Cannot Tell a Lie

When a character or group of characters is by nature unable to tell any untruths, whether they be magical beings who are bound by that magic, speakers of a language that makes it impossible, or simply unable to grasp the concept of lying, that character Cannot Tell a Lie.

How restrictive this inability to lie is varies from character to character. For some, they are unable to deceive, following the letter of the law as well as its underlying meaning. For others, they are able to be Metaphorically True, omit important information, and carefully use Exact Words, allowing for False Reassurance or even Malicious Slander and acting as a sort of Technical Pacifist version of a Consummate Liar.

It is also worth remembering that "incapable of being dishonest" does not equate "all-knowing". More often than not, a character with this condition is just as capable of making mistakes and coming to wrong conclusions as everyone else, and may accidentally end up saying something untrue, simply by sincerely believing that they are telling the truth, while said version of the "truth" is actually based on faulty, incomplete, or even downright wrong information.

Children are prone to it, being too innocent to think of suppressing the truth — many truths have been blurted out by unwitting children — but this cannot be relied on; most children outgrow it (although some of them retain the tendency and grow up to be bad liars).

Some characters are very bad liars or broadcast some obvious signal when they lie. Those are not examples of this trope, although the results are effectively identical (the character can utter a lie, but can't fool anyone).

Characters that are temporarily forced to tell the truth, but otherwise can lie are under the effects of Truth Serums. Characters who are capable of lying, but choose not to Will Not Tell a Lie. If they're sworn to keep a secret, they will very quickly discover Keeping Secrets Sucks.

It should be noted that this trope is for characters who Cannot Tell A Lie as a character trait, which means that at all times they are incapable of lying. If the character is under the effect of a Truth Serum, it doesn't count. However, if said Truth Serum had a permanent effect, especially if it were applied before the main narrative, then that example is valid. Bad writers will use Metaphorically True to get away with "misunderstandings."

Trope Namer is George Washington from his famous story about a cherry tree, who oddly is a better example of Will Not Tell a Lie. Ironically this is clearly a lie as said by Cracked.

See also Knights and Knaves, Language of Truth. Not to be confused with Bad Liar.

Contrast Compulsive Liar.

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Examples:

Anime & Manga

• Belldandy and other Goddesses First Class from Ah! My Goddess are absolutely incapable of telling lies. They're still able to simply say nothing when it's necessary to conceal information, but of course this can be quite revealing in its own right. After passing the Goddess First Class test, Urd declines the promotion (which would have allowed her full access to her immense power, far greater than even Belldandy's) and remains Second Class because she deems the ability to lie more useful than brute strength in protecting her family.
• Variation: immortals from Baccano! are incapable of using aliases in the presence of other immortals, instinctively blurting out their real names if they try.
• Much of Death Note seems to rely on the idea that one of the rules for the death gods forbids them from lying to the people that hold their books. They are not, however, required to tell the user everything. Ryuk makes a living out of leaving out that last bit of information.
• Any augur in Fushigi Yuugi: Genbu Kaiden. Augurs must speak the truth, as they will lose their prophetic powers if they lie. Whether this actively means they are forbidden from lying or are incapable of lying is not explored. Seems to be the former, though, as there are two instances in the story where an augur has lied.
• In the Harukanaru Toki no Naka de - Hachiyou Shou anime, after Ran loses her memories, the main characters decide that it will be better if she doesn't remember anything about her connections with the Oni Clan. Yasuaki, for certain reasons, fails to understand why they don't tell her everything, to the point of asking directly why they are lying. When he eventually does tell her the truth in order to figure out how the Oni Clan's curse works, all sorts of troubles proceed to happen. The manga explores this even further. Yasuaki, who insists that he has no heart or emotions, wonders at one point why people tell lies, implying that, indeed, he doesn't understand the concept of lying (yet). When Kotengu gets killed, however, Yasuaki ends up lying to Akane that he is still alive just to make her stop crying. This event confuses him a lot, as he apparently believes that, not being human, he wasn't supposed to be able to lie.
• From Magi: Labyrinth of Magic, a person's rukh cannot lie. They will tell you exactly how they feel about you, and even if they shut up you'll hear their thoughts.
• Kazuo Tengan's forbidden action in Danganronpa 3: The End of Hope's Peak High School is this. If he lies, his bracelet will inject him with a deadly poison.
• In Pluto, robots aren't supposed to be able to lie, as part of being Three Laws-Compliant. However, the more advanced an AI is, the more like a human they are... and humans can lie. The "perfect" AI is even able to lie to himself, deluding himself into thinking he's human.
• In Princess Tutu, Mytho doesn't understand much because of losing his emotions, including not understanding the concept of lying... at least, until he begins to regain his emotions. The first time in the series he does tell a lie, Fakir reacts in shock.
• Puella Magi Madoka Magica: Kyubey cannot technically lie, as he comes from a purely rational alien species. This does not, however, prevent him from invoking his Exact Words and You Didn't Ask. He also did not deem it necessary to tell them everything, becoming genuinely confused when all the girls got angry at him for "hiding the truth". Kyubey did intently hide some information to keep things in his favor though...
• In Usotsuki Satsuki wa Shi ga Mieru, despite her reputation as being the exact opposite of this trope, Satsuki herself. At first, it just seems that she dislikes lying, but it becomes clear when her friends try to goad her into at least telling a meaningless lie by eating her lunch until she does that she can't bring herself to be dishonest on any level, which kills their main strategy for how to deal with student president Kai Mikami. The reason she's like this is later revealed to be a form of self-punishment: the last time she lied was when she tried to explain to her father why she didn't do anything when she discovered her mother bleeding out on the floor, knowing he wouldn't accept the real reason (she confused her mother for a hallucination, as her corpse-seer abilities were just beginning to manifest), and he immediately calls his daughter out for the shallow attempt at deceiving him.
• Trueman from Yu-Gi-Oh! GX, sort of. He claims this is the case, which is how he got his name (he named himself, actually), but he does tend to use deceit and dishonesty many times in non-verbal ways, using illusion to prey on victims.

Art

• And when did you last see your father? depicts a scene from the English Civil War. A Royalist household (mother with her two daughters and her son) is questioned by Parliamentarian soldiers about the patriarch's whereabouts. The moment presented is the one where the young son of the family is asked "When did you last see your father?" (hence the title). It is in fact never revealed whether he did the most sensible thing (to lie and to save his father's life) or actually Cannot Tell A Lie and, being the very incarnation of innocence (he even is Colour-Coded for Your Convenience), tell the truth and blow his father's cover. In the background, his two older two sisters and his mother can be seen anxiously sobbing, making this a tearjerker moment.

Asian Animation

• Happy Heroes: Inverted and invoked by Big and Little M. in Season 2 Episode 10. The two use a flying saucer that zaps people into being unable to tell the truth; the people gain ten pounds for every truth they do tell.

