Problem of the Two Doors: Classic Logic Puzzle

[@thomasgrable1746]

"One of us always tells the truth, the other one always lies." "Oh my god, Carl, I said I was sorry!"

[@calebwalters1869]

If one of them says this whole line then he gives away that he's the one that always tells the truth, because the liar would have to lie about how it works. Similarly if the liar says one of us 'always' lies, then he just told you that he doesn't always lie. But if the liar says that one of us always tells the truth, then neither of them will always tell you the truth.

[@Nuclearburrit0]

​@calebwalters1869 the lier gave the setup. Turns out both guards sometimes lie and both doors will kill you

[@w1ndgeneral226]

Barbarian takes his ax and kills the first guard. "Is he dead?" *"......no."* "This one liar."

[@princessmarlena1359]

Carl: “Oh, what a LIE! D’ooohohohoho!”

[@tclanjtopsom4846]

Seriously Flanders 😢

[@nigeria774]

"barbarian takes axe and kills first guard" "is he dead?"

[@copycruel]

U came from that video too?

[@redbaronmars4176]

@@copycruel we are sheep fr

[@talleywa5772]

Now you don't know what door is safe.

[@lordfarquaaaaaaaaaaad8311]

"No" "This one liar"

[@bearyvr6]

In this video the situation is stated that u can only ask 1 question

[@benji1901]

don't ask a question, just go to one door, open it and push the guard through. If you hear screams of death then that was the danger door.

[@davidtherwhanger6795]

That was my thought.

[@wesscoates5676]

Ahh, but what if you pushed the liar guard through the safe door, and he fakes the screams of death, thereby tricking you into going through the danger door?

[@davidtherwhanger6795]

@@wesscoates5676 Then just ask thru the door "Are you dead?" when the screaming stops.

[@wesscoates5676]

@@davidtherwhanger6795 uuuuuhhh... huh... that might work.

[@TheLifeOfKane]

The guard guards the door... your plan failed. Just ask him what the other guy would say, this isn't a logical PUZZLE its a kindergarten riddle

[@AdultToons]

Sometimes I need shit explained to me like I'm a newborn.

[@rogerkearns8094]

The words I've ever heard actually addressed to a newborn were, 'Breath, baby breath!' She was my daughter and she breathed just fine, as soon as she felt like it. :)

[@rwarren58]

Man, the test for newborns these days are brutal. 😁

[@ChaotiX1]

its very simple. ask one guard the question: "If I wanted to go through the safe door, which door would HE tell me to go through" and whichever door the guard answers, you pick the opposite door.

[@brigittakovacs7861]

'Takes barbarian axe kills one' "Is he ded"? "No" "This one lie"

[@KingOfSciliy]

Unfortunately, you still don't know which door leads to safety and you wasted your one question.

[@patrickrannou1278]

"Not problem!" Take axe to door. Grabs 2nd knight and throws him inside. If barbarian hears screamings: "Ah good me found danger door!"

[@Doctor_Straing_Strange]

but then you have no questions left to ask

[@vegaswithdrawal4132]

​@@patrickrannou1278Nope. The lying guard would fake his screaming, fooling you into thinking it's the death door when it's not.

[@cmonman7664]

But they are trained guards and would hack you. They wouldn't let you get close. Hence that's why they are guards

[@Smol_Schan]

This was very helpful. Usually I can never understand this riddle, but this helped me understand it.

[@BrainFoodforLife]

Soooo happy to hear this! Check out the new ones when you get the chance!

[@romellolane1030]

​@@BrainFoodforLife2:48 this is assuming that the liar tells the truth still leaving you at a loss

[@kevindomenechaliaga8085]

For those who didn't understand: Asking what door the other guard would tell me is safe, always leads to a false answer. If we ask the liar guard ¿What would the other guard say, if i asked wich door is safe? The liar guard would point to the damger door, since the other truthful guard would do the oposite. If we make the same question to the truthful guard, it would answer as the liar, and also point at the danger door. Thus, asking ¿What would the other guard say if we asked wich door is safe? always has the danger door as an answer. This way, we know wich is the danger door, and that the remaining door is the safe one :D I hope this explains it more concisely

[@matthewdavis9437]

It's guaranteed to point to the dangerous door, yeah. 😂 It's a good question.

[@howyoutubesmells]

you shold be the one who have made this video.

[@nagashtheforsaken]

Thank you! This video did a horrible job of explaining this.

[@khajiithadwares2263]

You include both the guards in the question since each have 50% chance of telling a lie, together they have 100%. So you get the wrong answer of whatyou ask. If you ask for safety you are pointed towards danger. If you ask for danger you are pointed towards safety.

[@mikehigbee2320]

Thank you. You explanation is comprehensible. The video, not so much.

[@rabbithedragon]

This puzzle becomes next level when there's only 1 door 1 guard and he lies half the time but you get 3 questions to figure out weather it's currently safe to walk through the door.

[@maximized_1]

Does it like change to a dangerous one as soon as he lies?

[@kevindomenechaliaga8085]

He's playing this game on very hard mode 😅 I'll definitively give it a think ¿Do you have a solution? If you do, hats off 🎩

[@HansDelbruck53]

whether, not "weather".

[@Arthus_Thenesus]

"Are you telling lies each other time?" Yes: He told the truth, next one gonna be lie, just do the opposite. No: He lied. Trust him.

[@Ozinarg]

This riddle is wrong. You get one question total, not one question per guard. Otherwise, you could just ask gaurd number 1: "whats 2+2?" If they lie, you know the other gaurd is the truth teller, and you can safely ask them which way is safe. If they do not lie, you know the other guard is the liar, and ask them which was is safe and then do the opposite of what they say.

[@ericbucher8636]

But you are still asking two questions.

[@G81L4L]

@@ericbucher8636yeah that’s exactly what he’s saying read the comment lol

[@taperhunter8671]

But you don't need to ask them both. He was just demonstrating that they would agree and you should pick the opposite.

[@TheShadowprototype]

The 2+2 doesn't work because you can only ask one question total, so you wasted your question. Because you weren't supposed to look for who's the one who lies, you were supposed to look for the wich door is safe. Let's say the danger door is left and safe one is right. "¿What would the other guard say, if i asked wich door is safe?" always lead to the same answer logically, wich the honest guard will respond with "the other guard will lead you to the left door (danger door)", meanwhile the lying guard will respond with "the other guard will lead to the left door (danger door)" so you know you should do the opposite thing because BOTH say, since the answer will always be the same one. Even if you ask wich door is the danger door, they both will "agree" with the other. It was never crucial to know wich one is the liar, but to find wich door is the good one

[@mkultrak8226]

Thanks, I was lik huh

[@theblackheart5727]

I doubt I’ll ever wrap my head around this conundrum. Thanks a lot Ricky, Steve, and Karl.

