The distinction system/environment is the Starting Point for Luhmann’s systems theory. No system is independent of its environment, since a system is constituted drawing a Boundary through its operations and thereby differentiating itself from what does not belong to it, i.e., its environment. No system can operate Outside of its boundaries [→Operation/Observation]. Without an environment to distinguish it from, no system could be determined. A system is an autonomous domain in which particular conditions apply that Escape From the One-To-One Correspondence with the states in the environment [→Autopoiesis].
Defining a Boundary does not mean isolating the system. Operations are always internals operations, but at the level of observation the boundary can be overcome and different forms of interdependence between system and environment can be identified. Every system needs a whole range of environmental conditions: a social system, for instance, requires the availability of psychic systems that participate in the communication, alongside a compatible physical environment (e.g., temperatures within a particular range, appropriate levels of gravity) and many other conditions. In addition, one and the same event can belong simultaneously to the system and to its environment. A particular event can, for instance, be an element of both a social system (as a communication) and a psychic system (as thought), even though these systems reciprocally belong to the environment of the other [→Interpenetration and Structural Coupling]. This →Event is subject to conditions that are always different inside the system and in its environment.