NOTE: Although the following article has not been revised for this edition of the Encyclopedia, the substantive coverage is currently appropriate. The editors have provided a list of recent works at the end of the article to facilitate research and exploration of the topic.

Systems theory is much more (or perhaps much less) than a label for a set of constructs or research methods. The term systems is used in many different ways (Boguslaw 1965; 1981, pp. 29–46). Inevitably this creates considerable confusion. For some it is a "way" of looking at problems in science, technology, philosophy, and many other things; for others it is a specific mode of decision making. In the late twentieth-century Western world it has also become a means of referring to skills of various kinds and defining professional elites. Newspaper "want ads" reflect a widespread demand for persons with a variety of "system" skills...