Revolutionary and incendiary, The Second Sex is one of the earliest attempts to confront human history from a feminist perspective. It won de Beauvoir many admirers and just as many detractors. Today, many regard this massive and meticulously researched masterwork as not only as pillar of feminist thought but of twentieth-century philosophy in general.

De Beauvoir’s primary thesis is that men fundamentally oppress women by characterizing them, on every level, as the Other, defined exclusively in opposition to men. Man occupies the role of the self, or subject; woman is the object, the other. He is essential, absolute, and transcendent. She is inessential, incomplete, and mutilated. He extends out into the world to impose his will on it, whereas woman is doomed to immanence, or inwardness. He creates, acts, invents; she waits for him to save her. This distinction is the basis of all de Beauvoir’s later arguments.

De Beauvoir states that while it is natural for humans to understand themselves in opposition to others, this process is flawed when applied to the genders. In defining woman exclusively as Other, man is effectively denying her humanity.

The Second Sex chronicles de Beauvoir’s effort to locate the source of these profoundly imbalanced gender roles. In Book I, entitled “Facts and Myths,” she asks how “female humans” come to occupy a subordinate position in society. To answer this question—and to better understand her own identity—de Beauvoir first turns to biology, psychoanalysis, and historical materialism. These disciplines reveal indisputable “essential” differences between men and women but provide no justification for woman’s inferiority. They all take woman’s inferior “destiny” for granted.

She then moves to history to trace the emergence of male superiority in society, from nomadic hunter-gatherers through the French Revolution and contemporary times. Here she finds ample examples of female subordination, but again, no persuasive justification for them. History, she argues, is not an immutable “fact,” but a reflection of certain attitudes, preconceptions, and injustices.

De Beauvoir next discusses various mythical representations of women and demonstrates how these myths have imprinted human consciousness, often to the disservice of women. De Beauvoir hopes to debunk the persistent myth of the “eternal feminine” by showing that it arose from male discomfort with the fact of his own birth. Throughout history, maternity has been both worshipped and reviled: the mother both brings life and heralds death. These mysterious operations get projected onto the woman, who is transformed into a symbol of “life” and in the process is robbed of all individuality. To illustrate the prevalence of these myths, de Beauvoir studies the portrayal of women by five modern writers. In the end of this section, de Beauvoir examines the impact of these myths on individual experience. She concludes that the “eternal feminine” fiction is reinforced by biology, psychoanalysis, history, and literature.

De Beauvoir insists on the impossibility of comparing the “character” of men and women without considering the immense differences in their situation, and in Book II, entitled “Woman’s Life Today,” she turns to the concrete realities of this situation. She traces female development through its formative stages: childhood, youth, and sexual initiation. Her goal is to prove that women are not born “feminine” but shaped by a thousand external processes. She shows how, at each stage of her upbringing, a girl is conditioned into accepting passivity, dependence, repetition, and inwardness. Every force in society conspires to deprive her of subjectivity and flatten her into an object. Denied the possibility of independent work or creative fulfillment, the woman must accept a dissatisfying life of housework, childbearing, and sexual slavishness.

Having brought the woman to adulthood, de Beauvoir analyzes the various “situations,” or roles, the adult woman inhabits. The bourgeois woman performs three major functions: wife, mother, and entertainer. No matter how illustrious the woman’s household may be, these roles inevitably lead to immanence, incompleteness, and profound frustration. Even those who accept a less conventional place in society—as a prostitute or courtesan, for example—must submit to imperatives defined by the male. De Beauvoir also reflects on the trauma of old age. When a woman loses her reproductive capacity, she loses her primary purpose and therefore her identity. In the final chapter of this section, “Woman’s Situation and Character,” de Beauvoir reiterates the controversial claim that woman’s situation is not a result of her character. Rather, her character is a result of her situation. Her mediocrity, complacency, lack of accomplishment, laziness, passivity—all these qualities are the consequences of her subordination, not the cause.

In “Justifications,” de Beauvoir studies some of the ways that women reinforce their own dependency. Narcissists, women in love, and mystics all embrace their immanence by drowning selfhood in an external object—whether it be the mirror, a lover, or God. Throughout the book, de Beauvoir mentions such instances of females being complicit in their Otherness, particularly with regard to marriage. The difficulty of breaking free from “femininity”—of sacrificing security and comfort for some ill-conceived notion of “equality”—induces many women to accept the usual unfulfilling roles of wife and mother. From the very beginning of her discussion, de Beauvoir identifies the economic underpinnings of female subordination—and the economic roots of woman’s liberation. Only in work can she achieve autonomy. If woman can support herself, she can also achieve a form of liberation. In the concluding chapters of The Second Sex, de Beauvoir discusses the logistical hurdles woman faces in pursuing this goal.