Finding models [of systems]

Even though a model may have a simple form, it may not be at all easy to find. Indeed, many of the models in this chapter took me a very long time to find. By far my most common mistake was trying to build too much into the basic structure of the model. Often I was sure that some feature of the behavior of a system must be built into the underlying model—yet I could see no simple way to do it. But eventually what happened was that I tried a few other very simple models, and to my great surprise one of them ended up showing the behavior I wanted, even though I had in no way explicitly built it in.