When women get even a bit of education, the whole of society improves. When they get a bit of healthcare, everyone lives longer. In many ways, it has never been a better time to be a woman: a fundamental shift has been occurring. Yet from Toronto to Timbuktu the promise of equality still eludes half the world's population. In her 2019 CBC Massey Lectures, Sally Armstrong illustrates how the status of the female half of humanity is crucial to our collective surviving and thriving. Drawing on anthropology, social science, literature, politics, and economics, she examines the many beginnings of the role of women in society, and the evolutionary revisions over millennia in the realms of sex, religion, custom, culture, politics, and economics. What ultimately comes to light is that gender inequality comes at too high a cost to us all.