Comic Books

• Batman: The Riddler, Depending on the Writer. A bit of belated backstory says that his father beat him for winning a contest, wrongly thinking he cheated. As a result, Ngyma has an outright compulsion to tell the truth, as expressed through his riddles. In one story, he tries not to leave clues, but cannot stop himself, and when Batman catches him, Riddler says that he needs to go to Arkham because there's something wrong with him.
• In Courtney Crumrin and the Night Things, it's mentioned by the narrator that the Night Things are incapable of lying. Because of this, it tends to not occur to them that non- Night Things can lie to them.
• Empowered: Telepaths can't lie through telepathy, or even hide the truth. Whenever they say something even slightly untrue, the truth shows up in parenthesis, representing another band of communication underlaying the first. This most often shows up when they try to be polite, but their angry curses come through anyway.
• Loki: Agent of Asgard hits Loki of all people with this. After the inversion is undone they just can't take falsehoods any more, not even benign ones or jokes. They're not literally unable to tell them but all come out incredibly weak and make them feel so bad about them that they correct themself immediately. They theorize that this is either an after effect of the inversion, or being in the middle of the truth wave, or maybe they're just sick and tired of untruths or some combination of these. This prompts them to be suicidally honest with Verity and Thor.
• Piffany from Nodwick is apparently so naturally pure that she feels constrained to blurt out the truth even when it would be dangerous.
• In a Paperinik New Adventures short they have fun with the story of Little George Washington and the cherry tree. It ends up with a time traveler coming back in time to prevent little George from chopping down the tree (so that his son's teacher won't have an example to quote when she'd say truth is to be rewarded), only to find out that he landed on the tree and little George decided it was easier to 'confess' that he, George, chopped it down rather than trying to explain the truth.
• Wonder Woman is this Depending on the Writer. This wasn't the case originally when she had a secret identity, but after DC's first reboot in the 80s, the secret identity was discarded and she was depicted as being so honest she gained the sobriquet, Spirit of Truth. The reason she cannot lie also varies, with some writers attributing this to the Lasso of Truth preventing her from lying and others having her as too sweet to lie. (The consensus currently seems to be a bit of both: she cannot tell a lie while she's holding the lasso, but even when she isn't, she Will Not Tell a Lie.)
• An interesting case with X-23. Laura is very well-known for her Brutal Honesty and being Innocently Insensitive. Because she was created as a Living Weapon covert operative and assassin, she certainly has the capability to lie in order to maintain her cover on missions, but outside of this context she consistently shows an inability to do so. It's a major bit of Character Development in her solo series when she lies to the child of one of her victims to spare him the pain of revisiting the loss of his parents.

Fan Works

• Abraxas (Hrodvitnon): Lying is an alien concept to San, and Ghidorah for that matter. That being said, it doesn't mean Ghidorah's heads are incapable of psychological manipulation. According to the author, San regards the act of withholding information as a waste of thought. The author furthermore states that this trope was a big influence on Ghidorah when it formed a particularly dark part of its Evil Plan for Monster X after learning of human metaphors.
• Achakura in Kyon: Big Damn Hero, as Nagato programmed her. She even complains she can't lie about her weakness.
• Child of the Storm has Doctor Strange as being caught somewhere between this and Will Not Tell a Lie — that is to say, it's not entirely clear which applies, and he's not exactly minded to say. The evidence, such as his reaction when he's accused of lying (while admittedly on the edge of sanity at the time, he snaps and informs the person who accused him that if they weren't a child/teenager and under a lot of strain themselves, he would have killed them on the spot) suggests that it's a combination of the two: he started out able to lie, decided that he Will Not Tell a Lie, and at some point swore an oath so that he's unable to lie. Of course, as is frequently noted, this is by no means the same as being honest, and his habit of telling the literal -- and often selective -- truth is part of what makes him such a dangerous and effective manipulator.
• How Friendship Accidentally Saved Magical Britain: Due to having soul bits in common with the Weasley twins, Tom is unable to lie specifically to them, as their shared souls act like a compulsion that keeps him from doing anything more than misdirecting them, which will only slow the likes of Fred and George down for a little bit. Lying to literally anyone else is fair game, though.
• In And the Truth Shall Set You Free Harry, due to accidentally swallowing a bottle of Veritaserum as a baby, is utterly unable to lie. An escaped Bellatrix Lestrange, of all people, teaches him how to give Mathematician's Answers and half-truths before he starts Hogwarts.
• In Harry Potter and the Ritual of Love's Memory, after the Battle of the Department of Mysteries, Umbridge is enraged to realise that she has been exposed to various potions through samples being spilled over her during a confrontation with the Death Eaters. A particular consequence of this is that she was dosed with Veritaserum and all evidence indicates that she will now be permanently unable to lie, allowing Sirius (previously cleared after Crouch Jr. went to trial) to confirm various anti-werewolf laws she arranged to pass, as well as Harry and his friends confirming that they had the best Defence marks in their year.
• In Mega Man: Defender of the Human Race, robots generally can't lie, except for ones with advanced programming, like ProtoMan. As of episode 7 this also includes Guts Man, Cut Man, and Magnet Man.
• Discord in Romance and the Fate of Equestria is trapped in this state. Mostly it leads to a lot of needless rambling and Did I Say That Out Loud moments. Being Discord, he's good at invoking Exact Words.
• The main character of The Twilight Child is this mixed with Will Not Tell a Lie. She's near-incapable of lying in any form, and should she actually attempt it she'll either immediately backspace or her vocal cords just shut down on her. It also thwarts her Stepford Smiler tendencies as well.
• In Sight, Zanpakutou spirits can't lie due to being the manifestation of their wielder's soul. As a result, it's easy for Ichigo to tell when their wielder is lying because the zanpakutou will look extremely guilty for the lie.
• A Boy, a Girl and a Dog: The Leithian Script: In the Halls of Mandos nobody can lie. It's physically impossible. A soul can refuse to answer or tell something what they believe is the truth, but nobody can intentionally tell a lie.
• In Calamity Jane Meets Doctor Isles, Maura retains her inability to lie, to the extent that, when she and Jane are invited to Boston, Jane decides to pose as Maura's husband, and they have to spend some time during the trip working out how Maura can discuss their ‘marriage’ without anything said being an actual lie. Apart from referring to Jane with male pronouns, Maura never tells her old friends any real lies, easily referring to Jane by her old alias of 'Jake' and simply saying that she and Jake can't have children of their own for reasons she'd rather not disclose.
• In Brother on Brother, Daughter on Mother, Rachel Connor is just a lousy liar. She tries to cover the fact that she's an illegal genetic augment after her Healing Factor blocks Borg assimilation, but Alicia Gantumur doesn't buy it, saying whatever the real explanation is, she won't push it "as long as the Captain knows." Later, Eleya's time-travelling future daughter comments that she was sent back in time instead of Connor, her superior, because Connor still hasn't learned to lie convincingly several decades on.
  Reshek Taryn: I clean her out every time we play poker.
• In Cuckoo Bird, faeries like Izuku cannot tell lies because they suffer an excruciating slashing and burning sensation in their throat whenever they do. Because of this, they specialize in misleading and tricking others with Metaphorically True statements to get around this.
• The Pieces Lie Where They Fell: Wind Breaker has trouble lying even to himself, as per his Element (though it doesn't keep him from lying when he absolutely has to), which got him into a lot of trouble as a kid. He was given alcohol to overcome it when he was nine, resulting in a lot of problems for him later in life. He also has no poker face as a result.
• My Deepest, Darkest Secret: It's mentioned that this version of werewolves are this as a side effect for being able to sense lies, being physically unable to lie. Strangely enough, this trait came in handy when the vampires considered teaming up with the werewolves, as they're too sincere.

Films — Animation

• Up: If only Russell could've laid low about his discovery of Kevin.
• Wreck-It Ralph: Felix appears unable to lie to Ralph about the fact they threw a party without him, and he doesn't tell an apparent falsehood anywhere else in the movie either.

Films — Live-Action

• The newer generation of replicants in Blade Runner 2049 are implied to always tell the truth due to their obedience programming. This ultimately proves untrue, as we see K tell Lieutenant Joshi that he killed the replicant child; Luv makes it explicit right before she murders the lieutenant.
• Mephistopheles from Ghost Rider (2007) claims so.
• The titular character in i am sam is mentally challenged and doesn't understand the concept of lying which causes problems with his lawyer who wants him to "tweak" the truth a little in court.
• The Invention of Lying takes place in a world where no one can lie, except for Ricky Gervais's character. Despite no one being able to lie, it's actually not a very nice place — there is no religion, no fiction, and because people are brutally honest (or at least incapable of blurting out inconvenient truths) everyone is cruel, crass or prone to over-sharing.
• Marta, the nurse of the murder victim at the center of Rian Johnson's whodunit Knives Out, is such a nice person that any time she tells a lie, she vomits immediately out of sheer shame. The best she can do is hold it back for a few minutes at most.
• Jackson Rippner in Red Eye never lies. This has led to some fans theorizing that his joke about killing his parents was actually true.
• In Superman: The Movie, Supes tells Lois he never lies. Not once.

