Subject: Review of Permutation City by Greg Egan (possible spoilers)

From: "Danny Yee" <[email-masked]>
Date: Tue, 19 Dec 1995 16:56:42 GMT

Permutation City
		by Greg Egan
		Review Copyright 1995 Danny Yee

Warning: some may consider that there are spoilers in this review

If one could simulate a human being completely, at the level of fundamental
physics, would the simulation be human in some sense?  It's hard to argue
otherwise without resorting to some kind of essentialism, but one obtains
some disconcerting results if one follows through on such a functionalist
metaphysics.  If all that "matters" are fundamentally mathematical
relationships, then there ceases to be any important difference between the
actual and the possible.  (Even if you aren't a mathematical Platonist, you
can always find some collection of particles of dust to fit any required
pattern.  In _Permutation City_ this is called the "logic of the dust"
theory.)

In the 2050 world of _Permutation City_, nothing as unrealistic as physical
level simulation is possible, but there are "Copies" of people.  These are
ad hoc simulations employing knowledge from all levels of biology -- at the
synapse and neurotransmitter level in the brain, but at much higher levels
of abstraction for "less important" organs.  These Copies are run in an
environment simulated along similar lines (some of it in great detail, some
of it just sketched in).  Due to processing limitations they run at best at
one-seventeenth of the rate of ordinary human beings and sometimes much more
slowly, depending on the available processor power.  There is also something
called the Autoverse, an extremely complex cellular automata (a souped-up
version of Conway's "Life") which produces a world broadly similar to ours
but with different physics, chemistry, and biology.  This is so
computationally intensive that only simple micro-organisms have been
discovered (created?), and they don't seem to evolve.  As a result the
Autoverse is considered more of a toy than a serious research proposition;
it is just a hobby for freelance programmer Maria Deluca.  Copies and the
Autoverse are the technological innovations crucial to the plot, but Egan
also has lots of other ideas about what the future might be like, socially
as well as technologically.

Paul Durham is convinced by the "logic of the dust" theory mentioned above,
and plans to run, just for a few minutes, a complex cellular automaton
(Permutation City) started in a "Garden of Eden" configuration -- one which
isn't reachable from any other, and which therefore must have been the
starting point of a simulation.  This is set up to run Copies of Paul, Maria
and sixteen rich Copies seeking immortality, and to expand in such a way as
to provide them with effectively unlimited computing power.  (And in order
to provide something interesting to watch, this automaton is also set up to
simulate an entire Autoverse world, which is why Maria is involved.)  The
idea is that the simulation need only run for a few minutes (at a slow-down
of 250 to 1) and when stopped will continue ("running on the dust"), because
it will be more plausible to its inhabitants that it have done so.  I didn't
fully understand the need for this elaborate set-up, but I guess it makes
for a better story than "well, all possible worlds exist, and I'm going to
tell you about one of them".

Part two is set entirely within the simulated Permutation City.  Eventually
the logic of the Autoverse (which has evolved intelligent beings who, I
think rather implausibly, manage to think up a simpler explanation for the
Autoverse than the logic) starts to erode the logic of the automaton
simulating it, and things fall apart.  I found this part was less engaging
-- if still interesting -- and the actual ending unsatisfying.  I guess it
was never going to be easy ending a novel that could, without inconsistency,
have had absolutely *any* ending (including ones where causality just goes
completely haywire).

_Permutation City_ is as good as _Quarantine_, and won't disappoint Egan
fans.  While I really enjoy the way Egan plays with philosophical ideas,
however, I would really like to see him write a more "ordinary" science
fiction novel.  This would give him a chance to explore the wealth of other,
less profoundly metaphysical ideas he has produced.

%T	Permutation City
%A	Greg Egan
%I	Millenium
%C	London
%D	1995
%O	paperback
%G	ISBN 1-85798-218-5
%P	310pp
%K	science fiction

18 December 1995

        http://www.anatomy.su.oz.au/danny/book-reviews/