This introduction presents an overview of the key concepts discussed in this book. The book starts by addressing issues most closely related to peer disagreement, and gradually broadens in scope to include increasing amounts of political detail. Throughout, it concerns voiced dissent—disagreement that has come to light or been communicated. The kinds of disagreements and the topics of dissent move from the academic and abstract to the realistic and political. With regard to voicing disagreement, one of the goals of the book is to attend to real social factors affecting agent's ability to participate in conversation. Informed by work in psychology, legal theory, and political philosophy, the book gives due attention to the social facts on the ground while also offering clear and precise analysis of disagreement and dissent in the real world.