Re: Propositions (Fritz Lehmann)
Date: Thu, 12 May 94 02:03:29 CDT
From: (Fritz Lehmann)
Message-id: <>
To:, interlingua@ISI.EDU,
Subject: Re: Propositions

     I said:
>>     Yes, the notions of "propositions" which have been discussed here
>>in an ontology, not in the logic.  Except for the extreme end of the
>>(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
>>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
>>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.)

     McCarthy said:
>I think Fritz Lehman is mistaken in saying that languages admitting
>paradoxes of belief and desire depend on humans being involved.
>Computer programs will also sometimes be in the position of having
>something as a goal under one set of names and its opposite as a goal
>under another set of names.

     No, I agree with this absolutely.  I said "representations among signs
and sign-makers"; I specifically do not limit this to human beings. (I made
sure to note "or other real-world facts for other examples" but I should have
added "or any thing" after my "_to_ anyone".  I believe representation is
most often a chain-like linkage of triadic (ternary) sign-relations in
Charles Peirce's theory of formal semiotics (which is rigorous and
mathematical compared with modern "semiotics" rubbish).  Each sign relation
is a triadic relation (essentially indecomposable into dyads) among
representer, represented and the "interpretant" to whom (or rather to which)
the representer represents the represented.  The "meaning" travels along this
linkage (often picking up and losing information at each step).  How high-
level a creature has to be to have a sign-representation is the subject of a
lot of debate; Walker Percy said even Heller Keller didn't have it until her
transcending realization about the hand-sign for "water".  I on the other
hand put it much lower, down among the transistors and thermostats.  (Wlodek
Zadrozny of IBM has a promising theory about this.)  I still think, however,
that _some_ physical or "functional entities" must be presumed to exist in
the ontology before any of the "impure" notions of proposition have any
relevance or even the ability to be defined.  (By "impure" I mean other than
"up to logical equivalence" -- I guess there is some leeway there, though,
since you might say "up to intuitionistic logical equivalence" or something.)

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