Folklore

• George Washington was said to have remarked, "I cannot tell a lie", and admitting to chopping down his father's cherry tree. However, this is a myth. Even if it were true, it would be a matter of choice rather than inability (i.e., Will Not Tell a Lie rather than Cannot Tell a Lie).
• According to legend, Thomas Rhymer gained the gift of prophecy after being captured by The Fair Folk and trading his ability to lie for his freedom.

Literature

• In Alien in a Small Town, compulsive honesty is the alien Jan's main cultural hat. They are descended from communally-living prey animals, and had to cooperate constantly to survive. This gives them a reputation for rudeness, though with practice they can at least learn the human concept of tact. They can keep secrets, though, as long as they can avoid having to lie outright in order to keep them.
• Most of Isaac Asimov's robots in his Robot Series (the earlier ones, at least) cannot knowingly lie.
  • Greg Powell and Mike Donovan mention this explicitly in one story as they try to figure out why their robot's recollection of recent events doesn't match the facts.This probably relates to the Second Law, because when a human asks a direct question of a robot, that implies an order to respond truthfully... but smarter robots can deceive, mislead, and keep secrets, primarily when they are trying to uphold the First Law (no harming humans). Robots who are trying to balance conflicted directives may give meaningless answers when questioned ("The matter admits of no explanation"), or simply refuse to answer.
  • "Liar! (1941)" has an instance of a robot lying repeatedly. When, by accident, a robot develops telepathic powers, it lies to people when it knows that the truth would hurt them (which would mean breaking the First Law). Unfortunately for the bot, humans have so many conflicting emotions, and lying to them can ultimately cause even more harm. Susan Calvin destroys the robot with a Logic Bomb after one of its lies indirectly wounds her.
• Belgariad: Dalasian seeresses are unable to lie. They can refuse to speak (as Cyradis demonstrates several times through the Malloreon).
• In Jannie Lee Simner's Bones of Faerie: Faerie Winter the human children who have faerie powers seem incapable of lying. Faeries themselves also seem unable to lie, but, they are very good at bending the truth.
• Subverted in one of the humorous stories of Jaroslaw Hasek ("The Brave Soldier Schwejk") where a kid is cursed with the inability to tell a (convincing) lie. Hilarity Ensues when he is sent to fetch sausages and a stray dog "robs" him. Of course nobody believes him. After one day of psychic waterboarding by his parents, he finally admits he did it, prompting him to sigh: "Finally! Now I can lie!"
• The titular character of Bronwyns Bane is cursed to always lie, but her usual speech is straightforward and easily inverted, so to people who know her curse she is effectively always telling the truth.
• In Teresa Edgerton's Celydonn books, Prince Tryffin has, as one of his geasa, that he must never knowingly tell a lie. Since breaking a geas brings terrible bad luck, this makes Tryffin's life interesting.
• Christopher Chant from Diana Wynne Jones's Chrestomanci books has this problem when in contact with silver. Before he discovered what was causing it so that he could just avoid silver he learned to get by with telling the truth, but letting the hearer draw the wrong conclusion. He's also a traveler across dimensions, and one scene features an exchange with a school friend about getting some books for a girl in one of these dimensions. He says (paraphrased): "'I need to get a girl some books as a present. What kind of books do girls like?' When his friend looked at him strangely, he added, 'I have this cousin called Caroline.' It was perfectly true; he wasn't to know that the last sentence had nothing to do with the previous ones." And it works.
• In The Chronicles of Prydain, whenever the bard Fflewdur Fflam lies, the strings of his magical harp break. He does it a lot anyway.
• Circle Of Magic 2000:
  • In James MacDonald and Debra Doyle's Circle of Magic series, if a wizard lies, they permanently lose the ability to do magic.
  • The fairies have it even worse. A wizard can go for meaning rather than precise wording, but a fairy must, for instance, carry out all his promises exactly.
• In James Morrow's City Of Truth, the citizens of Veritas undergo painful conditioning that forces them to always tell the truth, often bluntly; cars have names like the Plymouth Adequate, and the plot is set into motion by something that happens to the protagonist's son at Camp Ditch-the-Kids.
• In Codex Alera The Marat don't have the concept of lying. They will refer to someone as "mistaken", but the concept of intentionally stating something false is unknown to them.
• Diary of a Wimpy Kid: Rodrick Rules has Greg become this (along with a heaping dose of Brutal Honesty) at one point after his mother gets fed up with his lying and threatens to ground him if he continues. At one point, she asks him to tell someone that she’s not home, and he refuses unless she steps outside the house (while it’s raining, no less). Needless to say, she doesn’t force him to be honest after that.
• Earthsea, A Wizard of Earthsea: When Ged is speaking with Yevaud, he reminds himself that while humans cannot lie while speaking Dragon, Dragon is Yevaud's birth tongue, and they may have different rules. He can't assume dragons tell the truth by default.
• Discworld:
  • In Equal Rites, there is a short mention of a tribe of people who don't lie, except for their leader/face to the world, who they, as a testament to their honesty, call the Tribe Liar, which other people find slightly uncomfortable to deal with (they'd much prefer the Zoon use terms like "diplomat" or "public relations officer", as they feel they're being mocked). Esk meets a Liar who is a kindhearted merchant.
  • William de Worde from The Truth, although physically capable of speaking an untruth, was so heavily-conditioned not to lie by his tyrannical father that even harmless fibs for politeness's sake leave William's internal monologue nervously reassuring him that it's okay. Half-truths are another story.
  • Mr Thunderbolt, the troll lawyer in Raising Steam is "diamond through and through", and would crack if he told a lie. Presumably the same thing goes for his uncle, Mr Shine.
  • The N'Tuitif tribe in The Last Hero are a society no imagination whatsoever; every statement they make is absolute truth, because they can't conceive of anything that's even Metaphorically True, let alone blatantly false. This even extends to things when there seems to be no logical way they could know the truth — their Just So Stories are unadorned descriptions of evolutionary processes, possibly making them the only people on the Disc apart from Ponder Stibbons and the God of Evolution who really believe in it.
• Similarly, the faeries in The Dresden Files are unable to tell a direct lie, but that doesn't stop them from being shifty, misleading SOB's. It's been noted that when dealing with fae, there is no "spirit of the law," only the letter.
  • In Cold Days it's revealed that Maeve has gained the ability to lie and has been telling everyone things they'd never have believed without the assumption that it can't be a lie.
  • There is also mention of a young changeling who is also very skilled with illusion magic, who could potentially rock the power balance of the Fae courts simply by having illusory copies of themselves lie to people.
• The A!tol in Glynn Stewart's Duchy Of Terra series are capable of lying but typically don't bother because, being similar to terrestrial squid, their changing skin coloration reveals their emotional state, making them their own Living Lie Detector. Individuals are fully capable of being underhanded, criminal, and treacherous, but keeping it a secret relies on not putting themselves in a situation where they'd be forced to lie to someone who understands their colour patterns.
• Justified in The Faraway Paladin. The spellcasting system in the setting relies on speaking, writing, and/or tracing Words from the Language of Magic, which is also the linguistic ancestor of all the world's languages. Since the Words underpin the very fabric of reality, lying in any language can degrade the powers of magic-users, so as a rule they do not do so.
• The faeries in The Folk of the Air are unable to lie, although they will do their best to bend or otherwise talk around the truth. That Jude, as a human, is capable of lying both makes her a valuable asset in any mission that requires deceit. It also makes a huge chunk of the supporting cast automatically doubt anything she says.
• Tavis Burdun, in the Twilight Giants trilogy of Forgotten Realms novels, is a firbolg (a type of small giant), which basically makes him incapable of lying. Some other characters theorize that since he was raised by humans, he might have picked up their ability to lie, but he hasn't. Even being deceptive without actually saying something untrue makes him start to sweat and feel sick.
• The Four Horsemen Universe: Tortantulas can't lie due to being Literal-Minded, and as such can suffer Blunt Metaphors Trauma and sometimes need to rely on their Flatar partners to keep them out of trouble with species that can lie. They also hate human jokes for much the same reason.
• The Houyhnhnms in Gulliver's Travels have no concept of lying, being enlightened beings. This paves the way for yet more satire.
• In the Haruhi Suzumiya novels, Kyon noted on more than one occasion that Yuki wouldn't lie. Who knows if this is Will Not Tell a Lie or Cannot Tell A Lie, but he is convinced that it is this trope.
  Kyon: Nagato, have you seen Asahina-san's contact lens?
  Yuki: I haven't.
  Kyon: (internally) Nagato replied without flinching. I had a feeling she's lying.
  • In a technical sense, Nagato was lying to ‘’Haruhi’’; she was lying to Kyon so she wouldn’t know the truth. When Haruhi’s out of the picture, Nagato comes clean to Kyon.
• In the Heralds of Valdemar series, Tremane has a spell put on him by the Son of the Sun, Solaris, that makes him unable to lie. The Heralds can cast a spell that compels people to tell the truth as well, which they use when hearing cases as circuit judges.
• In Immortals After Dark, natural born (but not made) vampires feel violently ill if they attempt to lie.
• In The Inheritance Cycle, anyone speaking the Ancient language cannot lie.
  • The elves are the only ones who speak it as their everyday language, and they're well-practiced in deceiving without speaking a literal untruth.
