This article deals with the incapacity of reason - generally thought as intelligence and a knowledge linked to science, history, to a systematic learning - to assumes itself as the perpetrator of abominable acts as it were a suprahuman thing. It approaches a probable motivation of this thought - the illusion of a necessary rupture with the sensible world to elaborate a true knowledge - and estimate through the criticism of some historical analyses of the Eugenics and Holocaust the importance of the notions of myth and mythology as supporters of the peculiar blindness of the reason.
rationality; withdrawal from the world; appearances; blindness; myth; Eugenics; Holocaust.