https://www.pixiv.net/en/artworks/125076972

Don't forget the expiration date.

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?”

can you unpack the logic in that last part for me?

“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.

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

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

Those are two questions.

You could rephrase it to

“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’.

These are mythical beings no? Surely you would need to be specific, it's kind of their thing.

Nope. One question, multiple data points requested.

if one lies then the whole setup does not work because of how they both stated the rules.

She's asking for two different series of numbers.

The numbers are part of the same set as the longer string

oh I see, thank you

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.

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.

Which goes to say that neither of them 'always lies', this version seems a bit messed up in the setup.

Always lying is, in many ways, telling the truth /s

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.

That's right, we've all seen Labyrinth

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)

You’d be surprised, given the replies I’ve had

You remind me of the babe

Maybe the liar accepts multiple questions

https://en.wikipedia.org/wiki/Liar_paradox

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.

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?

Semantics! I love it. Like Gollum's last Riddle answer

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.

What babe?

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.

The babe with the power.

First, ask which is the exit. Then, ask anything. The exit is whatever the guy that didn't answer the second question stated