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Double Liar Paradox (Jourdain's paradox)


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63 replies to this topic

#21 urkspleen

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Posted 21 November 2007 - 03:38 AM

Putting it simply, you cannot assume out of ignorance that either side is true. However, you cannot assume either is false also. In a case like this, you need a third party to verify a fact. If the back was a liar though, you do not know how often it lies, when it lies, what it lies about, etc. Taking that in stride, the front can be true or false depending on the condition. There are many different scenarios: They could also both be liars, their positions can be switched around, etc. Again, you need the third party for verification.
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#22 Chris flying one

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Posted 24 November 2007 - 08:39 AM

Very, very simple answer. Both sides are false.
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#23 shadow

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Posted 06 December 2007 - 04:05 AM

just burn the card
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#24 Bluemoon

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Posted 29 February 2008 - 04:23 PM

The lying example doesn't work. Lying and not telling the truth are entirely different. When you lie, you are telling someone something that you believe is incorrect. When you don't tell the truth, you are still able to say what you believe, be incorrect, and not be lying about it.

The tricky part with this paradox is that one statement means nothing without the other. In any event where the statement can stand alone it's not a paradox. Ex: "This statement is false." The statement that is being called false is false, while the entire sentence is true. What is false does not include the word false itself.

The only circular part about this problem is trying to figure it out. The problem itself isn't circular, they both exist at the same time, in the same space.

Even knowing that, I'm having a hard time getting out of the circle. Can anyone else get out of it?


I think what I'm reading there is that the statement being referred to is false, not the statement being called false is false, with what was said there's only 1 statement, you can go around in circles if you try and break it down. Theoretically, anything you say can be either condensed or broken down depending on what it is. I am confused by what he means by What is false does not include the word false itself, perhaps implying that the word false in the statement isn't false? Any thoughts?
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#25 maps157

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Posted 26 March 2008 - 05:17 PM

Back side
Inscription on the other side is true this is not true

Face side
Inscription on the other side is not true this card is true but if the other card is false it can't be.
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#26 beyond-logic

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Posted 30 March 2008 - 02:31 AM

It seems to me that the simple explanation to this paradox lies in it's title. "Double Liars"

Let F be the Face side and B be the Back. After you have read both sides, it seems that B declares opposite to that of F and vice versa. Therefore both statements are false (or if you prefer), the statement that: The two statements cancel each other.

Therefore neither statement is true and both are liars hence 'Double Liars'.

Edited by beyond-logic, 30 March 2008 - 02:31 AM.

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#27 kmccain1985

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Posted 02 April 2008 - 10:30 PM

wouldn't both sides be false?
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#28 peanut

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Posted 11 April 2008 - 08:30 PM

If it isn't true that it's true..........then it's not true.
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#29 Phoenix of Chaos

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Posted 22 April 2008 - 11:02 AM

What is ironic is the fact that, because the front sentence is correct, the back sentence is incorrect, and the sentence on the back is also false. It also fails to mention which side of the card it speaks of; don't forget a card has three dimensions, the third is just very, very small. Think of that.
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#30 lords8n

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Posted 25 April 2008 - 04:30 PM

it is just like in math.
rule 1) 0 * anything is.... 0
rule 2) infinity * anything is... infinity

whats 0*infinity?
what is that absence of everything * the fulfilliment of everything?

its impossible to end the problem, unless u know calc.

i do believe that it is an infinit loop. but then again, it could be based on how u read it. and your thought process


This is not a paradox at all. It's absolutely simple.

Sure INFINITY TIMES ANYTHING = INFINITY.
But ZERO is NOT anything, it is NOTHING.

If I ask for something ZERO times, I get ZERO somethings in return.
If I ask for everything ZERO times, I get ZERO everythings in return.
If I ask for INFINITE somethings, I get INFINITE somethings in return.
If I ask for INFINITE nothings, I get INFINITE nothings in return.

ZERO, the absence of something, governs this equation, and therefore results in an answer of ZERO.

Keith
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