Info Starships Fleet Yards Treknology

Episodes Database Fandom Community

Vulcan Lies and Errors

by Joe Richardson

T'Pol Spock Tuvok Other Vulcans The "Big Lies"

"Vulcans are incapable of lying." This is a myth that was brought up by the Romulan commander in TOS: "The Enterprise Incident". The myth was refuted as soon as in the very same episode, because Spock was lying to her all the time, and most obviously when he pretended to kill Captain Kirk with the "Vulcan Death Grip". Still, the myth was quoted a couple more times in Star Trek, and was frequently alluded to by Spock as some sort of running gag in the TOS movies. Here, Spock consistently insisted that he wouldn't lie but only "omit" or "exaggerate" facts. This raises the question whether Vulcans generally lie less frequently than other humanoids, or perhaps only if they were ordered to do so, and whether they may have a particular reason to be embarrassed when they are caught lying.

The following is a list of occurrences of Vulcans not telling the truth, some of which may qualify as lies. Note that in many of the cases Vulcans perhaps don't lie in a narrow sense (as a conscious deception) but one of the following rationales may apply:

They were mistaken about something they took as a fact.
They made a prediction that turned out inaccurate or premature.
They were subject to delusions.
They changed their mind about something they said earlier.
They made an ironical remark (although Vulcans are often said not to have a sense of humor either).
Facts that apparently prove them wrong may not hold up to a more thorough investigation.

T'Pol

T'Pol said "Vulcans don't touch food with their hands" before using a fork with great precision (ENT: "Broken Bow"). On the other hand, Spock can be seen eating meat with his hands around 5,000 years earlier (TOS: "All Our Yesterdays") and the Vulcans considered eating deer in the 1950s (ENT: "Carbon Creek"). In the latter case it becomes clear that eating meat is considered "savagery" however.
T'Pol played along with with Captain Archer's request that she'll tell Trip that "Rock People" were present on Archer IV when they were only imagined (ENT: "Strange New World").
After Archer suggested wine for a possible invitation to Captain Vanik, a Vulcan, T'Pol states "Vulcans don't drink wine." She later drinks wine herself before telling a story in a later episode (ENT: "Breaking the Ice", "Carbon Creek").
A boy playing hide and seek asks T'Pol whether she has seen a girl named Nadine, upon which she tells the "truth" that she doesn't know which girl is named Nadine - although she should be aware that Nadine has to be the girl she has seen hiding in an access port (ENT: "Fortunate Son").
A Klingon ship visited by the Enterprise appeared to have escape pods (ENT: "Bounty"). This is in contrast to T'Pol's statement that "Klingon ships don't have escape pods" (ENT: "Sleeping Dogs").
After the mission to the Klingon ship, T'Pol pretended that she had to extend the decontamination cycle. She apparently did this in order to be able to spend more time relaxing in the decon chamber with its pleasant absence of smells (ENT: "Sleeping Dogs").
T'Pol told a long story about Vulcans landing on Earth in the 1950s. If it was really a made-up story then her suggestion that her ancestor was involved is not true. If it was a loose historical account then her initial explanation of visiting the site purely for geology is not true (ENT: "Carbon Creek").
After the crew all became obsessed with trivial tasks, T'Pol insisted that she was unaffected. It appeared that she was obsessed with the trinary star system however (ENT: "Singularity").

T'Pol's (still) voluntary mind-meld in ENT: "Fusion"

