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Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!grady
From: grady@ucbvax.ARPA (Steven Grady)
Newsgroups: net.puzzle
Subject: Re: Figure me this...
Message-ID: <3174@ucbvax.ARPA>
Date: Fri, 9-Nov-84 16:16:40 EST
Article-I.D.: ucbvax.3174
Posted: Fri Nov  9 16:16:40 1984
Date-Received: Sat, 10-Nov-84 09:39:29 EST
References: <1689@ucf-cs.UUCP>
Reply-To: grady@ucbvax.UUCP (Steven grady)
Organization: University of California at Berkeley
Lines: 25
Summary: 

This problem, although a classic, is not the best version of this type
of problem.  A book which I highly recommend is "What is the Name of
this Book (the Riddle of Dracula and other mysteries)" by Raymond
Smullyan.  Basically, the book consists of about 200 of these kinds
(liars, truth-tellers, etc.) of problems, along with other assorted
stories and problems involving logic.   An example from near the end
of the book, which shows some of the more interesting aspects of thios
type of puzzle is (I paraphrase):
You're in Transylvania.  There are two types of people, humans and vampires.
Humans always say what they believe, and vampires always say the opposite of
what they believe.  To make things interesting, there both sane and
insane people.  Thus there are sane humans, insane humans, sane vampires,
and insane vampires.  A moments thought wil show that in most circumstances
only sane humans and insane vampires will speak the truth.  But consider,
if a Transylvanian says "I believe X", can you determine whether X is true?
Can you determine anything about the speaker?  

Note: this is not the hardest type of problem.  One also gets into "Elite"
Transylvanians, who use the words "bal" and "da" for yes and no, not necessarily
repectively.  Also included is an understandable explanation of Godel's theorem,
and various stories, aneccdotes, jokes to entertain when your mind is
not working at it's best.  
				-Steven Grady