Sometime in the eighteenth century, sex as we know it was invented. The reproductive organs went from being paradigmatic sites for displaying hierarchy, resonant throughout the cosmos, to being the foundation of incommensurable difference: "women owe their manner of being to their organs of generation, and especially to the uterus," as one eighteenth century physician put it…. Here was not only an explicit repudiation of the old isomorphisms but also, and more important, a rejection of the idea that nuanced differences between organs, fluids, and physiological processes mirrored a transcendental order of perfection. Aristotle and Galen were simply mistaken in holding that female organs are a lesser form of the male's and by implication that woman is a lesser man. [p149]

The context for the articulation of two incommensurable sexes was, however, neither a theory of knowledge nor advances in scientific knowledge. The context was politics. There were endless new struggles for power and position in the enormously enlarged public sphere of the eighteenth and particularly the postrevolutionary nineteenth centuries: between and among men and women; between and among feminists and antifeminists. When, for many reasons, a preexisting transcendental order or time-immemorial custom became a less and less plausible justification for social relations, the battleground of gender roles shifted to nature, to biological sex. Distinct sexual anatomy was adduced to support or deny all manner of claims in a variety of specific social, economic, political, cultural, or erotic contexts. [p152]

The promises of the French Revolution -- that mankind in all its social and cultural relations could be regenerated, that women could achieve not only civil but personal liberties, that family, morality, and personal relations could all be made afresh -- gave birth not only to a genuine new feminism but also to a new kind of antifeminism, a new fear of women, and to political boundaries that engendered sexual boundaries to match. [p194]

The ostensibly neutral language of liberalism also left women themselves without a voice of their own and initiated a feminist discourse of difference in search of one. [p197]

Desire was given a history and the female body was distinguished from the male's, as the shattering transformations of European society between the seventeenth and the nineteenth centuries put unbearable pressure on old views of the body and its pleasures. A biology of cosmic hierarchy gave way to a biology of incommensurability, anchored in the body, in which the relationship of men to women, like that of apples to oranges, was not given as one of equality or inequality but rather of difference. This required interpretation and became the weapon of cultural and political struggle. [p207]