  • A character uses the Ancient language to tell a shocking revelation to the hero (that they are secretly brothers, both sons of the The Dragon). Later on it is revealed to not be the case, but Murtagh certainly believed it to be true, so he was able to say it without issue.
• In the Jacob's Ladder Trilogy, a conversation between the AIs Samael and Jacob Dust reveals that their programming prevents them from lying. However, the same conversation also brings up the fact that there's nothing preventing them from deceiving by withholding information.
• Journey to Chaos: Ordercrafters cannot lie because "Order does not abide lies". They're not even allowed Exact Words. This is because Order's honesty is one of the Magical Underpinnings of Reality. The world would not make sense if the god stabilizing reality lied or allowed anyone using his power to lie.
• Falcon shapeshifters in Amelia Atwater-Rhodes's Kiesha'ra series are able to detect blatant lies very easily through their magic, and so most falcons never blatantly lie to avoid trouble. Falcons, however, are also well-versed in the arts of misleading and half-truths, and being misled is no excuse for wrongdoing.
• Ann Leckie:
  • "Nalendar" 'verse of short stories, Physical Gods can't speak untruth without their powers automatically trying to adjust reality to make the statement true, which can be debilitating or even deadly for them. One deity gets around this by adopting a system of slang with his allies, which lets him say things that appear obviously false to those not in the know.
  • Her full novel The Raven Tower runs on the same rule: Gods can speak in ambigious terms, lie by omission, or couch their language in "here is a story I once heard", but speaking outright falsehoods either drains or kills them depending on the magnitude of the lie.
• In the Lensman series, one of the first aspects demonstrated of using the Lens is that one cannot telepathically lie with it. This was mostly seen in First Lensman, when the Lens is first introduced to Civilization and the Galactic Patrol used that aspect as a selling point for prospective entrants; insist on a Lensman using telepathy and you'll always get the truth from them, even if it becomes Brutal Honesty at times. This becomes one of several aspects (alongside being of exceptional mental character and incapable of being imitated) that gains the Lensmen complete trust throughout Civilization: setting the stage for the remaining books.
• The Lion, the Witch, and the Wardrobe: When the Witch meets animals having a Christmas party, she demands to know who gave them all the food. In their terror, they immediately confess that it was Father Christmas. The Witch is so outraged, that she offers to forgive them, if they admit they were lying. One of the young squirrels then shrieks "he has, he has, he has," while beating the table with a spoon. The Witch then turns them and their food to stone.
• Trolls from Malediction Trilogy are unable to lie. They overcome this obstacle by cleverly manipulating truth and letting their listeners draw their own conclusions without outright lying.
• Patricia Briggs's Mercy Thompson series:
  • The fae cannot speak an untruth. Which does not mean that they are honest; they often use weasel words such as "I have heard" to deceive without lying. Also, werewolves can smell lies (through things like perspiration and heart rate), and as the protagonist was Raised by Wolves she has great trouble lying even to mundanes, preferring instead to use Exact Words. In one instance, when John Smith enters the room, another character says "See, I told you Bob Green would come!" implying that John Smith is Bob Green without actually saying it outright.
  • Asil uses the same means of Loophole Abuse in Cry Wolf, when he's compelled to tell the truth by the villain's magic but needs to conceal Bran's identity ("I told you Bran would send Tag...").
• The Mermaid's Sister: Auntie's mother was Faerie, so she's incapable of saying or even thinking a lie. However, she can use Exact Words, such as telling Clara she was brought by a Delivery Stork when she was actually brought by someone whose middle name means "stork".
• In Me, Who Dove into the Heart of the World, the autistic savant Karen is incapable of either lying or fantasizing. She considers it an advantage because she's more connected to reality and her senses than most people.
• The faeries from Holly Black's Modern Faerie Tales. Instead they just "Bend the truth until it snaps under its own weight." i.e, they can't lie per se, but are very, very fond of leaving out important information or "little details" that could be willfully damaging to the hearer. Oh, and the clever use of puns employed in the last book.
• The protagonist of William Sleator's Others See Us cannot lie, at least until he gains telepathy and realizes everyone around him is lying even especially to themselves.
• Humans can access magic in Pact and Pale by making deals with supernatural creatures to use their powers. A major consequence of this is that magic users and supernatural creatures aren't supposed to lie, because this means that the humans and Others they have agreements with can't trust the liar's word and they lose a hefty amount of their power as a result. Naturally, this fails to stop anyone from telling half-truths or using Exact Words.
• Due to a cookie-stealing incident as a toddler, Rod Allbright of Bruce Coville's Rod Allbright Alien Adventures cannot lie when asked a direct question. This leads to a number of instances of Cassandra Truth once Grakker et al show up, including the titular response to a teacher's asking where his math assignment is. Subverted at the end of the book, though, when he finally gets a lie out and it's believed... but only because it was a believable lie, unlike the "aliens ate my homework" truth.
• In his writings the Austrian satirist Alexander Roda Roda (1872-1945, born Sándor Friedrich Rosenfeld) parodied the little George Washington and the cherry tree tale in a story "from an American school primer": Young Abraham Lincoln and a playmate together chop down a cherry tree belonging to Lincoln's father. When the father asks them about it, the playmate fingers young Abe, who says: "I cannot tell a lie, father, I did it." — "That is exemplary behaviour, son, I see that you will become President one day." Turning to the other boy the father added: "You, however, who would not admit..." — "Save your breath, Mr. Lincoln, I'm James Buchanan, US President from 1857 to 1861."
• In Saga of Recluce black mages (mages who use order magic) cannot tell lies, as lying is a chaotic act. Trying to lie will get them a negative reaction depending up how powerful they are: a starting trainee order mage might just feel uncomfortable, a fully fledged mage of ordinary power would get stomach cramps, and a archmage level order mage would get a splitting headache. And they can't use anything like Metaphorically True, Exact Words or False Reassurance to get around it, because it's the intent to deceive which causes the negative reaction.
• In James White's Sector General novels, the Kelgian species are unable to lie because their fur ripples in such a way that any Kelgian can tell what any other is feeling, which makes lying impossible for them.
• Lightbringers in Shadow of the Conqueror are forbidden to lie due to the Incorruptible Pure Pureness that their powers require. If they ever do tell a lie, they instantly lose them.
• Shatter the Sky: The Prophet of the Aurati cannot lie. It's linked to her power of prophesying.
• Yorick (•̀ᴗ•́)و ̑̑ in The Skull of Truth by Bruce Coville was "blessed" with the inability to lie. This led him to become a jester, the only position in which one could tell the king the truth and get away with it. It was implied this also led to his painful death, after which he became the title skull.
• The troll mirror from "The Snow Queen" is incapable of lying but it also cannot reflect the good parts of anything.
• Meursault in The Stranger. It does not occur to him to lie. Interestingly, he's not terribly concerned about other people telling the truth; he never corrects their assumptions about him.
• In Tamora Pierce's Tortall Universe books, one cannot lie around Griffins. Even their feathers share some of these properties; Kel uses them to see through illusions.
• In Uglies, Frizz from Extras has a surgery in order to force himself to only tell the truth. He says he did this because he realized he was lying all the time and needed to get better. Apparently it sparked a whole clique.
  • It causes problems later, though. Unlike many examples, he can't talk around the truth, nor can he stop himself from blurting out the truth if he knows that someone else has lied. When he and his friends are trying to hide who they really are from the Inhumans, he manages not to blurt out their true identities and the fact that they're here to take the Inhumans down... for about two minutes.
  Aya: You can't let Tally know about Radical Honesty. There's no telling what she'll do if she finds out you could ruin her plans.
  Frizz: So let me get this straight, Aya-chan. You want me, a person who can't lie, to lie about the fact that I can't lie?
  Hiro: We need another plan.
• In Dan Abnett's Warhammer 40,000 Gaunt's Ghosts novel Blood Pact, the witch cannot lie. About anything. And foresees the future. And babbles — she cannot even keep quiet.
• West of Eden. Yilanè are incapable of lying due to the way they communicate. When Vaintè realises that her ustuzou (human) slave Kerrick can say things that are not true, she uses this to murder a rival using an ustuzou arrow, while Kerrick tells everyone that he saw an ustuzou fire it.
• The Wheel of Time: The first of three magically binding vows the Aes Sedai take is to "speak no word that is not true". This was intended to inspire trust, but because most Aes Sedai are masters of being Metaphorically True, Exact Words, and Lying by Omission, they have earned more of a reputation for deception. This also leads to a Wham Line when an Aes Sedai blatantly lies, proving that they had turned traitor (members of the Black Ajah, a secret group of Darkfriends within the Aes Sedai, magically forswear the Three Oaths during their initiation).
• The fey in the Wicked Lovely series cannot lie, but they more often than not engage in 'creative truth telling', as per being The Fair Folk.
• In Plaidder's Women on Fire series, shriia are required to tell the truth at all times; a shriia who tells a lie permanently loses her ability to make magical fire, the signature shriia magical ability.
• In Young Wizards, it's not so much that wizards can't lie; it's more that it's highly ill-advised. Since wizards basically change reality through the use of language, things they say have a tendency to come true whether they meant them or not.

