Systems Theory Overview

Systems theory takes a holistic approach to understanding the world. As opposed to focusing on the parts of a system it looks at the system’s relations and functioning.

Systems theory is a set of theoretical concepts used to understand a wide variety of phenomena in terms of a model called a system. It is based upon a method of reasoning called synthesis. Synthesis is a holistic paradigm that understands entities in terms of their nexus of relations and functioning within the whole environment that they are a part of.


Of course, people have been coming up with abstract theories about how the world works for a long time. Some ancient Greeks thought everything was made of earth, water, fire and air, whilst others came to the conclusion that it was the expression of perfect geometric forms. Over the years our theoretical systems have grown into large and sophisticated bodies of knowledge such as philosophy, mathematics and the many areas of theoretical science, although these theoretical frameworks are often limited to relatively specific areas of interest. During the 20th century, systems theory emerged as a new theory that draws upon many core concepts within these pre-existing methods to develop a more abstract framework that is designed to be universally applicable to all domains.

System Model

In order to achieve such a general relevance, system theory starts with the abstract concept of a system and then applies this to modeling various different phenomena from biological to social and technical systems. The model of a system can be loosely defined as a set of parts often called elements that form a whole, which is referred to as the system. A system exists within an environment and has a boundary that differentiates the system’s exterior from its interior. An example of this might be a country, interior to which are all the people, institutions and other elements that constitute the nation as an entire system. Whilst exterior to its boundary is the international political environment.

System’s Functioning

The model of a system is used in many different areas most prominently within engineering

A system can be either open or isolated. Isolated systems do not interact with their environment, but most systems are open, meaning there is an exchange of energy and resources between the system and its environment. The passing of energy or resources from the exterior of the system’s boundary to the interior is termed an input, whilst the reverse is termed an output. Systems develop or function through the input of energy or resources from their environment. They process this energy by transforming it to create an output. If this output is of some value to its environment, it can be termed energy. If on the other hand, it is of negative value it may be termed entropy, a scientific term for lack of order, disarrangement or in more familiar terms, we might call it waste. An early use of this type of model was during the development of the steam-engine where scientists and engineers were thinking about the amount of fuel inputted to the engine relative to the power output and heat energy wasted. By using this model they could create a quantifiable ratio between them that we would now term the efficiency of the system. Of course, this same reasoning can be applied to a wide variety of phenomena from the processing of energy within a plant cell to the efficiency of a business organization.

Hierarchical Structure

We can model systems on various scales. Thus, elements can form part of systems that themselves form part of larger systems and so on. This is termed nesting or encapsulation and helps us to analyze a system on various levels whilst hiding away the underlying complexity. Systems theory explores many other areas such as emergence that raise key questions about the relationship between the parts within a system and the whole, that is, how elements can function together or self-organize to create some new, emergent structure as an entirety. Other areas such as cybernetics deal with a system’s control mechanism that allows it to adapt and respond to changes within its environment through positive and negative feedback loops.


Systems theory has found application within a wide variety of areas, forming the foundation for many new subjects such as systems psychology, systems engineering and systems ecology, to name but a few. All of which place a greater emphasis upon a more holistic and contextualized approach to understanding the world around us.

Cite this article as: Complexity Labs, "Systems Theory Overview," in Complexity Labs, May 6, 2015,