T'Pol states that she was coerced into the mind meld which lead to her getting Pa'nar Syndrome. In fact she openly allowed it to take place initially, but it was only later that she became distressed and wanted it stopped. She never lost her commission as a result of her wording as it's the mind-meld practice that was found offensive not the syndrome (ENT: "Stigma").
T'Pol said "I have Pa'nar Syndrome. It doesn't make a difference how I contracted it." This turned out to be untrue as she was allowed to keep her commission after they heard of a coerced mind meld being the cause (ENT: "Stigma").
T'Pol was in sickbay after she complained of a headache in an attempt to avoid Movie Night. Doctor Phlox examined her, finding there was nothing wrong with her (ENT: "Horizon").
T'Pol said "I have no interest in horror movies." then shortly after watching Frankentein, she said "I'm reading biosigns on the planet. To quote Doctor Frankenstein, it's alive." and later T'Pol stated she was looking forward to the sequel "Bride of Frankenstein" (ENT: "Horizon").
T'Pol said "We'll return what we don't use." After she and Archer raided a 21st century ATM, the money is never shown to be repaid (ENT: "Carpenter Street").
In an Orion slave auction T'Pol shouted "I'm not for sale!" She was in fact sold soon afterwards (ENT:"Borderland").
On Vulcan, T'Pol stated "I am a Syrranite. We don't lie." If her other quotes on this list are counted as lies this is not true, she wasn't exactly telling them the truth either (ENT: "Kir'Shara").
Trip stated "I'm going to perform a cold start in less than two minutes." T'Pol said "That's not possible!" It was done just as Trip said, so it was possible (ENT: "Divergence").

Spock

Spock was telling himself "I am in control of my emotions... in control of my emotion.." before he breaks down in tears (TOS: "The Naked Time").
Spock stated "Vulcan has no moon." (TOS: "The Man Trap"). A large moon-like body was seen in Vulcan's sky just a few years later (TAS: "Yesteryear"). "Star Trek: The Motion Picture" initially showed two moon-like bodies near what is likely to be Vulcan, although these were edited out of later releases.
In the Abramsverse, Delta Vega is so close to Vulcan that the old Spock can apparently see the planet in the day sky of Delta Vega ("Star Trek (2009)"). Maybe Vulcan is the moon, Delta Vega is a quasi satellite, or they are a double planet?
Spock withheld important evidence at a court hearing on the Enterprise to ensure the ship reached the restricted Talos IV. It was later revealed that Spock went along with pretense that the court existed while it and the commodore were all imaginary so he could help poor Captain Pike (TOS: "The Menagerie").
20th century Captain Christopher noticed the strange conduct and/or the female voice of the Enterprise's computer and said: "I take it that a lady computer is not routine." Spock explained it as follows: "We'd put into Cygnet XIV for general repair and maintenance. Cygnet XIV is a planet dominated by women. They seemed to feel the ship's computer system lacked the personality. They gave it one -- female, of course" (TOS: "Tomorrow is Yesterday"). Regarding Christopher's actual question Spock does not tell the exact truth because a female voice is routine.
Before he nerve pinches the Eminiaran guard, Spock said, "Sir, there's a multi-legged creature crawling on your shoulder" where there wasn't one (TOS: "A Taste of Armageddon").
Spock reminded Kirk "that this is a silicon-based form of life and McCoy's medical knowledge will be totally useless." It wasn't useless (TOS: "The Devil in the Dark").
Spock pretended to be a Trillium merchant to the Klingons (TOS: "Errand of Mercy").

The "Rice Picker" lie in TOS: "The City on the Edge of Forever"

