Chapter 2 makes the case for looking at state sovereignty as a social construction rather than as a definitional absolute. In other words, it argues that “sovereignty” does not have a specific meaning, defined by law or concept and static over time. Rather, it is a practice, and the content of sovereignty as a practice changes over time. The chapter reviews various ways in which sovereignty is understood in international relations, and the analytical utility and limitations of using the concept in these ways. It discusses the Peace of Westphalia in this context, since “Westphalian sovereignty” is a sufficiently common trope in international relations theory that it cannot be ignored (this discussion reappears in various places throughout the book), and argues that the Peace actually has fairly little to do with the contemporary practice of state soveriegnty. It also briefly discusses methodology, and how understanding sovereignty as a social construct can address questions of both power in and change of sovereignty in ways that conceptualizing sovereignty as a definitional absolute cannot.