This article aims to highlight the epistemological influences and theoretical problems that are articulated around the conception of the register of the real in Jacques Lacan's teaching, which is constantly referred to in relation to the question of the transmission of psychoanalysis. It is argued that the influences of Hegel and Koyré are decisive for a conception of the real as rational, and as impossible, respectively, being widely used by the psychoanalyst to situate the impasses of the transmission of psychoanalysis, in close relation with a debate with the philosophy of science and epistemology. The crucial role attributed to logic and its use by the psychoanalyst in the search for a formalization of the impasse that constitutes the subject of the unconscious is also highlighted.