argues that ideologies are mental fictions whose function is to veil the true nature of a given society. They originate unconsciously in the minds of those who seek to stabilise a social order. Utopias are wish dreams that inspire the collective action of opposition groups which aim at the entire transformation of society. Mannheim shows these two opposing elements to dominate not only our social thought but even unexpectedly to penetrate into the most scientific theories in philosophy, history and the social sciences. This new edition contains a new preface by Bryan S. Turner which describes Mannheim's work and critically assesses its relevance to modern sociology. The book is published with a comprehensive bibliography of Mannheim's major works.