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.

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 "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."[1]


The term is widely used by systems theorists. It 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. 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. When "side effects" or "unintended consequences" reveal that system behavior is poorly understood, then taking the POSIWID perspective allows the more political understandings of system behavior to be balanced by a more straightforwardly descriptive view.

The term is used in many fields including biology[2] and management.[3]

See also[edit]


  1. ^ Beer, Stafford (2002). "What is cybernetics?" (PDF). Kybernetes. MCB UP Ltd. 31 (2): 209–219. doi:10.1108/03684920210417283. Archived from the original (PDF) on 2016-04-26.
  2. ^ Boogerd, Fred (2007). Systems Biology. Amsterdam: Elsevier Science. ISBN 0-444-52085-6.
  3. ^ Ward, Aidan; Smith, John (2003). Trust and Mistrust : Radical Risk Strategies in Business Relationships. John Wiley & Sons. ISBN 978-0-470-85318-4.