What always bugs me about this in popular culture is that you only get to ask one guard the question, not both. So the question you would ask here would be:
“If I asked the other guard for a credit card number, expiry date and security code that wasn’t yours, what is an answer they could give me?”
Wouldn't it be easier to just ask something like "is red a color?" To one guard?
I think the original riddle also had 2 doors and the question was something like "which door would your partner say leads to freedom" iirc, which makes both point to the one that leads to death.
You only get one question to one guard. So if you ask ‘is red a colour’, you find out which guard is lying, but not which door is the correct one (or either of the guards’ credit card info)
“If I asked the other guard for a credit card number, expiry date and security code that wasn’t yours, what is an answer they could give me?”
Truth guard: the other guard lies => if asked for details that weren’t the truth guard, must lie => tells details that are truth guard’s => truth guard tells you these correct details
Lie guard: other guard tells truth => could state any details that are not lie guard’s => lie guard must therefore tell you their credit card info
So you get one of the guard’s info. You could change it to a specific guard’s info if you’d like.
“If I asked the other guard for an example of a credit card number, expiry date and security code that weren’t the details of the guard I am currently talking to, what is an answer they could give me?”
if you’re worried about misinterpretation.
If you were to ask the lying guard for ‘an example of a credit card number, expiry date and security code that weren’t the details of the other guard’, they would necessarily have to give the correct details, which the truth guard would pass on
If you were to ask the truthful guard for ‘an example of a credit card number, expiry date and security code that weren’t the details of the other guard’, they would necessarily not be the correct details. However, the truthful guard could answer with any incorrect details, and so the complement of the set of details the truth guard could give is only the correct details, which the lying guard would therefore have to give. That’s why you ask for ‘an example’.
If you were to ask the lying guard for ‘an example of a credit card number, expiry date and security code that weren’t the details of the other guard’, they would necessarily have to give the correct details, which the truth guard would pass on
Couldn't they just lie and give you a non-working example?
Or are you hinging your question on a variation of "don't tell me the other guard's credit card information", which you expect the lying card to contradict and tell you?
You’re asking for an example of details that aren’t those of the other guard. If they give you a non-working example, then the lying guard has been truthful. Which is a contradiction.
Consider the question ‘what is an example of something that is not a cat?’. Any answer that is not a cat is truthful; therefore the lying guard must give an example of a cat.
Ah, ok, so to clarity, you could also ask, "tell me anything that isn't the other guard's number," and they have to tell you exactly the other guard's number.
Since both guards said that they will only answer one question, it doesn't matter what the first question is, after the second question you will know who always tells the truth.
an easy cope out: "I don't know" unless he's actually memorised the number its a truth, I know I don't remember more than the last 4 on any of my cards.
34 Comments
slazer2au@lemmy.world · 58 pts · 31d
Don't forget the expiration date.
pirc_lover@feddit.uk · 46 pts · 31d
What always bugs me about this in popular culture is that you only get to ask one guard the question, not both. So the question you would ask here would be:
“If I asked the other guard for a credit card number, expiry date and security code that wasn’t yours, what is an answer they could give me?”
schema@lemmy.world · 10 pts · 31d
Wouldn't it be easier to just ask something like "is red a color?" To one guard?
I think the original riddle also had 2 doors and the question was something like "which door would your partner say leads to freedom" iirc, which makes both point to the one that leads to death.
pirc_lover@feddit.uk · 18 pts · 31d
You only get one question to one guard. So if you ask ‘is red a colour’, you find out which guard is lying, but not which door is the correct one (or either of the guards’ credit card info)
tetris11@feddit.uk · 7 pts · 31d
can you unpack the logic in that last part for me?
pirc_lover@feddit.uk · 9 pts · 31d
Truth guard: the other guard lies => if asked for details that weren’t the truth guard, must lie => tells details that are truth guard’s => truth guard tells you these correct details
Lie guard: other guard tells truth => could state any details that are not lie guard’s => lie guard must therefore tell you their credit card info
So you get one of the guard’s info. You could change it to a specific guard’s info if you’d like.
tetris11@feddit.uk · 11 pts · 31d
I guess I'm not getting it. Couldn't the "that wasn't yours" part be misconstrued to allow for anyone's info?
