Knowledge differs from science, and presupposes a teleological vision of reality; the desire to know, independently of all practical utility, is an anthropological constant. Modern science, by contrast, has undergone the following transformations: it does not consider reality teleologically, it aims at practical utility, it furnishes falsifiable hypotheses, and it is a collective enterprise. We must therefore inquire into the ethos of the scientist and into the problem of the relevance of research.