Couplage structurel
structural coupling (anglais)
In Maturana and Varela’s framework, the way a system with operational closure interacts with its environment without the latter dictating its internal states. Recurrent interactions with the environment trigger changes in the system—they *perturb* it—but do not specify them: the environment prescribes nothing; it merely enables a selection whose form it does not determine. A structurally coupled system is thus distinct from a machine whose input/output behavior is externally fixed by a designer: through its history of coupling, it constructs the very world to which it responds.
Under structural coupling with a medium, these configurations generate selection, an ongoing process of satisficing that [...] triggers (but does not specify) change in the form of viable trajectories.
Varela first introduces the concept through a minimal example: Bittorio, a cellular automaton subjected to random disturbances. Nothing in its design programs it to recognize anything; yet, given its form of coupling with its environment, it eventually responds only to certain sequences—it becomes, in effect, an “odd-sequence detector.” What the environment does is not instruct Bittorio; it triggers (but does not specify) change—it sparks transformations whose form depends on the system’s own structure, not that of the environment.
This is the principle Varela extends to both evolution and cognition: the environment triggers (but does not specify) change. A structurally coupled system thus preserves its autonomy precisely in how it responds to what affects it.
Varela explicitly contrasts this regime with that of a computer: the meaning of a sequence typed on a keyboard is assigned from the outside, by the system’s designer—it is a strict input-output relationship. A living system, however, is almost never reducible to this schema: the meaning of any given interaction is not prescribed externally but emerges from the system’s own organization and history.
Structural coupling ≠ the input-output relationship of a keyboard: in one case, the environment dictates; in the other, it merely perturbs. Structural coupling ≠ enaction: coupling is the mechanism and its history; enaction is the broader thesis that this history of coupling brings forth a world—cognition itself. Without closure, there is no system to couple; without coupling, an operational closure would remain a system without a world.