I don't know :) - Ahsan Ali aka. Slick from IM

The puzzle actually has a solution. - Dave Winer

1, 2, and 3. - Tudor Bosman

The first three. Anyone who wasn't having coffee could safely say "no". If anyone before the fourth said no, it would be indeterminate. - Matt Mastracci

No one gets coffee. 4 answered for all of them. - Ahsan Ali aka. Slick

The first three were unsure, the forth one was the only one having coffee, he said no because he is the only one to have coffee. - Moobie

Well, they're *not* at the Nonlinear Cafe, that much I can deduce :) - Micah Wittman

Tudor and Matt got it. The question wasn't "Who wants coffee?" - Dave Winer

Fourth knows she doesn't want coffee, so she says no, they will not ALL be having coffee. - Arek Dreyer

FF is good for puzzles. If you don't want to see the answer you don't have to. :-) - Dave Winer

But what about upside down coffee cups? - Arek Dreyer

What if the question was "Does anyone want coffee?" - Arek Dreyer

If the question was "Does anyone want coffee?" then we wouldn't be here talking about this now. :-D - Moobie

Arek, the answer would then be "nobody gets coffee". - Matt Mastracci

maybe, maybe, maybe, yes. (Arek, these would have to be the answers, for it to make sense). - Panayotis Vryonis

The first three are ordering coffee, but don't know if the rest are. The last is not, and can safely say "No." Any other answer doesn't work, AFAICT. - Tanath

Why is it ruled out that the fourth gets coffee? He could be merely mistaken. Him not getting coffee is not a warranted true belief until he, in fact, doesn't get coffee. - Mark Trapp

the first three get coffee. the first three all would have been able to say "no" if they were not having coffee since that would mean they were not ALL having coffee. But because they were having coffee, and didn't know what the remaining people were going to answer, they could only say "I don't know". - David Aronchick

All four get coffee because the waitress was confused by their indirect method of answering her question so when she returned she simply left the pot on the table. - Garin Kilpatrick

Coffee for all! :) - Garin Kilpatrick

She returns with 3 coffees for the guys who said I don't Know. - Louis Rossouw

Where's the credit to Will Shortz and Merl Reagle??? http://www.npr.org/templat... btw - I like @DavidAronchick's answer! - Mark Chance

Excellent. I'll ask that the first person I'll be interviewing for a job :-) - Till

@Till: "Will you be having coffee?" "-Yes" "-You are hired!" - Jemm

Friendfeed works well for this. With the answer in the comments it is not immediately visible and gives the reader an opportunity to think before seeing the solution. - Scott Magoon

Apparently this was on NPR yesterday. I heard it from a friend who (I guess) must have heard it there. - Dave Winer

Reminds me of the Amtrak announcement at limited stations, "All doors will not open." - Jim Spath

We all know the answer to who gets coffee. It is 42. But who got the decaf? Did they use milk, non-dairy creamer, sugar, artificial sweetener...? That is the true test, the real conundrum. Answer that please. - Richard

1,2,3 couldn't say yes due to order but didn't say no so they each wanted one - Mark Essel from iPhone

No-one knows if they will all be having coffee or not until the fourth says 'no' because he surely knows the answer to her question ie that he does not want any. Waitress and other three now know they will not 'all' be having coffee so she brings enough for three. They give her a large tip. - Denise Danks

Should I try to answer this question before or after I have coffee this morning?? - Jannifer @wordsforliving

as the question was "will you *ALL* want coffee" , then there must be three OR LESS coffees delivered, as the fourth person was definitely not having coffee, being the only one who KNEW they wouldn't ALL be having coffee - kosso

The first three guys get coffee. If any of them didn't want coffee, then the answer for them would have been "no". - Otto

@Samuel Wood: I would disagree. The first three HAVE to say 'I dont know' as they have no idea if they will ALL get coffee. It doesn't mean they all chose to have coffee at all. - kosso

I'll have a coke and a muffin to go - Johnny Worthington

@kosso: If the person themselves did not want coffee, then they would instantly know the answer is no, they all did not want coffee, because that person didn't want coffee. The only way somebody can answer "I don't know" is a) he wants coffee and b) he's not sure if the other three do or don't want coffee. - Otto

1, 2 & 3 were having coffee, since their answer was YES, but they could not confirm if they would ALL be having coffee. The fourth one was the only one who could really answer the question, after hearing everyone elses' answer. He did not want any coffee, so he replied NO. (i.e.: whoever did not want coffee would have been in a position to give a negative answer. The fact that it was the last one is logiacal, but tricky) 3coffees please - constantinos alexacos

I think any of the earlier ones could have said no if they didn't want coffee, but then the riddle would be unanswerable, yes? Because the later responders would have to say no whether they wanted coffee or not. - Jandy, ConcertMaven of FF from iPhone

Exactly, Jandy. - Brome

I think that was an extremely patient waitress. - Ian Mulvany

Yes, the puzzle should have mentioned that not only is the waitress patient but she was a logician as well. - Dave Winer

first three. i'm with louis. - Marg Uerite

Only the person who gave the 'right' answer gets coffee, but he said no. - Bob Boynton

The answer is me. Because answering logic puzzles before I've had my coffee is too damned hard. - Steven Perez

all of them get coffee - excpet the last bugger - Peter Dawson

1,2 & 3 get coffee, as answering "no" means "not all 4 of us": the last is the only one who can see the whole picture, so the first three cannot say "yes" - they lack information. Starting with the first: if he wants coffee, he just knows that 1 on 4 will be served and his answer is "I don't know" (he doesn't know about the other 3). If he doesn't want coffee, then he knows for sure that, whatever the others say, it won't be 4 on 4 - so his answer would be "No" (and the fact that he doesn't know about the others becomes irrelevant) - Fabio