We have seen that explanations provided by economics largely rest on a fundamental postulate that is generally known as the rationality principle and that used to be interpreted by most economists as the principle in virtue of which entrepreneurs tend to make decisions that maximize their profits in the context of the constraints to which they are subjected. Yet, throughout the history of economic thought, this principle, thus interpreted, has been one of the favourite targets of opponents of mainstream economics. How can it be claimed that entrepreneurs are so systematically oriented towards profit maximization when it has often been observed that many of them let themselves be guided by entirely different considerations (prestige, maintaining good relationships, avoiding exhausting and costly calculations that are not sufficiently rewarding, etc.), which moreover are frequently based on emotive states? It is difficult, in effect, to believe that actual entrepreneurs resemble these maximizing machines that are readily resorted to by the designers of economic models.