The concept of ideology is notoriously elusive, and yet - at the same time - it is fundamental to the whole of social science. For to study ideology is to ask such questions as: where do our ideas about society and politics come from? Are such ideas socially determined? If so, what validity can they claim? In this brief yet comprehensive introduction, Professor McLellan looks at the origins of the concept of ideology, analyses its use in the Marxist and non-Marxist traditions, and assesses the various uses to which it has been put in recent social and political theory, particularly the connection between ideology and the 'end of history' debate. This is a book for all those interested in a clear presentation of the most basic concept in the philosophy of the social sciences. This second edition has been revised and updated and a new chapter on Ideology and the 'End of History' has been added.