The purpose of a system is what it does (POSIWID) is a heuristic in systems thinking coined by the British management consultant Stafford Beer, who stated that there is "no point in claiming that the purpose of a system is to do what it constantly fails to do". It is widely used by systems theorists, and is generally invoked to counter the notion that the purpose of a system can be read from the intentions of those who design, operate or promote it. When a system's side effects or unintended consequences reveal that its behaviour is poorly understood, then the POSIWID perspective can balance political understandings of system behaviour with a more straightforwardly descriptive view.

Origins

Beer published the phrase for the first time in his 1979 book The Heart of Enterprise. Thereafter he repeated the phrase many times in public addresses. Speaking to the University of Valladolid in October 2001, he said:

According to the cybernetician, the purpose of a system is what it does. This is a basic dictum. It stands for bald fact, which makes a better starting point in seeking understanding than the familiar attributions of good intention, prejudices about expectations, moral judgement, or sheer ignorance of circumstances.

Uses

Organizations establish principles that define their ideal purpose; POSIWID proposes that the organization's actual principles are demonstrated by practice. For example, an organization that has a high rate of accidents and illness may claim that its values are health and safety, but applying POSIWID shows that the organization's practices contradict those values.

From a cybernetic perspective, complex systems are not controllable by simple notions of management, and interventions in a system can best be understood by looking at how they affect observed system behaviour. The term is used in many other fields as well, including biology and management. Whereas a cybernetician may apply the principle to the results inexorably produced by the mechanical dynamics of an activity system, a management scientist may apply it to the results produced by the self-interest of actors who play roles in a business or other institution.

Examples

In Heart of Enterprise, Beer gave the following examples as applications of the heuristic.

  • Imagine a luxury car which is unreliable due to requiring frequent repair. Is the purpose of the car luxury transport, or is it rather to be the focus of extraordinary attention in maintenance?
  • Imagine a rail transport service which challenges its potential passengers with difficult booking options. Is the purpose of the railway to transport passengers, or is it rather to set passenger expectations that they should limit railway use and seek other travel options?

See also

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