The truth guard could recite someone else's credit card (which would still be a win), but the lie guard could fabricate false numbers completely
pirc_lover@feddit.uk · 5 pts · 31d
You could rephrase it to
if you’re worried about misinterpretation.
If you were to ask the lying guard for ‘an example of a credit card number, expiry date and security code that weren’t the details of the other guard’, they would necessarily have to give the correct details, which the truth guard would pass on
If you were to ask the truthful guard for ‘an example of a credit card number, expiry date and security code that weren’t the details of the other guard’, they would necessarily not be the correct details. However, the truthful guard could answer with any incorrect details, and so the complement of the set of details the truth guard could give is only the correct details, which the lying guard would therefore have to give. That’s why you ask for ‘an example’.
sem@piefed.blahaj.zone · 2 pts · 30d
Couldn't they just lie and give you a non-working example?
Or are you hinging your question on a variation of "don't tell me the other guard's credit card information", which you expect the lying card to contradict and tell you?
pirc_lover@feddit.uk · 2 pts · 30d
You’re asking for an example of details that aren’t those of the other guard. If they give you a non-working example, then the lying guard has been truthful. Which is a contradiction.
Consider the question ‘what is an example of something that is not a cat?’. Any answer that is not a cat is truthful; therefore the lying guard must give an example of a cat.
sem@piefed.blahaj.zone · 2 pts · 30d
Ah, ok, so to clarity, you could also ask, "tell me anything that isn't the other guard's number," and they have to tell you exactly the other guard's number.
tetris11@feddit.uk · 2 pts · 31d
oh I see, thank you
Meruten@lemmy.dbzer0.com · 1 pts · 31d
These are mythical beings no? Surely you would need to be specific, it's kind of their thing.
wonderingwanderer@sopuli.xyz · 6 pts · 31d
That's right, we've all seen Labyrinth
pirc_lover@feddit.uk · 7 pts · 31d
You’d be surprised, given the replies I’ve had
wonderingwanderer@sopuli.xyz · 4 pts · 31d
You remind me of the babe
snooggums@piefed.world · 2 pts · 30d
What babe?
wonderingwanderer@sopuli.xyz · 2 pts · 30d
The babe with the power.
HubertManne@piefed.social · 37 pts · 31d
if one lies then the whole setup does not work because of how they both stated the rules.
Funkt4st1c@lemmy.world · 17 pts · 31d
I think the assumption is that the explanation of rules are either exempt, or part of the riddle, or explained by a third (fourth?) party.
I do agree though, this pisses my pedantic ass off.
HubertManne@piefed.social · 1 pts · 31d
you know I just realized it would work if the one that says the one always lies does not always lie but then your effed.
Funkt4st1c@lemmy.world · 2 pts · 31d
Always lying is, in many ways, telling the truth /s
Naz@sh.itjust.works · 2 pts · 31d
https://en.wikipedia.org/wiki/Liar_paradox
SystemDisc@feddit.org · 2 pts · 31d
Maybe the liar accepts multiple questions
ragas@lemmy.ml · 2 pts · 30d
Since both guards said that they will only answer one question, it doesn't matter what the first question is, after the second question you will know who always tells the truth.
SystemDisc@feddit.org · 2 pts · 29d
First, ask which is the exit. Then, ask anything. The exit is whatever the guy that didn't answer the second question stated
ekZepp@lemmy.world · 7 pts · 31d
Those are two questions.
RustyNova@lemmy.world · 12 pts · 31d
Nope. One question, multiple data points requested.
ekZepp@lemmy.world · 3 pts · 31d
She's asking for two different series of numbers.
birdwing@lemmy.blahaj.zone · 8 pts · 31d
The numbers are part of the same set as the longer string
sem@piefed.blahaj.zone · 1 pts · 30d
Semantics! I love it. Like Gollum's last Riddle answer
Pika@sh.itjust.works · 4 pts · 30d
an easy cope out: "I don't know" unless he's actually memorised the number its a truth, I know I don't remember more than the last 4 on any of my cards.
Wataba@sh.itjust.works · 2 pts · 31d
The one doing the explaining has to be truthful anyway, otherwise its just a Samurai Jack situation and they're both liars.
In the first panel theyre both being truthful. Just sayingm
ITGuyLevi@programming.dev · 2 pts · 31d
Which goes to say that neither of them 'always lies', this version seems a bit messed up in the setup.
atan@lemmy.ml · 1 pts · 31d