[@barukkazhad8998]

😂..feel the door to see if its hot

[@domatron1578]

Look lads ive got some post for God here

[@barukkazhad8998]

@@domatron1578 😆😆😆😆😆

[@barukkazhad8998]

@@domatron1578 a moronic genius

[@HelloThere.....]

You find a way to make them both say the same answer, IF they do so, then you know it's the opposite. The truth teller will accurately predict which door the liar will say is safe and that is always the danger door, and when that prediction matches you know that the liar was lying and that it's the opposite door. Remember you're not asking them each which door is safe, you're asking them which door they think the other will say is safe. By doing so you know that the truth teller will out the liar by correctly predicting his lie.

[@josephrusso4748]

The key factor that you omitted is that each guard knows that the other guard will respond in the opposite way. There are actually two ways of asking this question, you can ask about the door that leads to death which will reverse your response based on a yes or no answer. So there are two ways of asking this with 8 possible scenarios.

[@RectanerTreadway]

are you saying that the Liar would actually double-bluff?

[@josephrusso4748]

@@RectanerTreadway no because they have to lie, if they double bluff or lie about lying they would be telling the truth by default and also second guessing the lie

[@RectanerTreadway]

@@josephrusso4748 yes true. I get what youre saying now. One can either ask re: the door to heaven, or you can ask re: the door to hell.

[@nagashtheforsaken]

I see a lot of people not getting the riddle. Part of this is because it's horribly explained in the video. First off, the guards can't speak except to answer one question (not one question each). So the instructions to the riddle have to be given by a third party, or a message on the wall or etc. Second, this riddle involves two riddles in one, really. You have to determine which guard is lying, and which door is safe, and you only have one question. By asking either of the guards "which door would the other guard say is safe", you solve both riddles in one question. In either case, whether you ask the liar or the truthful guard, and no matter which door they guard, they will always pick the same door. So you can ask either guard the question and choose the opposite.

[@hobowithawaterpistol9070]

The biggest problem in this riddle is not knowing which guard is the liar and which is telling the truth. With that knowledge, you can then ask a trick question.

[@luiginishimura]

When I first learned this riddle, I learned a different answer. You ask either guard 'What would you say if I asked you which door was safe?' The honest guard honestly tells you which is safe, because that's what he would say if you asked him. The lying guard will give you the right answer because he's lying about the wrong answer.

[@BrainFoodforLife]

Same logic no?

[@RoderickEtheria]

Yes.

[@NotABirdd]

​@@BrainFoodforLifedifferent logic, your method ensures both guards lie, his method ensures both guards tell the truth

[@biscuit6924]

That doesn't make any sense

[@RoderickEtheria]

@@biscuit6924 Yes it does. The question is a multistage one. If you ask "Which way leads to safety?", both guards have a specific way to answer. If you ask "Which way would you say...?", you are putting them in the position to answer about what they would say, which they have to follow with their method. A lie about a lie when there is only two options results in the same as the truth about a truth.

[@Pelerin985]

"Do you have your helmet on your head right now?" "No." "Thank you to be such a good liar."

[@NovaBoiii]

Fr, it’s so simple

[@davidjones-vx9ju]

@@NovaBoiii yea... so which door is safe?

[@NovaBoiii]

@@davidjones-vx9ju Ask them 🗿 You know which one lies and which one doesn’t

[@davidjones-vx9ju]

@@NovaBoiii you only get one question

[@KingOfSciliy]

@@NovaBoiii Just finding the liar doesn't mean you've found the door that leads to safety. It was never established that the liar automatically guards the danger door and vice versa.

[@Njorl]

You can do this with one guard. State that the one guard either always lies or always tells the truth. Then ask, " If I were to ask you which door leads to safety, which door would you indicate?" Note, you are NOT asking which door leads to safety. You are asking how they would answer if they WERE asked that question. If the guard always tells the truth, then obviously he will point to the door that is safe. If the guard always lies, he will first consider what he would answer to "which door leads to safety?" If he was asked that question he would lie and indicate the unsafe door. However, to answer the question that is actually asked he has to lie about how he would answer, so he indicates the safe door.

[@patrickrannou1278]

Many D&D RPG players know this riddle. So I made the room with two undead knights, and an undead priest. The undead priest is the one presenting the riddle. So the players assume the typical two doors puzzle situation, so ask the question the "good solution" way, asking one knight what the other knight would say. If they try to ask the priest he says he doesn't know which door is the safe door. So they get a door that they "logically" think is the safe one, and go there. However, their entire premise is wholly faulty: Nothing proves to the players that the undead priest is actually telling the truth about the entire situation! In fact the 3 undeasd can say whatever they want! Both doors simply lead to more dangers, and the "good solution" of assuming the undead priest said the truth, actually leads to the worse of these two rooms. The 3 undead in the room know they can't beat the PCs directly in a fair fight, so they hope to avoid direct combat until the PCs have to start facing the threat of one of the next rooms, and then quickly arrive to attack the PCs "in their back", while they are already busy fighting! Suddenly making the fight way tougher. The only "hints" that the PCs should not believe the priest, is a previous encounter with the same type of undead knights (they all have the same heraldry symbol on their shields armor robes and vestments), to show how lying, cunning, and manipulative, such undead can be, with that 1st undead trying to befriend the PCs, offering to act as their guide to lead them to the treasure "if they then promise to bring him to a holy temple so he can be buried with the proper blessings and rituals so his soul can find peace" (a load of BS). But then he leads them straight into some deadly trap, that he activates directly himself, by pulling a secret lever, and then attacks them while insulting them for being "such stupid naive suckers". Plus 2nd hint the history analysis of their heraldic symbol reveals that that their clan of knights got cursed to undeath because they were super evil. So the "true" proper way to handle the "two doors puzzle room" is just to directly attack the 3 undead. I can make OTHER puzzles, but the 2 doors one is just so well known in the gaming community, it is better to use it as a red herring lol. Basically the big lesson is "Don't thrust monsters!"

[@artistpoet5253]

I thought the puzzle allows only one question to only one guard. You're not supposed to be able to cross check the result against the other guard.

[@n00blamer]

when you ask "what would the other dude answer" -kind of question you get both lie and truth in the spoken answer, the truth won't modify the lie it remains a lie so now you sneaked the lie to always be in the spoken answer. Since you know the spoken answer is always a lie you just take the other door.

