From newshub.ccs.yorku.ca!torn!utcsri!rpi!zaphod.mps.ohio-state.edu!cs.utexas.edu!milano!cactus.org!wixer!sparky Tue Nov 24 10:52:30 EST 1992
Article 7682 of comp.ai.philosophy:
Newsgroups: comp.ai.philosophy
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>From: sparky@wixer.cactus.org (Timothy Sheridan)
Subject: Re: Self-Reference and Paradox (was Re: Human intelligence...)
Message-ID: <1992Nov17.224249.25388@wixer.cactus.org>
Organization: Real/Time Communications
References: <26551@optima.cs.arizona.edu> <Bxtqon.I97@unx.sas.com>
Date: Tue, 17 Nov 92 22:42:49 GMT
Lines: 59

In article <Bxtqon.I97@unx.sas.com> sasghm@theseus.unx.sas.com (Gary Merrill) w
rites:
>
>In article <26551@optima.cs.arizona.edu>, gudeman@cs.arizona.edu (David Gudema
n) writes:
>|> In article  <BxtBwx.LvH@unx.sas.com> Gary Merrill writes:
>|> ]In article <1992Nov14.151559.13227@oracorp.com>, daryl@oracorp.com (Daryl
McCullough) writes:
>|> ]|>
>|> ]|>     This sentence is false.
>|> ]|>
>|> ]|> refers to an unrestricted notion of falsity, and is therefore
>|> ]|> meaningless. We can replace "false" by a restricted notion of falsity
>|> ]
>|> ]This sort of thing has been tried before.  One problem is that the display
ed
>|> ]sentence is *not* meaningless in any normal sense of this term.  We
>|> ]know perfectly well what it means -- and that's the problem.
>|>
>|> The term "meaningless" is ambiguous here.  There are many examples of
>|> problematic meanings in language.  For example, what does the word
>|> "unicorn" denote?  What does "nothing" denote?  Clearly, both words
>|> have a meaning in some sense, but neither has a "normal" denotation.
>|> If you take the view that sentences denote their truth values, then
>|> the liar's paradox can be taken as another example of the same thing.
>
>The liar's paradox is quite independent of the position that sentences
>denote their truth values.  Moreover, "meaningless" appears to be unambiguous
>in the above context.  My point was that the meaning of the sentence
>is sufficiently clear for us to use it in common inferences.
>
>The analogies to "unicorn" and "nothing" are weak and unconvincing.
>Surely it is not suggested that "This sentence" fails to denote as
>"unicorn" does or as "nothing" does.
>
>Certainly if we wish to take the position that a sentence is a *name*
>that *denotes* something, then we may court various problems.  Thus
>it is wise not to take that position.  Unfortunately, the liar remains
>with us.
>--
>Gary H. Merrill  [Principal Systems Developer, C Compiler Development]
>SAS Institute Inc. / SAS Campus Dr. / Cary, NC  27513 / (919) 677-8000
>sasghm@theseus.unx.sas.com ... !mcnc!sas!sasghm


The sentence "this sentence is false" has two logical conclusions.

A-- that it is true

B-- that it is false

since both of these are implied it is both TRUE *AND* FALSE.
It is thiat fact which contradicts other commonly held beleifes that a
sentence is never true and false at the same time.
Clearly there are such sentences but they are not usfull since they covertly
asert that a sentence can be true and false.  This is not a very good axiom
to have in your ontology.:)

Timothy Sheridan


