Three logicians walk into a bar

Question

Three logicians walk into a bar. The bartender asks: "Does everyone want a beer?"

The first logician says, "I don't know." The second logician says, "I don't know." The third logician says, "Yes."

Explain the three answers. What does each logician know at the moment they speak, and why is the third able to answer for all three?

Accepted Answer

Each logician knows only their own preference. The first two want a beer but cannot speak for the others; the third wants one too and, hearing the first two, can answer for everyone: Yes. The first logician. She knows whether she wants a beer. If she did not, the answer to "does everyone want a beer?" would be a definite no, and she would say so. She says "I don't know", which reveals that she does want one; she simply cannot speak for the other two. The second logician. He now knows the first wants a beer. If he did not want one himself, he would say no. "I don't know" reveals that he does w…

Three logicians walk into a bar

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