In the previous chapter, Building Blocks, we presented the basic "concepts" and "language" used to describe the structure underlying complex system behavior. We put forth the case that a well-known set of time paths can describe, individually or in combination, the behavior of virtually all dynamical systems. We introduced the idea that all dynamic behavior in the world occurs due to the interaction between stock and flow variables, and the interaction between sets of stocks/flows within larger feedback loops.

In this chapter, we use these ideas to explore the underlying system structure responsible for the basic families of time paths including: exponential growth and decay, goal-seeking behavior, system oscillation, and s-shaped behavior. To do this, we develop a sequences of small simulation models that explain the major modes of systems behavior, while presenting some the basic mathematics behind computer simulation.