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4 B. Edmonds and R. Meyer

understanding of human society. Thus, this book does not deal with models of
single individuals or where the target system is dealt with as if it were a single
entity. Rather it is the differing states of the individuals and their interactions that
are the focus here.
Complexity—the phenomena of interest result from the interaction of social actors
in an essential way and are not reducible to considering single actors or a
representative actor and a representative environment. It is this complexity
that (typically) makes analytic approaches infeasible and natural language
approaches inadequate for relating intricate cause and effect. This complexity
is expressed in many different ways, for example, as a macro/micro link, as the
social embedding of actors within their society and as emergence. It is with these
kinds of complexity that a simulation model (of the kind we are focussing on)
helps, since the web of interactions is too intricate and tedious to be reliably
followed by the human mind. The simulation allows emergence to be captured in
a formal model and experimented upon.
Since this area is relatively new, it involves researchers from a wide variety of
backgrounds, including computer scientists, sociologists, anthropologists, geogra-
phers, engineers, physicists, philosophers, biologists and even economists. The field
is starting to mature and this handbook is part of that process. We hope that it will
help to introduce and guide newcomers into the field so as to involve more minds and
effort in this endeavour, as well as inform those who enter it from one perspective
to learn about other sides and techniques.

1.2 The Context: Going Back to Herbert Simon

This handbook is in memory of Herbert Simon, since he initiated several key strands
that can be found in the work described here.
He observed how people behave in a social system instead of following some
existing framework of assumptions as to how they behave (Simon 1947). That is, he
tried to change the emphasis of study from a normative to a descriptive approach—
from how academics think people should be behaving to how people are observed to
behave. Famously he criticised “armchair” theorising, the attempt to make theories
about social phenomena without confronting the theory with observation. There is
still a lot of “armchair” theorising in the field of simulating social complexity, with
a “Cambrian explosion” of simulation models, which are relatively unconstrained
by evidence from social systems. If the development of this work is seen as a sort
of evolutionary process, then the forces of variation are there in abundance but the
forces of selection are weak or non-existent (Edmonds 2010).
Importantly for the simulation of complex social systems, Simon observed
that people act with a procedural rather than substantive rationality—they have a
procedure in the form of a sequence of actions that they tend to use to deal with
tasks and choices rather than try to find the best or ideal sequence of actions (Simon