ABSTRACT
In this chapter, the authors fasten their attention on powerful currents transforming the present scene, but even if they have understood them well, any inferences they draw about the future may be upset through the influence of unforeseen, volatile elements. It is remarkable that currents strongly affecting the future are in general fairly well perceived. Consequently, if Swift's contemporaries had thought of the trend as a rapid one (a matter of one generation), they would have committed a practical error far greater than the conservative who would have quite denied its existence. The importance of assigning a speed to a "course" of things is thus clear. The authors show how much influence an aleatory event can exert on the general course of things. Coherence is one of the economist's intellectual constraints-the different sectors must supply one another with adequate inputs for the desired outputs.