[@benwebb4424]

You only need to ask one question. "What door would the other guard say is safe?". There are only two possible setups, Guard A is telling the truth, or Guard A is telling lies. If Guard A is telling the truth whatever he says that Guard B would say is the safe door is would be the danger door since Guard B is lying and Guard A is telling you what Guard B would actually say. If Guard A is the liar than whatever door he says Guard B says would be the safe door would also be the danger door since Guard A is lying about what Guard B would say and Guard B would tell you which door the safe door is. In either scenario whatever door the guard you ask "What would the other guard say is the safe door?" says is the danger door and you should pick the opposite door.

[@Paguo]

In the case that one Guard is explaining the charade, wouldn't that be the one speaking the truth?

[@wraithscythe1178]

Our astronomy teacher my sophomore year in high school gave us this problem at the beginning of the semester just for fun. End of the semester I figured it out for the whole class. One of the best teachers I ever had.

[@HellokittyLevel]

I did it in a couple minutes skill issue get your money up not your funny up

[@Мопс_001]

Basically the point of the riddle is to make a question that would result in the same answer from any of the guards. And at the same time this question gives us the answer to the riddle. So the only way to do it is to "connect" the guards to each other by the question

[@hobowithawaterpistol9070]

But the narrator doesn’t tell you which one is lying and which one is telling you the truth. Without that info it’s 50/50!

[@Мопс_001]

@@hobowithawaterpistol9070 I advise you to watch the video again

[@benwebb4424]

@@hobowithawaterpistol9070 It isn't. Guard A is either always lying or always telling the truth. You don't need to know if he's telling the truth or not; you just need to know which door to go through. "What would the other guard say is the safe door?" gets you to that answer in a single question. If Guard A is telling the truth, they will give you Guard B (liar)'s answer - which will be the danger door. If Guard A is the liar, they will give you the opposite of what Guard B would say - Guard B would tell you the safe door so the answer Guard A would give you is the danger door. It doesn't matter if Guard A is telling the truth or lying, by asking what Guard B would say Guard A will always tell you the danger door is the safe door so you just go through the opposite door of what Guard A says is safe.

[@eskailerwhite.7593]

😪 i still cannot understand

[@RectanerTreadway]

Rules: Guards are identical, although technically this does not matter for our logic, it helps to envision them this way to grasp the set of variables in this equation. Only they know who is the Liar and who is Truth. Only they know who is guarding the passage to paradise. It is not at all guaranteed that the Liar guards hell, nor that Truth-teller guards paradise. You must also basically assume that the Liar intends to see you pick “the bad door” because in the roles of this puzzle, your own role is defined as you intending to pick the “good” door i.e. "Get out of the Dungeon". The conceit of the puzzle is that having a Liar involved at all presents the main conflict for us. We must neutralize this conflict somehow. The goal is not to *fixate* on the liar and figure out who is who; the goal is to formulate a question that *reduces* the odds. A question that makes all the variables "non-randomized" but a better way to state this is, "to make all these variables incriminate the same culprit". Game: Scenario to prove the theory Theory 1 - Honest guard in front of Hell. (To be known as Door U for Undesirable in our process of elimination. The door to paradise will be known as Door Y for YES.) You can’t just ask the Honest-Guard if he’s guarding paradise because you must assume that he could very well be lying. And you can't just ask him "what am I wearing?" or something redundant, because even if you prove that he's a liar, you still haven't proved that he is guarding the door that you need to select. So, here we are, there's two inscrutable guards in front of two indiscernible doors, and I have no choice but to decide randomly who to ask a single question. A. If I end up asking the HONEST guard “what would the other guy tell me to pick” he’d tell me *honestly* that the “other guy” would tell me *dishonestly* to choose his door aka Door U. -- This is logical because he's telling us that the Liar would want us to choose Door U (which both guards know as being Hell, and the Liar is interested in foiling our plans because I guess our enemies hired him to do that). B. If I end up asking the LIAR (still unbeknownst to me his credibility) and ask same question "what would that other guy tell me to pick", he would default to his duty of lying, and tell me *dishonestly* that the other guard would "Pick His own door" aka Door U, again. Theoretically, this is dishonest because all we are allowed to assume via our theory is - that whoever the honest guard is, he would never advise us to pick Door U if we asked him directly. In other words, we need to assume if the honest guard is ever asked "what door should I pick" he will always tell us "the truth" aka technically "our truth" aka "the thing we want" aka Door Y. While we cannot actually prove on-the-spot that the liar is lying, the phrasing of the question against the available facts allows us to eliminate 1 perilous door from our choices, no matter which guard we end up asking. Because the fact that the liar will exclusively provide misinformation is exactly what our clever question is taking advantage of: It's this process of elimination which means that "a second question" is not required. It is true however, that in the reality of this scenario, order to pick the right door, you MUST first ask the question. The question is required because it helps us receive more concrete data, and it's only with that new data can we THEN make our logical deduction. Therefore via the process of elimination which is now possible, you can determine that the other door, aka the only other door in front of you aka Door Y; is your remaining selection. So to summarize; in both instances, Door U is alleged as the door to choose. No matter who I end up posting the question to, in both cases Door U will be alluded to, because in both cases the Liar will be responsible for tainting all the available data, giving you the opposite of what youre searching for. Knowing this, you also deduce that you must choose the opposite door from what is told to you "as conjecture", after asking that question which theoretically forces either of them to acknowledge an opposing factor, and thus both will indicate the exact same door.

[@eskailerwhite.7593]

@@RectanerTreadway what a deep explanation, thanks bro!

[@RectanerTreadway]

@@eskailerwhite.7593 i was stuck on this for a while myself so I understood your pain and wanted to alleviate the suffering if possible

[@ulfberht4431]

Basically the answer is this: the guard that tells the truth would give you the answer of what the other guard would say which is the wrong answer since the other guard is a liar and the one you asked is the truthful one. In essence, he’s giving you the answer of what the other would say. The guard that lies knows the other will tell the truth and since he lies he will give you the wrong answer as well because he’s a liar and that is not what the other guard would say. In conclusion, the answer will always be the opposite of what the guard said, no matter which one you ask.

[@natas9967]

You and all of us..

[@wubuck79]

This has been probably my favorite riddle or brain teaser since a pastor told it to me almost forty years ago. I was about eight years old and when he told me the answer it kind of blew my mind at the time lol

[@PhilipPerez-PLC]

I thought you can only ask one question, period. Not one question to each guard, for a total of two questions.

