The intention of this work is to present the theoretical and epistemologic position of Jacques Lacan, the conceptual foundation to construct the response to both fundamental questions that concern the subjective field; the question for the being and the question for the sexuality.
The stickiness of the idea of the being upon a sexuality condition, articulates both terms in the illusion of an identity thought as the identical with itself. The modality with which from the discourse of the psychoanalysis the above mentioned notion is re-formulated, implies the mathema as the foundation of the formulas of the sexuation. This is it while I reject to any definition by the route of the being, but including a way for the truth supported on the singularity of the subject.
Keywords: Lacan - Neologism - sexuation