The plan of a history of this kind was a matter that called for some amount of deliberation. It was felt that, being a history, fairly close correspondence with the chronological order was required, which meant either taking a note of every individual doctrine, or breaking up the work into as many distinct histories as there are separate schools. The former procedure would necessitate giving a review of a great number of doctrines in a single chapter, which could only have the effect of leaving a very confused impression upon the reader’s mind. The alternative proposal is open to the objection that, instead of giving us a general outline, it merely treats us to a series of monographs, which prevents our realising the nature of that fundamental unity that in all periods of history binds every doctrine together, similar and dissimilar alike. We have attempted to avoid the inconveniences and to gain something of the advantages offered by these alternative methods by grouping the doctrines into families according to their descent, and presenting them in their chronological order. This does not mean that we have classified them according to the date of their earliest appearance; it simply means that we have taken account of such doctrines as have reached a certain degree of maturity. There is always some culminating-point in the history of every doctrine, and in deciding to devote a separate chapter to some special doctrine we have always had such a climacteric in mind. Nor have we scrupled to abandon the chronological order when the exigencies of the exposition seemed to demand it. The first epoch comprises the end of the eighteenth and the beginning of the nineteenth centuries. It deals mainly with the founders of Classical political economy, with the Physiocrats, Smith and Say, and with Malthus and Ricardo, the two writers whose gloomy forebodings were to cloud the glory of the “natural order.” The second epoch covers the first half of the nineteenth century. The “adversaries” include all those writers who either challenged or in some way disputed the principles which had been laid down by their predecessors. To these writers five chapters are devoted, dealing respectively with Sismondi, Saint-Simon, the Associative Socialists, List, and Proudhon. A third epoch deals with the middle of the nineteenth century and the triumph of the Liberal school, which had hitherto withstood every attack, though not without making some concessions. It so happened that the fundamental doctrines of this school were definitely formulated about the same time, though in a very different fashion, of course, in the _Principles_ of Stuart Mill in England and the _Harmonies_ of Bastiat in France.