Because interdependence exposes everyone around the world in an unprecedented way, governing global risks is humanity’s great challenge. Think of climate change; the risks of nuclear energy and proliferation; terrorist threats (qualitatively different from the dangers of conventional war); the collateral effects of political instability; the economic repercussions of financial crises; epidemics (whose risks increase with greater mobility and free trade); and sudden, media-fueled panics, such as Europe’s recent cucumber crisis.