This book is about the conceptual foundations of an intermediate way between liberalism and socialism: a synthesis of classical (Ricardian) and Keynesian political economy. Classical theory deals with proportions between individuals or collectives and society in tackling problems of distribution and value. Keynesian theory is concerned with the scale of economic activity as explained by effective demand. The economy considered is primarily a monetary production economy, not a market or a planned economy. The author sets up a system linking political economy with other social sciences, i.e. sociology, law, and politics in the traditional sense, thus establishing the unity of the social sciences. To complete the picture, issues of method associated with the theory of knowledge in the social sciences and the problem of linking theory with historical reality are also covered.