This article can be characterized as a ‘rediscovery’ of a notion of psychoanalysis that had disappeared or had been confused by later operations. The authors explore a Freudian notion that has been unjustly misunderstood, especially because of the multiple ways in which ‘Unglaube’ – disbelief – has been translated. We shall establish the archaeology of this term in Freud by extracting its three significant modes. Firstly, paranoiac disbelief designates an unconscious process of the rejection of belief in the subject's first encounter with a sexual reality that is always traumatic. Secondly, the obsessional neurotic's disbelief, which we shall call ‘incredulity’, is a secondary, less radical refusal of belief, one that is different from its paranoiac counterpart. Finally, we shall envision a third – dialectical – type of disbelief, which Freud called ‘act of disbelief’ and which will enable us to approach the fundamental epistemic and ethical stakes for psychoanalysis.