Three logicians enter BAR4U.
Barman: Will each of you guys order a beer?
L1: I don’t know.
L2: I don’t know.
L3: Yes.
Please comment.
All three logicians are interpreting the barman's question as an inclusive OR: If they know any of them does not want a beer then the answer is no; and only when all three want a beet the answer is yes.
If either L1 or L2 did not want to order a beer then they would have said No. The lack of No indicates both L1 and L2 want a beer.
But since neither knew what L3 wanted they could not say yes either. So L1 and L2 both said "I don't know".
L3 hears both these responses and then knows both L1 and L2 want a beer and since L3 also wants one himself he now knows all three of them want a beer and answers "Yes".
Solution
