Gaetano Mosca, an Italian legal and political theorist and statesman, was born in Palermo. He was one of several social theorists, including Vilfredo Pareto and Robert Michels, who gave currency to the conception of ruling elites and their circulation as being the basic characteristic of politically organized societies. Mosca outlined his conception in Sulla teorica dei governi e sul governo parlamentare and elaborated it in his major work, Elementi di scienza politica, first published in 1895 and considerably expanded in the third edition, which appeared in 1923 (translated as The Ruling Class).

The Elementi ranges over a large number of problems in the philosophy of history and in the analysis of political organization and development. Mosca speculated about the stages of political and social development, the types of political and social systems, the role of moral forces and religions in political organization and change, the function...