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Topic: Real-world example of the liar paradox
Replies: 6   Last Post: Jul 6, 2013 8:01 PM

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Posts: 117
Registered: 11/1/11
Re: Real-world example of the liar paradox
Posted: Jul 6, 2013 5:24 AM
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On Saturday, July 6, 2013 5:08:41 PM UTC+10, Paul wrote:
> Nick Davies's book, Flat Earth News, says "it is a very safe bet that
> there are mistakes in this book." Later, I met the author and reminded him
> of this quote, and asked him what the mistakes were. He replied that the
> only error he knew of was extremely minor. (He described the error, but I
> forget the details.) If we tweak this account just a little bit and deem
> the book to be free of mistakes, then we get the liar paradox -- the only
> mistake in the book is the assertion that there are mistakes in the book.
> Paul Epstein

I made a quick program for this ...

herc said [liar bethy ]

bethy said
[liar herc] &
[herc said [liar bethy]]
truthful bethy
liar herc

> if you always lie, and you say that I am a liar, then I must be telling
> the truth, which means that you do always lie (?).

but I think my automated Proof got her!

5 assert herc [ liar bethy ]

7 true X :-
assert P X
truther P

8 false X :-
assert P X
liar P

10 truther X :-
assert P [ liar X ]
liar P

11 liar X :-
assert P [ liar X ]
truther P

liar herc ?

liar X
assert P liar X
assert P liar [ herc ]


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