In this volume Robert C. Tucker looks critically at the later writings of Marx and Engels, not only as political theory but as the ideology for political revolution. From the vantage point established in his earlier work--that there is a continuity underlying Marx's writing from the newly discovered manuscripts of 1844 to the mature work, Capital--Professor Tucker examines Marx as a social, moral, and political theorist, and a theorist of modernization. The Marxian Revolutionary Idea is followed, in thought and application, through infancy to maturity, in success and failure, and finally as it has been transformed by modern socialism.