[@madnessbydesignVria]

It is one question: "What would the other guard say is the danger door?" The liar will lie, and the truthful one will answer as the liar would, thus both giving the same answer - the lie. Then you go through the other door.

[@Tetra-Noctis]

I believe a more efficient questionto either the liar guard and the thruthful guard: 2 + 2 equals?

[@tgooda4672]

And how does that help you?

[@greenrobot5]

Hold your hand in front of them and ask how many fingers you're holding, the one that says 5 is the one telling the truth

[@SubSxnic.]

But now u used your one question and don’t know which door is safe

[@tgooda4672]

And what use is that? You’ve now used up your question with no way to find out which is the safe door

[@greenrobot5]

@@tgooda4672 lol, I didn't know it's only one question per door

[@Tovek]

The door is a lie. You are in the safe room and the two guards are your new food source.

[@RandomsFandom]

You dont ask the guards about what is behind them, you ask them about what is behind you.

[@Cinnamon_Rolls_Out_Of_The_Oven]

But then you don’t know which door is the death door and life door

[@RandomsFandom]

@@Cinnamon_Rolls_Out_Of_The_Oven you must first determine which one lies, then you can ask about the door

[@Cinnamon_Rolls_Out_Of_The_Oven]

@@RandomsFandom the whole point of the riddle is you can only ask them both one question.

[@MasonMcLeodFilms]

@@Cinnamon_Rolls_Out_Of_The_Oven Dude tried to be all 500 IQ Batman Professor X but just completely missed the point of the riddle lol

[@hobowithawaterpistol9070]

@@RandomsFandomYes, thank you! That’s what I say! It’s an impossible riddle! The odds are 50/50!

[@BloodyAlex92]

"How many fingers am I holding up?"

[@BrainFoodforLife]

Only one question

[@KingOfSciliy]

Plus, you've only found the liar. You still don't know which door they are guarding.

[@G81L4L]

@@KingOfSciliythat’s what the reply is implying bruh

[@RoderickEtheria]

​@@G81L4Ltruthteller is not necessarily guarding a specific door.

[@NotFoundead]

I can't! I really can't! People not understanding this even after the explanation just blows my mind away. It literally took me 5mins to solve this. Seems like critical thinking, following simple rules and use of logic is not a thing anymore. You can ONLY ASK 1 question to ONLY 1 of the guards. So, you ask one of the guards (doesn't matter which one) something like: "If I were to ask the other guard which door is the correct one, what would he answer?" If you ask the truth teller, he's gonna tell you the wrong door (because that's what the liar would answer). If you ask the liar, he's also gonna tell you the wrong door (because that's the opposite of what the truth teller would answer). By knowing this, you don't need to ask the question to both guards. You don't even need to know which one is which. Since the outcome is the same in both scenarios, the other door will always be the correct one. Side note: Asking for the wrong door, would also work, in that case you'd pick the same door as the guards. Literally the same, but reversed.

[@n00blamer]

Simpler way to think about this is that the spoken answer contains what either guard would have answered on his own, in other words... the spoken answer IS ALWAYS A LIE because one of them is a liar, we simply guaranteed that the lie is always in the spoken answer.

[@hobowithawaterpistol9070]

@@n00blamerWhy would we assume the truth teller would not speak the answer?

[@n00blamer]

@@hobowithawaterpistol9070 I didn't say he wouldn't, both would answer whatever question you ask is a given in this puzzle.

[@hobowithawaterpistol9070]

First of all just because you think you figured it out doesn’t mean you’re better than others because they can’t figure it out or they take a while to! Every body learns at a different pace! Second, it appears to me that while the outcome may be the same as you say, there’s no possible way of you knowing which door is safe if you don’t know which guard is the truth teller and which is the liar! You are still at 50/50 without that information! If I’m wrong, then please tell me is it door A (left door) or door B (right door), and please explain how you know that!

[@n00blamer]

@@hobowithawaterpistol9070 I know which door is a safe because whichever guard I ask, the answer contains a lie. I ask "what would the other guard say about your door, safe or death?" It does not matter which door I am standing in front of, or which guard is at that door. If the guard I ask is a truthful he will say truthfully what the other guard would say, the other one would lie and this guard will then tell what the liar would answer so the answer must be lie. If I ask the liar guard he would lie what the truthful guard would have answered so the answer is again a lie. This way the answer is always a lie no matter which guard you ask. So, if I am in front of safe door the answer would always be it is death door. If I stand in front of safe door the answer would always be it is the death door. So I know which door is which. I come back to what I wrote above: the spoken answer always contains a lie because both guards answers are combined. Truth is always truth, a lie reverses the answer.. there always is reversion because we ask what the other guard would say, so both lie and truth are combined. Truth won't change lie, and lie changes truth.. so answer is always a lie. Another way to think about it is that truth is positive (+1), and lie is negative (-1), answer is +1 * -1 = -1, answer is always negative.. negative means lie and positive means truth.

[@Dandyman69]

“Is this the door that leads to safety?” “Did the other person lie?”

[@zg3671]

Finally, after all these years, that episode of Yu-Gi-Oh now makes perfect sense to me. Ever since watching that episode I thought it was madness but alas it was shear brilliance and you explained it so simply and elegantly. Well done ✅.

[@jemandoondame2581]

Which episode is it?

[@AlexiosKasagiannis]

@@jemandoondame2581its somewhere in duelist kingdom

[@SilverBolt316]

​@jemandoondame2581 its in season 1 where yugi & joey duel he paradox brothers its part 2. and i was thinking the same thing

[@tjkatz]

Honestly, this was a pretty confusing explanation and I knew the answer going in.

[@unexpectedTrajectory]

You can also ask a hypothetical: "If I asked you if this was the door that leads to death, would you say yes?" If it is the door that leads to death, truthful will say yes, but liar will also say yes, because he is lying about the answer he would give you (a double negative) - "Yes, I would tell you yes (not true), this is the door that leads to death," getting him to lie about his lie has forced him to tell the truth. The same works in front of the safe door, where the same question will make both of them say no.

[@ismaelbalima1]

but u don’t know who the liar is?

[@tclanjtopsom4846]

A double negative only applies to maths.😂

[@snottyboy9983]

@@tclanjtopsom4846 thats not true

[@baphomet-san]

“Is my red jacket, red?” “No” Goes to other guard: “Is your door safe?” “No” “We good”

[@tomosjackson4760]

But you can only ask 1 question, so how can you know what they both agree on?

