A system of opinions which, being founded on a system of accepted values, determines the attitudes and behavior of men with respect to desired objectives of development of the society, social group or individual.

Adam Schaff (1967), "Functional Definition, Ideology, and the Problem of the 'fin du siècle' of Ideology." L'Homme et la Société, April-June 1967. pp. 49-61; p. 50