The subject of the course that I shall offer this year at the Collège de France is the economy and society—or, better, the traditional ecodemography of the world long gone—as they “functioned,” if one may use this term, from the fourteenth to the eighteenth century, or, more precisely, from 1300-1320 to 1720-1730. Forsake of convenience, this world will be de-limited by the present frontiers of France—a decision of pure form with no implication of tri-color or fleur-de-lys. We shall be concerned with about 15 to 20 million people in every period, although there will be long intervals between actual dates. To be sure, a similar study could be carried out (and probably will be if it has not been already) among our neighbors: Germany, Italy, without a doubt Spain, but possibly not the British Isles. One of the paradoxes of such an undertaking is that the Kingdom of England, where The World We Have Lost was first defined with such penetrating insight, is of all western countries the one where that world was the least typical and the least stable.