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Systems thinking is a way of making sense of the complexity of the world by looking at it in terms of wholes and relationships rather than by splitting it down into its parts. It has been used as a way of exploring and developing effective action in complex contexts, enabling systems change. Systems thinking draws on and contributes to conceptual systems, systems theory, and the system sciences.
The word system has several overlapping meanings in the history of science. In 1674, Robert Hooke used the term "System of the World" to describe how planets relate to the fixed stars mapped out by the catalogue of Hipparchus or Ptolemy's Almagest.: p.24 : 450 He also used it to compare the Ptolemaic and Copernican models of the cosmos. In 1687, Isaac Newton answered Hooke's ideas in the third book of his Principia Mathematica, also titled The System of the World.: Book three Newton shifted the definition, describing the universe not as a visual arrangement of stars, but as a mechanical, physical system governed by gravity. This approach continues as the field of dynamical systems to this day, where a system of equations is solved to predict how objects move.

By 1824, the Carnot cycle presented an engineering challenge, which was how to maintain the operating temperatures of the hot and cold working fluids of the physical plant. In 1868, James Clerk Maxwell presented a framework for, and a limited solution to, the problem of controlling the rotational speed of a physical plant. Maxwell's solution echoed James Watt's (1784) centrifugal moderator (denoted as element Q) for maintaining (but not enforcing) the constant speed of a physical plant (that is, Q represents a moderator, but not a governor, by Maxwell's definition).
Maxwell's approach, which linearized the equations of motion of the system, produced a tractable method of solution.: 428–429 Norbert Wiener identified this approach as an influence on his studies of cybernetics during World War II and Wiener even proposed treating some subsystems under investigation as black boxes.: 242 Methods for solutions of the systems of equations then become the subject of study, as in feedback control systems, in stability theory, in constraint satisfaction problems, the unification algorithm, type inference, and so forth.
Systems thinking, born from the visionary contributions of theoretical biologist Ludwig von Bertalanffy, computer scientist Jay Forrester, and their contemporaries, reached its zenith in the 1990s with the release of Peter Senge’s seminal work, The Fifth Discipline, a landmark in intellectual exploration.


...What is a system? A system is a set of things ... interconnected in such a way that they produce their own pattern of behavior over time. ... But the system’s response to these forces is characteristic of itself, and that response is seldom simple in the real world
— Donella Meadows: 2
[a system] is "an integrated whole even though composed of diverse, interacting, specialized structures and subjunctions"
— IEEE (1972): 582
"a system is a collection of things that are interconnected and interdependent from which stuff emerges"
-Walls & Flach (2025)
Living systems are resilient, and are far from equilibrium.: Ch.3 Homeostasis is the analog to equilibrium, for a living system; the concept was described in 1849, and the term was coined in 1926.
Resilient systems are self-organizing;: Ch.3
The scope of functional controls is hierarchical, in a resilient system.: Ch.3
Frameworks and methodologies for systems thinking include: