All of his professional life, Eli Heckscher was concerned with the methodology of economics and economic history. Straddling both disciplines, it was essential for him to come to grips with the problem of what one discipline could learn from the other and vice versa (Findlay 1998; Findlay and Lundahl 2002; Henriksson and Lundahl 2003). Gradually he also introduced the use of statistical time series in his works, notably his four-volume magnum opus about the economic history of Sweden from the time of Gustav Vasa (1523-1560) to ''the present,'' which in practice meant the early nineteenth century. As he moved from the sixteenth to the eighteenth century the availability of quantitative material increased, and Heckscher made use of it. However, he steadfastly refused to be bound by the strict limits imposed by the ''hard'' facts when it came to the interpretation of a certain epoch. He certainly took great care to weed out hypotheses not grounded in facts, but he was no stranger to hypothetical reasoning either. Such reasoning was needed for arriving at a historical synthesis, and the refusal to go beyond just what the sources would reveal, after thorough critical scrutiny, was for him to stop short of attempting a synthesis. The present essay should be seen as the effort of two economists to provide a building block for a historical synthesis. We would like to combine Heckscher's plea for economic theory in economic history with his insistence on historical synthesis into a plea for economic theory in historical synthesis. The roots of the essay are found in economic theory, which we employ very much in the fashion that Heckscher used it in his historical works: as a device for explaining the equilibrating processes in economic history during a determined period. We also share with Heckscher the conviction that it is difficult to use economic theory to explain transitions from one historical epoch or era to another. Here factors exogenous from the point of view of