Winner of the 2014 European Book Prize.

A "United States of Europe," Winston Churchill proposed in 1946, could "as if by a miracle transform" that "turbulent and mighty continent." "In this way only," he continued, "will hundreds of millions of toilers be able to regain the simple joys and hopes which make life worth living."

Today, nearly seventy years later, over 500 million people live in the member states of the European Union - a greater number than in any other political community save for China and India. The currency of the Union, the euro, is used...