This chapter serves as an introduction and outlines the aims of this book. The book proposes a new conception of freedom: “freedom as social cooperation” (FSC). Against traditional accounts of negative, positive, and republican liberty, FSC presents freedom as an ongoing, collaborative practice through which individuals mutually support one another’s projects. The first aim of the book is theoretical: to develop FSC as an original contribution to political philosophy. The second aim is practical: to use FSC as the foundation for a theory of liberal democracy. The work argues that liberal democratic institutions—such as the separation of powers, private property, markets, social services, and legal protections—can be understood as evolved mechanisms that enable and sustain large-scale cooperation. By interpreting these institutions through the lens of FSC, the book provides a unified explanation of how political and economic systems function in societies where individuals pursue interdependent life plans.