This dissertation examines the development of new theories of kinship in France in the second half of the twentieth century. It focuses on the works of the anthropologist Claude Levi-Strauss and of the psychoanalyst Jacques Lacan, both of whom proposed radical reformulations of kinship, foregrounding the Incest Prohibition as the primary regulatory mechanism of society. Since Lacan and Levi-Strauss came to similar conclusions on this topic around the same time, in the early 1950s, this study asks why and how their theories on kinship gained such recognition, not only from the French social sciences, but also from legislators and politicians who relied on some of their most difficult concepts-such as the symbolic-to enact a series of laws concerning the family. Rather than taking the texts of Lacan and Levi-Strauss as merely engaging in abstract theoretical questions, I wish to argue that these authors were in fact in dialogue with the social and political context in which they were writing, and that their ideas on kinship must be understood within the numerous changes in French public policy concerning the family following the war. More specifically, I am interested in the argument made by several contemporary French anthropologists and psychoanalysts that kinship, as defined by Levi-Strauss or Lacan, is coextensive with French Republicanism and consequently, that a new organization of the family that would challenge the foundational role of sexual difference (as in the case of gay parenting for instance) would remain politically, ethically, and culturally illegitimate.