Examining a wide range of theoretical and practical problems and challenges facing nations in the 21st century, this collection of essays addresses the triangular relationship between peace, security and development. Questions are raised about the relevance of the UN system in the coming decades, and the contributors reflect on past experiences and relevant philosophical inquiries. Specific cases and experiences are examined that are considered representative of the relevance/irrelevance of past collective actions in the security and non-security fields, and new ideas and concepts for integrating theory and practice are suggested. Topics discussed include peacemaking and peacekeeping, arms control, economic development, human rights and the critical role of education. One of the underlying themes of the volume is that the challenges of the 21st century will be of unprecedented magnitude, and that unless the UN system is reformed and revitalized it runs the risk of becoming irrelevant.