This is a world of increasing unpredictability in which we are left, to a much greater extent than we expected, at the whims of our leaders, who are less bound by external frameworks and feel freer to make it up as they go along. We should be choosing those decision makers more carefully than ever — just when electorates seem less inclined to do so.

These are dark clouds. But the end of the old system does not have to mean the end of cooperation. We still have many of the components of an effective world order. We have a rich web of international institutions, many of them largely invisible, which manage the links among nations, from civil aviation to the internet. Treaties are still largely observed. International law and sovereignty can be hard to enforce and defend, but many of us still deplore the breaches. The very existence of an international public opinion can still put pressure on our leaders. Many of the organizations of the fading structures, among them the United Nations, the World Trade Organization and the World Bank, are increasingly drained of resources and meaning, but they still exist.

In a much-discussed speech in Davos in January, Prime Minister Mark Carney of Canada, months before trade talks with the United States broke down, described the end of Pax Americana as the end of a “pleasant fiction.” But other countries could push back, he said, particularly if they banded together in coalitions of shared values with shared goals. A number of middle powers, including Canada, Australia and Japan, are working together to fill the gap left by the withdrawal of the United States from its former role as the benevolent superpower.

Change is hard, but clinging to the old ways can be a dangerous delusion. In the summer of 1914, the British foreign secretary, Sir Edward Grey, and many others in positions of power in Britain and across Europe assumed that the latest crisis in the Balkans would be settled, as similar ones had been before, by a conference of the great powers. He failed to understand how rapidly Europe was moving to war and to use Britain’s great power to bring the different sides together. The First World War changed Europe and the world for good.

By 1945, Britain, the Soviet Union, the United States and their allies had fought two brutal world wars in the space of three decades. When they created the architecture of the existing order, they were very clear on what they wanted to prevent. The previous frameworks had failed, and they would create something new that would not.