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Double Liar Paradox (Jourdain's paradox)


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63 replies to this topic

#31 archurro

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Posted 29 April 2008 - 09:39 PM

veryy niice.
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#32 Silencio Suenos

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Posted 01 May 2008 - 07:53 AM

If the front of the card reads that the sentence on the backside of the card is false then the sentence on the front side of the card would be true to as the sentence on the back of the card as being false. :lol:

THINK ABOUT IT :excl:

Front

THE SENTENCE ON THE OTHER SIDE OF THIS CARD IS FALSE.

Back

THE SENTENCE ON THE OTHER SIDE OF THIS CARD IS TRUE.
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#33 theshredder157

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Posted 03 May 2008 - 06:05 PM

That's the first Paradoxe I ever heard
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#34 fehn

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Posted 12 May 2008 - 04:26 PM

Maybe this will help, The truth is the absnce of a lie and a lie is the absence of truth.
So, when one side declares to be truth, it is declaring the absence of a lie. Then, when the other side declares the opposite site to be a lie, it is declaring the absence of truth in the opposite side. In conclusion both statements declare that there is a lie. So it is a lie.
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#35 shioty

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Posted 13 June 2008 - 03:37 PM

THE SENTENCE ON THE OTHER SIDE OF THIS CARD IS FALSE.
is TRUE

THE SENTENCE ON THE OTHER SIDE OF THIS CARD IS TRUE.
is FALSE
Becouse THE SENTENCE ON THE OTHER SIDE OF THIS CARD IS say [THE SENTENCE ON THE OTHER SIDE OF THIS CARD IS FALSE.]


)IF FALSE is TRUE > TRUE is FALSE
IF TRUE is FALSE > FALSE is TRUE
IF TRUE is TRUE > FALSE is FALSE
IF FALSE is FALSE > TRUE is FALSE
...is TRUE or FALSE?
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#36 logician

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Posted 16 August 2008 - 03:26 AM

I don't quite understand the fascination with 'paradoxes' of this sort, which basically come down to which of the two statements are true, if any.

I am blue.
I am red.

Am I blue or red? Maybe I'm green. Doesn't matter, both cannot be true.

The truth is on the other side.
The other side holds no truths.

Or is that just it? We enjoy 'trapping' the mind in a room with mirrors on both the wall we are facing and the wall directly behind, and looking at the infinite reflections that result?

I just don't get it. Can someone tell me what I am missing?

I am reminded of the "bullet that pierces all vs. armour that cannot be pierced" contradiction. Similar situation, both just cannot exist. One is right, the other is wrong, or maybe both are wrong, but the contradictory elements cannot both be right.



The simple explanation is :
The two statements cannot be assigned a true or false value to make them consistent simultaneously
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#37 ninethcircle

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Posted 19 October 2008 - 09:47 AM

Back side
Inscription on the other side is true

Face side
Inscription on the other side is not true

this is not necessarily a logic paradox although it seems to be contradictory, True does not always mean correct that is only one possible meaning, therefore there it is logical to assume in a situation like this the intention is not to say weather or not the sides are correct...

here is some definitions for true

# consistent with fact or reality; not false; "the story is true"; "it is undesirable to believe a proposition when there is no ground whatever for ...

well... we know its not that one.

# accurately placed or thrown; "his aim was true"; "he was dead on target"

This one could work.

# devoted (sometimes fanatically) to a cause or concept or truth; "true believers bonded together against all who disagreed with them"

this one doesnt make much sense...

# truthful: expressing or given to expressing the truth; "a true statement"; "gave truthful testimony"; "a truthful person"

This one wouldn't appear to work but it implies intent also, so it may work especially with the common usage factor of this definition probably just being 'honest'

# conforming to definitive criteria; "the horseshoe crab is not a true crab"; "Pythagoras was the first true mathematician"

wouldn't work...

# dependable: worthy of being depended on; "a dependable worker"; "an honest working stiff"; "a reliable source of information"; "he was true to his word"; "I would be true for there are those who trust me"

This one actually works very well, to be dependable in general does not mean you are always completely correct

# genuine: not pretended; sincerely felt or expressed; "genuine emotion"; "her interest in people was unfeigned"; "true grief"
This one also works very well in the way that implies intent and beliefe in the statement rather than whether or not it is factual.

# true(a): rightly so called; "true courage"; "a spirit which true men have always admired"; "a true friend"

doesnt really work well...

# true(a): determined with reference to the earth's axis rather than the magnetic poles; "true north is geographic north"

once again doesnt work well...

# true(a): having a legally established claim; "the legitimate heir"; "the true and lawful king"

also doesn't work well...

# on-key: in tune; accurate in pitch; "a true note"

does'nt work unless the coin doubles as 2 tuning forks. lol

# accurately fitted; level; "the window frame isn't quite true"

works in the sense that the text may not be straight on one side lol

# as acknowledged; "true, she is the smartest in her class"

doesn't work

# proper alignment; the property possessed by something that is in correct or proper alignment; "out of true"

also works in the sense that the text may not be straight on one side lol

# make level, square, balanced, or concentric; "true up the cylinder of an engine"

another that works in the sense that the text may not be straight on one side lol




I dunno i might be completely out there with this comment i thought lateral thinking could help solve a logic problem by using logic in a paradox discussion I shall call this latogic or maybe logeral
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#38 lil-xander

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Posted 22 December 2008 - 04:37 AM

lets look at this in a very basic algebra way

cross multiplying

the saying on the other side is true

the saying on the other side is false


this can be said as

Father = what mother says is true

Mother = What father says is false


so therefore mother is true and father is false

so we simplify into

- = +
------
+=-


we cross multiply and get

2+
---
2-


which brings us to

+
--
-

if you think of it as a fraction then the whole solution is negative

when everything is negative it means that everything is false

therefore what they both say is false

simple math

Credits to PlayTheMindGame fr the mother father thing

Edited by lil-xander, 22 December 2008 - 04:39 AM.

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#39 Xxbrainy_punkXx

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Posted 31 December 2008 - 03:10 AM

This is like a never-ending paradox
1. The sentence on the other side of this card is false
2. The sentence on the otherside of this card is true

If side 1 is true by saying side 2 is false, doesn't it also mean that side 2 is false by saying side 1 is true, which would make side 1 false even though it is true. This reminds me of when an unstoppable force meets an immovable object. You just can't win.
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#40 isaac

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Posted 15 October 2009 - 09:55 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


Well... wouldn't it be infinitely nothing? zero for infinity? Like the classical idea of a blackhole, to find infinite mass, look for the least of anything?
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