After a 20th century policeman finds Spock and Kirk, Kirk is asked to explain Spocks ears "They're... actually easy to explain..." Spock added "Perhaps the unfortunate accident I had as a child." Any accident as a child wouldn't be the cause of his pointed ears (TOS: "The City on the Edge of Forever").
After seeing Spock making something, Edith Keeler asked "What on earth is that?" Spock replied "I am endeavoring, to construct a mnemonic memory circuit using stone knives and bearskins." This is not true (TOS: "The City on the Edge of Forever").
After the challenge of a fight to the death against Kirk, Spock said "I will do what I must, T'Pau, but not with him," he still started fighting Kirk anyway (TOS: "Amok Time").
T'Pau told Spock "Live long and prosper, Spock." Spock replied "I shall do neither, I have killed my captain and my friend" (TOS: "Amok Time"). Spock didn't kill Kirk, he just thought he did.
After Spock reacted with extreme excitement to news that he didn't kill Kirk, Doctor McCoy said "You can't tell me that when you first saw Jim alive that you weren't on the verge of giving us an emotional scene that would have brought the house down." Spock explained "Merely my quite logical relief that Starfleet had not lost a highly proficient captain" (TOS: "Amok Time").
Spock told McCoy, "I do not respond to hunches, no transporter malfunction was responsible for the disappearance.... No known natural phenomena could have caused that beam, does that clarify the situation?" McCoy says "No, it doesn't, it's still a fancy way of saying that you're playing a hunch" (TOS: "The Gamesters of Triskelion"). If McCoy's correct Spock was incorrect about not responding to hunches.
Spock stated that "History cannot be changed" (TOS: "Spectre of the Gun"). He obliviously changed his mind after a time travel event lead to an Andorian replacing him on the Enterprise (TAS: "Yesteryear").
Also, in "Star Trek (2009)", history was obviously altered. On second thought, we may discount this occurrence because for all intents and purposes, the Kelvin Timeline is a parallel universe and the history of the original timeline has not changed.

The "Vulcan Death Grip" lie in TOS: "The Enterprise Incident"

A Romulan commander said "There's an old saying, or perhaps a myth, that Vulcans cannot lie?" Spock replied by saying "It is no myth." Later in the same episode Spock pretended to kill Kirk with a "Vulcan Death Grip" and quite clearly lied about it (TOS: "The Enterprise Incident").
Spock stated "I do not desire a ship of my own" (TOS: "The Enterprise Incident"). He nevertheless became a captain in later years ("Star Trek II: The Wrath of Khan").
On Stratos Spock said to Droxine that she awakened him, he was already awake (TOS: "The Cloud Minders").
Spock told Zarabeth that his home is "millions of light-years away". This is quite a big "exaggeration" as even the galaxy isn't very wide compared to that distance (TOS: "All Our Yesterdays").
Kirk asked Captain Spock for a damage report while their communications were monitored by Khan Singh. Spock replied "Admiral, if we go by the book, like Lieutenant Saavik suggested, hours could seem like days." Kirk then acknowledged this. Spock told him "The situation is grave, Admiral, we won't have main power for six days, auxiliary power has temporarily failed, restoration may be possible, in two days, by the book, Admiral." This report later turned out to be false and Saavik said "You lied!" to Spock who claimed "I exaggerated" ("Star Trek II: The Wrath of Khan").
Spock told Kirk "You ordered me to kill my brother." Kirk replied "Sybok couldn't possibly be your brother because I happen to know for a fact that you don't have a brother." Spock then admitted "Technically you are right I do not have a brother... I have a half-brother." ("Star Trek V: The Final Frontier").