[@AnthonyWilliams-bp5mn]

The question was if you were the other guard what would you say. The truth telling one would say the other guard is safe while the liar would say he’s is safe. That’s in scenario 1 if the truth one is guard the safe path and the lying one is guarding the certain death path. Based on that logic you would not only identify who’s the liar and who’s telling the truth but you would know not to pick the path they both say.

[@robbie_the_mastermind2176]

Walks up to one of the guards and sniffs ‘Did you poop your pants?’

[@dariusq8894]

Anyone else get "Labyrinth" flashbacks? 😂

[@pyrrhicvictory6707]

I'm amazed so few people got the reference.

[@riact123]

Yep! The moment I saw the thumbnail, I thought of Labyrinth.

[@bassage13]

@@pyrrhicvictory6707 It's not a reference to Labyrinth. It's a very old puzzle. Labyrinth referenced this well known puzzle.

[@pyrrhicvictory6707]

@@bassage13 Fair enough but I bet it was popularised by Labyrinth

[@dannybursace9151]

I clicked on this earlier today & watched Labyrinth later on…I could not believe it..never heard of this puzzle before then twice in one day…life is weird like that sometimes

[@wrg1183]

Easy! Ask both if they will walk through the door first, before I have the opportunity?

[@LNC4P]

Thanks for explaining the riddle from "The Labyrinth"!

[@BrainFoodforLife]

Glad it was helpful! I'm a sucker for these.

[@RoderickEtheria]

Labyrinth has a broken form of the riddle, as they break the rules of the riddle while getting the information for the riddle out.

[@deanstanley2125]

How would the guards enter the dungeon? They would have to come in through the safe door so by observing them entering you have your answer

[@BrainFoodforLife]

Interesting hijack of the task Captain Kirk but this ain't the Kobayashi Maru! hahaha

[@notapplicable8957]

There's a more clever way of doing this though. You ask the guard in front of you "Would the other guard tell me his door is safe?" Because there are only two possible combinations of doors, the guard standing in front of the safe door ends up having to answer 'Yes' in 100% of cases. You can't know which guard told you this or if he was lying or not, but you can know from his answer if the door is safe because they will always answer this question in opposition to each other and the person who answers yes is always standing in front of the safe door, due to how their principles force them to answer.

[@TheJM5]

How many fingers am I holding up if one says the right number than its the truth but if the other says the wrong number then he lies

[@123Mathzak]

But what if the truth teller is guarding the death door?

[@infinitevoid227]

That’s the catch, you only get the one question. After you figure out who the liar is, you are out of questions and will never know which door is safe.

[@TheJM5]

Well can’t you ask the other one the question

[@infinitevoid227]

@@TheJM5 nope only one question for one guard. It’d be too easy otherwise

[@TheJM5]

@@infinitevoid227 that’s stupid then how do I know who’s lying

[@cmcollis]

Bro, Sarah taught me all I need to know here.

[@Horntsnest1]

in the end you still asked two questions... am I wrong?

[@TheFilipFonky]

You are wrong. You ask one guard "what would the other guard say is the safe door?" and then you do the opposite of whatever answer you get. Just one question.

[@tohian]

@@TheFilipFonky Actually, OP is right. If you listen to the video at 3:00, the narrator clearly says “you have to do the opposite of what they agree on”. But in order to know what the guards agree on, you have to ask 2 questions. So this question is somewhat flawed.

[@RectanerTreadway]

@@tohian the narrator here is implying that they would *theoretically* agree on the same door if asked the same singular question. in other words, you only need the 1 question to prompt them both into giving you the same response meaning no matter who you ask, you can safely assume what the other will say

[@zdzdhhfdzhzdhdzheherh33]

@@tohian it's not. They would always agree on the same door.

[@Amaipuppy]

They would both answer at the same time but you still get the right answer, so it's one question.

[@RTPManny]

Just ask either one of them "I beg your pardon but can lead me through the safe door?", if the guard is the truth teller he will lead you through the safe door, if the guard is the liar, he will lead you through the safe door because leading you through the dangerous door would be an admission of truth to which the liar is incapable of doing. If the premise is that they do not physically move and will only respond to you then ask either one of them "why do you guard the safe door?" the truth teller will say something like "I guard the safe door due to XYZ reasons" and then you walk through. If the truth teller is in front of the dangerous door he will say something like "though I guard this door it is in fact not safe" so you go to the other door, if you get the liar and ask him "why do you guard the safe door?" The liar would immediately expose himself for being a liar because he cannot admit to being a guard as well as admit to guarding the door because he lies about everything, so you'll know he's the liar. Therefore, whether or not he is standing in front of the safe or dangerous door is irrelevant because he'll have to say something along the lines of "you are mistaken, for this passage before you is dangerous / safe" and then you just do the opposite of what he said. The point of argumentation that I'm presenting to you is that within the premise of this situation specifically is that the guards are here to respond to your question, not debate you on it and that it is possible to ask a single question and get multiple answers.

[@kazekagekid]

“Are you a guard?”

[@tigrenaranjo]

How would this question lead you to know which door is the safe option? With this question you only know who is lying and who isn't, and as you only have one question, this doesn't answer which door is safe

[@kazekagekid]

@@tigrenaranjo”you can ask one of them only one question” is not violated by asking them to answer two different questions, one each. his solution asking the same question may be more elegant, but mine’s cleaner, and he didn’t state that limitation in the prompt as clearly as when he’s working through it. he arguably violated his own prompt if you’re going to be that pedantic, since he had to ask both guards a question anyway.

[@kazekagekid]

@@tigrenaranjoalternatively, you can also figure out the answer to this general riddle with one question if you’re listening carefully and given the prompt by one or both of the guards. the one who says they are guards or guarding a door is 95% the truth-teller unless they’re not actually guarding anything.

[@kaptainkittens583]

@@kazekagekid I think the implication is pretty clear you could only ask one question, to only one guard, to determine which door is safe, and the answer he gives in the video does not violate his rule; he simply demonstrates the answers each guard would give for each scenario to cover the possibilities, and that no matter which guard you ask or which door they are in front of - you only need to ask one of them and always choose the other door as the safe one.

[@kazekagekid]

@@kaptainkittens583​​⁠ “you can ask one of them only one question” 0:37

[@wenaolong]

You could even just ask either guard whether the other guard would answer that the door he guards is safe. If it isn't, then either guard would answer "yes", if it is, then either guard would answer "no". In the former case, you go through the door behind the guard to whom you are posing the question, in the latter, you go through the door about which you are posing the question. When the guard you ask says "no" about what the other guard would say concerning whether his door is the safe door or not, you go through that one. If he says yes, that's the wrong door. This works whether the guard you ask is a truth teller or a liar, and you need ask only one question: "If asked, would the other guard tell me his door is the door to safety?"

