The unconscious according to Freud is neither Lacan's first teaching, the unconscious coextensive with language, nor that of his second teaching, the unconscious linked to the Borromean structure and its effects on the body and speech. What is it? In fact, the unconscious is the object of a science that develops through different hypotheses. In this essay, I wanted to show the consistency and the coherency of these hypotheses, from their topological and clinical references. Thus, based on the invention of the Lacanian concept of fundamental fantasy and the mathemes that define it, it is necessary to establish a correlation between a theoretical, clinical, and practical approach concerning this hypothesis of the unconscious that is more coherent. In retrospect, it is with such intrication that Freud emphasizes the theoretical field of psychoanalysis as falling exclusively within the field of the unconscious.