In her book, Beauvoir examines why women are treated as inferior and subordinate to men. In studying this issue through the lenses of history, biology and psychology, she finds much evidence that women have been treated as inferior but no logical reasons why this should be so. Therefore, she concludes that myths or false stories have been constructed to justify treating women as second class and in defining them as mutilated or incomplete men.
Myths include the myth of maternity or the "eternal feminine" that defines woman by her reproductive capacity and robs her of her individuality in favor of casting her as the abstract symbol of "life."
Another myth is that menstruation is a threat that becomes much exaggerated. Beauvoir writes
... since patriarchy, only harmful powers have been attributed to the bizarre liquor flowing from the feminine sex. Pliny in his Natural History says: “The menstruating woman spoils harvests, devastates gardens, kills seeds, makes fruit fall, kills bees; if she touches the wine, it turns to vinegar; milk sours …”
An old English poet expresses the same thought:
Oh! Menstruating woman, thou’rt a fiend From whom all nature should be closely screened!
Beauvoir also discusses the virginity myth. She explains that men demand women come to them as virgins out of a myth of wanting to possess them. However, she writes
the idea of possession is always impossible to realize positively; the truth is that one never has anything or anyone
In the beauty myth, the woman must be eternally young and healthy, to hide from the man the reality of his own mortality. Older women, even older virgins, are seen as repellent because they remind the man that he too will die.
The woman is the "Other," not herself but what reflects back to the man what he wants to see. Conversely, what he doesn't like is mythically exaggerated and made repellent in the woman. In all of this, the real woman is lost.