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Re: Realworld example of the liar paradox
Posted:
Jul 6, 2013 5:24 AM


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!
http://phpprolog.com/TRUTHERLIAR.png
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 ?
HEAD 1 liar X TAIL 1 assert P liar X assert P liar [ herc ] FALSE 1 FAIL
Herc 
www.phpPROLOG.com ONLINE DATABASE AND LOGIC SOFTWARE