[@RecordSlowrun]

Simple solution: “Is the lying guard in front of the door to safety” Honest guard in front of door to safety: No. Honest guard in front of door to death: Yes. Lying guard in front of door to safety: No. Lying guard in front of door to death: Yes.

[@MiniMagi]

How do you know which guard is the lying guard tho?

[@JustSomeKittenwithaGun]

​@@MiniMagiCheck their comment again. It gives the same outcome for the corresponding door regardless of who is by it.

[@MiniMagi]

@@JustSomeKittenwithaGun I don't get it. -Edit Ohhhh. It's not about knowing who the lying or truthful guard is, but the answers they give. "No" leads to safety. Appreciated~

[@safetybeachlife]

The door to safety is always the guard who says “No” Or the other door to the one who says “Yes”

[@Chaytonioio]

@@MiniMagi I'll try to give my understanding of their comment so you'll hopefully understand it better. If either guard said no, you should go through his door regardless as the other comment described. If either said yes, go through the opposite door. Why? Remember, you only need to ask that one question to ONE guard only, but this still works if you're allowed to ask them both the same question. “Is the lying guard in front of the door to safety?” Guard says NO: If they're the liar, the actual truth is "YES". The other guard MUST say no as well because otherwise there would be 2 lying guards. You can safely go through this door. “Is the lying guard in front of the door to safety?” Guard says YES: If they're the liar, the actual truth is "NO." Again, the other guard MUST say yes or he'd be a liar as well. Go to the opposite door of the guard you asked. Basically, you know which guard is lying because this question is really good and non-contradictory. However, this is a contradictory question IF this condition is met: If you asked them this specific question and one guard said yes, but the other guard said no it contradicts this question and this forces the truthful guard to lie. Understanding this potential paradox is pretty helpful in understanding the solution. If they both were to say no (or yes) at the same time to the question, then we know for a certain it isn't contradictory. Well, I hope this didn't confuse you even more. I had to think pretty hard about it too.

[@kevinogill6726]

Easy. Ask either guard which door the other guard would say is safe. Then choose the opposite

[@calemlinke773]

the fact that you have to ask them what the other guardian would say makes too much sense if you think about it for a while... it's too easy, but not very well known yet.

[@n00blamer]

yup; we know there is always a lie in the answer, the truthful dude won't affect it. the question has to include what both dudes would answer and there we go.

[@annonymousannonymous9586]

I remember seeing this logic puzzle in both Samurai Jack & the OG Powerpuff Girls series.

[@lazyreaps]

I like how Rick and Morty solved this 😂😂😂

[@goobusgoobert]

Thats why i came here lol

[@RikoShot24]

Same

[@edwardfindley8483]

"How many fingers am I holding up?" This a isn't a puzzle, more of a thought experiment on how to make something way more complicated than it needs to be.

[@nobodyknowsforsure]

Alternative option... Me *cocks shot gun* "Which is the right door...?" Guardian1: "Ho ho Mortal, surely you jest, you would not dare t--" *bang* kills first door guardian. Me: "You were saying??" Guardian2: "Holy shit! It's the door over there - the one over there!" Me: "Thank you..."

[@maxcrayola3074]

Then you go to the door he pointed and you go throw with confidence thinking its the right door cause you think that killing the other gaurd made the last guard tell the truths. But unfortunately for you, you actually killed the guard that always tell the truths and the one alive must and always tell a lie. So he lied to you and you go to the death door and you die.

[@nobodyknowsforsure]

@@maxcrayola3074 Guard goes on break...sits on toilet...ppl bust open his toilet taking him away. "Who are you people??!!" The man you killed, had a device in his heart, he instructed us that if he were to die today that we were to take two of you...though I only see one...in any event... welcome to the squid games...

[@jsc1jake512]

Another alternative: physically hurt them in some way then ask if it hurts

[@TheFilipFonky]

@@jsc1jake512 That tells you who the liar is, but not which door is safe.

[@runelt99]

You: enters Guardian2:.... Hehe sucker

[@robbie_the_mastermind2176]

If there was one guard named Kairos Fateweaver, ask him any questions and he would will give you three answers, all of which are true, and horrifying to know."

[@HeyItsThattGuy]

"what color is my hair" done

[@infinitevoid227]

You only get one question

[@RitsuSakuma69]

​@infinitevoid227 *They would both answer the question tho? That's literally the entire point of the riddle!*

[@HeyItsThattGuy]

He's right I'm wrong, they answer the question and I now know who the liar is but have no idea which door is safe

[@booyah344]

​@RitsuSakuma69 yes but even though you've found the liar you can no longer ask about the doors

[@sadoo0797]

The point isn’t to figure out which one lies it’s to figure out which door is safe

[@andrewg.carvill4596]

The classic problem has one unstated assumption, namely that the guards both know about the other being either truthful or a liar. If they didn't know each other, the truthful guard would truthfully answer "I don't know which door the other guard would tell you is safe" while the lying guard, it seems, could not give any logically coherent answer to the question.

[@vegaswithdrawal4132]

This is a setup, both guards read their roles for the day before clocking in to work. If they don't play along, or screw it up like morons, they will be terminated immediately. 🔥

[@natas9967]

If you ask the wrong guard first you're screwed.

[@aldobanuelos6614]

Nah if you asked "what would you say is the safe door if you were the other gaurd?"it doesn't matter who you asked because they would give you the same answer. Then you just choose the opposite of that answer.

[@natas9967]

@@aldobanuelos6614 reading that hurts.. I am still lost.

[@cantfindawayout]

@@natas9967 Guard A always lies and stands before door X. Guard B tells the truth and stands before door Y. You don't know whether X or Y is the good door. The riddle assumes that the truthful guard will point at the good door. If you ask the liying guard what the other guard would choose, he would lie and point at the wrong door. If you ask the truthful guard what the other guard would choose, he would tell you the truth and point at the wrong door. Therefore, no matter which guard you ask, you always get your answer. You choose the other door since both guards will point at the 'bad' door. Hope this helps :)

[@shawbag11]

Easy puzzle just ask if i was to ask the other guy what door to go though what would he say. then u just do the opposite of whatever they say since both guards would agree on the wrong answer.

