Talcott Parsons and Robert Merton both see social reality in terms of the development of institutions and patterns of variables that define roles within institutions. Parsons offers a grand theory that attempts to account for the whole system while Merton addresses a middle range of theories concerning societal anomie and theories of deviance. Where Parsons suggests pattern variables as controls, Merton examines modes of adaptation to social institutions.
Parsons finds institutional patterns which carry the rules and norms governing our social structure. He begins with the system and finds that every social system is a functioning entity, or a system of interdependent structures and processes tending to maintain relative stability and distinctiveness of pattern and behavior. It is analogous to an organism which is relatively independent from environmental forces:
It "responds," to be sure, to the environmental stimuli, but is not completely assimilated to its environment, maintaining rather an element of distinctiveness in the face of variations in environmental conditions (Parsons 143).
Institutional patterns serve as norms and also to define a situation, for any situation is defined in terms of a selection of those aspects which are functionally related to particular orientations, values, interests, and sentiments of the individual.
Certain focal patterns can be discerned which define roles and positions. Such role definitions entail a number of elements conferring legitimacy upon any individual taking that role. Parsons uses the example of the role of physician and cites a number of aspects of the pattern variables that define the role. For society, such pattern variables serve to institute an automatic control function on both ordinary personal social relations and on the institutionalization of medical practice:
In the latter case it should be kept clearly in mind that not only does the physician "control" ...