Anthro.Net

Parsons developed his ideas during a period when systems theory and cybernetics were very much on the front burner of social and behavioral science. In using systems thinking, he postulated that the relevant systems treated in social and behavioral science were "open," meaning that they were embedded in an environment consisting of other systems. For social and behavioral science, the largest system is "the action system," consisting of interrelated behaviors of human beings, embedded in a physical-organic environment.

To survive or maintain equilibrium with respect to its environment, any system must to some degree adapt to that environment, attain its goals, integrate its components, and maintain its latent pattern, a cultural template of some sort. These are called the system's functional imperatives.