Book excerpt: Epistemic Communities, Constructivism and International Environmental Politics brings together 25 years of publications by Peter M. Haas. The book examines how the world has changed significantly over the last 100 years, discusses the need for new, constructivist scholarship to understand the dynamics of world politics, and highlights the role played by transnational networks of professional experts in global governance. Combining an intellectual history of epistemic communities with theoretical arguments and empirical studies of global environmental conferences, as well as international organizations and comparative studies of international environmental regimes, this book presents a broad picture of social learning on the global scale. In addition to detailing the changes in the international system since the Industrial Revolution, Haas discusses the technical nature of global environmental threats. Providing a critical reading of discourses about environmental security, this book explores governance efforts to deal with global climate change, international pollution control, stratospheric ozone, and European acid rain. With a new general introduction and the addition of introductory pieces for each section, this collection offers a retrospective overview of the author’s work and is essential reading for students and scholars of environmental politics, international relations and global politics.