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Barber Paradox (Russell's Paradox)


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142 replies to this topic

#61 boen

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Posted 21 May 2008 - 09:04 AM

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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#62 Schwarp

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Posted 14 July 2008 - 06:23 AM

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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#63 logician

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Posted 16 August 2008 - 02:40 AM

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, 16 August 2008 - 02:48 AM.

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#64 drakethatsme

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Posted 26 August 2008 - 01:30 AM

He Could shave himself outside of the village.... Then he wouldn't be "in" the village..... -_- <_<
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#65 RainThinker

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Posted 24 September 2008 - 04:50 AM

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, 24 September 2008 - 04:50 AM.

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#66 Guest#0

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Posted 06 October 2008 - 11:07 PM

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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#67 Jorgomli

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Posted 04 February 2009 - 03:22 PM

Can someone else not shave the barber?

Or can we say that because people DON'T shave themselves that they CAN'T, or do not possess the ability to shave at all?
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#68 cgarcia

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Posted 08 February 2009 - 03:48 AM

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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#69 BillFab

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Posted 15 February 2009 - 06:59 PM

either he doesnt shave or the other barber shaves him!
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#70 whackptu

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Posted 19 February 2009 - 06:01 AM

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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