International Encyclopedia of Systems and Cybernetics

R.L. ACKOFF defines the environment of a system as "a set of elements and their relevant properties which are not part of the system, but a change in any of which can produce a change in the state of the system" (1972).

He adds:"Thus a system's environment consists of all variables which can affect its state" (Ibid).

Some variables changes are frequent and obvious. Other are infrequent, nearly imperceptible, are or seem irrelevant. Such changes, the most difficult to detect, are also the more potentially unsettling.

The vocabulary used in the former paragraphs: "relevant, obvious, imperceptible, detect", indicates that the distinction between the system and its environment, as witnessed by the observer, is more or less arbitrary, even if some criteria "are better (in relation to goals and means) than others" R. VALLÉE, 1995, p.17).

The environment-system correlation also offers an interesting evolutive aspect. Starting from the simplest molecules on, the more and more complex systems that appeared through time showed a tendency to absorb a growing number of environmental elements and to create their own internal organization (endowed with organizational closure). As such, an "invironment" must be protected from excessive disturbances from outside. The environment-system correlation may be variable in time, for example through an evolution from passive adjustor systems to more active regulator ones. This can be obtained by a number of features and the corresponding devices:

1. The most primitive systems adapted by simple responses to outside stimuli, as for example running away from unsuitable conditions.

2. More evolved systems created sets of alternate behavior, corresponding to a variety of possible environmental disturbances. This supposed the appearance of a kind of storage of previous experienced environmental sequences, and of a selection device for chosing the adequate response to specific situations. This implies at least a limited knowledge of the environment's properties. Inherited genetic codes store such knowledge, and learning is a way to acquire it, while memory is a way to store it.

3. As the system's internal image of its environment becomes more complete (which is the case for man), it becomes evermore able to control and to transform it, and even re-create it… but also at the same time and in some sense, more dependent of it. This may be dangerous for any human system if its understanding of its relation with its environment is not adequate.

→ Reference (frame of); Variable (environmental)