Spock told Kirk "This is a new brig, Captain, it's escape-proof." Kirk asked "How do you know?" Spock answered with "The designers tested it using the most intelligent and resourceful person they could find, he failed to escape." They did escape, albeit with outside help ("Star Trek V: The Final Frontier").
Captain Spock: "There is an old Vulcan proverb: only Nixon could go to China." This is a minor Earth event from before first contact, so is highly doubtful to be of Vulcan origin ("Star Trek VI: The Undiscovered Country").
Spock said "Klingons have no tear ducts." ("Star Trek VI: The Undiscovered Country"). Excluding part human Klingons, Worf talked about Kahless and how he "wept the oceans into existence." This suggests he had tear ducts (TNG: "Birthright").
Spock said to Captain Scott "I understand you're having difficulty with the warp drive, how much time do you require for repair?" Scott replied by saying "There's nothing wrong with the bloody thing." Spock then told Scott "If we return to Spacedock, the assassins will surely find a way to dispose of their incriminating footwear, and we will never see the Captain or Doctor McCoy alive again." Scott then says "Could take weeks, sir" ("Star Trek VI: The Undiscovered Country").
After Scott had agreed to pretend the engine had trouble, Spock asked Valeris to "inform Starfleet Command that our warp drive is inoperative." Valeris again thinks this is "a lie?" Spock again makes up another term, this time it's "an error" ("Star Trek VI: The Undiscovered Country").
Spock said "An ancestor of mine maintained that when you eliminate the impossible, whatever remains, however improbable, must be the truth". Since Sherlock Holmes is not real this is either a lie or someone else in his family quoted Sherlock Holmes ("Star Trek VI: The Undiscovered Country").
Spock told Valeris "In 24 hours we will agree this conversation did not take place." Valeris replies with "a lie?" Spock says it's "an omission" ("Star Trek VI: The Undiscovered Country").
After history was changed, Spock had to visit his past self on Vulcan, he lied to himself and others by claiming he was Selek (TAS: "Yesteryear").
Spock said "Andorians are not known for their charity" (TAS: "Yesteryear"), yet the Andorians helped Earth during the Xindi War several times for no gain (ENT season 2 et al.).
While being attacked by Klingons during a Tribble infestation, Spock suggests "We could always throw Tribbles at them." Captain Kirk replies with "I thought Vulcans didn't have a sense of humor." Spock then says "They don't." (TAS: "More Tribbles, More Troubles"). Spock's statement is unlikely to be serious.
After Kirk's shirt has the words "Kirk is a Jerk" written on it, laughter erupts and Kirk says "When you all finish laughing, I'd appreciate an explanation." Spock then claimed, "I never laugh" (TAS: "The Practical Joker"). Spock is seem laughing in earlier episodes (TOS: "Plato's Stepchildren", "This Side of Paradise"), albeit not on free will.
Spock warned to Kirk that "the ship will not fit," Kirk insisted it will fit. After the ship barely gets through, Kirk brags "See, I told you it would fit!" Spock however isn't sure that it qualified ("Star Trek Into Darkness").
Spock lies about the destiny of the Discovery, saying that the ship has been destroyed. It is also his proposal to deny the existence of the Discovery and of his own sister, Michael Burnham (DIS: "Such Sweet Sorrow II").
Spock tells Chekov that there has never been a mutiny on a Starfleet ship (TOS: "The Tholian Web"). He lies, because he knows very well of Michael Burnham's mutiny on the Shenzhou, for which she was convicted (DIS: "Battle at the Binary Stars"). But his lie falls under the ban established in DIS: "Such Sweet Sorrow II".

