It’s impossible to characterize a historical period before it’s over, but I think one plausible name for our era will be the Age of the Charlatan. Everywhere you turn there seems to be some kind of quack or confidence man catering to an eager audience: Fox News hosts like Sean Hannity have moved from pushing ill-informed opinion to flat-out conspiracy mongering; pickup artists sell “tried and true” methods for isolated young men to seduce women; and sophists pass off stale pedantries as dark and radical thought, selling millions of books in the process. In politics, too, our highest office is occupied by a man who was once aptly called a “carnival barker.”

What makes us so vulnerable to charlatans today? In part it’s the complexity of the modern world and the rate of technological and social change: Quackery provides what Saul Bellow once called a “five-cent synthesis,” boiling down the chaotic tangle of the age into simple nostrums. Modern life bombards us into exhaustion and boredom as much as anxiety; sometimes we are just looking for entertainment in a surprising notion.

But I think we have also forgotten that charlatans exist, or that they exist for us, and not just for other people. We all like to think of ourselves as pretty sharp, and the term itself sounds old-fashioned: We laugh at how people in the past fell for phony remedies, but never suppose we could fall for the same tricks.

A largely forgotten book from an earlier and similarly discontented era offers insight. In 1937, a journalist named Grete De Francesco published a volume called “Die Macht des Charlatans,” or “The Power of the Charlatan,” a history of the quacks and mountebanks that roamed Europe in the Middle Ages and early modern period. She was Austrian and had been a writer for the Frankfurter Zeitung, but with the Nazis in power, it makes sense that her book about demagogues’ manipulating crowds was published in Switzerland.