Abstract: this essay aims to describe the difference between intentional action and rational action, in order to criticize the Misesian postulate of economic rationality identifiable with the metaphor of homo oeconomicus. In his intellectual production, Karl Popper exposed the conjectures and confutations theory to build a solid scientific approach to the study of human actions, resorting to the Darwinian evolutionary theory, underlining its limits and its possible compensation with the Lamarckian one. He reached the conclusion that the rationality of human conduct is never total, approaching (unconsciously) much more the Weberian canons than those of the Austrian school of economics.