Side note The common definition of a mutiny requires a conspiracy, but Burnham evidently acts on her own. Technically speaking, it does not appear to be a mutiny. But her actions are called a mutiny no less than 17 times in the series, including the wording of the indictment and other statements such as by superior officers that we can expect to be reliable and accurate. There is no doubt it is indeed a mutiny by 23rd century standards, and that Spock lies to Chekov about it.

Spock pretends to be an inhabitant of Kiley 279 (SNW: "Strange New Worlds").
In TOS: "Dagger of the Mind", Spock explicitly tells McCoy that he has never performed a mind meld with a human. This retroactively becomes a lie because he mind-melds with La'an Nooonien-Sing (SNW: "Memento Mori").
After they have switched bodies, Spock and T'Pring maintain the impression that they are who they look like (SNW: "Amok Spock").
Spock tells Nurse Chapel: "Vulcans cannot lie. At least not in the way that humans can" (SNW: "Amok Spock").
Spock pretends to have an affair with Nurse Chapel, to get T'Pring to end their betrothal. Chapel later tells him: "Lying isn't your strong suit" (SNW: "The Serene Squall").

Tuvok

Tuvok reveals his deception in VOY: "Caretaker"

Tuvok told Chakotay "that I was assigned to infiltrate your crew, I am Janeway's Chief of Security." This means Tuvok lied about himself and pretended to be a Maquis for a considerable time beforehand (VOY: "Caretaker").
Janeway told Tuvok that she "spoke to your family before I left." Tuvok asked "Are they well?" Janeway replied "Well, but worried about you." Tuvok said "That would not be an accurate perception, as Vulcans do not worry." If Vulcans don't worry, why was he so concerned about his family's wellbeing? (VOY: "Caretaker").
Chakotay asked Tuvok "Can I ask you to be honest with me, Lieutenant?" Tuvok replied "As a Vulcan, I am at all times honest." Chakotay shot back "That's not exactly true, you lied to me when you passed yourself off as a Maquis to get on my crew!" Tuvok defended his actions "I was honest to my own convictions within the defined parameters of my mission." This is hardly "honest at all times" (VOY: "State of Flux").
Tuvok missed a shot at a game of snooker and said "Perhaps the ship's stabilisers are not operating at peak efficiency" This is a made up excuse (VOY: "Jetrel").
Tuvok told Janeway "I've observed that Captain Sulu drinks a cup of tea each morning so I thought he might enjoy a Vulcan blend." Janice Rand came in and said "Oh, trying to make lieutenant in your first month, I wish I'd have thought of that when I was your age as it took me three years just to make ensign." Tuvok assured Janice "I have no ulterior motive." Janeway then said "You've never brought me tea." It's not certain, but it did look as if he was aiming for promotion from Sulu by being extra helpful, as Janeway didn't get the same treatment (VOY: "Flashback").
Captain Janeway remarked "Tuvok, if I didn't know you better, I'd say you miss those days on the Excelsior." Tuvok replied "On the contrary, I do not experience feelings of nostalgia." Before adding "But there are times when I think back to those days, of meeting Kirk, Spock and the others, and I am pleased that I was part of it." It sounds like he was nostalgic after all (VOY: "Flashback").
Marayna asked Tuvok and Kim "There's a luaw tonight, you're coming, aren't you, both of you?" Tuvok replied "No" while Harry Kim said "Yes". They both went to it so Tuvok was wrong (VOY: "Alter Ego").
Later at the event, Marayna told Tuvok "You're the only one not wearing a garland!" Tuvok said "It seems somewhat excessive." Then Marayna replied "I don't believe you!" A surprised Tuvok said "I beg your pardon?" Marayna stated "I think you are trying to isolate yourself and make a public protest at the same time." Tuvok asked for an explanation. Marayna told Tuvok "You didn't want to be here in the first place, being the only one without a garland sets you apart from the others, allowing you to symbolically maintain your solitude, and since everybody can see that you're the only one without it, you're letting them know that you'd rather be somewhere else." Tuvok replied "Your logic is impeccable." This suggests Tuvok's reason for not wearing the garland was false (VOY: "Alter Ego").
Takar, a hostile scientist, warned Janeway "I can kill you and your crew in an instant." Janeway replied "Go ahead, without us, you won't prevent this ship from being torn apart... and even with my crew working I say the odds of us getting through this are what, one in ten?" Tuvok then "corrected" her by adding "One in twenty, at best!" This statement from Tuvok scared Takar away and Janeway remarked "I hope you were exaggerating about those odds." Tuvok then said "I was not!" The ship survived in good condition and since his comment helped Janeway it looks like an exaggeration (VOY: "Scientific Method").
Talking to Nimira, Tuvok insinuated that he would usually communicate telepathically if it were not for the many non-telepaths in Starfleet. But Vulcans were never known to use telepathic communication among their own species, although they may be capable of it. Well, Tuvok was just speaking of himself and he may have had special training (VOY: "Random Thoughts").
Janeway asked Tuvok to distract Leonardo da Vinci with small talk. Tuvok said "Vulcans do not make small talk." Leonardo da Vinci asked Tuvok "Where exactly are you from?" Tuvok said "Scandinavia." This is a lie as he's from Vulcan, more precisely from the "Vulcanis Lunar Colony" (VOY: "Concerning Flight").
Seven of Nine asked "Am I correct in assuming that Vulcans are incapable of lying?" Tuvok replied "We are capable of telling lies, however, I have never found it necessary to do so." Then after Seven asks "You have never lied?" Tuvok added "Only under orders from a superior officer" (VOY "Hunters"). This means he never told Seven that he did lie, but the opposite until she asked again.
Ensign Sam Wildman when on her deathbed asked "Who's going to look after Naomi?" Tuvok replied "You should not concern yourself with that now." She is Naomi's mum and should be concerned however (VOY: "Once Upon a Time).

