This was the dominant PARADIGM in sociology in the 1950s and 1960s, being associated in particular with a group of social theorists centred around PARSONS at Harvard University. Much of the early inspiration for systems theory came from an attempt to establish parallels between physiological systems in medical science and social systems in the social sciences. In Parsons (1951), a voluntaristic theory of action is combined with a systemic approach to two-person interactions. In later work, Parsons provided a general theory of social systems as problem-solving entities, which sought to integrate sociological theory with developments in biology, psychology, economics and political theory. Every social system has four sub-systems corresponding to four FUNCTIONAL IMPERATIVES, namely adaptation (A), goal-attainment (G), integration (I) and pattern-maintenance or latency (L). These four sub-systems can be conceptualized at various levels so that, for example, the basic AGIL pattern also corresponds to the economy, polity, societal community and institutions of socialization. In adapting to their internal and external environments, social systems have to solve these four problems in order to continue in existence, and they evolve by greater differentiation of their structures and by achieving higher levels of integration of their parts. Parsons attempted to show the validity of the systems approach through a diversity of studies - of the university, politics, religion and professions.

Although widely influential in the study of political processes, industrialization, development, religion, modernization, complex organizations, international systems and sociological theory, the theory has been extensively criticized. The arguments against social systems theory are:

1. it cannot deal adequately with the presence of conflict and change in social life;

2. its assumptions about equilibrium and social order are based on a conservative ideology;

3. it is couched at such a level of abstraction that its empirical referents are often difficult to detect and hence the approach is of little value in actual sociological research;

4. its assumptions about value consensus in society are not empirically well grounded;

5. it is difficult to reconcile notions about structural processes and functional requirements with the theory of action, which emphasizes the centrality of purposeful choice by individual actors;

6. the teleological assumptions of systems theory cannot explain why certain societies experience underdevelopment or de-industrialization;

7. many of the propositions of the theory are tautological and vacuous.

For example, in the last analysis the existence of a social system is the only real evidence of its adaptation to its environment. In short, modern systems theory appears to reproduce all the essential weaknesses of nineteenth-century EVOLUTIONARY THEORY.

In the late 1950s and early 1960s, critics of FUNCTIONALISM and systems theory argued in favour of CONFLICT THEORY as an alternative perspective. In the 1970s, Marxist theory, with its focus on change, conflict and contradiction, came to be seen as the major alternative to systems theory. However, there is now a recognition that:

1. Marxist theory itself is based on a concept of the SOCIAL SYSTEM;

2. systems theory is not inevitably tied to assumptions about static equilibria or to a conservative ideology;

3. there are models of systems other than those developed in the biological sciences, which do not depend on an ORGANIC ANALOGY.

For example, cybernetic models of social systems provide an alternative to crude analogies between social and biological systems by examining the importance of information in exchanges between sub-systems. Further possibilities for the development of systems theory were opened up by HABERMAS in the analysis of the legitimation crisis (1973) of contemporary capitalism. Systems theory does not in principle preclude notions of contradiction, conflict and change in the analysis of social systems. The consequence of these developments is that the concept of social system is not uniquely tied to any particular branch of sociology, but is a concept which is basic to all sociological paradigms. After the death of Parsons in 1979, there was a revival of interest in Parsonian sociology, especially in Germany. In turn, this development produced a re-evaluation of systems theory in the work of LUHMANN.

READING: Wallace (1969); Alexander (1982; 1984)