Systems theory constituted one of the most influential new approaches which gained popularity in the social sciences by the mid-20th century. It developed as an alternative to the economic approach although sharing with it a number of assumptions about the individualistic and interest-guided nature of political and social relationships. However, as against the view that society was held together by rational exchanges between individuals, as rational choice theorists had assumed, systems theorists focussed on the ‘macro’ level, on the study of society, or groups, as integrated and functional systems. The nature of social systems was conceptualized by analogy with biological or cybernetic systems. The objective of systems theory was to understand society as a whole by studying the interrelated processes and relationships which contributed towards the continuity and survival of the system. Systems theorists maintained that society is an interdependent whole held together by an elaborate system of exchanges between the system and its environment, and between a system and its subsystems. The political and economic subsystems were important components of modern social systems, each governed by its own set of relationships. For instance, systems theorists like Talcott Parsons, and David Easton, basing their model on the experience of industrialized, capitalist, societies, conceptualized the social system as including political and economic subsystems each with relatively well-defined boundaries and functions. They maintained that the relationships between the political, economic, and social, dimensions of social life, between state and market, and political power and capital, could be described effectively in terms of this model.