Not only are citizens ignorant about essential scientific, civic and cultural knowledge, she said, but they also don’t think it matters.

Image Susan Jacoby, author of The Age of American Unreason. Credit... Chester Higgins Jr./The New York Times

She pointed to a 2006 National Geographic poll that found nearly half of 18- to 24-year-olds don’t think it is necessary or important to know where countries in the news are located. So more than three years into the Iraq war, only 23 percent of those with some college could locate Iraq, Iran, Saudi Arabia and Israel on a map.

Ms. Jacoby, dressed in a bright red turtleneck with lipstick to match, was sitting, appropriately, in that temple of knowledge, the New York Public Library’s majestic Beaux Arts building on Fifth Avenue. The author of seven other books, she was a fellow at the library when she first got the idea for this book back in 2001, on 9/11.

Walking home to her Upper East Side apartment, she said, overwhelmed and confused, she stopped at a bar. As she sipped her bloody mary, she quietly listened to two men, neatly dressed in suits. For a second she thought they were going to compare that day’s horrifying attack to the Japanese bombing in 1941 that blew America into World War II:

“This is just like Pearl Harbor,” one of the men said.

The other asked, “What is Pearl Harbor?”

“That was when the Vietnamese dropped bombs in a harbor, and it started the Vietnam War,” the first man replied.

At that moment, Ms. Jacoby said, “I decided to write this book.”

Ms. Jacoby doesn’t expect to revolutionize the nation’s educational system or cause millions of Americans to switch off “American Idol” and pick up Schopenhauer. But she would like to start a conversation about why the United States seems particularly vulnerable to such a virulent strain of anti-intellectualism. After all, “the empire of infotainment doesn’t stop at the American border,” she said, yet students in many other countries consistently outperform American students in science, math and reading on comparative tests.

In part, she lays the blame on a failing educational system. “Although people are going to school more and more years, there’s no evidence that they know more,” she said.