Rent, or unearned income, is a pervasive concept in contemporary economics. Economists of all stripes see today's global financial system as riddled with harmful rents. Still, most deny these are intrinsic to capitalism and insist they can be eliminated with the right policies. It begs the question, why is rent theory so critical of the present but so optimistic about the future? In Mother of Capital, Matthew Costa delves into the intellectual and social history of charging for the use of property to solve this puzzle. Centering rent as the engine of capitalism's historical emergence in medieval Europe offers a groundbreaking, systematic history of the practice. The book also traces the history of resistance from below and unearths a neglected body of critical rent theory. Weaving complex strands of social and intellectual history into a vivid, lively, and original explanation of how our society came to be, Costa boldly intervenes in contemporary debates about the origins and future of capitalism, the nature of social change, and history itself.