ABSTRACT
If the rationality principle is really the cornerstone of economic explanations, we may expect to observe its presence in economic thought as soon as the latter began to be an explanatory and not only a descriptive and normative intellectual enterprise.1 Pretending to precisely determine a moment in time that would correspond to the birth of an explanatory type of economics would obviously be preposterous. Nonetheless, it seems reasonable to claim that somewhere in the second half of the eighteenth century, economists, influenced by the enthusiasm aroused by Newtonian science, began to devote more and more of their energy to explaining how an economy can work efficiently and, as we will see, their explanations were effectively based on the rationality principle. From this period on, throughout the whole history of economic thought, this principle has continuously animated the increasingly sophisticated explanations proposed by economists. It is true, however, that for the sake of conceptual precision economists were brought to characterize rationality in ways more and more remote from the somewhat fluid concepts associated with this fundamental rationality principle, in such a way that the exact role of the latter has almost been forgotten. Therefore, the two first chapters of this book will show why this principle has, nonetheless, remained a determinant throughout the history of economic thought, despite the fact that, in the minds of economists, it was progressively superseded by more specific views on rationality having less and less to do with what is properly called the rationality principle. It is in this context that the workings of the rationality principle will be analysed from its implicit adoption by eighteenth-century economists to recent debates about rationality in experimental economics and decision theory. My claim is that much of the confusion surrounding the role of rationality in economics is due to this increasing gap between the notion of rationality invoked in modern economic models and the rationality principle properly understood. It will be concluded from all these considerations that, while successive representations of the rational agent as maximizer, homo oeconomicus or consistent chooser have frequently been the target of devastating arguments, these criticisms have been so far from refuting the fundamental rationality principle itself that most of them have been made in the very name of this principle.
