There are two certainties about our future: almost all of us will be poorer, and the deadliest canker threatening many people will be self-pity. We all succumb sometimes, but it will be a yardstick of courage, among society’s “haves,” to resist feeling sorry for ourselves.

It helps to know some past, which is where historians such as me spend our working lives. I study the great upheavals of the 20th century, but others live with the Roman Empire, the Middle Ages, and so forth.