Originally arising as a philosophical problem, Freud elevated the "unconscious" to the central concept of psychoanalysis. The authors trace the development of the term in all its diversity and distinguish between a vertical and a horizontal model of the unconscious. While the vertical unconscious operates like a repression machine, the horizontal corresponds to a resonance space. According to the guiding idea of psychoanalytic and depth psychological therapies, it is necessary to address the vertical level in the form of making the unconscious conscious, with the aim of restoring the ego to being "master in its own house." In contrast, the horizontal model takes into account the multiple resonances in the therapeutic situation, which, according to Freud's dictum "the unconscious understands the unconscious," are of utmost importance for the formation of the therapeutic relationship.