Three Logicians Walk into a Bar

Jeff250 · Post by **Jeff250** » Sat May 05, 2012 2:52 am

Three logicians walk into a bar.
The bartender asks them, "Does everybody want a beer?"
The first logician says, "I don't know."
The second logician says, "I don't know."
The third logician says, "Yes."

Pandora · Post by **Pandora** » Sat May 05, 2012 1:43 pm

Ha! Brilliant!

Enzo-03 · Post by **Enzo-03** » Sat May 05, 2012 1:57 pm

snoopy · Post by **snoopy** » Sat May 05, 2012 5:48 pm

I get it!

roid · Post by **roid** » Sat May 05, 2012 6:24 pm

how does the 3rd one know that the first 2 DID want beers?

:?

Top Gun · Post by **Top Gun** » Sat May 05, 2012 7:29 pm

That took me a disturbingly long time to figure out.

Jeff250 · Post by **Jeff250** » Sat May 05, 2012 8:28 pm

roid wrote:how does the 3rd one know that the first 2 DID want beers?

Spoiler:

If you don't want a beer, then you can immediately answer "no," since you know that not everybody wants a beer. Since the first two didn't answer "no," the third knows that they want a beer.

roid · Post by **roid** » Sat May 05, 2012 9:58 pm

aaaaaaaaaaah of course

. thanks

Isaac · Post by **Isaac** » Sat May 05, 2012 10:53 pm

roid wrote:aaaaaaaaaaah of course . thanks

x2

I'm not at full mental brain thing at this hour.

snoopy · Post by **snoopy** » Sun May 06, 2012 5:30 pm

Jeff250 wrote:
roid wrote:how does the 3rd one know that the first 2 DID want beers?

Spoiler:

If you don't want a beer, then you can immediately answer "no," since you know that not everybody wants a beer. Since the first two didn't answer "no," the third knows that they want a beer.

# 3 is making assumptions about people's desired being static. What if someone changed their mind?

Jeff250 · Post by **Jeff250** » Sun May 06, 2012 6:45 pm

I suppose the joke breaks if they're temporal logic-ians.

Tunnelcat · Post by **Tunnelcat** » Mon May 07, 2012 10:32 am

Isn't "I don't care" more logically accurate than "I don't know"?

fliptw · Post by **fliptw** » Mon May 07, 2012 11:28 am

tunnelcat wrote:Isn't "I don't care" more logically accurate than "I don't know"?

only if you are snarky.

Tunnelcat · Post by **Tunnelcat** » Mon May 07, 2012 3:13 pm

I'm not being snarky. Think about it. The logic is different between the 2 pronouncements.

fliptw · Post by **fliptw** » Mon May 07, 2012 3:30 pm

tunnelcat wrote:I'm not being snarky. Think about it. The logic is different between the 2 pronouncements.

"I don't care" is the snarky version of "I don't know". Both versions give the barkeep the same information concerning the disposition of the group to beer.

Tunnelcat · Post by **Tunnelcat** » Mon May 07, 2012 3:50 pm

"I don't care" is different from "I don't know". "I don't care" implies that either choice would be fine, so make it for me. "I don't know" implies that I don't have enough information to make the choice one way or another, which means I need more information to give a definite answer to the question.

fliptw · Post by **fliptw** » Mon May 07, 2012 5:28 pm

tunnelcat wrote:""I don't know" implies that I don't have enough information to make the choice one way or another, which means I need more information to give a definite answer to the question.

The barkeep only cares if the group wants beer or not; any answer besides yes or no does him no good.

Foil · Post by **Foil** » Mon May 07, 2012 7:47 pm

I'm going to steal this one to post on my facebook page, Jeff.

Tunnelcat · Post by **Tunnelcat** » Mon May 07, 2012 8:54 pm

fliptw wrote:
tunnelcat wrote:""I don't know" implies that I don't have enough information to make the choice one way or another, which means I need more information to give a definite answer to the question.
The barkeep only cares if the group wants beer or not; any answer besides yes or no does him no good.

Well, I guess it's just semantics then. It comes down to whether you think "I don't know" is a null. I'm of the opinion that "I don't care" is a better null. Maybe I'm being too nit picky.

Jeff250 · Post by **Jeff250** » Mon May 07, 2012 10:29 pm

"I don't know" reveals information to the third logician about the first and second logicians' preferences. It's not clear to me how "I don't care" would do this.

Tunnelcat · Post by **Tunnelcat** » Tue May 08, 2012 5:03 pm

Still not sure.

"I don't know" usually means one doesn't have enough information to make a choice.

"I don't care" usually means, "Whatever you're having is fine by me. I'm cool". Maybe I'm reading too much emotion and not enough logic into this one.

Enzo-03 · Post by **Enzo-03** » Tue May 08, 2012 5:16 pm

Hmm..

In my digital design class we have "don't cares", which I think is where the voltage level could be either a 1 or a 0 and no matter which one it is, the logical value of whatever circuit element it goes to wouldn't change.

Something like that. I've slept since we actually did anything with don't cares.

Jeff250 · Post by **Jeff250** » Tue May 08, 2012 6:37 pm

tunnelcat wrote:"I don't know" usually means one doesn't have enough information to make a choice.

"I don't care" usually means, "Whatever you're having is fine by me. I'm cool". Maybe I'm reading too much emotion and not enough logic into this one.

For the joke to work, in order for the third logician to have enough information to answer "yes," it's crucial that the first two say that they don't have enough information to answer the question. Since he knows that they don't have enough information to answer the question, he knows that they must want beer.

roid · Post by **roid** » Tue May 08, 2012 7:58 pm

I love that no-one is angry that we are ruining the joke.
You are my people.

Foil · Post by **Foil** » Wed May 09, 2012 8:11 am

Jeff250 wrote:For the joke to work, in order for the third logician to have enough information to answer "yes," it's crucial that the first two say that they don't have enough information to answer the question.

Yep. "I don't have any information" is almost an oxymoron, because it is inherently informative!

Tunnelcat · Post by **Tunnelcat** » Wed May 09, 2012 2:57 pm

Jeff250 wrote:
tunnelcat wrote:"I don't know" usually means one doesn't have enough information to make a choice.

"I don't care" usually means, "Whatever you're having is fine by me. I'm cool". Maybe I'm reading too much emotion and not enough logic into this one.
For the joke to work, in order for the third logician to have enough information to answer "yes," it's crucial that the first two say that they don't have enough information to answer the question. Since he knows that they don't have enough information to answer the question, he knows that they must want beer.

Ooooooooooooooooh, now I get it. I was thinking more in terms of emotional logic than pure logic. With emotional logic, "I don't care" means that you want the other person to go ahead and choose for you, while "I don't know" actually means "I don't know what I want, let me think about it for a moment". That's what I get for having a female brain. Different thought process altogether, am I right guys?

Spock could never understand emotional logic. It has a totally different set of rules than pure mathematical logic does.

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