The current global resurgence of religion is more wide ranging than a clash of civilizations driven by religious extremism, terrorism, or fundamentalism. This global cultural and religious shift is challenging our interpretation of the modern world - what it means to be modern - as a variety of social and religious groups struggle to find alternative paths to modernity. This book examines what this means for the key concepts and theories of international relations - international conflict and cooperation, diplomacy, the promotion of civil society, democracy, nation-building, and economic development-and how it is transforming them. The book serves as a guide for what it means to take cultural and religious pluralism seriously in the twenty-first century.