I am a Professor of Political Science at The University of Pennsylvania. My research is focused on civil wars, ethnic conflict, and international relations. You can read my published work in the American Political Science Review, World Politics, The Journal of Conflict Resolution, Perspectives on Politics, and other journals. Michael Doyle and I co-authored Making War and Building Peace, a book about United Nations peacebuilding, published by Princeton University Press in 2006. Paul Collier and I co-edited Understanding Civil War: Evidence and Analysis, two volumes of case studies on civil war, published by the World Bank in 2005. I am currently working on several article-length projects related to civil war as well as two book-length projects: the first analyzes the causes of conflicts over self-determination; the second is a book on international relations theory, applying insights from social psychological theories of identity formation to explain nation-building and war.