Poullain de La Barre's De l'égalité des deux sexes is one of the earliest and most important statements on the difference between "sex" and "gender." Published in 1673, Poullain's treatise argues that the popular opinion of the inferiority of women is little more that socialized prejudice, legitimized by historians and philosophers who falsely assign their bias to nature rather than to their own psycho-sexual fears of female power.

Gerald MacLean's critical edition of the 1677 English translation helps today's readers understand how and why male-dominated societies have continued to subordinate women by maintaining that sexual difference is a hierarchical relation. In his introduction, MacLean examines why Poullain's ideas were largely ignored when they appeared in England and demonstrates how the false distinction between sex and gender has been systematically obscured by cultural forces.