The purpose of a system is what it does

The purpose of a system is what it does (POSIWID) is a systems thinking heuristic coined by Stafford Beer,^[1] who stated that there is "no point in claiming that the purpose of a system is to do what it constantly fails to do".^[2] The term 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 behavior is poorly understood, then the POSIWID perspective can balance political understandings of system behavior with a more straightforwardly descriptive view.

Origins of the term

Stafford Beer coined the term POSIWID in his books^[3] and subsequently used it many times in public addresses. In his address to the University of Valladolid, Spain, in October 2001, he said:^[1]

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 judgment, or sheer ignorance of circumstances.

Uses

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 behavior. The term is used in many other fields as well, including biology^[4] and management.^[5] 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.

See also

• Duck test
• The proof of the pudding is in the eating (Wiktionary)
• Systemantics