[@whosthere8658]

Everyone seems to not realize they give themselves away without needing to ask a question. Let me explain. The first one says "One of us speaks nothing but the truth." This is a true statement so whichever says this is the one who tells the truth. Hence why the liar can only say the statement " The other nothing but lies." This one is calling the other a liar as to still abide by only telling lies. So he is the liar. Simple and easy. just ask the one who told the truth which door is safe.

[@bugoobiga]

Not really... ...The first one says "One of us speaks nothing but the truth." The liar could be saying this about himself, lying like always. The other then says "The other, nothing but lies." This then would still be a truth by the truth teller.

[@brettstover1850]

Definitely wrong. 😑

[@nagashtheforsaken]

@@bugoobiga But that's not what they say. It's always one of us always tells the truth and one of us lies. The riddle is supposed to have a third party, or a note on the wall, or something like that, with the instructions, so the guards don't talk unless you ask a question. In this scenario, the OP is correct, the doors cannot give the proper answers. Both doors would have to state "We both always tell the truth".

[@Garviel-Loken]

This is called the liars paradox and has no answer because the initial premise is the lie. The "riddle" cannot be said by the guards if the statement "one of us is telling the truth, the other only lies" is factual If the guards say half of the statement each, both are liars. If you label the guards as Truth and lie you can see it Truth: one of us speaks the truth (True) Lie:The other only lies (true) Or Lie: One of us speaks the truth (true) Truth: the other only lies (true) In both scenarios both guards are telling the "truth" which makes both of them liars.

[@bugoobiga]

incorrectomundo "One of us speaks nothing but the truth," could be said by the liar, referring to his own lying self as the one that is truthful. That would hold true to his mandatory lie.

[@vandaahll]

How can we do the opposite of what they agree on when we can ask1 guard 1 question?

[@BrainFoodforLife]

Phrasing

[@madnessbydesignVria]

It's not that they agree, it's that they will, by their nature, give the same answer. Asking what the 'other one' would say means the liar will lie, and the truthful one will honestly tell you the lie the other on would say - resulting in the same answer, so you only need to ask one. The answer will be a lie, so you do the opposite.

[@aseellop]

just ask him if hes holding a shiled lol

[@brianh5878]

That would let you know who’s lying but you wouldn’t know if he was standing in front of the death door or safe door

[@peris_arts_film9699]

@@brianh5878but if the guard answers yes to holding a shield. You now know he tells the truth. Then You can ask the other guard if he’s standing in front of the safe door. If he answers yes; well then you know to go through the other door

[@scurvyswashbucklingDM]

​@@peris_arts_film9699You can only ask one question.

[@RectanerTreadway]

@@peris_arts_film9699 1 question only is the game

[@peris_arts_film9699]

@@RectanerTreadway aight fine. Bring a friend

[@clairepulsipher6287]

This solution assumes honesty on the part of the entity explaining the rules, which is an unknown quantity. It doesn't matter if it is written on the wall, spoken by a third party, or spoken by one or both guards themselves. There is no way to determine if the person who says "one guard is always honest, and one guard is always truthful," is himself being truthful or lying.

[@entropybentwhistle]

There’s the possibility they’re both a couple of psychopaths who are making it seem like your only way forward is one or the other door, when both actually lead to your demise and you were just supposed to continue down the hall to the exit.

[@williammeyer2584]

I thought you could only ask one question between the two of them, not one question for each guard?

[@samuelfernandesoliveira]

It's just showing what would happen per scenario. If you asked the liar if his door was safe, (and it waa dangerous) he would say yes. The same would happen to the truthful one.

[@ayrish24]

1 question , your asking more than 1

[@maxcrayola3074]

his asking only one question. the question is "if i ask the other guard which door is safe, what would he say?" and whatever they both agree on you pick the opposite

[@maxcrayola3074]

@Wes & TKP 66-02 Yes it does you just don't get it so let me explain. The best way I can explain it is that you have to ask one guard irl and create the same scenario in your mind but your asking the other guard the same question. That being said you don't know which guard is honest and which guard is a lair. Lets just say you happened to ask the liar irl. So if you ask the lair, "if I ask the other guard which door is safe, what would he say?" The lair knows that the other guard will tell the truth and point to the safe door. So he lies and point to the death door. Now create the same scenario in your mind and picture yourself asking the other guard, "if I ask the other guard which door is safe, what would he say?" The honest guard knows that the lair will pick the death door. So he tells the truth and point to the death door. Both guards in irl and in your mind always agrees and point to the same door. Soooo... All you have to do is pick the opposite of what they agree on.

[@TonyAlmeida1]

No it's still one question. What I think you're confused about is everybody, including the video, saying, "what they both agree on" making it sound like you're asking both guards, but you're not...you're just asking one guard (either one) "which door would the other guard pick." Walk that scenario in your head with both guards and it will make sense.

[@TuranTahaAli]

I think there is kore than one way to solve this. My way is asking "Is there a truthful guard standing at the safe door?" and pass through the gate of the guard who says yes.

[@allthingsnu4673]

Seems like this was overly complicated.

[@ChicCanyon]

Because it is

[@themoretruthfultruth]

This one is so old. Why did someone even bother to make a video about it. This riddle was even in the movie Labyrinth.

[@LJLMETAL]

You can also ask which door would the other guy say would lead to certain death.

[@stephenjames6080]

If you are restricted to asking "one of them only... one question" (0:38-0:41) then how can you identify which of the doors they disagree on ? Surely you would need to ask both of them the same question (ie 2 questions instead of one !)

[@tezzerii]

The whole point is that if you ask the right question, the answer is the same whichever guard you ask. So you only have to ask one.

[@davidjones-vx9ju]

this is making the assumption that each guard knows that one lies

[@Gnomelotte]

I think it is a given that they do.

[@davidjones-vx9ju]

@@Gnomelotte that was not "given" in the problem

[@Buffbuffrules]

How do we even know which guard is the liar and which one is the truthful one? Because that takes 1 question to figure out and then we need another question to ask the truthful guard where the safe door is.

[@mrdeadmonsters]

What i ask one guard, “ Is this a door” and if he says no, he is the liar, and if he says yes, he is the truth teller

[@d.godummyy]

“What color are the walls of this room?” If answered correctly I’d ask the other guard if their door is safe if the answer is yes, I know they’re lying.

[@BrainFoodforLife]

You’re going the right direction but you have to ask both the same question in this iteration.

[@ssimpson3288]

An even safer question would be to ask "Are my eyes opened or closed?" while your eyes are opened. You're going to know which one is telling the truth/lie really easily and then you ask the other guard if the door they're standing in front of is the danger door.

