If there are four equations and only three variables, and no one of the equations is derivable from the others by algebraic manipulation then there is another variable missing.

Houdton: Cap and Gown Press 1987. Sutton The Radical Marxist. D.

Parsons analyzed the work of Émile Durkheim and Vilfredo Pareto and evaluated their contributions through the paradigm of voluntaristic action. For Parsons "structural functionalism" was a particular stage in the methodological development of the social science and "functionalism" was a universal method; neither term was a name for any specific school. Parsons was also largely responsible for introducing and interpreting Max Weber's work to American audiences.