Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!snorkelwacker!mit-eddie!media-lab!minsky
From: minsky@media-lab.MEDIA.MIT.EDU (Marvin Minsky)
Newsgroups: comp.ai.philosophy
Subject: Re: emergent properties
Summary: Let's be sensible about "emergence".
Message-ID: <3499@media-lab.MEDIA.MIT.EDU>
Date: 29 Sep 90 23:12:37 GMT
References: <1990Sep29.213139.2876@watdragon.waterloo.edu>
Reply-To: minsky@media-lab.media.mit.edu (Marvin Minsky)
Organization: MIT AI Lab, Cambridge MA
Lines: 71

The most naive idea of "emergence" is that of a behavior-phenomenon
which appears in observing a group of things, that cannot be predicted
from knowing all about each individual.  This is uninteresting.  A
less trivial ideas of emergence is a behavior that can't be explained
in terms of the parts and their interrelationships.  But that's too
general, because of an ambiguity of what we mean by "their
relationships."

By the way, note that "emergence" itself is not a dyadic relationshiop
between a system and its behavior.  It is a triadic relationship
between the system's structure, its behavior, and the observer's
usually incomplete understanding of the relation between the first two!

What is fascinating is the extent to which, in science, it has so
often sufficed merely to know the dyadic relationships of the objects,
just two at a time.  This is the case in Newtonian mechanics; all the
forces are simply dyadic, and one has only to sum them to find the
accelerations that determine all the trajectories.  (Perhaps there is
something slightly triadic about this, however, because the
inter-forces alone don't suffice; they must all be referred to the
same coordinates, so as to obtain the proper vector sums.)

In general relativity it is not so simple, because of each particle
affecting the geometry of space, and thus changing the distance
vectors of the other pairs.  Still, the participations of each
particle in the overall differential equation is enough to explain all
the trajectories -- assuming you have the right equation.

In quantum electrodynamics as well, I have the impression that, again,
there are no mysterious emergents, in the sense that the two-at-a-time
exchange-interactions account for everything. However, each exchange
implies a new particle, and you have to include the two-at-a-time
interactions of all of these, hence the annoying infinite series.
Also, now things are a little different, for many-particle problems,
because the equations can no longer be solved within a manifold of
fixed dimension, because they require , not in a low-order vector
space they require the dimensionality of at least the
configuration-space.  Despite all that complexity, however, one still
feels that the predictions come directly, albeit in a complicated
manner, from one's understanding of the elemetary particules and their
local interactions.  No mysterious emergents.

Returning to the Newtonian situation, we could easily enough conceive
of a universe in which certain triadic interactions had unique and
"irreducible" effects, so that one could not make predictions on the
basis only of low order interactions.  Imagine a universe that were
Newtonian, with all forces depending on linear sums of
pair-relationships; that would determine all the orbits of planets,
stars, and galaxies.  But suppose also that some capricious God
imposed one extra, arbitrary law: whenever three stars form an
equilateral triangle, then they simply disappear.  That would appear,
to a classical physicist, to be an "inexplicable emergent" -- until it
was added as a new law of nature.

The amazing thing is how rarely anything resembling an "inexplicable
emergent" has ever reigned for very long in the history of Science --
except for transient periods before better theories remove the need
for the assumption of extra, special laws.  The moral is that,
whenever you're pretty sure you are dealing with a "genuine emergent",
you're proably making a mistake that reflects the primitive scientific
culture of your time.  The longest holdout was "life", or the vital
spirit, whose reduction commenced with Pasteur (and Darwin) and was
pretty much buried with Watson-Crick.  

A present-day holdout is "consciousness", and this is well illustrated
by Penrose's dogmatic naivites.  It is no accident, I suppose, that he
does not cite the suggestions I made about consciousness in "The
Society of Mind", in which I suggest that most of the phenomena
involved are related to (limited amounts of) short term memory.  If
so, future AI machines will be much more conscious than humans are,
and may also have much less sense of mystery about it.