Pessimism and optimism in International Relations theory have reflected the dominance of state-centrism in world politics. Competing paradigms have taken for granted that the core problematics of concern are the domestic consolidation of nation-states and their interaction in ‘international’ relations, seen as two-level games. Pessimism stemmed from war, domestic vulnerability and interstate economic competition, optimism from liberal pacification, economic interdependence and global governance. However, this perception of world politics is increasingly outdated. Since the mid-to-late twentieth century, a dialectic of globalisation and fragmentation has led to a complex restructuring of the world system, above the state, below the state and cutting across states, from financial crises to the ‘intangible economy’ to security and climate change. The ‘new pessimism’—and optimism—is rooted in response to this transformation.