From Simulation to Theory (and Backward)

Abstract

Of late, due to the perceived advantages of the generative paradigm (Epstein 2002, 2005; Arthur 2004), a generative variant of agent based modelling and simulation, i.e. Agent Based Generative Social Simulation (ABGSS), has received a great impulse. In this paper, weak ABGSS, i.e. the thesis that growing a social effect is necessary but insufficient to explain it, is supported. Casting a critical eye on the debate about generative simulation, it will be argued that ABGSS needs to be fed by, but at the same time provides feedback to, two theoretical complxements which must be formulated prior and independent of simulation itself: (a) bottom-up theory of general local rules, and of the process from them to macroscopic effects; (b) theory of downward causation, showing how local rules are modified by the effects they contribute to achieve. This twofold thesis will be carried out while discussing three main examples of social phenomena: the witness effect, Schelling’s segregation model and the ethnic homogeneity of violence, and the minority game.