Re: Propositions (Fritz Lehmann)
Date: Thu, 12 May 94 00:50:29 CDT
From: (Fritz Lehmann)
Message-id: <>
To:, interlingua@ISI.EDU,
Subject: Re: Propositions

---------------begin quoted matter:
>> The finest minds in Western civilisation havn't come to a consensus
>> on this in hundreds of years.  We should be very sceptical of a
>> committee of even the *very best* computer scientists claiming it
>> has a 'standard'.
>Agreed, it would be sheer hubris to propose *the* standard account of
>propositions.  What might more modestly be hoped for, however, is for
>several conceptions of proposition to be isolated and, drawing upon
>existing literature and powerful new formal techniques, theories
>corresponding to each of these conceptions to be made available as
>separate ontologies.

Mike, Richard Fikes, Tom Gruber, and myself discussed this point recently.
We had in mind that a "standard" ontology could contain several
distinct theories, each defining a different notion of proposition
(or perhaps we should have a single theory defining PROPOSITION1,
PROPOSITION2, etc.).  We never had in mind that a single notion
of proposition would suffice for all applications.  Thats why we
suggest putting propositions into an ontology rather than
into KIF itself.
- Bob
Robert M. MacGregor                           
-----------end quoted matter

     Yes, the notions of "propositions" which have been discussed here belong
in an ontology, not in the logic.  Except for the extreme end of the spectrum
(the end in which all logically equivalent propositions are one), all the
rest of the ideas have to to with representation and semiosis.  As in: Did
Oedipus want to marry his mother?- yes because he wanted to marry Jocasta,
and Jocasta was his mother, therefore he wanted to marry his mother.  The
fallacy of this example, and similar limits to substitution, has to do with
the nature of people, knowledge and desires, or other real-world facts for
other examples.  In a universe in which nobody exists and nothing represents
anything else (_to_ anyone), I don't believe that the "spectrum" exists at
all.  The different degrees and kinds of "proposition" are dependent on
semiosis and representation among signs and sign-makers.  The only remaining
issue for the logic is the relation between a quoted sentence and the same
sentence, unquoted.  (If quoted sentences have any logical status at all,
that is.)

                          Yours truly,   Fritz Lehmann
4282 Sandburg Way, Irvine, California 92715, U.S.A.
Tel.: (714)-733-0566  Fax: (714)-733-0506