As everyone knows, Sherlock Holmes, gentleman sleuth and mastermind, died in 1891 at Reichenbach Falls in Switzerland. In “The Final Problem,” Arthur Conan Doyle describes Holmes struggling with his arch nemesis Professor Moriarty, with both men plunging to their deaths in the end.

Except, as everyone also knows, he didn’t. Holmes returns in “The Adventure of the Empty House,” explaining that he’d been wandering the world for the past three years, traveling to such places as Italy, Iran, and Tibet. (Hmm, reminds me of someone… who can it be?)​

And how did he survive his duel with Moriarty? How did he survive the long fall?

2016 has turned into a year of walls. Late last year Hungary built a fence on its southern borders to keep out refugees. Last month the British began building a wall in Calais, France, also to block migrants. It wasn’t that long ago when the English Channel was good enough. And of course, throughout the year we have been subjected to a certain presidential candidate’s repeated promise of building a “big, beautiful wall” on the U.S.-Mexican border, with the fanciful proviso that Mexico would pay for it.

Well, if you’re thinking about building a big, beautiful wall to keep out foreigners, you might want to consult the Chinese. I hear that they have some experience in the matter.

According to the “Records of the Grand Historian” by Sima Qian, written in the 1st century B.C., what we now know as the Great Wall of China began as a series of disconnected fortifications. The northern members of the Warring States, a series of seven kingdoms that divided China from the 5th to the 3rd century B.C., had constructed them to keep out barbarian tribes from the north. ​

I’d like to think that Voltaire would be shocked to learn that the merits of vaccination remain up for debate, or rather are up for debate once again, nearly three centuries after he wrote extolling the practice.

From 1726 to 1729, the great Enlightenment Philosophe lived in England. Drawing on experiences from these years, in 1733 he published a volume of essays now known as Letters on the English or Letters on the English Nation. Letters, because each essay was written as though a letter addressed to his fellow French. Covering a wide range of topics from Westminster parliamentarianism to Isaac Newton to Alexander Pope, the Letters generally presented the British in a favorable light in contrast to the French. They were, in a way, well-intentioned propaganda to goad the French into catching up with their rivals across the Channel wherever, in Voltaire’s view, they had fallen behind.

And in Letter XI, Voltaire addressed the practice of inoculation or vaccination. In his telling, Lady Wortley Montague, wife of an ambassador to the Sublime Porte of Ottoman Turkey, brought knowledge of smallpox inoculation back with her to Britain, where the practice was now widespread.

In the Islamic tradition, the Quran is believed to be a recitation that the Prophet Mohammed made under divine inspiration. The angel Gabriel or Jibreel (he of the Annunciation in Christian tradition) is believed to have given him the text. Therefore Mohammed is not considered the author of the Quran but only a conduit for the divine.​

But the words and deeds of Mohammed when not divinely inspired are also important to Islam. A report describing such words and deeds is called a hadith (Arabic: حديث). And in fact, hadiths are the source of many important Islamic teachings, including rules relating to prayer.

It is sometimes pointed out that Steve Jobs, American titan, was the son of a Syrian immigrant. It is also often pointed out that the grudging European and American responses to Syrian refugees today parallel the American response to Jewish refugees from Europe on the eve of the Holocaust, down to ships full of desperate men, women, and children being turned away.

But few seem to be recalling that the greatest American (fictional) hero of all, Superman, was conceived as a Jewish refugee. Perhaps doing so would seem to trivialize the very serious public debate. But our imagination, in which we invest our deepest yearnings, is as good a moral compass as any.

Perhaps ironically, Superman’s Judaism is actually well-documented. Several books have been written spelling out the case for Clark Kent as an Ashkenazi Jew, with titles like “Up, Up and Oy Vey,” “From Krakow to Krypton,” and “Superman Is Jewish?” Here, then, are the basic facts: 

Yesterday Hungarians held a referendum on the resettlement of Middle Eastern refugees in Europe, which of course has been a subject of great and often ugly controversy.

History may not repeat itself exactly, but it rhymes. The Romans dealt with a refugee crisis once, and it almost destroyed the empire. In fact, in a way it did, indirectly leading to the final downfall of the Western Empire in 476.

The real beginning of the story, according to Edward Gibbon, happened on the borders of China. At the end of the First Century A.D., after many years of war, the Chinese finally defeated the Huns. This was the event that led the subject of my book, Gan Ying, a veteran of the Hunnic wars, to depart on a mission to Rome. But the same event also caused many of the Huns to begin migrating westward.

​Eventually one group of Huns, “a race savage beyond all parallel” according to Roman historian Ammianus Marcellinus, marched into the territory of the Goths in what is now southern Russia and Eastern Europe and defeated them. The Goths fled their homeland and, in 376, amassed on the banks of the Danube River, the border of the Roman Empire. Here,