General Systems Theory (GST)
Systems theory provides a common language for the understanding of all complex entities. The theory was proposed in the 1940s by biologist Ludwig von Bertalanffy. Many fields of science (e.g., the social and political sciences, communication sciences, and engineering) use a systems approach (systems thinking, or systems perspective) in researching, describing, and understanding phenomena. A systems perspective provides a way of understanding the dynamics of interacting parts of a system.
Each system is an independent entity, with a boundary containing a holistic collection of elements. All systems seek stability (homeostasis). To remain stable they must sense, decide, and act (analogous to input, processing, and output). Thus, all systems interact with their environments, receive feedback, and either adapt to maintain homeostasis, or decline into entropy (disorder or nonfunction).
In examining the behavior of any person, or the behavior and dynamics of human relationships, groups, or nation-states, it is helpful to have an understanding of qualities common to all systems. GST is a unifying theory. Instead of studying people as discrete entities, we study them in relation to their environments.