All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Logic
In a bar (Posted on 2015-05-19) Difficulty: 1 of 5
Four logicians walk into a bar.
The barman asks “Does everyone want a drink?”
The first logician says, “I don’t know”.
The second logician says, “I don’t know”.
The third logician says,“I don’t know”.
The fourth logician says “Yes”.

Please explain.

No Solution Yet Submitted by Ady TZIDON    
No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Solution (perhaps?) | Comment 1 of 2
If the first logician did not want a drink, she would immediately answer, "No." Since she doesn't do that, she must want a drink. However, she doesn't know what her 3 colleagues want, so she must reply, "I don't know."

The second logician wants a drink and realizes the first logician also wants one but, by the same analysis, #2 doesn't know what their other 2 colleagues want. So, she too replies, "I don't know."

Ditto for logician #3 who knows that #1, 2, and 3 want a drink but none of them knows #4's state of thirst.

Logician #4 knows she wants a drink and has reasoned that each of her 3 colleagues also wants one. She, therefore, confidently answers, "Yes" to the barman and orders 4 single malt Scotches, each. (It's her turn to buy for the logician's club annual outing.)


  Posted by JayDeeKay on 2015-05-19 09:52:01
Please log in:
Remember me:
Sign up! | Forgot password

Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (4)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Copyright © 2002 - 2018 by Animus Pactum Consulting. All rights reserved. Privacy Information