My thesis makes a theoretical and empirical contribution to the understanding of international society and governance by comparing the development pathways of Europe and North East Asia and these regions' respective responses to the financial crisis and to the climate change challenge. The novelty of my approach lies in conceiving of nationalism and multilateralism as competing but compatible principles of order in international society. These two organising principles form ideological institutions of international society and have shaped constitutive institutions such as sovereignty, international law and the economy. They determine role and power relationships between states. I start by researching how these ideological beliefs have changed the world: how was Confucianism replaced by nationalism in NE Asia and nationalism by multilateralism in Europe? The anarchy of Westphalian Europe has evolved into a syndicated supranational hierarchy in the EU, while the Confucian hierarchy in pre-modern NE Asia has given way to nationalist rivalry and territorial conflicts between Japan, China and Korea. Today the two regions – one integrated, one conflicted – play leading roles in global governance of a complex world of issues. The EU is guided by its multilateralist DNA, while NE Asia handled the financial crisis and the climate change challenge with a nationalist approach. In the theoretical part I am taking the English School's approach beyond its euro-centrism and also examine the contributions of the new Chinese school of International Relations.