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From: minsky@media-lab.media.mit.edu (Marvin Minsky)
Subject: Re: UNIFIED MODEL FOR KNOWLEDGE REPRESENTATION? (IMPOSSIBLE
Message-ID: <1991Jun12.232457.2962@news.media.mit.edu>
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Organization: MIT Media Laboratory
References: <9106110020.AA17886@lilac.berkeley.edu> <133090@tut.cis.ohio-state.edu> <1991Jun12.130817.3621@kingston.ac.uk>
Date: Wed, 12 Jun 1991 23:24:57 GMT

In article <1991Jun12.130817.3621@kingston.ac.uk> is_s425@kingston.ac.uk (Hutchison C S) writes:
>Conversely, if sentences do not express propositions about the world that
>can be true or false (referring instead, for example, to speakers' 
>"perceptions" or internal representations of the world), then how can
>conversants ever know that they are talking about the same thing(s)?

The reductio ad absurdum is appropriate.  Conversants never do, in
fact, know that they are talking about the same things.  It is always
a matter of convention, convergence, and good fortune -- even in the
case of "mathematical truths".  When you and I both talk about "that
chair over there", our internal models differ substantially, but not
enough to make most practical interactions too difficult.  And the
cchir itself changes imperceptibly from one moment to the next as it
loses and gains atoms and suffers thermal agitations of its internal
degrees of freedom.  There is no chair, indeed, from a modern physical
point of view, only boundaries imposed by observers; my decorator
friend regards this chair and that other one as a possibly conflicting
pair, my fried the carpenter sees it as a possibly unsound linkage of
glue and sticks, and so on.  Let's grow out of this unproductive idea
of formal semantics, and low-level childish, religious, primitive
ideas about truth, and get on with the work of making machines that
can solve problems and communicate with one another as best they can.