Alfred Marshall, on whose Principles of Economics all contemporary English economists have been brought up, was at particular pains to emphasise the continuity of his thought with Ricardo's. His work largely consisted in grafting the marginal principle and the principle of substitution on to the Ricardian tradition; and his theory of output and consumption as a whole, as distinct from his theory of the production and distribution of a given output, was never separately expounded. Whether he himself felt the need of such a theory, I am not sure. But his immediate successors and followers have certainly dispensed with it and have not, apparently, felt the lack of it. It was in this atmosphere that I was brought up. I taught these doctrines myself and it is only within the last decade that I have been conscious of their insufficiency. In my own thought and development, therefore, this book represents a reaction, a transition away from the English classical (or orthodox) tradition. My emphasis upon this in the following pages and upon the points of my divergence from received doctrine has been regarded in some quarters in England as unduly controversial. But how can one brought up a Catholic in English economics, indeed a priest of that faith, avoid some controversial emphasis, when he first becomes a Protestant?

But I fancy that all this may impress German readers somewhat differently. The orthodox tradition, which ruled in nineteenth century England, never took so firm a hold of German thought. There have always existed important schools of economists in Germany who have strongly disputed the adequacy of the classical theory for the analysis of contemporary events. The Manchester School and Marxism both derive ultimately from Ricardo,—a conclusion which is only superficially surprising. But in Germany there has always existed a large section of opinion which has adhered neither to the one nor to the other.