This book provides a novel theory of the philosophy of public health and public policy. It is addressed both to philosophers and to policymakers, inviting policymakers to rethink the nature of public policy, and philosophers to rethink the nature of philosophy. The book is divided into three parts. Part I argues that a number of popular philosophical tools such as thought experiments are poorly calibrated for providing guidance to policymakers. It advances a new approach to philosophy, which draws both on pragmatism and on complex systems science. Part II examines the role of ethical values in public health. It argues that certain commonly expressed worries about public health paternalism are much less convincing than is often thought. It further argues that individuals have a right to public health. If a state does not take easy steps to reduce risks to health, then it will often violate individuals’ right to public health, and should be criticized as a Neglectful State. Part III integrates the complex systems analysis developed in Part I with the ethical framework developed in Part II. It examines three spheres in which public health policy needs to make choices—responsibility, equality, and networks, focusing on three challenges: (1) how to make use of judgements of responsibility, and whom to hold responsible; (2) how to specify the goal of health equity and how to pursue it and (3) the implications of the fact that most health risks are contagious or can be amplified by socially mediated networks of causes.