Feminist arguments against the concept of biologically determined gender identity began with the assertion by Simone de Beauvoir (1908–1986) that women are not born but made. The sex-gender paradigm was taken up widely in the 1970s and 1980s in feminist arguments for rights denied to women and girls on spurious biological grounds. The emphasis of feminist analysis was thus skewed toward deconstructions of gender, while sex itself remained relatively unexamined. Some feminist positions took advantage of the notion of a "real" or "natural" femininity that existed prior to the impositions of capitalist patriarchy, although ultimately all arguments for women's equality were undermined by such essentialism, to a greater or lesser extent.
In a groundbreaking essay published in 1975, Gayle Rubin coined the term "sex-gender system" to describe the ways in which societies transform biological sex into cultural gender and align the processes of human reproduction with those of economic production. Rubin's analysis places marriage, kinship systems, and heterosexuality at the heart of the sex-gender system. Her hypothesis exposed certain contradictions and differences that were particularly marked within American feminism at the time. One of these concerns the legacy of African Americans, whose slave ancestors were denied marriage and kinship and therefore a place in the sex-gender system as Rubin describes it, and for whom gender consequently has different meanings. The situation of African Americans draws attention to the need to conceptualize gender and its relationship with other social systems within historically specific frameworks. Lesbians also fall outside the gambit of Rubin's sex-gender system: by opting out of heterosexuality and its attendant kinship structures, they become radically other to the system. Although this outsider status legitimated lesbianism as a logical and effective expression of feminist dissent, it also contributed to the creation, in the 1980s, of an idealized image of lesbian sexuality that was widely rejected by queer culturalists in the 1990s. The "sex-gender system" failed as a universal paradigm but succeeded in establishing the importance of mapping convergences between particular social and economic systems in the production of gender.
The recognition that differences among women are at least as important to feminism as differences between women and men has enriched feminist thinking massively, but it has also placed the fundamental assumption of feminism—the commonality of women—under great pressure. Postmodern critical theorists see this as a good thing, potentially enabling the emergence of multiple and mutable sexual identities. In Gender Trouble (1990), the most widely influential deconstruction of gender identity published in the 1990s, Judith Butler argues that feminist assertions of the commonality of women as a group unwittingly contribute to the regulation of gender relations. Membership of the class of women, according to Butler, is not the inescapable consequence of biological femininity. Gender identities are not expressions of an essential core but performances built from citations and imitations specific to a given context. The hegemony of patriarchal heterosexuality is therefore neither natural nor inevitable. Butler argues that performances that subvert, confuse, or ironize gender norms have the power to unsettle or even unseat those norms. However, this reformulation of gender is not without drawbacks. Its dissolution of the concept of women as a class or category could be premature. Feminism is the struggle for women as a class and for the disappearance of that class, but it is possible that women as a class might disappear from postmodern feminist discourse while continuing to exist in all their diversity within other discursive and social formations. Further, the notion of gender identity as "free-floating" and flexible needs to be circumscribed by a recognition of the effects that normative social forces and their uneven application have on people of different cultures and conditions. Individualistic subversions of gender norms are not equally possible for all and do not necessarily benefit those who are left behind in the ghetto of women.