From its etymological roots, sex is related to a scission, Latin for sectus, secare, meaning "to divide or cut." Therefore, regardless of the various studies applied to defining sex as inscribed by discursive acts, i.e. merely a 'performatively enacted signification, ' there is something more to sex than just a social construction or an aprioristic substance. Sex is irreducible to meaning or knowledge. This is why psychoanalysis cannot be formulated as an erotology nor a science of sex (scientia sexualis). In this matter, sex escapes the symbolic restraints of language; however, it is through its failure that it manifests itself through the symbolic, e.g. symptoms or dream life. So, what is sex? Sex and Nothing embarks upon a dialogue between colleagues and friends interested in bridging psychoanalysis and philosophy, linking sex and thought, where what emerges is a greater awareness of the irreducucibility of sex to the discourse of knowledge and meaning: in other words, sex and nothing.