Tuvok activates the "photonic cannon" in VOY: "Tiner, Tenor, Doctor, Spy"

While trying to scare away the "Hierarchy" that watched the EMH's day dreams earlier, the EMH pretended to be captain and said "Activate the photonic cannon." Tuvok then hesitated before the EMH (or ECH!) said "That was an order." Tuvok then went along with the play acting and stated "Activating the photonic cannon." The cannon was not real, just something from a dream so he couldn't activate it anyway (VOY: "Tinker, Tenor, Doctor, Spy").
Tuvok shouted "I'm not a Vulcan, not anymore" when in a crazed state (VOY: "Riddles").
At Tuvok's birthday party, Janeway noted "So it's not long before you hit the big three digits?" (VOY: "Fury"). Janeway witnessed Tuvok's memory of 80 years ago when he said "I was 29 years old" on the Excelsior (VOY: "Flashback"). So Janeway knowingly made an incorrect statement about him being less then 100 at his public celebration, but why? One possible explanation is that Harry Kim and Tom Paris were speculating about Tuvok's age, trying to get him to tell, but he wouldn't (VOY: "Alice"). So maybe Tuvok suggested Janeway not reveal how old he was. Only other explanations are that Janeway is confused or making some kind of joke.
After capturing the impostor Dala, Janeway threatened to extradite her to the Telsians. She gave Tuvok a cue to tell the prisoner about the conditions in Telsian prisons. Tuvok hesitated, but then told Dala the following, which he made up on the spot: "Barely habitable. Inmates often die of malnutrition before they are brought to trial. Torture is commonplace, as is disease, including several incurable forms of psoriasis." Janeway was particularly amused about the psoriasis part (VOY: "Live Fast and Prosper").
Janeway asked Tuvok "We have known each other now for how long?" Tuvok replied "Approximately twenty years." Later Janeway added "I have always been honest with you, but you've been keeping something from me!" Tuvok then said "I don't know what you mean." Janeway said "Don't you, it took exhaustive research, sifting through terra-quads of data, separating fact from rumor, but I eventually arrived at the truth." Janeway turns around with a cake and says "Happy Birthday!" Tuvok blows out his birthday candle only because "it was a fire hazard." Janeway could have been right that he was not honest with her, considering they knew each other for 20 years, and the candle was not a fire hazard in that case (VOY: "Fury").
Neelix asked Tuvok "Did I ever tell you about Salvoxia?" Tuvok replied "If I say yes, will it prevent you from telling the story?" Although not lying, Tuvok is considering doing so (VOY: "The Haunting of Deck Twelve").
When investigating a crime, Tuvok told Janeway "I have worked meticulously, yet he has outwitted me each time!" Janeway asked "How can you be sure it's a 'he'?" Tuvok replied "I can't. But I am." This statement contradicts itself, as both can't be true (VOY: "Repression").
When Tuvok was at a First Contact Day celebration on the ship, he said "Vulcans do not dance." Tuvok did dance later on even. Before Tuvok danced, and was refusing to do so, Neelix said "But it's tradition," Tuvok then replied "There is no tradition, this ceremony is entirely your invention." Janeway interupted by adding "This is an official ship function, Commander, don't make me order you to dance!" I would doubt that Neelix invented the First Contact Day celebration, perhaps the dance but not everything else (VOY: "Homestead").
Another potential lie is when Tuvok states "Vulcans don't experience fear." But he seemed to have stage fright over dancing (VOY: "Homestead").
A hospitalised Tuvok said "I know you." Janeway replied "That's right. I'm your friend, remember?" Tuvok stated "You are an impostor... Janeway visits on Sunday, today is Thursday, logic dictates that you are not who you claim to be." It was the real Janeway (VOY: "Endgame").
After Bashir suggested destroying Deep Space Nine, Mirror Tuvok said "It is highly unlikely that anyone assigned to such a mission would survive." Bashir did survive the mission though (DS9: "Though the Looking Glass").

