This book develops an alternative way of understanding international relations as social relations. Mainstream theorists - and their post-modern critics - leave people out. Constructivism puts people, their activities, and their social arrangements at the forefront. It is now recognized as the most important recent breakthrough in international relations theory. Written in a lucid style, the book shows how this new approach can be applied to major issues of our times, such as national identity, gender and labor equality, and Internet governance.