Live-Action TV

• Gary Bell on Alphas, as a result of being autistic and having poor social skills. He's been working on it, though.
  Gary: I do lie, I've been practicing. It's a social skill. Like the other day when I said I was gonna have a pudding pop, I was lying 'cause I don't like pudding pops. ... That was a lie, I do like pudding pops. I just knew we didn't have any.
• Drogyn on Angel could not tell a lie. Therefore, he always got upset when people asked him questions. Joss Whedon said that he had Drogyn not be able to lie so that when he said Fred cannot be brought back, the characters would have to believe him. This comes in useful for Angel's later Batman Gambit where he has his team believe all sorts of lies he has planted like his involvement in Fred's death. Drogyn goes to the characters with information of Angel's betrayal extracted from a demon who attacked him on Angel's orders. Although the information is false, Drogyn himself believes it, and the others must believe he's not lying.
• Taro Momoi from Avataro Sentai Donbrothers takes his incredibly literally. Whenever he attempts to utter an untruth, he temporarily dies.
• A Bewitched episode has Endora casting a spell on Darrin that renders him incapable of telling anything but the exact truth... which proves problematic for the guy, since he's in advertising and all.
• Sheldon Cooper from The Big Bang Theory has great difficulty with lying and must either admit when he's told falsehoods to others or engage in an elaborate covering-up of them.
• Blake's 7. Zen or Orac are sometimes used to verify a statement, as computers are not capable of lying in The 'Verse. Unless they've been taken over by the Monster of the Week, of course.
• Doctor Who:
  • In Series 6, it's revealed that the Silence want to kill the Doctor because sometime in the future, "on fields of Trenzalore, at the fall of the Eleventh, when no living creature may speak falsely or fail to give answer, a question will be asked. A question that must never, ever be answered." The question? Doctor who?
    • "The Time of the Doctor" reveals a truth field is the reason no one can speak falsely. The Doctor uses it to his advantage when the Cybermen attempt to build one of them out of wood to get through the Papal Mainframe's forcefield. The Doctor manages to convince it that his sonic screwdriver reversed the polarity on its Hand Cannon to shoot out the back. When the Cyberman doubts, the Doctor points out that the truth field would not allow him to lie. The Cyberman considers that and flips the weapons around... which fires out the front and blows a big hole in the Cyberman. (He told the truth about what he'd set the screwdriver to do — he just didn't mention that it doesn't work on wood.)
• Frasier: Frasier becomes physically nauseous when he violates his ethics and he adamantly refuses to lie under oath, even if there's no way he could ever get caught. Niles is so honest that any attempt to lie causes his nose to bleed.
  • But that doesn't stop either of them from lying to women and creating some pretty ridiculous situations.
• In one episode of House, the Patient of the Week is a mother who has a dynamic with her daughter that they are always very open with each other to the point of Brutal Honesty (i.e. the preteen daughter knows details about her mother's sex life). House eventually pieces together that the mother actually has a single, massive secret that she feels she can't tell her daughter — that the daughter isn't her biological child — so the extreme honesty with regards to every other facet of life was an overcompensation for not telling her daughter this one significant thing.
• In one episode of Hustle, Ash suffers a head injury resulting in this condition temporarily, right before he's about to close a "deal" with the mark. The mark proceeds to ask a direct question, whether there's any reason at all he shouldn't give Ash 500k. He can't tell a lie, but he can tell the truth sarcastically.
• Kingdom Adventure: Both The Emperor and The Prince are stated to have this trait in the flashback episode detailing how the kids first met the Prince. This makes the villains underestimate them.
• My Name Is Earl: Randy can't tell a lie. Not until he's had exactly four beers, anyway. In one episode that involved the gang infiltrating the Winky-Dinky Dog HQ in hopes of stealing enough to avenge the (second) burning of Pop's Hot Dog Cart, Randy is seen presenting at a board meeting (on his first day, no less!) with cans of beer at his feet.O
• In The Other Kingdom, fairies had been shown to be incapable of telling even a white lie, meaning they have to speak what's on their minds. Princess Astral is no exception to this rule, to the point where Morgan even uses this against Astral when she first discovers Astral's a fairy. Astral's often able to work around this using Exact Words where she technically tells the truth, just not the full truth. It seems that this trope only applies to the fairies, as trolls and elves are shown to be capable of lying.
• One of the Whammys on Press Your Luck is George Washington:
  I cannot tell a lie. You lose!
• Ficus, a parody of The Spock in the short-lived sci-fi comedy Quark. As he's an emotionless human plant, he simply doesn't see the point in sparing feelings that he doesn't have himself.
• On Red Dwarf, Kryten the android starts out like this, but with a lot of coaching and practice, he gets better. Or worse. Whatever.
• Maura Isles from Rizzoli & Isles physically cannot tell a lie.
  Jane: I thought you said you couldn't lie!
  Maura: What do you mean? I can't!
  Jane: You did.
  Maura: Only one time, when I said I'd finished my homework and I hadn't, and I immediately went vasovagal. [clarifies] Fainted.
• The sitcom Roseanne had one episode when one of Jackie's friends tells her to lie to Roseanne:
  Jackie: I can't lie to her.
  Friend: Sure you can.
  Jackie: No, seriously, I can't.
  Roseanne: (from the back of the restaurant) Jackie, could you come over here for a minute?
  Jackie: I'm busy.
  Roseanne: No, you're not!
  Jackie: You see?
• On Shadowhunters, the Seelies are unable to lie, but they find other ways to manipulate the truth.
• The story of Little George Washington and the cherry tree is mocked in the "Magnum Opus" episode of Sleepy Hollow when Ichabod and Abbie play game of Who Am I? and Ichabod cannot guess off the clue of "cannot tell a lie".
  Ichabod: George Washington? He was our Liar-in-Chief. He formed the Culper Spy Ring. That was a network of liars.
  Abbie: Thank you, colonial myth-buster.
• Star Trek: Voyager: Seven of Nine is initially incapable of lying for a while after being separated from the Borg. Justified, as it's pretty much impossible to hide the truth while part of a Hive Mind.
• Elnor from Star Trek: Picard was raised by the Qowat Milat, a sect of Romulan warrior nuns who believe in constant Brutal Honesty (or, as they call it, Absolute Candor); as a result, he really doesn't understand the idea of deception. His crewmates have to tell him to keep his mouth shut so that he doesn't blow an undercover op.
• The Twilight Zone (1959):
  • In "The Whole Truth", after buying the Model A, Harvey Hunnicut finds out to his horror that he can't tell a lie. Since he's a used car dealer who specializes in selling junk cars, his business is ruined. He eventually sells it to Nikita Khrushchev.
  • In "Hocus-Pocus and Frisby", the aliens mistake Somerset Frisby's tall tales about his own past for an incredible variety of impressive accomplishments because they have no idea what lying is.
• Supernatural:
  • In "You Can't Handle the Truth", the goddess Veritas' curse is that if anyone in town asks aloud for the truth, everyone that person interacts with will be compelled to speak truths to the asker (particularly dirty or embarrassing truths that they usually keep repressed).
  • In "Moriah", Jack inflicts the magical version of this trope on everyone on Earth, until Chuck appears and cleans it up.
• The Wheel of Time (2021): The first oath which the Aes Sedai take is to "speak no word that is not true", and they are bound by magic against it. However, they make judicious use of exact words when necessary to mislead others.

