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chemically) stable, such composite systems in turn can provide the building
blocks for further construction. Through repetition, the process gives rise to a
hierarchical 4 and modular structure that Simon claims to be the signature of
systems with organized complexity. 'Direction,' he explains, 'is provided to the
scheme by the stability of the complex forms, once these come into existence.
But this is nothing more than survival of the fittest - that is, of the stable'.
(p. 191)
In these few words, Simon shows that even pre-Darwinian evolution can be
described in terms of a principle of selection, provided, i.e., that selection be rein-
terpreted in terms of stability or persistence, rather than of survival and reproduc-
tion. In doing so he anticipates the recent arguments of Alex Rosenberg, Frederic
Bouchard, and others 5 for reformulating (and thereby extending) Darwinian the-
ory by replacing 'fitness' with 'persistence'. In this view, biological survival
is just a variant of persistence, and reproduction a way of ensuring persistence
through increasing the population (like autocatalysis). But one needs to be a bit
careful here in our definition of stability - we are not interested in the stability
of rocks, and perhaps not even of the limit cycles of dynamical systems closed
to informational or material input. Rather, we are interested in the stability of
nonequilibrium systems that are by definition open to the outside world, not
only thermodynamically but also materially. Furthermore, we are particularly
interested in stability with respect to likely perturbations. Perhaps a better word
would be robustness. The systems that endure are those that are robust with
respect to the kinds of perturbations that are likely to be encountered. The critical
questions then become, first, how do new ways of persisting arise? And second,
how are they integrated into existing forms?
In neo-Darwinian theory, novelty arises through chance mutations in the
genetic material and integrated into existing population by selection for the
increased relative fitness such mutations might provide. In Simon's account,
especially as Wimsatt (1974) subsequently elaborated it, novelty arises through
composition (or combination), is further elaborated by the new interactions that
the proximity of parts bring into play, and, finally, integrated into the changing
population by selection for increased relative stability. Of particular importance
in Wimsatt's account is the stability of the composite acquired with the passage
of sufficient time 'to undergo a process of mutual coadaptive changes under
the optimizing forces of selection' (i.e., selection of the stable) (1974, p. 76).
4 Simon's use of the term hierarchy has led to a certain amount of confusion in the literature, for it is often
read as referring to relations of authority. Simon attempted to clarify his own use of the term as referring to
'all complex systems analyzable into successive sets of subsystems' (p. 185), and as distinct from authoritarian
structures (which he called 'formal hierarchies'), but a certain political valence continues to be read into his
arguments (see, e.g., Agre, 2003).
5 See, e.g., Bouchard (2004); Rosenberg & Kaplan (2005)
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