Other Vulcans

Ambassador Soval

At a meeting with Andorians, Soval said "Vulcans don't drink." Then he decided to drink for the occasion straight away (ENT: "Cease Fire").
Soval gives Tucker a data module and says "This shows the gaps in our satellite surveillance, when beam-ins can't be detected." Tucker replied "We're not exactly cleared to have this." Soval then says "Have what? All I see is a Starfleet data module" (ENT: "The Forge"). He knew it had restricted data on the module.

Doctor Yuris

Yuris told a Vulcan hearing on T'Pol's commission, that she was forced to have a mind meld "against her will" to justify her having Pa'nar Syndrome. T'Pol then complained "You gave me your word!", as he earlier promised not to tell. Even Archer, a human, kept quiet on this matter (ENT: "Stigma").

Syrran

When on the run as a fugitive, Syrran, leader of the Syrranites, lied about his name to Archer and T'Pol in the desert during a storm, he called himself Ebdel (ENT: "Awakening").

T'Pring

Spock's betrothed wife was extremely deceitful to Spock during the ceremony, she was scheming and planning on cheating with Stonn regardless of the result from the ceremony, although she doesn't technically lie (TOS: "Amok Time").
After they have switched bodies, Spock and T'Pring maintain the impression that they are who they look like (SNW: "Amok Spock").

T'Pau

Although T'Pau doesn't technically lie, she doesn't tell Kirk that it's a fight to the death until after he agrees to it, which is deceitful (TOS: "Amok Time").

Ambassador Sarek

Sarek said "Tellarites do not argue for reasons, they just argue" (TOS: "Journey to Babel"). Although argumentative, they have reason as it's considered a sport on Tellar (ENT: "Bounty").
Sarek lied to Kirk when asked for his location during an ambassador's death, Sarek said he was "meditating" later he said he was "incapacitated" after his medical condition was discovered (TOS: "Journey to Babel").
Spock agreed with Sarek that his wife was too emotional, then asked "Why did you marry her?" Sarek replied "It seemed the logical thing to do." (TOS: "Journey to Babel"). This is contradicted by Sarek, as after her death in a timeline altered after the marriage, he said "You asked me once why I married your mother, I married her because I loved her" ("Star Trek (2009)"), so was it love or logic, Sarek?
Sarek told Spock in disguise "You saved my son's life, Selek, there is no way I can fully repay you for that." Spock asked for him to "Try to understand your son, Sarek of Vulcan, that will be repayment enough for me." Sarek replied "What a strange request, but I will honor it" (TAS: "Yesteryear"). However, a century later when Sarek died it's revealed they did not understand each other at all (TNG: "Unification").

Sarek crying in TNG: "Sarek"

Captain Picard told Sarek "I saw you crying!" Sarek denied it, "I do not cry" he said. Picard insisted "I was there, I saw the tears." Sarek corrected him by saying "You exaggerate, I recall only one tear." This means he did cry after all (TNG: "Sarek").

Lieutenant Saavik

After Kirk was about to beam to a risky area, Saavik stated "General Order 15: No flag officer shall beam into a hazardous area without armed escort." Kirk responded by saying that "there's no such regulation." Saavik looked somewhat surprised by the reply. Either she was trying to assist Kirk by making up general orders, or Kirk didn't remember it?

Sybok

Sybok stated "The people of your world once believed the world was flat, Columbus proved it was round" ("Star Trek V: The Final Frontier"). This is untrue, the Earth was known to be round, and the length of the equator was already calculated at the time, Columbus was trying to prove that the distance between East Asia and Europe was shorter than expected, and he was wrong. It was much later that Magellen's voyage proved it was round empirically.

