In an era marked by geopolitical fragmentation and global crises, how can we envision a more stable and inclusive planetary order? This pioneering volume calls for a radical rethinking of international relations—moving beyond the Westphalian state system to embrace a civilizational dialogue rooted in shared histories, values, and mutual concern. The collection brings together leading scholars to explore the idea of tianxia (all under heaven) as a conceptual and moral framework for reimagining global order. Drawing from East Asian traditions and others, contributors interrogate concepts like empire, liberalism, Confucianism, and cosmopolitanism to assess the possibilities of intercultural cooperation in a post-national future. At the heart of the book is a critical yet hopeful proposition: that civilizational dialogues—despite the exclusionary implications of such discourse—can help us imagine planetary futures beyond binaries like "the West and the Rest." Instead of universalizing one worldview, the chapters advocate for "differing for one another," a relational equity that acknowledges diversity and fosters solidarity through accommodation, empathy, and shared planetary concerns such as climate, pandemics, and global justice. With contributions spanning political theory and comparative philosophy to historical reflection and Confucian civic education, Beyond the Nation-State offers not only a critique of current global paradigms but also a constructive path forward.