System thinking is, quite simply, thinking about a question, circumstance, or problem explicitly as a system—a set of interrelated entities. System thinking is not thinking systematically. The objective of this chapter is to provide an overview and introduction to systems and system thinking.

System thinking can be used in a number of ways: to understand the behavior or performance of an existing system; to imagine what might be if a system were to be changed; to inform decisions or judgments that are of a system nature; and to support the design and synthesis of a system, which we call system architecture.

System thinking sits alongside other modes of reasoning, such as critical reasoning (evaluating the validity of claims), analytic reasoning (conducting an analysis from a set of laws or principles), and creative thinking, among others. Well-prepared thinkers use all of these modes of thought (cognition) and recognize when they are using each one (meta-cognition).

This chapter begins by defining what a system is and exploring the property of emergence that gives systems their power (Section 2.2). Subsequently, we examine four tasks that aid us in system thinking:

1. Identify the system, its form, and its function (Section 2.3)

2. Identify the entities of the system, their form and function, and the system boundary and context (Section 2.4)

3. Identify the relationships among the entities in the system and at the boundary, as well as their form and function (Section 2.5)

4. Identify the emergent properties of the system based on the function of the entities, and their functional interactions (Section 2.6)

These tasks will be explained sequentially, but real reasoning is rarely sequential and more often iterative. As discussed in Chapter 1, methods are the ways of organizing such tasks to achieve a concrete end. Methods are usually or often applicable. The principles on which the methods of system thinking are based are also presented in this chapter.