The answer depends on the contextual frame and measure for such analysis. That being said, Simone de Beauvoir’s The Second Sex is generally acknowledged as a groundbreaking addition to the discourse of feminism. In addition, The Second Sex makes a significant contribution to the philosophy of existentialism. Existentialism was a heretofore male-dominated philosophical sect featuring prominently the work of de Beauvoir’s lover, Jean-Paul Sartre. Yet existentialism concerns human existence as a whole, and the gaps in the early literature concerning the female existent are only significantly taken up by de Beauvoir’s writings in the late 1940s and early 1950s. Her best-known work, The Second Sex, was published in France in 1949.
De Beauvoir’s was one of the first female voices to argue that the female concept of the self is circumscribed by a patriarchal society that insists on women taking their sense of self from others, viz. men like their husbands and fathers. She wrote of the existential danger posed to the woman who “resign[s] [herself] to [her] lot without attempting to take any action” (The Second Sex, H. M. Parsley ed. (1952), 119) and “by dint of doing nothing but contemplate herself...annihilates herself” (Id. at 666). In this sense, feminism is for de Beauvoir a fundamentally existential issue.
So, too, is love. A “woman in love” according to de Beauvoir “gives up her transcendence, subordinating it to the essential other” (Id. 611) and turning the object of her affection into a deity: “she will humble herself to nothingness before him. Love becomes for her a religion” (Id. at 604). Love in the shape of idolatry is a form of bad faith in Sartre’s sense, an opiate to soothe the pain of existence, one that assists in the forgetting of one’s self and the subordination of one will in the name of another. Love in this sense can be a veritable form of self-deception that inhibits the possibility of experiencing transcendent freedom. De Beauvoir argued instead for love rooted in free existence for both parties.
In contrast to the woman in love, an “emancipated woman,” is a woman who makes her own destiny, lives by her own rules, and is herself the subject of active transcendence and authenticity. De Beauvoir argued that women required concrete financial, health, and educational independence in addition to rights on paper (such as enfranchisement) if they were to be truly free. Artistic fulfillment for a woman is next to impossible without freedom, de Beauvoir argued, because of the ripple effects patriarchally bound notions of the self have on women’s artistic ability and authenticity.
The Second Sex received some pushback from second-wave feminists in the 1970s who were reclaiming the women’s role in the home and took offense to de Beauvoir’s labeling of activities considered quintessentially “feminine” as male-contrived tools of patriarchal oppression. More recently, de Beauvoir’s rooting of the self in existence as opposed to in identity has been revisited as a foundation for coalitional politics (see Elaine Stavro, Rethinking Identity and Coalitional Politics, Insights from Simone de Beauvoir, Canadian Journal of Political Science Vol. 40(2) June 2007).