Music

• The narrator of "A tongue that cannot lie" by Karine Polwart.
• Sir Mix-A-Lot cannot lie (nor can other brothers deny) when it comes to his love of a large posterior.
• Invoked by Arlo Guthrie in "Alice's Restaurant", when asked if he knows how a huge mound of garbage including an envelope with his name on it ended up somewhere it shouldn't.
  And I said, "Yes, sir, Officer Obie, I Cannot Tell A Lie... I put that envelope under that garbage."
• In the song "The Criminal Cried" from Gilbert and Sullivan's operetta The Mikado, after Ko-ko begins giving the townspeople's account of the execution (which did not actually take place) the chorus sings, "We know him well/ he cannot tell/ untrue or groundless tales—/ he always tries/ to utter lies/ and every time he fails."

Myths & Religion

• Cassandra was cursed to tell true prophecies which nobody would ever believe, and was driven mad by it.
• Depending on the version, The Fair Folk can't lie. ...Though they WILL find loopholes, bend things around, and take a very loose interpretation of "truth."
• Thomas the Rhymer, a.k.a. "True Thomas", is said to have had this trope imposed upon him by a Faerie Queen in the late 13th century.
• The author of Hebrews in The Bible states that it is impossible for God to lie. That doesn't mean that God cannot deceive people (He's God, after all, nothing is beyond His power), it's just that He sees it as against his nature.

Radio

• An episode of X Minus One featured a reptilian "lawyer" whose race is incapable of lying (although they don't have to say the entire truth either). This is put to the test when a Jerkass character tries to get under another character's skin by mocking his home planet, who the latter keeps saying is the most beautiful place in the galaxy. The Jerkass gets the reptilian to admit the other character's planet has been ravaged by an asteroid shower and is hardly the paradise he thought it was, but to his shock the reptilian wholeheartedly agrees that the planet is the best place there is because the planet is named after the reptilian's word for "home".

Tabletop Games

• Dungeons & Dragons
  • The "Zone of Truth" spell prevents anyone in the target area from lying while the spell lasts, but it does not compel people to answer questions.
  • Forgotten Realms NPC Malik el Sami yn Nasser suffers from truth-spell cast by goddess of magic personally, so it looks like he's not going to recover any time soon. By the way, he was given a title "Seraph of Lies" soon after that incident.
  • In some versions of the game, paladins (and occasionally other characters) cannot tell a lie. They aren't literally forced to tell the truth, but risk losing their powers if they do so.
• Exalted: The Ebon Dragon is a partial inversion; as the cosmic incarnation of bastardry, he can't tell the truth... unless said truth would horribly fuck with whoever hears it.
• GURPS: An optional Disadvantage is "Cannot Lie": any character with this trait is unable to lie, and if they try, they will either "blurt out the truth or stumble so much that the lie is obvious." It does not prevent them from stealing or other unlawful acts (honesty is a separate disadvantage).
• In Nomine:
  • While Seraphim can lie, doing so is very bad for them, and can easily and very quickly lead to them ceasing to be Angels, or at least being loaded down with Discords (the game's version of disadvantages). They can give themselves some wiggle room by using Exact Words or choosing not to challenge the incorrect conclusions of others, but ever there there's only so much that they can push their luck. Their demonic counterparts, the Balseraphs, are exceedingly talented lie-smiths and can convince others that it is the truth, but they must believe their own lies, at least for the few moments needed to say them. They also suffer Discord if they do anything to contradict their own claims (such as saying "I will not shave your head" and then do just that).
  • Much like their Seraph archangel, all of Litheroy's servants cannot lie or deceive, and gain dissonance if they do. In fact, they're often more extreme about this than even non-Litherite Seraphim, because under normal conditions a Seraph can use Exact Words or otherwise try to deceive without explicitly committing to a falsehood; Litheroy's servants can't. This extends to not being able to explicitly deny their angelic natures is asked or to take Roles. In Heaven, they get on great; on Earth they run into problems.
• Pathfinder: Apocrisiariuses generate a zone of truth wherever they go and are incapable of speaking any sentence that contains a lie, even if they don't know what the truth is. They prefer painful truths and can be tempted by the offer of them, and are immensely skilled torturers, with the limitation that the victim's survival is only guaranteed until they've given up the first secret.
• Warhammer 40,000: Kairos Fateweaver is a two-headed Lord of Change who knows everything due to being thrown into the Well of Eternity. Unfortunately, he's also insane, and while one head will answer truthfully and the other falsely, no one knows which head is right (and they switch too).
• The World of Darkness:
  • Changeling: The Dreaming: Inverted with the Pooka; their Frailty is that they can never tell the whole truth. Some players tend to find the perfect mixture of truth and lies, but more than a few tend to rely on, "There is not a large army of chimera charging down Main Street!"
  • Werewolf: The Forsaken gives us the Fire-Touched tribe of werewolves. They follow Rabid Wolf, whose Ban is that he may not let a false statement lie. Not only does this bar the Fire-Touched from lying, they actually have to challenge any statement they hear that they know is a lie, no matter the consequences.