Lieutenant Valeris

Valeris was discovered as a traitor, so she was lying all the time ("Star Trek VI: The Undiscovered Country").
Kirk asked for names from Valeris, who replied "I do not remember." Spock claimed it's "a lie." Valeris picked up Spock's technique and said it's "a choice." A mind meld found that she did know the names ("Star Trek VI: The Undiscovered Country"). So she was lying about not knowing the names.

T'Paal

T'Paal was pretending to be Tallera, a Romulan mercenary, so was dishonest there. She did tell Picard the truth about her identity later, but told him she was a spy trying to "find the stone of Gol" to prevent isolationalist Vulcans from getting this telepathic weapon, in reality it was her who was part of that group and she was planning to use it (TNG: "Gambit").

Sakonna

The Vulcan member of the Maquis went to Quark to buy arms. After being arrested she said to Quark that she did "the logical thing." Quark then lectured her on third Rule of Aquisition "Never pay more than you have to." Sakonna says that's "logical" but added she is "willing to pay any price". Quark says it's more logical to "negotiate peace" as everyone was on a level field before so it'll be cheaper to attain peace. She then looked stunned as if her logic was proven incorrect (DS9: "The Maquis").

Captain Solok

After the Niners baseball team celebrated getting a point against his Vulcan team, Solok went and yelled at Odo "Umpire, this is completely improper!" Solok added "The game is not over!" He then realised he shouldn't be touching Odo due to game rules and Odo said "You're gone!" The game was over for him, but later Sisko said he looked "emotional" and Solok denied it despite being visibly upset that the game didn't go as expected (DS9: "Take Me Out to the Holosuite").

Ensign Vorik

Tuvok said "Lieutenant Torres is out of contact on the planet." Vorik during pon farr replied "Then I'll find her, she needs me, and I need her!" Tuvok stated "It's a more sensible strategy to get her back to Voyager, and then decide on the correct resolution." Vorik insisted "The resolution must be that we become mates, it's only logical!" Tuvok said "Torres has never been a great follower of logic" (VOY: "Blood Fever"). Although it appears Vorik (and Tuvok?) consider this logical, it isn't as a Vulcan woman was on board Voyager anyway (VOY: "Repression").

Data

Although not a Vulcan (McCoy wasn't sure ;-)), Commander Data is added here as he automatically assumed Vulcans cannot lie (TNG: "Data's Day"). This is important as he is an android with great intelligence and should have a valid reason before he considers that to be true.

The "Big Lies"

"Time travel is impossible"

Ambassador Soval said the "Vulcan Science Directorate has determined that time travel is impossible" (ENT: "The Expanse"). This is contradicted by many episodes, most notably when Spock performed the calculations for time travel to to the 20th century ("Star Trek IV: The Voyage Home").

High command lies

When accused of deception, as he hid his melding ability, Soval said "Deception has never been a stranger to this room" (ENT: "Awakening"). This is a suggestion the High Command frequently lies.

"Melders are a minority"

It is explicitly stated by physicians that only a small percentage of Vulcans are capable of mind melds because of what is seen as a genetic defect (ENT: "Stigma"). T'Pau says she could initiate the capability of melding in everyone (ENT: "Kir'Shara").

"Pa'nar is incurable"

According to T'Pau, the notion that Pa'nar should be incurable is "another lie perpetuated by the High Command." (ENT: "Kir'Shara").

Holding back technology

Vulcan claims to be Earth's ally and also claims to assist Earth's development. Archer thinks they are holding Earth back however (ENT:"Broken Bow"). Regardless, they refuse to share their technical advances in warp and tractor beams with Earth (ENT: "Breaking the Ice"). In real life, the refusal to share knowledge routinely goes along with the denial of the existence of such information.

Discovery denial

Spock proposes to Starfleet Command to keep the very existence of the Discovery, the spore drive, Control and the Red Angel under wraps, under the penalty of treason. He even decides to keep the existence of his sister Michael Burnham secret, not speaking of her to anyone (DIS: "Such Sweet Sorrow II").