Chapter four analyses the period between the French Revolution and the First World War. For the first time, Europeans believed that it was possible to reorder societies to create new futures. Politics was turned towards a future that was open to human action. These ideas generated paradoxical results. The revolutionary urge to reshape societies according a rational plan sparked twenty-five years of wars and uncertainty. The turbulence of these years generated two consequences. First, at the Congress of Vienna in 1815, the experience of unpredictability gave rise to an idea that international politics requires active and multilateral management. This pragmatic approach, born out of uncertainty, increased predictability in the international system. Second, it created a yearning for certainty. A number of ideologies and sciences emerged claiming that societies are governed by underlying laws that can be discovered and manipulated. In the closing decades of the nineteenth century, determinist world views dominated modern thinking and would play a key role in the outbreak and conduct of the First World War.