After the Berlin Wall came down in 1989 and almost a year before the Soviet Union collapsed in late 1991, US President George H.W.

Bush proclaimed a “new world order.” Now, just two months into Donald Trump’s second presidency, Kaja Kallas, the EU’s top diplomat, has declared that “the international order is undergoing changes of a magnitude not seen since 1945.” But what is “world order” and how is it maintained or disrupted?

In everyday language, order refers to a stable arrangement of items, functions or relations. Thus, in domestic affairs, we speak of an “orderly society” and its government. But in international affairs, there is no overarching government. With arrangements among states always subject to change, the world is, in a sense, anarchic.

Anarchy is not the same as chaos, though. Order is a matter of degree: it varies over time. In domestic affairs, a stable polity can persist despite a degree of ungoverned violence. 

After all, organized and unorganized violent crime remain a fact of life in most countries. But when violence reaches too high a level, it is seen as an indication of a “failed state.” Somalia may have a common language and ethnicity, but it has long been a site of battling clans; the “national” government in Mogadishu has little authority outside the capital.

The German sociologist Max Weber famously defined the modern state as a political institution with a monopoly on the legitimate use of force. 

But our understanding of legitimate authority rests on ideas and norms that can change. Thus, a legitimate order stems from judgments about the strength of norms, as well as simple descriptions of the amount and nature of violence within a state.

When it comes to world order, we can measure changes in the distribution of power and resources, as well as in adherence to the norms that establish legitimacy. We can also measure the frequency and intensity of violent conflict.