Hamlet: Methinks it is like a weasel. Polonius: It is backed like a weasel. Hamlet: Or like a whale? Polonius: Very like a whale. The essence of a model is that it represents β if it is not a model of something it is not a model at all Zeigler , Wartofsky A random bit of code or set of equations is not a model.
The point of a model is that one can use the model to infer or understand some aspects about what it represents. To completely understand a model β its construction, properties and working β one needs to understand how it does this mapping. This piece focuses attention on this mapping, rather than the internal construction of models.
What a model reliably represents may be a single observed situation, but it might satisfactorily represent more than one such situation. A model that only represents one case has no generality at all and may be more in the nature of a description.
If every situation we observe is essentially different, then no such theory is possible. However, we hope that this is not the case for the social world and, indeed, informal observation suggests that there is, at least some, commonality between situations β in other words, that some kind of reliable generalisation about social phenomena might be achievable, however modest Merton This piece looks at two kinds of applicability β analogical applicability and empirical applicability β and critiques those that conflate them.
Although the expertise of the authors is in the agent-based modelling of social phenomena, and so we restrict our discussion to this, we strongly suspect that our arguments are true for many kinds of modelling across a range of domains. In the next sections we contrast two uses for models: as analogies ways of thinking about observed systems and those that intend to represent empirical data in a more precise way. There are, of course, other uses of model such as that of exploring theory which have nothing to do with anything observed.
