This book is a sustained argument for a creative and progressive social science. Modern social theory, despite an optimistic gloss, is profoundly pessimistic about social life and social inquiry. This pessimism is traced to the explanatory failures of social theory: failures that are shared by apparently disparate schools of thought. The book traces these similarities across non-Marxist and Marxist writings and in British, continental European and North American authors. It also shows the persistence of negative features over time, tracing cycles of hope to despair in successive generations. Specific examples of explanatory problems given unprogressive treatment are chosen from the mainstream of current sociology. How the re-definition of categories and processes can solve these problems progressively is demonstrated. The object is to turn social science towards the real problems of society whose creative solution will expand human competence and practical resources.