“The concept of a system appears throughout the social and natural sciences and has generated a body of literature of its own (‘general systems theory’). A system is any pattern of relationships between elements, and is regarded as having emergent properties of its own, over an above the properties of its elements. The system is seen as possessing an inherent tendency towards equilibrium and the analysis of systems is the analysis of mechanisms which maintain equilibrium, both internally and externally, in relation to other systems.
The functionalism of Talcott Parsons offers the fullest employment of systems theory in sociology (see especially The Social System, 1951). In Parsonsonian terms, social system can refer to a stable relationship between two actors, to societies as a whole, to systems of societies, or indeed any level between these. All are analyzed principally in terms of their so-called cybernetic aspects; that is, as systems of information exchange and control, where equilibrium is maintained through symbolic exchanges with other systems across boundaries, In economic systems, for example, the exchange is not usually direct but mediated by money. Power is the medium of exchange in political systems.
More recently Anthony Giddens, (Central Problems in Social Theory, 1979) has criticized this conception of the social system on the grounds that systems do not possess emergent properties over and above the social actors who comprise them, but are rather produced and reproduced by structured and routine social practices. The systematic properties of social systems thus stem from the nature of social action rather than the system itself.”
Excerpted from: Matthews, Gordon, ed. Oxford Dictionary of Sociology. New York: Oxford University Press, 1994.