This volume is a collection of the best essays by Prof. Michael Doyle on the topics of liberalism and peace. The connection between liberalism and peace is important because liberal republics have proven to be the dominant practice in the international system. For many, they are the ideal of modern politics and their separate peace has emerged as the most significant and stable zone of peace in modern world history. This collection includes Prof. Doyle's seminal articles from the 1980s, which helped launch the 'Democratic Peace' debate, through to the policy implications of liberal internationalism in the post-Cold War era. The volume concludes with a new essay that addresses a variety of criticisms that have been made of his interpretation of the liberal peace. This book will be essential reading for students of democratic peace theory, International Relations theory, foreign policy, political science, and peace and security studies.