140 replies to this topic

[rookie1ja]

Barber Paradox (Russell's Paradox) - Back to the Paradoxes

Analogue paradox to the paradox of liar formulated English logician, philosopher and mathematician Bertrand Russell.
There was a barber in a village, who promised to shave everybody, who does not shave himself (or herself).
Can the barber shave himself and keep the mentioned promise?

Edited (better wording?):
In a village, the barber shaves everyone who does not shave himself/herself, but no one else.
Who shaves the barber?

[sharknateher]

Barber Paradox (Russell's Paradox) - Back to the Paradoxes

Analogue paradox to the paradox of liar formulated English logician, philosopher and mathematician Bertrand Russell.
There was a barber in a village, who promised to shave everybody, who does not shave himself (or herself).
Can the barber shave himself and keep the mentioned promise?

Well, this appears to be a simple English rules question. Because of the location of the commas in this sentence, we could re-word the sentence to read: "There was a barber in a village who does not shave himself (or herself), who promised to shave everybody." Therefore the answer is yes, of course, the barber, who does not shave himself can shave himself and keep the promise to shave everybody.

However, given the nature of the question, I believe the question being asked is " There was a barber in a village, who promised to shave everybody who does not shave himself or herself." In which case the paradox lies in the concept that he promises to shave those people who do not shave themselves. He can, of course, keep this promise. There is nothing in the barber's promise that says he can only shave those people who do not shave themselves. He can shave people who shave themselves too, even himself.

[banebrain]

I understand that this is supose to tease saying that if he shaves everyone that doesnt shave and he doesnt shave he must shave himself but then if he continues to shave himself he must stop because he now does not not shave himself. Yet nowhere in the riddle does it say he is incapable of shaving someone who already shaves =] just saying.... and it is worded rather oddly like sharknateher said, so I'm not sure if I have this down right.

[axmillia]

Just because the barber promises to only shave those who don't shave themselves doesn't mean they shave everyone who doesn't do it themselves.

[mathemagister]

The mainpoint is that he (the barber) is part of "everyone."

[savagegamer90]

This is the original paradox, one that can't be solved



In a village, the barber shaves everyone who does not shave himself/herself, but no one else.

Who shaves the barber?

[peartree]

Perhaps there is another barber in the village and many of the villagers get shaved by him. This being the case our barber could keep his promise to shave everyone who does not shave him/her self including himself, because he too gets shaved by the other barber.

[biemer_m5]

The barber sets forward an action that causes him to be shaved.
In other words an external event caused by him result to the desired outcome.

[lordhydra2003]

maybe the barbers beard doesn't grow it is possible (I've met people who do not need to shave) he keeps his promise and everybody is happy it does not say that his beard grows

[peartree]

What you say is very true 'Lordhydra2003' but let me tell you this; if I were that barber, you wouldn't be coming into my shop, nomatter how many heads you've got that need shaving!

Of course it's possible that all the men have gone off to war and there are no males left who need a shave. Maybe the barber gets shaved by his mother. This leaves his promise to shave everyone who doesn't shave him/herself highly questionable.