literature/CityOfIllusions''). Apparently, they used that ability to overthrow TheFederation and take over... until a thousand or so years later, they were defeated by a race which was capable of detecting their lies.

A Language of Truth is a particular language or form of communication in which lies are inherently impossible or inexpressible. This is a frequent feature of {{Telepathy}},[[note]]because, as [[HighMiddleAges scholastics]] said, lying is saying one thing and thinking another, so you can't lie if you think and speak in the same act[[/note]] but it can also appear for more overt languages. A LanguageOfMagic may be this or, slightly differently, it may ''cause'' anything said in it to ''become'' true. Beware, of course, the ConsummateLiar who is either outright immune or uses ExactWords and other forms of deception to get around this inconvenience.

* In Creator/DavidEddings' ''Literature/{{Belgariad}}'' and ''Literature/{{Malloreon}}'' series, it is impossible to tell a lie in the language of wolves. At one point a wolf wants Ce'nedra to stop talking. Garion tells her the wolf wants to sleep. When he tells the wolf to close her eyes to pretend to sleep, the wolf is amazed that is possible to say things that aren't true in the human language.

* Before they became LivingLieDetectors for law enforcement, the ghatti of the ''Ghatti's Tale'' series first had to learn what lying was, as like the Clan, their language is a gestural one in which successful lying is impossible.

A RealLife LanguageOfTruth [[http://www.crockford.com/wrrrld/wilkins.html can't]] [[https://secure.wikimedia.org/wikipedia/en/wiki/Russell%27s_paradox possibly]] [[http://en.wikipedia.org/wiki/Gödels_incompleteness_theorem exist]] - not if you want it to be able to express ''every'' true statement. Consider:

->This statement cannot be translated into a LanguageOfTruth.

-->This statement cannot be translated into a LanguageOfTruth.

--->While the Old Speech binds a man to truth, this is not so with dragons. It is their own language, and they can lie in it, twisting the true words to false ends, catching the unwary hearer in a maze of mirrorwords each of which reflects the truth and none of which leads anywhere.

** Its most famous example is the red truth. '''[[red:If anything is said in red text, it must be true. If it's not true, it cannot be said in red text.]]''' An infallible language of truth sounds like an ''incredible'' power in a MysteryFiction -- but it's mostly used by supernatural beings to torment the protagonist with information that doesn't need to be evidenced or explained. In particular, while red truth can't be used to outright lie, it can (and will) be definitely used to mislead and deceive.

* ''TabletopGame/Numenera'' has [[ShapedLikeItself Truth]], a scholarly language which the Church says cannot be used to lie. Played with, however, in that not everyone buys this.

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* ''VisualNovel/UminekoWhenTheyCry'' has the red truth. '''[[red:If anything is said in red text, it must be true. If it's not true, it cannot be said in red text.]]''' An infallible language of truth sounds like an ''incredible'' power in a MysteryFiction -- but it's mostly used by supernatural beings to torment the protagonist with information that doesn't need to be evidenced or explained. In particular, while red truth can't be used to outright lie, it can (and will) be definitely used to mislead and deceive.

* ''VisualNovel/UminekoWhenTheyCry'' has the red truth. '''[[red:If anything is said in red text, it must be true. If it's not true, it cannot be said in red text.]]''' An infallible language of truth sounds like an ''incredible'' power in a MysteryFiction -- but it's mostly used by supernatural beings to torment the protagonist with information that doesn't need to be evidenced or explained.
** In particular, while red truth can't be used to outright lie, it can (and will) be definitely used to mislead and deceive.