Currencies will plummet, markets will crash and there will be rioting on the streets of capitals. Followed, perhaps, by the outbreak of war. Several times last week while reading about the possible consequences of Britain’s decision to leave the EU I had a powerful sense of déjà vu. But how can that be possible if Brexit is, as I was repeatedly assured, an event without precedent in my lifetime? Even more puzzling, why, if only half of such apocalyptic predictions are to be taken seriously, am I not particularly worried? Could it be because the whole thing has more than...