Tools or Toys?
On Specific Challenges for Modeling and the Epistemology of Models in the Social Sciences

Eckhart Arnold

1 Introduction
2 The role of models in science
    2.1 The nature of models
    2.2 Where models get their credentials from
3 Why computer simulations are merely models and not experiments
4 The epistemology of simulations at work: How simulations are used to study chemical reactions in the ribosome
5 How do models explain in the social sciences?
6 Common obstacles for modeling in the social sciences
7 Conclusions

2 The role of models in science

2.1 The nature of models

In the recent philosophy of science literature it has become popular to conceive models as “mediators” between theory and empirical reality (Morgan/Morrison 1999) or, what amounts to more or less the same, as a link between theory and reality (Winsberg 2001). I take this notion to imply three core aspects about models:

  1. Theoretical foundation: Models are at least partially derived from theories. They contain “laws of nature” that are taken from one or more background theories.
  2. Semi-autonomy: Models are not just logical consequences from theories and facts. The construction of models involves model building techniques like simplification and approximation, the inclusion of auxiliary assumptions or other “tricks of trade”. In extreme cases a model may even contain assumptions that contradict the theory (K_uuml_ppers 2005, 2.14).
  3. Relation to a target system: Models are related to target systems in the real world. The relation between model and target system is at least one of similarity.

I do not claim that this concept of a model covers all types of models that occur in science, but only that it describes the most commen kinds of models. In fact, by dropping any of these requirements meaningful boundary cases can be derived: If a model does not have a theoretical foundation, it is either a purely phenomenological model or a model of data. If a model is not partially independent from its background theories, i.e. if it can logically be derived from the theory and known facts, then it is not a model any more but simply the application of the theory to a particular instance of the laws of the theory. Finally, if the model is not related to a particular target system then it is a purely theoretical model or a “speculative model” or a “toy model”.

Saying that a model provides a link between theory and reality is not meant to imply that models are the only possible way how theory can be linked to reality. A theory can also be linked to reality via intermediate theories or by simple “application of the theory” in the just mentioned sense. It is true that very often theories cannot be applied in a simple straight-forward manner but still sometimes some theories can.

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