Psychoanalysis and ethnology occupy a privileged position in our knowledge not because they have established the foundations of their positivity better than any other human science, and at last accomplished the old attempt to be truly scientific; but rather because, on the confines of all the branches of knowledge investigating man, they form an undoubted and inexhaustible treasure hoard of experiences and concepts, and above all a perpetual principle of dissatisfaction, of calling into question, of criticism and contestation of what may seem, in other respects, to be established.