With the fall of the Roman Empire, the world’s progress was set back by centuries in the realms of government, economics and law, but also in science, technology, and the arts — areas which took years to regain their former glory. Would the end of the present American-dominated order have less dire consequences, asks Robert Kagan. Probably not. In fact, he writes, the present world order was largely shaped by American power and reflects American interests and preferences. If the balance of power shifts in the direction of other nations, the world order will change to suit their interests and preferences. Things like democracy, free markets, and the peace among great powers that has reigned for the better part of six decades could very well become a distant memory. The better idea doesn’t have to win just because it is a better idea. It requires great powers to champion it.