Models as mediators
I was most interested in the chapters looking at the place of computer simulations in relation to theories, models and observations. I particular R. I. G. Hughes examines the Ising model of magnetism, and asks what the success of the model tells us about the underlying system. Also Stephan Hartmann looks at Quantum Chromodynamics, for which Lattice QCD computations can provide results which match observations, but simpler models are needed to understand what is actually going on. Several of the chapters look at this tension between trying to provide a theoretically correct explanation and building a practical model, for instance in the theory of superconductivity. Four of the chapters concern economic models, and the issue here seems to be that some sort of simplification is vital in a model - if you use too complex a model then it is likely that it will neither provide any insight into the problem, nor match the 'real world' particularly well.
Those with an interest in this area might like to look at the papers from the Models and Simulations (Paris, 2006) conference