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The purpose of a system is what it does

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The purpose of a system is what it does (POSIWID) is a systems thinking heuristic coined by Stafford Beer,[1] who observed 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[edit]

Stafford Beer coined the term POSIWID and 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.


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[3] and management.[4] 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[edit]


  1. ^ a b Beer, Stafford (2002-01-01). "What is cybernetics?". Kybernetes. 31 (2): 209–219. doi:10.1108/03684920210417283. ISSN 0368-492X.
  2. ^ Komlos, David; Benjamin, David (2021-09-13). "The Purpose Of A System Is What It Does, Not What It Claims To Do". Forbes. Archived from the original on 2021-09-13. Retrieved 2022-06-11.
  3. ^ Hofmeyr, Jan-Hendrik S. (2007). "The biochemical factory that autonomously fabricates itself: A systems biological view of the living cell". In Boogerd, Fred C.; et al. (eds.). Systems biology : philosophical foundations (1st ed.). Amsterdam: Elsevier. p. 224. ISBN 978-0-444-52085-2. OCLC 162587033.
  4. ^ Ward, Aidan; Smith, John (2003). Trust and mistrust : radical risk strategies in business relationships. Chichester, West Sussex: Wiley. ISBN 978-0-470-85318-4. OCLC 51966365.

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