This introductory chapter offers an overview of the core themes addressed in The Oxford Handbook of Peaceful Change in International Relations. It begins with a discussion of the neglect of peaceful change and the overemphasis on war as the source of change in the discipline of international relations. Definitions of peaceful change in their different dimensions, in particular the maximalist and minimalist varieties, are offered. Systemic, regional, and domestic level changes are explored. This is followed by a discussion of the study and understanding of peaceful change during the interwar, Cold War, and post–Cold War eras. The chapter offers a brief summary of different theoretical perspectives in IR—realism, liberalism, constructivism, and critical as well as eclectic approaches—and how they explore peaceful change, its key mechanisms, and its feasibility. The chapter considers the role of great powers and key regional states as agents of change. The economic, social, ideational, ecological, and technological sources of change are also briefly discussed.