Incest prohibition

Incest prohibition is presented not merely as a ban on sexual relations between close relatives but as a rule that helps organize social relations between kin groups. In Simone de Beauvoir’s account, its significance lies in the outward movement it requires: marriage connects groups that might otherwise remain closed upon themselves, and women become the means through which that connection is made.

Exogamy and the purpose of the rule

The discussion distinguishes the prohibition of incest from the practice of exogamy. Drawing on Claude Lévi-Strauss’s analysis, Beauvoir argues that the incest prohibition is not the original cause of exogamy. Rather, it gives negative form to a positive social aim: marriage outside the group produces relations between groups. The point is not, in this account, that marriage within the group carries an inherent biological danger. It is that outward marriage yields a social benefit by establishing reciprocal connections.

Women as Instruments of Exchange

The rule also exposes the unequal terms on which this connection is organized. Beauvoir’s account presents women as part of the goods exchanged between clans: a group is not to keep women for its own exclusive use but to make them instruments of communication with another group. A woman becomes “other” not through an innate quality, but because her position in the social structure marks her as belonging outside the marrying group. The prohibition therefore links kin groups while treating women as the means of that link, rather than as equal parties who determine its terms.

Incest prohibition within a wider structure of dependence

The account places this rule within a broader argument about women’s social position. A biological relation of mutual need between the sexes has not, by itself, produced social equality: just as economic need links master and enslaved person without freeing the latter, sexual desire and the desire for descendants have not liberated women. Their relation to men is instead shaped by unequal power, legal disadvantage, and customs that can leave formally recognized rights unrealized. Incest prohibition thus belongs to a social order in which relations between groups may be organized through marriage while women remain subordinate within the arrangements that connect them.

Historical and Legal Context

The rule appears within a longer history in which kinship, property, and authority were reorganized around the family. In Beauvoir’s account, Roman society moved from a probable association between exogamy and matrilineal organization toward patriarchy after the death of Tarquinius, as agricultural property and the private estate made the family the nucleus of society. The Roman woman’s marriage could place her under her husband’s authority, while other arrangements left her property under guardianship and her person subject to competing claims by husband and father. These variations show that rules governing marriage did not operate in isolation: their effects depended on who controlled property and familial authority.

The account later connects women’s legal dependence to the persistence of patriarchal family structures. The Napoleonic Code restored and hardened marital subordination, while nineteenth-century reforms proceeded slowly: divorce, abolished in 1826, returned in 1884 under restrictive conditions, and the married woman’s legal status was modified in 1938 and 1942 without achieving equality between spouses. These examples do not identify the incest prohibition itself with any one statute; they situate marriage rules within legal orders that repeatedly assigned women unequal status and constrained their choices.

Social Meaning and Limits

The argument’s central distinction is between a rule’s social function and an alleged natural necessity. Incest prohibition can help create connections beyond the kin group, but the account does not treat the resulting arrangement as proof that women are naturally suited to serve as links between men or groups. Instead, the social position that makes a woman “other” is produced by her place in a structure. The prohibition therefore illuminates how kinship rules can organize reciprocity between groups while withholding equal agency from the women through whom that reciprocity is established.