Starting with the reference to "Plato’s dictum" that Freud added in the second last page of the first edition of The Interpretation of Dreams (1900), the author explains the convergences between the conception of dreams expounded by Plato in The Republic and Freud’s fundamental insights. The analysis of bibliographic sources used by Freud, and of his interests, allows us to make the hypotheses that Freud not only omitted the acknowledgment of Plato’s theoretical genealogy of "the via regia [royal road] to the unconscious", but also the possibility that The Republic constituted a tacit source of inspiration for the composition of The Interpretations of Dreams.
Keywords: Freud, Plato, dream, unconscious, historiography