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From: norm@ariel.UUCP
Newsgroups: net.ai
Subject: Re: A topic for discussion, phil/ai persons.
Message-ID: <630@ariel.UUCP>
Date: Tue, 15-May-84 17:49:41 EDT
Article-I.D.: ariel.630
Posted: Tue May 15 17:49:41 1984
Date-Received: Wed, 16-May-84 04:41:53 EDT
References: <277@wxlvax.UUCP>
Organization: AT&T-ISL, Holmdel, NJ
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The computer needs to be able to distinguish between "metaphysically identical"
and "essentially the same".  This distinction is at the root of an old (2500
years?) Greek ship problem:
Regarding Greeks ship problem: When a worn board is replaced by a new board,
the ship is changed, but it is the same ship.  The difference leaves the
ship essentially the same but not identically the same.  If all the boards
of a ship are replaced one by one until the ship is entirely redone with new
boards, it is still the same ship (essentially).  Now, if all the old boards
that had been removed were put together again in their original configuration
so as to duplicate the new-board ship, would the new old-board ship be iden-
tically or essentially the same as the original old-board ship? Assume nailless
construction techniques were used thruout, and assume all boards always fit
perfectly the same way every time.

We now have two ships that are essentially the same as the original ship,
but, I maintain, neither ship is identical to the original ship.  The original
ship's identity was not preserved, although its identity was left sufficiently
unchanged so as to preserve the ship's essence.  The ship put together with 
the previously-removed old boards is not identically the same as the original
old-board ship either, no matter how carefully it is put together.  It too is
only essentially the same as the original ship.

A colleague suggested that 'essence' in this case was contextual, and I
tend to agree with him.

Actually, even if the Greeks left the original ship alone, the ship's identity
would change from one instant to the next.  Even while remaining essentially
the same, the fact that the ship exists in the context of (and in relation to)
a changing universe is enough to vary the ship's identity from moment to mo-
ment.  The constant changes in the ship's characteristics are admittedly very
subtle, and do not change the essential capacity/functionality/identity of the
ship.  Minute changes in a ships identity have 'essentially' no impact.  Only
a change sufficiently large (such as a small hole in the hull) have an
essential impact.

"Essence" has historically been considered metaphysical.  In her "Introduction
to Objectivist Epistemology" (see your local bookstore) Ayn Rand identified
essence as epistemological rather than metaphysical.  The implications of this
identification are profound, and more than I want to get into in this article.
Philosopher Leonard Peikoff's article "The Analytic-Synthetic Dichotomy", in
the back of the newer editions of Rand's Intro to Obj Epist, shows how crucial
the distinction between essence-as-metaphysical and essence-as-epistemological
really is.
Read Rand's book and see why the computer would have to make the same distinc-
tion.  That distinction, however, has to be made on the CONCEPTUAL level.  I
think Rand's discussion of concept-formation will probably convince you that
it will be quite some time before man-made machinery is up to that...
Norm Andrews, AT+T Information Systems (201)834-3685 vax135!ariel!norm