All these variations, from Paley to Hayek, around the theme ‘Ideas rule the world of human affairs and its events’, suggest a number of questions. It might be interesting, for example, to examine in more detail the place and the precise function of this specific thesis in the particular intellectual campaign undertaken by each of its diverse proponents. But my main concern here, however, will not be with any particular economic philosophy; what I shall try to do, instead, is to raise a few questions of a more general and philosophical scope, in order to consider not the substantive content but rather the basic assumptions underlying this wide and reasonably clear–cut agreement between economic philosophers. What kinds of arguments or approaches may be brought forward in order to support the alternative view, viz. that ideas and theories have only a very limited effect, if any, in the determination of man's actions?

In this chapter, I will consider some of the most radical attempts to dismiss ideas entirely from the picture and thus to explain human behaviour in purely mechanical terms – the ‘man–machine’ thesis. The aim is to reconstruct some of the critical moments in the history of the scientific challenges – via increasingly refined physical explanations of all observed phenomena – to the assumption which first made (and still makes) moral and economic philosophy intellectually viable enterprises.