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Barber Paradox (Russell's Paradox)


rookie1ja
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The paradox is not eternal......so if the barber went one day without shaving, then he could shave himself and be shaving someone who did not shave himself.....even if it was for only a day :)

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  • 2 weeks later...

Okay. IMHO :

the barber promise to shave anyone who does not shave himself.

and the question is "Can the barber shave himself and keep the mentioned promise?"

right?

so. I think the barber not promise to " NOT SHAVE anyone who sahve himself" right?

so, why the barber would break the rule if he shave himself?

the promise only said that he (the barber) will shave anyone who does not shave himself. so, the other who shave himself still can be shaved by the barber right? include the barber.

Edited by EGG HEAD
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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?

Not reading all the other posts, and dare I ask if the lady shaves herself - I have two pictures in my mind. one is similar to my old aunt who had almost a moustache when she was in her eighties, and the other is not for this forum!

Possibly a non shaving lady barber

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Thus, the barber is female and has no facial hair. She does not shave herself, but shaves everyone else.

The barber promises to shave everyone who doesn't shave themselves:

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

If the barber (or anyone else in the village) is a woman (or child) who does not NEED to shave, then they don't shave themselves, which means the barber (man, woman, or child) must therefore shave them - if they need it or not. So the 'barber is a woman/child' exit does not work.

Edited by Steve Luke
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  • 2 weeks later...

If the barber did not shave him self so far, then he can

do so and keep the mentioned promise.

Otherwise, he can be shaved by his assistant or another barber.

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  • 1 month later...

I think that it is saying he can shave once, but after that point he can not shave again.

He can shave himself from the moment he makes this promise because he hasn't shaven yet, but once he shaves, then he is not allowed, because he has shaven himself.

Although, if you are taking into consideration that he has not said he will not shave those who shave themselves, then it changes.

BUT is it not the job of a barber to shave those who haven't shaven, because how can he shave those who are already shaven.

He's just being a barber, and we all know they shave themselves too.

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  • 1 month later...
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?

Actually the original statement is incorrect and is not a paradox. The second one is correct. For the first one, the barber does shave himself/herself and also everyone who does not shave himself/herself. Hence the barber is not among those who does not shave himself/herself, so his/her shaving himself/herself does not play any role to keep his promise.

The second version is the special case of the normal diagonalization argument commonly used in Computer Science and is used to prove that a class of problems is unsolvable.

Edited by logician
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  • 2 weeks later...
  • 5 weeks later...
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! <!-- s:lol: --><!-- s:lol: -->

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. <!-- s:roll: --><!-- s:roll: -->

I agree with his mother shaving him, It makes a little sense.....

:lol: I feel sorry for the barber, not having left home yet, and still being shaved by his mother :lol:

Edited by RainThinker
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  • 2 weeks later...

If you think about it, and go through the steps, for this paradox, then this is the result:

If we assume that the back is false, and we start there, then the statment on the front is false that the statement on the back is true, which is essentially correct.

I highly doubt, though anyone will understand what the heck I just said.

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  • 3 months later...

If the barber never shaves, because he chooses not to, then can shave himself. "He shaves everyone who doesn't shave himself or herself." If he doesn't shave himself, then by virtue of not shaving he can do it.

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The barber doesn't shave, he simply trims.

By the way, it is mentioned "himself/herself". So if he shaves the beard of those who can't shave himself, what does he shave for the person who cannot shave herself. Oh my, I'd like to be the barber in this village.

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Ok. This one is simple.

It clearly says that the barber shaves everyone who doesn't shave him/herself.. therefore, the only people left in the village to shave the barber are the people who DO shave themselves.. correct? or incomplete?

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  • 3 weeks later...

I think i get it.

If he shaves everyone who doesn't do it him/herself, then if he shaves himself he can't shave himself 'cause he's the barber. But since his promise

to shave everybody, who does not shave himself (or herself).
is directed to everyone in the village, he could leave the village and shave himself then come back. So he can shave himself, after all!

Of course he could've asked someone else to do it, but the question specifically askes if he can shave himself. So my first answer is right, or at least sort of.

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  • 2 weeks later...

I agree w/ Bunny Master 12. It doesn't specify anywhere that the Barber can't leave the village to shave himself, so it's open to assume that he can.

Glitch: No where, they never mentioned it.

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I thought I posted a reply to this topic a few weeks ago but it seems to have disappeared. *shrug*

We do run into a paradox if we try to deal with this situation in "logical" terms: A shaves B; whenever B = A, that means A is shaving himself; etc.

In common-sense terms, though, there's no paradox. The verb "shaves" can describe two grammatically similar but physically very different activities:

A. Picture the action, "The barber shaves Joe." Joe is sitting, probably in a special chair with a headrest and footrest. The barber is standing over him using the tools of his trade.

B. Now picture the action, "Joe shaves himself." Joe is standing in front of a mirror, quite likely in his own bathroom, using a safety razor. If he were late getting somewhere he might even be shaving in his car, sans mirror, driving with the other hand.

When the barber shaves himself it looks like A., not B. We wouldn't normally describe it as "The barber shaves the barber." He doesn't sit in the chair while standing over himself with a razor; he shaves in his bathroom (or car) like everyone else. When he's shaving himself that way, he's a private citizen who -- on other occasions -- works as a barber. The barber shaves his customers (when they don't shave themselves). The private citizen shaves himself.

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