In this book I first endeavor to trace, in a series of studies of the contemporary source-material, the evolution of the modern “orthodox” theory of international trade, from its beginnings in the revolt against English mercantilism in the seventeenth and eighteenth centuries, through the English currency and tariff controversies of the nineteenth century, to its present-day form. I then proceed to a detailed examination of current controversies in the technical literature centering about important propositions of the classical and neo-classical economists relating to the theory of the mechanism of international trade and the theory of gain from trade. The annual flow of literature in this field has become so great in the last few years, and the claims on my time and energy from other unfortunately unavoidable activities of a quite divergent sort have been so heavy, that the completion of this book and the rendering of full justice to the recent literature have proved to be incompatible objectives. I hereby present my sincere apologies to the substantial number of economists who have in recent years made valuable contributions to the theory of international trade which are here either wholly neglected or treated more summarily than they deserve…. [From the Preface]