Trying again to respond

sowa <sowa@turing.pacss.binghamton.edu>
Reply-To: cg@cs.umn.edu
Date: Thu, 29 Apr 93 08:51:50 EDT
From: sowa <sowa@turing.pacss.binghamton.edu>
Message-id: <9304291251.AA25768@turing.pacss.binghamton.edu>
To: cg@cs.umn.edu, interlingua@isi.edu, phyayes@cs.uiuc.edu
Subject: Trying again to respond
Cc: dietrich@turing.pacss.binghamton.edu, sowa@turing.pacss.binghamton.edu

Pat,

After beginning my last note, I tried to go into vi to edit your note,
but vi also got hung up on the 80+ character lines.  So I gave up and
I'll just start a fresh round of comments:

In your earlier note, you labeled my approach as "eccentric".  That is
a debating ploy to put me on the defensive, so that you can dismiss 
the position as inappropriate for a proposed standard for kn. rep.
I responded by citing a long tradition from Aristotle's three-way
distinction of word, experiences in the psyche, and object to
Ogden & Richards' meaning triangle of word, concept, and object.

This morning, I checked Michael Dummett's _The Interpretation of
Frege's Philosophy_ (Harvard U. Press, 1981) and came across the
following passage (p. 39):

"The basic tenet of analytical philosophy, common to such disparate
philosophers as Schlick, early and late Wittgenstein, Carnap, Ryle,
Ayer, Austin, Quine, and Davidson, may be expressed as being that the
philosophy of thought is to be equated with the philosophy of language:
more exactly,

 (i) an account of language does not presuppose an account of thought,

 (ii) an account of language yields an account of thought, and

 (iii) there is no other adequate means by which an account of thought
       may be given."

This statement quite nicely summarizes the position I am advocating.
In developing a theory of concepts, I am starting from the evidence
of language, not from introspection or psychology.  When I talk about
concepts as the mediating level between word and object, I mean the
formal structures that I can represent on paper or in a digital
computer.  Their possible parallels to mental states or neural processes
are an interesting topic for psychology and neurophysiology, but nothing
in my approach critically depends on those parallels.

On page 41, Dummett continues that for Frege "it is the thought that
is primarily said to be true or false, and the sentence only in a
derivative sense.  He sometimes says that a sentence _expresses_
a thought and _stands for_ a truth-value.  But it seems that we ought
not to regard it as doing both things simultaneously, as it were,
that is, as being said with equal right to do each of them.  Rather,
it stands for a particular truth-value _in virtue of_ its expressing
a true or false thought."

To avoid dealing with such elusive, nonobservable things as thoughts,
Frege developed his Begriffsschrift (concept writing), which along with
Peirce's algebraic notation became the foundation for modern systems
of logic.  Although I prefer Peirce's graphic notation, all of these
systems can be construed as formal ways of talking about that elusive
level of thought or concepts.

You seem to claim, however, that logic should be related directly
to real-world things without any intervening level of "concepts"
or "models".  Although you use the word "model", you identify
at least some of those models with aspects of the real world.
I prefer to make a very clean distinction and say that none of
those models are the real world.  Instead, I adopt a version of
the meaning triangle for both individuals and collections:

Individual:    word  <-->  concept  <-->  thing

Collection:    language  <-->  model  <-->  reality

You keep using the term TMT (Tarskian Model Theory) for an approach
that relates symbols directly to things.  I keep insisting that you
are taking Tarski's name in vain, since he never related symbols
directly to physical objects; he only related symbols to abstract
set-theoretic constructions (or to mereology, which he used in some
of his writings instead of set theory).  That approach should more
properly be associated with Richard Montague, who tried to identify
Tarski's abstract models with the real world.  And even Montegovians
like Godehard Link and Nino Cocchiarella have been much more
sympathetic to my three-part distinction between language, model,
and reality than you have been.

As I said in my previous note, I was a mathematician in my youth,
but I also took a lot of courses in physics.  And I think that the
three-way distinction comes naturally to both physicists and
engineers.  They do not think of mathematics as a "science of
reality".  Instead, they think of it as a tool for constructing
abstract models.  Then physics is the science that uses those
models to study reality, and engineering uses those models to
manipulate or change reality.

I also claim that the three-part distinction is an accurate 
description of AI practice:  language (either formal or natural)
is mapped to abstract models constructed from data structures in
the machine; and those models are mapped to the real world by
pattern recognition systems and robot manipulators.

Summary:  The three-way distinction of language, model, and reality
has a long and honorable tradition ranging from Aristotle to
Ogden and Richards, from Frege to the analytical philosophers,
and from common practice in physics and engineering to common
practice in AI.

I will acknowledge that there have been some philosophers who
have tried to blur the distinction between models and reality,
but I don't believe that they deserve the sobriquet of TMT
or "Tarskian Model Theory".  Tarski never blurred that distinction,
and he would probably respond in the same way as Karl Marx, who
said "Je ne suis pas Marxiste."

John