LAUSR

Modularity is a key concept in building and evaluating complex simulation models. My main claim is that in simulation modeling modularity tends to degenerate for reasons inherent to simulation methodology. The argument will proceed by analyzing the techniques of parameterization, tuning, and kludging. They are—to a certain extent—inevitable when building complex simulation models but erode modularity. As a result, the common account of validating simulations faces a major problem, namely, a problem of holism. In the conclusion, I will ask to what extent holism sets limits to validation.