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Six Logicians

Posted by rajesh on May 19, 2013 – 9:09 pm

Six logicians finish dinner. The waitress asks, “Do you all want coffee?”

First logician: “I don’t know.”

Second logician: “I don’t know.”

Third logician: “I don’t know.”

Fourth logician: “I don’t know.”

Fifth logician: “I don’t know.”

Sixth logician: “No.”

Who gets coffee and why?


This post is under “Logic, wordfun” and has 4 respond so far.
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4 Responds so far- Add one»

  1. 1. Mishu Said:

    Hello,

    I am guessing that the first five will get coffee. Each logician knew only if he wanted or not coffee, but nothing about the others.

    So the only way to know that the statement “all want coffee” is false is by knowing that you don’t want it, under the circumstances (that they did not discuss this before).

    Based on this, the first five only answered what they could based on what they knew, that they do want coffee. The last one did not want so he was able to tell for sure that only some of them want, not all of them.

    If he would have been on any of the positions 1-5 it would have been impossible to predict as all the others after him would have said “No”

  2. 2. DP Said:

    I agree with Mishu. This first guy wants coffee, otherwise he would have said “no” to “Do you all want coffee?”. The second guy knows this, but also wants coffee, otherwise would have said “no”. Same for third, fourth, and fifth. The sixth guy could have simply said “yes” if he wanted coffee, since he now knows the others do. He doesn’t want any, so he says “no”.
    My guess is that no one gets coffee becuase the customers are the logicians, whereas the waitress was most likely referring to them as a group. As soon as the last guy says “no”, she must have thought they ALL do NOT want coffee.

  3. 3. ragknot Said:

    No! I don’t know either.

  4. 4. JohnP24 Said:

    It really depends on how you interpret “you all”. Is the waitress asking each person to speak for the entire group or is the waitress simply referring to each person as an individual and expects their response to be only speaking for themselves.

    Six Logicians would likely go with the commonly accepted usage of “you all” to mean they should speak for the entire group whereas the waitress would like each customer to respond individually for themselves.

    What if the first logician said yes? The waitress would have to respond with, “Do you all want Regular or Decaf?” It could get quite exhausting for the waitress if the logicians and the waitress are interpreting “you all” in two different ways.

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