Video Games

• The Advisors (the angelic and demonic characters that float around the screen) in Black & White are honour-bound to always provide you with truthful information, though both are free to follow their own agenda (getting you to perform good or bad deeds, respectively). It's all there in the manual.
• The Truth Vessels in Deadly Rooms of Death have this to improve reliability, as they were created to collectively serve as a living search engine. They also speak a language that was specifically designed to make misinterpretations impossible.
• In Fallout: New Vegas, Yes Man is programmed to be forthcoming with all information to anyone who asks for it. He acknowledges that this was probably rather short-sighted in hindsight from Benny, who was the one who had him reprogrammed.
• 343 Guilty Spark from Halo might fall into this trope, depending on how you think he was programmed and to what degree his rampancy has proceeded. Either way, nothing he ever says is untrue. He does withhold inconvenient facts if nobody asks about them, but it's more likely that it just doesn't occur to him to explain; he simply takes it for granted that anybody attempting to activate Halo would know what they were doing.
• Angels in Might and Magic: Heroes VI are incapable of lying, but are capable of deception by choosing not to tell all of the truth.
  • Might and Magic X, which takes place in the aftermath of Heroes VI, plays around with the usual expectations of that — turns out just because you can deceive by omission and Exact Words doesn't mean you are necessarily any good at it.
• Angélique the doll from Hidden City is created with very high morality, and as a result can only speak the truth.
• In Jay's Journey, the character of Puff (and other dragons like him) can't lie, but he can definitely omit information. When asked by a villain if he's seen Jay, he manages to twist the conversation into making it seem as though he has no idea who Jay is, all without lying. Specifically, he points out that he's traveling with a complete moron, which is true, while failing to point out that he's traveling with about a dozen other humans.
• Knights of the Old Republic II: The Sith Lords implies that the droids of Star Wars can't lie. It does this by way of a side-quest which involves stealing a Czerka Corporation droid, programming it so it can lie, and sending it back. It ends about as well as expected.
• My Cafe has Lucas, a scientist who claims to not know how to lie and is prone to telling Brutal Honesty as a result. He does manage to trick other people by withholding information.
• Touhou Project:
  • Oni are said to be incapable of lying, and may be able to instinctively detect when they are being lied to.
  Always honoring their promises, they can think of no other way to behave than to be fair and square.
  There are no youkai who are more honest than the oni.

  Perfect Memento in Strict Sense, Hieda no Akyu
  • One of Reimu's Informed Abilities is that she does not lie and will most likely respond to any question honestly, no matter how rude she is in the process. This is another trait that puts her in contrast with her best friend Marisa, who will often tell utterly pointless lies for the sheer sake of it.
  • This trope is also inverted with Sagume Kishin. You think Cassandra, a little further up this page, has it bad? As the goddess of the contrarian Amanojaku species, Sagume is unable to talk about any event without the universe itself opposing her in petty attempts to make her look like a Consummate Liar.
• In Unavowed, this applies to the Jinn race as a whole. They are compelled to always speak the truth, and even just the attempt to lie causes them unbearable physical pain, something which also serves to make them great Living Lie Detectors, as they also feel very uncomfortable when they sense that others in their vicinity are not speaking the truth. That said, Jinns can still get away with acts of trickery and subterfuge by using Exact Words, which means that they have a bit of a bad reputation in the supernatural community despite their inherent honesty.

Visual Novels

• Demons in Tyrion Cuthbert: Attorney of the Arcane are physically incapable of directly lying. However, they're capable of getting around this through use of Exact Words or simply not revealing the whole truth. At one point Tyrion himself is unable to lie, when he awakens his celestial potential.

Webcomics

• Quantum Cop of Casey and Andy can't lie — although he eventually gains the ability in the final arc as Character Development.
• The Feyn from City of Somnus, because their magical nature prevents them from lying. That is, outward lying. They can omit and reinterpret just fine.
• El Goonish Shive:
  • Abraham the wizard is sworn to an Oath of Truth. Interestingly, he deliberately avoids people so he won't have to reveal information he doesn't want to.
  • Another world is mentioned where Ancients (known as Immortals in the main world) are incapable of lying without bringing the wrath of their entire race upon themself. Immortals in the main world are under no such restriction, meaning that Tara the griffin (who is from this other world) is easily manipulated by an unscrupulous immortal in the main world because she falsely believes that he cannot be lying to her.
  • Ashley, as part of her "absurd goodness", finds it almost impossible to lie (she can do so if she thinks something beyond her own embarassment hinges on it, but she's not good at it). It's not exactly Will Not Tell a Lie, because there have been occasions when she's been perfectly willing to tell a lie, but blurted out the truth anyway. Since absurdly good characters never know they're absurdly good, she interpretes this as "not having a filter".
• In Ensign Sue Must Die, God Sue (aka Sue Prime) is physically incapable of stating anything she doesn't truly believe. Which is why it's a shock to her when she finds she can't actually say she loves Spock Prime.
• Gunnerkrigg Court: In Chapter 12, robots cannot lie. That is how the robot can tell Antimony is a robot: she says so.
  • And this is despite the fact that robots are actually seen lying in the comic, though their lies are almost always ridiculously transparent.
  • Reynardine cannot lie when talking with Antimony, who, in a Moment of Weakness, exploits this to force him to confront an Awful Truth she has angrily revealed to him. He turns the tables on her with another Awful Truth in response.
• Kill Six Billion Demons:
  • Subverted with angels. It's an in-universe misconception that they can't lie, as innately lawful entities, but White Chain does so anyway at the cost of it damaging the Containment Clothing that lets her manifest in the physical world. Must be a pretty strong misconception, since people overlook the fact that the lie literally cracks her facade.
  • White Chain proves to be terrible at poker, being utterly incapable of bluffing. Later, a small bluff at a key moment lets them win a very important fight. The Alt Text notes that while angels are terrible at bluffing, this is very different from not being able to bluff at all, and many people are caught off guard because of this.
• Misfile:
  • Vashiel has had his ability to lie removed entirely, as part of a punishment for past transgressions (it's implied he got a little too into smiting the wicked). His resulting unfortunate honesty when asked "Does This Make Me Look Fat?" led to what he described as "the most painful day ever".
    Past!Vashiel: Yes, but not nearly as much as the rest of your clothing.
  • He later says it's not absolute: if it were a situation of universal security (specifically, a "clear and present danger" to the filing system), he would be able to lie in order to uphold it. But of course, such a situation is incredibly rare. His vows are released during the climax; in the epilogue he admits to missing be incapable of self-deception.
  • For one that actually happened in the comic:
    Vashiel: Oh, just, we were supposed to get you to think that Kate was in the wrong so you'd be okay with letting us help you win the race by dealing with the spirit of her dead sister, only I totally wasn't supposed to be telling you this, and I blew it.
    Rumisiel: Why do we take you anywhere?
• Amorphs in Schlock Mercenary have a variant: They can and will lie in old-fashioned ways when dealing with non-amorphs, but amongst themselves, their favoured way of communicating is by sharing memories and giving them away like humans would hand over data on an USB drive. Amorphs absolutely will not entertain suggestions of self-modifying memories for sharing: The one time the concept is even brought up in front of Schlock, he responds halfway with revulsion and halfway as though the concept is impossible. This later becomes important to his shipmates: When the Toughs end up being brainwashed with false memories, Schlock (thanks to his biology) is the only one who is able to store a backup copy of his real memories and recover them independently. When the Toughs later end up being informed that they have been brainwashed by someone they distrust (thanks to the fake memories), Schlock vouching for their current memories being fake is the one piece of evidence Tagon will accept, as he knows how important accurate memories is to Schlock.
• Reggie from The Sword Interval is a played with example; he can lie, but doing so is harmful to him (as in, pieces of him crack and fall off). When he tells a big enough lie partway through the story, he almost dies as a result.
• Tower of God: Kang Horyang's icon makes it impossible for him to lie, deceive and withhold the truth. Not that he needs to do any of that.

