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From: smoliar@vaxa.isi.edu (Stephen Smoliar)
Newsgroups: comp.ai
Subject: Re: Fun with the semantics of paradox
Summary: What does "meaningless" mean?
Keywords: Undecidable, Ambiguous
Message-ID: <7282@venera.isi.edu>
Date: 17 Jan 89 15:14:09 GMT
References: <1883@buengc.BU.EDU> <2996@uhccux.uhcc.hawaii.edu> <905@ubu.warwick.UUCP>
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Reply-To: smoliar@vaxa.isi.edu.UUCP (Stephen Smoliar)
Organization: USC-Information Sciences Institute
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In article <905@ubu.warwick.UUCP> mirk@uk.ac.warwick.cs (Mike Taylor) writes:
>Two people have individually stated in this debate that there are 5
>truth values, these being True, False, Ambiguous, Undecidable and
>Meaningless.  It is intuitively clear to most people what is meant by
>a sentence being either true or false.  The latter three categories
>are not so clear.
>
>Am I right in thinking that an ambiguous sentence is one that can
>consistently be either true or false and that an undecidable one
>cannot be either?  What, then is a meaningless sentence?  Surely
>either an ambiguous sentence or an inconsistent one is meaningless?
>Or do people simply mean not well-formed?
>
>To clarify what I mean above by my understanding of the terms
>ambiguous and undecidable, I suspect that the sentence "This sentence
>is true" is ambiguous, since it can consistently be either true or
>false, and "This sentence is false" is undecidable, since it cannot be
>either.  Both sentences seem to me to be meaningless.
>
This has been giving me trouble, too.  Another possible interpretation is that
"meaningless" refers to sentences that are not well-formed;  but then, of
course, they are not really sentences, in which case it does not make sense
to talk of their having truth values.