Systems Thinking is generally contrasted to mechanistic or linear or reductionistic thinking. Cybernetics can be characterized as the science of systems thinking.
Mechanistic thinking is “machine like” and systems thinking is ecological.
Linear thinking focuses on linear chains of causality and systems thinking focuses on circles of causality. Conversations, feuds, infatuations, negotiations, and predator prey dynamics are all circular causal processes. The behavior of all complex systems is determined by networks of circular causal processes. The behavior of these systems can not be understood in terms of linear processes.
Reductionist thinking “understands” something by taking it apart and studying the constituent pieces. Systems thinking “understands” something by looking for the characteristics of the whole, especially the dominant circular processes that either generate change / growth or limit growth.
Until fairly recently most of science operated on the principle of reductionism / mechanistic thinking: study reality in greater and greater detail in order to understand it. In the 1940’s a number of scientists in widely different fields noticed that all of them were grappling with circular causality and none of them were really equipped to understand it. This led to a series of meetings over several years which included two of every kind of specialist (Weiner and von Neuman from math, Bateson and Mead from anthropology, etc.). After a couple of years of bloody combat where no one could understand any of the other specialists, they finally learned to talk to each other and cybernetics (Norbert Weiner’s famous book) was born as a discipline.
Ludwig von Bertalanffy was simultaneously developing the essentially parallel notions of General Systems Theory (his book of that title came out in 1951).
Today we have quite a number of laws of systems science / cybernetics that apply to all complex systems. These laws provide a lens, a way of understanding and studying, all complex systems, whether they are a cell, an organism, an ecology, a corporation, a nation or whatever.
I use the terms cybernetics and systems theory pretty much interchangeable although IMO there are some differences in emphasis and there are other knowledgeable scientists who would argue about that usage.
My take on the laws of systems (with much help from Allenna Leonard) is summarized in my blog piece What is Management Cybernetics? As the title implies, this piece emphasizes application of the laws to organizations. The laws presented in that essay are given an entire chapter of explication in my book on cybernetics.
In recent decades the term “cybernetics” has fallen out of vogue and has been largely replaced by “complexity theory” and “Complex Adaptive Systems”. As an old fossil, I personally prefer to stay with the earlier term