Web Original

• Cedar Wood from Ever After High cannot tell a lie outright.
• In Looming Gaia, all fae (elves, goblins, gnomes, sirene, cecaelia, and nymphs) are incapable of saying anything that they know isn't true. They can, however, twist the truth using Exact Words. For instance, you can see someone dead and ask a fae with a knife if they stabbed them, but if they actually slit their throat instead of stabbing, they can say no.
• In the GoAnimate "Grounded" videos, the groundees are incapable of not admitting their actions.
• SCP Foundation: Victims of SCP-1082 are not only unable (and unwilling) to lie — they won't even use euphemisms or non-literal language, and write and speak overly verbosely so as to leave absolutely no room for misunderstanding whatsoever.

Western Animation

• Ben 10: Ultimate Alien: Galapagus, one of the Andromeda Five aliens from the Andromeda Galaxy. But he learns.
• The Polymorphic Clone replacing William in Season 4 of Code Lyoko was never programmed to lie. He'd respond truthfully to any question asked by anybody, including about his true nature — although being quite stupid and literal-minded, it's probable he'd misinterpret the question. (And while he's aware another William exists, he still responds to William's name, which can get confusing.) This has caused serious troubles for Team Lyoko on a few occasions (like in episodes "A Lack of Goodwill" and "Down to Earth"). This may look like a big oversight coming from Jérémie, but he has hardly mastered the programming of artificial intelligences yet... and the only code at his disposal that could improve the Clone was the one used by Franz Hopper to create XANA, hence a way-too-big risk to take.
• Mrs. Thompson from Codename: Kids Next Door. Being unable to lie was a downside of the curse that made her the Were-Dog Queen.
• Gravity Falls: In Mabel's story in "Bottomless Pit!", she gets tired of Grunkle Stan's constant fibs and tricks him into wearing a pair of magical dentures that force their wearer to tell the truth. Unfortunately, they also remove his verbal filters so now he constantly blurts out Too Much Information, to Mabel and Dipper's distress.
• In Jamie's Got Tentacles!, the alien race the Blarbs don't lie or even pretend. This is why Jamie sometimes doesn't understand some things Erwin says or does.
• Dr. Wily thinks that robots Cannot Tell A Lie in the animated Mega Man (Ruby-Spears) series. Rock proves him wrong.
• An Al Brodax Popeye cartoon had Wimpy using vanishing cream to make himself disappear so he can escape Brutus' wrath. Popeye joins in on the trick, so when Brutus approaches him:
  Brutus: (angrily) Popeye, have you seen that moocher Wimpy?
  Popeye: Brutus, ya knows I never tells a lie. Nope. I hasn't seen him today.
• The Powerpuff Girls (1998):
  • Episode "Lying Around The House" has a little figure that grows every time the girls tell a lie. To get rid of it, they must tell the truth about their transgressions, which they eventually do. First done as issue #21 of the comic, "Big Fish Story".
  • "Not So Awesome Blossom" had the redheaded heroine forced to swear allegiance to Mojo Jojo in exchange for the safety of her sisters and the Professor:
  Blossom: How do you know I won't lie?
  Mojo: Because you're Blossom.
  Blossom: (defeatedly) Shoot!
• Rocky and Bullwinkle:
  • A Bullwinkle's Corner segment has our antlered hero reciting Edward Howard's "The Cherry Trees," with him sitting in one such tree on the grounds of Hatchet Manor (you can already see how this is going to end). When Lord Hatchet makes Bullwinkle and the branch he's on fall on him and knocking him out:
  Other man: I say...what's happened to Hatchet?
  Bullwinkle: I cannot tell a lie. I did it with my little cherry tree.
  • Bullwinkle flat-out states that his mother told him to never tell a lie in the Counterfeit Box Tops story arc.
• Franklyn from Viva Piñata cannot lie or keep secrets at all, this is played as a running gag in many episodes
• Zeke's Pad: After making himself king in "King of the Pad", Zeke discovers that his subjects are afraid of him. In an attempt to rectify this, Zeke strips everybody of the ability to lie. This backfires hideously when everyone starts going around telling everyone else exactly what they think of each other. As a result, feelings get hurt, people get mad, and an angry mob forms outside Zeke's house so they can tell him exactly what they think of him.

Real Life

• The famous SOE agent Noor Inayat Khan was taught by her Sufi cleric father never to tell a lie. Needless to say, some of her instructors thought this would cause fatal problems for someone being dropped into Nazi-occupied France as a wireless operator. She appears to have adapted, though; Hans Kieffer (head of the Gestapo in Paris) testified after the war that you couldn't believe a word she said under interrogation.
• Many autistic people have a hard time lying to others. Autistic people tend to be more literal thinkers, so the concept of deception (not addressing queries directly) is often difficult to grasp. It varies on a case-by-case basis; some can generally overcome this to some extent (at least enough to avert unnecessary Brutal Honesty), while others often have to enact significant mental preparations before being able to lie.
  • In a Subversion of this trope, due to often experiencing social rejection and bullying, autistic children can and do learn to lie to protect themselves, often more convincingly than their neurotypical counterparts.
• There is a myth that undercover cops, when asked if they are a cop, are legally required to tell the truth. This myth comes from a misinterpretation of "entrapment" laws^note Entrapmment law essentially states that an undercover policer officer can not do any action which would induce a person into committing a crime which he or she would not otherwise do. Simply allowing a person to commit a crime, not knowing that you are a police officer, and then witnessing said crime does not count as entrapment. as well as a misunderstanding of the Miranda Rights which requires a police officer to read a suspect's rights to them when they are arrested. There is actually no law which requires an undercover police officer to reveal themselves as such, as naturally any law to that effect would ruin sting operations and put police officers' lives at risk. That said, many police officers have actually said that they appreciate Hollywood perpetuating the myth, specifically because it makes their jobs so much easier. (That is to say, police officers are not required to tell the truth about being undercover, but criminals who watch a lot of movies may think that the police have to tell the truth, which makes said criminals easier to trick.)
  • For that matter, the police in general - at least in the US - are legally allowed to lie to you. To provide a few examples, they can claim to have evidence they don't have (generally to get someone to confess or provide evidence on another party), they can threaten property owners for not being allowed on the property even if they don't have a legal reason to enter, and they can provide false reassurances of safety to informants and witnesses. Regent University published a lecture about this topic on YouTube, aptly titled Don't Talk to the Police
• While deception of one's prey or predators (e.g. camouflage, bluffing) is commonplace throughout the natural world, in-species manipulative lying — the sending of false signals to other group members in order to exploit their belief in that signal — seems to be restricted to the most intelligent of social animals, such as monkeys.
• Subverted by a set of robots developed in an evolutionary system sometime. Here is an article how it went down, but basically, robots intended to search for some unspecified resource were supposed to flash a light to signal their finding. Eventually some robots started signaling when they didn't find it, or didn't signal when they found it, to hog it for themselves.
• Fun with etymology: Old German had its own term for such people, "alawari" (still recognizable as alles wahr=always true). This then slowly turned into the word "albern"=silly. There must be a moral somewhere...

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