Abstract
This paper asks how, in science in general and in economics in particular, theoretical models aid the understanding of real-world phenomena. Using specific models in economics and biology as test cases, it considers three alternative answers: that models are tools for isolating the ‘capacities’ of causal factors in the real world; that modelling is ‘conceptual exploration’ which ultimately contributes to the development of genuinely explanatory theories; and that models are credible counterfactual worlds from which inductive inferences can be made. The paper argues that the ‘credible worlds’ account captures significant aspects of scientific practice, even if many modellers see their work as conceptual exploration.
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Notes
I now regret the passages in Sugden (2000, p. 12) in which I claim that the modelling strategies of Akerlof and Schelling are clearly realist.
As an economist, I have a natural interest in this particular branch of theoretical biology. However, it would be a mistake to think of this literature as importing into biology a modelling strategy from economics. Initially, game-theoretic modelling in biology and in economics developed independently of one another (see Maynard Smith 1982, p. 10). In the 1970s, most economists interpreted game theory as the analysis of strategic interaction between perfectly rational players. The evolutionary interpretation of game theory, now fashionable in economics, began as an import from biology, drawing heavily on the work of Maynard Smith and his collaborators (e.g. Sugden 1986).
This issue is discussed by Maynard Smith (1982, pp. 4, 20–22).
In MSP’s paper, this analysis is framed in terms of a different model of conflict, the “War of Attrition”; but the arguments apply with equal force to the Hawk–Dove game.
Later, Maynard Smith (1982, pp. 85, 96) became aware of a few cases of what appear to be paradoxical ESSs in nature. He interprets the rarity of these cases as supporting the hypothesis that paradoxical ESSs are possible but unlikely.
Cartwright (2009) is particularly uncompromising in her rejection of what she sees as ungrounded inductive arguments. Most commentators on Schelling’s model accept that the mechanism it exhibits is highly robust in the domain of models (see, for example, the literature survey in Aydinonat 2007). Cartwright disagrees, on the following grounds. Given Schelling’s basic assumption that individuals prefer not to live in neighbourhoods in which their own colour is significantly outnumbered, segregated neighbourhoods evolve; this result is robust to different specifications of the space in which they interact. But if instead we assume that individuals always prefer more integration to less and are indifferent between being in the majority and being in the minority, the resulting patterns of segregation or integration are different for different specifications of the space (Pancs and Vriend 2007). Since this latter assumption is wholly different from Schelling’s, and leads to a very different system of dynamics, I cannot see how Schelling’s conjectures are called into question.
In this respect too, my approach is similar to Giere’s: see, e.g., Giere (1988, pp. 1–12, 22–28).
I take Mäki (2009) to be using the concept of ‘isolation’ in this weaker sense when he says that, in his “MISS” account, models are depicted “in terms of isolations and idealisations”.
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Acknowledgements
Previous versions of this paper were presented at a symposium on economic models at the 2006 Philosophy of Science Association conference in Vancouver and at a workshop on “Models as Isolating Tools or as Credible Worlds?” at the University of Helsinki in 2008. I thank participants in those meetings, and Emrah Aydinonat and an anonymous referee, for comments. The idea of using Banerjee’s model as an illustration was suggested by Maya Elliott. My work was supported by the Economic and Social Research Council of the UK (award no. RES 051 27 0146).
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Sugden, R. Credible Worlds, Capacities and Mechanisms. Erkenn 70, 3–27 (2009). https://doi.org/10.1007/s10670-008-9134-x
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DOI: https://doi.org/10.1007/s10670-008-9134-x