This text provides an excellent presentation, very clear yet rigorous, the problem of sex and sexual differentiation in the teaching of Lacan. It also has the virtue of being entertaining and not dodge the difficult articulation with the experience of the practice of psychoanalysis. Notably, in particular, developments around quantifier logic of Frege, which underlies sexuation formulas. Rationale rarely explored, which makes this work also is the product of an unusual research on the subject in the analytical environment. Therefore, its lecturra be useful both for those who are introduced into this issue and for those who are interested in deepening. At the same time opens perspectives essential to the construction of the psychoanalytic clinic of the not-all, beyond the classic phallic clinic, Lacan outlined at the end of his work.