With Donald Trump mulling an invasion of Iran, Vladimir Putin threatening to nuke Ukraine, and America’s last remaining arms-control treaty with Russia expiring earlier this month with little prospect of renewal, I find myself pondering two eternal questions. One involves a chicken; the other, Julius Caesar. In both instances, we are asked: Why? Why did the chicken cross the road? Why did Julius Caesar cross the Rubicon? What were they thinking? Or: Were they thinking? In the first instance, we are not expected to answer. How could we possibly know what a chicken is thinking? But in the second, we are. Where to begin?

The British philosopher of history R. G. Collingwood devoted much of his life to these issues. The author of many books, notably The Idea of History, which was published posthumously, he is best remembered for a single, powerful idea: the re-enactment of history.