During the colonial period in India, European scholars, British officials, and elite Indian intellectuals—philologists, administrators, doctors, ethnologists, sociologists, and social critics—deployed ideas about sexuality to understand modern Indian society. This book shows how deviant female sexuality, particularly the concept of the prostitute, became foundational to this knowledge project and became the primary way to think and write about Indian society. The book reveals that deviant female sexuality was critical to debates about social progress and exclusion, caste domination, marriage, widowhood and inheritance, women's performance, the trafficking of girls, abortion and infanticide, industrial and domestic labor, indentured servitude, and ideologies about the dangers of Muslim sexuality. British authorities and Indian intellectuals used the concept of the prostitute to argue for the dramatic reorganization of modern Indian society around Hindu monogamy. The book demonstrates how the intellectual history of modern social thought is based in a dangerous civilizational logic built on the control and erasure of women's sexuality. This logic continues to hold sway in present-day South Asia and the postcolonial world. Reframing the prostitute as a concept, the book overturns long-established notions of how to write the history of modern social thought in colonial India, and opens up new approaches for the global history of sexuality.