This work, by one of Europe's foremost social theorists, presents a critical history of the concept of ideology. The author's discussion ranges from the early conceptions of ideology to its current usage in the works of Barthes, Foucault, Habermas and others. Boudon develops a distinctive and original approach to the analysis of ideology. Drawing on a series of case studies, he seeks to explain how and why social actors adhere so readily to false or dubious ideas. In opposition to those views which associate ideology with irrationalism, Boudon develops a rationalist theory which helps to explain why certain ideas are believed by individuals and are thereby effective in the social world. Rigorously argued and clearly written, this work is a major restatement of Boudon's theoretical views and a timely intervention in current debates. It will be of particular interest to students of sociology, politics and philosophy.