Abstract
The same Latin word, ratio, is at the root of two intellectual traditions that are at once very different and interlinked. For moralists, reason has always been opposed to passions and, for modernists, to interests. For modern economists, on the other hand, rational choice often goes hand in hand with interest, to the point where the rational pursuit of interest has become a basic assumption. The opposite of the rational is, of course, the irrational, which includes not only passions but also various cognitive biases.
Reason is a normative idea, which is supposed to guide the behavior of agents in the public arena. La Bruyère notes that " Ne songer qu'à soi et aux autres, source d'erreur en politique ". To correct this error, we need to consider both others and the future, from an impartial perspective that gives equal weight to each person and each moment. In addition, we need to act on well-founded beliefs, which requires optimal investment in information gathering. It could be said that the inculcation of reason is the main task of the prince's preceptor.
Rationality is an explanatory idea, which is supposed to be able to account for action by reducing it to the agent's reasons, i.e. his motivations and beliefs, assumed to be well-founded. Although the hypothesis of rational action has proved fragile as an explanatory system, it retains normative importance in the sense of producing hypothetical imperatives : if you want this, do that. In this sense, the pursuit of rationality is the task of the prince's advisor. He tells him how to act to achieve his ends, whatever they may be, in the most efficient way. It is not his job to impose the demands of reason.
The empire of reason would be weak if it were not supported by rationality and self-love. In any society, there is a normative hierarchy of motivations, according to which one is blamed for doing a certain action by one motivation, and praised for having done the same action by another. More often than not, disinterested motives take precedence over self-interested ones. A rational actor driven only by self-interest will therefore have an interest in hiding it, so as not to attract blame. But the need for the esteem of others is undoubtedly less important than the need for self-esteem. To quote Jean Domat, " all the deference that the heart has for the mind is that, if it does not act by reason, we must at least believe that it acts by reason. "
