logical deduction - 3 Logicians Walk Into a Bar

Three logicians walk into a bar. The barman says, 'Does everybody want a drink?'

The first logician says, 'I don't know.'

The second logician says, 'I don't know.'

What does the third logician say?

---

Please provide a clear explanation of why each of the logicians reply in the way they do.

Answer

Question:

Does everybody want a drink?

The third logician answers:

"YES" if he wants a drink, "NO" if doesn't want it.

Reason:

The first says "I don't know" because he wants a drink, but doesn't know if everybody wants one. If the first didn't want a drink, he would have answered "No".
Same for the second, he wants a drink but doesn't know if the third wants one. So, the third answers "Yes" if he wants a drink, "No" if he doesn't.