Illuminating abstractions – Epstein on "Why model?"

posted: 1184 days ago, on Thursday, 2008 Nov 13 at 15:40
tags: psychology, modelling.

The current issue of JASSS (October 2008) has a thought-provoking contribution from Joshua M. Epstein, member of the External Faculty of the Santa Fe Institute and agent-based modeling guru.

Epstein gives his answers to the question "Why model?", and shares several reasons, above and beyond prediction, for building models. His short article should be included in every course taught on the subject.

The reasons he lists that most resonate with me is that models illuminate core dynamics, suggest dynamical analogies, and reveal the apparently simple to be complex (or, the apparently complex to be simple).

The most exciting aspect, however, is that a model can exhibit generative explanations, to use Epstein's term. This happens when "macroscopic explananda ... emerge in populations of heterogenous software individuals (agents) interacting locally under plausible behavioural rules." To reach a bit, insights from sociology, and the "laws" of group dynamics, emerge from the interaction of individual behaviour. The holy grail of the psychohistorian.

Epstein goes on to point out that models are good didactic tools; "they capture qualitative behaviours of overarching interest", for example. Moreover, they cultivate a certain "habit of mind":

"To me, however, the most important contribution of the modeling enterprise .. is that it enforces a scientific habit of mind, which I would characterize as one of militant ignorance – an iron commitment to 'I don't know'."

His closing paragraph deserves to be quoted in full:

"This is why science, as a mode of inquiry, is fundamentally antithetical to all monolithic intellectual systems. In a beautiful essay, Feynman talks about the hard-won 'freedom to doubt.' It was born of a long and brutal struggle, and is essential to a functioning democracy. Intellectuals have a solemn duty to doubt, and to teach doubt. Education, in its truest sense, is not about 'a saleable skill set'. It's about freedom, from inherited prejudice and argument by authority. This is the deepest contribution of the modeling enterprise. It enforces habits of mind essential to freedom."

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