Perhaps, Perhaps, Perhaps

If the first logician didn't want a beer then he would answer "No" because he could say with certainty that they did not all want a beer. But if he did want a beer he would have to answer, "I don't know" as he would not know if they all wanted beers.

Same is true for the second logician.

But the third logician, knowing that the answers of the first two meant that each of them did want a beer, and as he also wanted a beer, he could answer, "Yes!"