 In addition to the pursuit of formalization via mathemes, the seminars of the final decade of Lacan’s teachings also were preoccupied with reflections on his register theory, especially the register of the Real, and sexual difference (reflections often intertwined with each other). The program of formalization ostensibly enabled Lacan to reveal with exactitude the precise limits of the sayable and the representable, thereby touching upon the Real through showing what is not pinned down fully and adequately within the coordinates of the accessible, familiar “reality” co-constituted through the other two registers of the Imaginary and the Symbolic (see  2.1  below). Various aspects and facets of things sexual came to be associated by the later Lacan with the enigmatic evasiveness of the Real, including sexual difference. In one of his most famous seminars, the twentieth (Encore, 1972–1973), he theorized sexual difference as “sexuation,” depicting the non-biological, denaturalized subject-positions of masculinity and femininity in terms of formal logic. Therein, he purported to uncover an inherent, ineliminable structural discrepancy/gap separating the sexes, an inescapable condemnation of sexed subjects to being essentially, necessarily out-of-sync with each other (and even with themselves as split subjects). Lacan summarized this with an infamous one-liner: “Il n’y a pas de rapport sexuel” (There is no sexual relationship). This declaration scandalized many at the time. Moreover, the twentieth seminar in particular as well as connected portions of Lacan’s corpus from this same period served as powerful catalysts for crucial developments in French feminist thinking during the 1970s.