[@MarthKoopa]

YOU ONLY GET ONE QUESTION and you wasted it

[@malachigrindle7063]

It's simple. "Are you guarding a door?".

[@tegathemenace]

Finally one I can get my head around If I asked you the question "are the two guarded doors safe" would your answer be yes?. Case 1: The doors are both safe. The liar's answer to the inner question would be no. And he would lie that his answer would have been yes by saying yes.(Yes my answer would have been yes) His polar opposite would have an answer of yes to the inner question and his answer would also be "Yes my answer was yes". Which means if both doors are safe the answer is YES from either guard. You can now enter either guarded of the two doors. Case 2: One door is unsafe Given it's an "AND" question if it isn't Case 1 it's automatically Case 2. Not Case 3(none of the two are safe) because if that holds that means the 3rd is the only safe door. 2 doors have to be safe according to the rules. Moving on, either guard will answer NO if it's a Case 2 (use logic in case 1). If one of the doors are safe it means the other is the safe one. Which? Unknown. But no you are sure the second safe door is the 3rd This is built on : Double negative and Double positives are positive. (- × -) = (+ × +) = +) Instead of asking how the other would respond. I asked the guard how he himself would respond. I wish I could come up with the easy answer tho😂

[@dominik94rausch]

One always tells the truth, the other one never lies.

[@slayer8actual]

I have one question. It is divided into 32 subparts and will require you to show your work.

[@BrainFoodforLife]

😆

[@paulgreen9059]

Ask "If I asked you 'is your door safe?', what would you say?" That would work unless the guard got confused, I suppose.

[@Zebrah-real]

"am i bald" "yes?"

[@hobowithawaterpistol9070]

This Riddle is flawed because it does not tell you which guard is honest and which one is lying. Therefore trying to trick one guard or the other is impossible if you have no idea which one is the truth teller and which one is the liar! If I try to use trickery it doesn’t matter! Gordon Gekko said it best “Information is the greatest commodity I know of!”

[@BrainFoodforLife]

That’s the entire point.

[@madnessbydesignVria]

It doesn't matter which one is lying, you need to know which door is safe. By asking what the other guard would say, you insure getting the lie, and do the opposite.

[@Hadouken9000]

"One can only tell the truth, the other can only lie." All right, so tell me the color of my shirt.

[@123Mathzak]

Ask the guards if theyre a guard who’s guarding a door, and go with the guard who says yes because obviously the guard who says no is lying.

[@hobowithawaterpistol9070]

You can only pick one guard and ask him a question. You can’t ask them both!

[@DuckTheAssasin]

​@@hobowithawaterpistol9070 Wrong, You can ask both guards the same question, but you can only get one answer from each.

[@AlphoGman]

I ask what 1+1 is or how many fingers I am holding up.

[@TinyFord1]

That only tells you who is the liar and who tells the truth, but it reveals NOTHING about the door and you don’t have a second question

[@RandomsFandom]

Third option. Go through a door at a 50/50 option

[@ericbucher8636]

Just randomly select a door and go through it. We are all going to die eventually.

[@saintmateo]

Me, blowing my one question just to vent: "Dude, there's probably a dragon or something at the end of this dungeon anyways, so even if I pick the right door my odds of survival are not great. Does it even matter to you if I die in the next room or if I die to the boss at the end?" The guard: "Wow, I'm supposed to be the liar but that is a bleak perspective to share. Now I feel bad, here, take these healing potions in case there is a dragon."

[@cl0ud985]

"which door will the other guard tell me to choose?" Liar: "He will say X." (he is lying!) Truth: "He will say X." (the liar would say the wrong door.) Walk through Y... Doesn't matter who you ask, just pick the opposite.

[@cakedo9810]

If you were the other knight in the room, which would he say is the correct door? Then go in the opposite door.

[@RecklessFables]

A mistake many riddlers make is when they state the puzzle, they have one of the guards as the speaker. This breaks the rules of the riddle unless the truth guard is the speaker... which also breaks the riddle.

[@annonymousannonymous9586]

If you were Naruto you would just make two shadow clones & have them try both doors, the one who dies got the bad door, the one who lives got the good door, problem solved.

[@jellygodgames2139]

Go up to the first guard and ask, how many fingers am I holding up? Let’s say you’re holding up two, and the guard says three. Then go to the other door and ask, is this door safe? If he says yes go through it, if no don’t go through it and go to the other door. If the first guards says, 2 fingers, that means he is telling the truth. Go to the next guard and ask if the door is safe, if he says no go through it, if he says yes go to the other one.

[@mariosebastiani3214]

only 1 question allowed, not multiple ones

[@jellygodgames2139]

You can ask each of them one question, my question to the first guard is the fingers one, my question to the second guard be about if the door is good or nah

[@TriAzF]

@@jellygodgames2139You can ask one question period. Not one question to each. This video words it a bit weirdly but the problem is based on only have one question. If you could ask 2 questions, than yes your solution works (or any solution where the first question just verifies one of the guards identities), but it is barely a puzzle at that point.

[@jellygodgames2139]

@@TriAzFyear ur right he just words it weird

[@SKIT..CENTRAL]

But I thought only 1 of them could answer you so if only 1 can answer then the other won't say anything to help you figure out which is lying and which isn't

[@benji1901]

It's still the opposite of the answer whoever you ask. Door 1 = safe, If you ask true guard what the liar guard would say, the liar guard says door 1 is danger; danger being the opposite. If you ask liar guard what door true guard would say, he would lie and claim true guard would say door 1 is danger; danger being the lie. Both answers are door 1 = danger, which is the opposite of what is it. So even though you ask one question you can automatically just do the opposite of the answer.

[@BWills32]

So for the favorable outcome, do the opposite of "what the other guy would say?"

[@Rexieley]

My solution: Asking "Is your door safe?" to the first guard. Yes or no, keep that answer in your head. And then asks the second guard with the stupidly obvious question like: "Is THIS a door?" and points towards the door they are guarding. If the answer is a yes, don't trust the first guard. If the answer is a no, trust the first guard.

[@The_Holy_Wooomy]

ask "Am I alive?"

[@Kyzen_Wrell]

But isn’t the only way they could admit that there’s one truth teller and one liar false? Because if the liar is saying “the one of us would speak only lies” that would be telling the truth. The only way they could both make that statement is if they were BOTH lying.

[@ZeldaSam1]

The logic of this riddle will always elude me.

[@BrainFoodforLife]

Watch to the end and all is revealed!

[@crismon0726]

me: pushes a guy me again: did i push you?