Ever since I read Fortune’s Formula I have been a fan of William Poundstone’s work. He has the ability to take topics I would dismiss in a couple of paragraphs and create page-turning books out of them. Head in the Cloud: Why Knowing Things Still Matters When Facts Are So Easy to Look Up (Little, Brown), his latest effort, deals with a subject I touched on in my review of A Field Guide to Lies. It’s a tricky subject, one that inevitably leads to charges of elitism. But these charges are misplaced. Knowing stuff really does matter.

Public ignorance is so well documented that it has become a staple of late-night comedy. Who’s the vice president of the United States? In 2010 41% of adult Americans didn’t know (and this finding came from a poll by the Pew Research Center, not a test for dementia).

Poundstone undertook his own research into what the typical American (at least one with an Internet connection) does and does not know. He used Internet panel surveys, which means that theoretically participants could cheat, although he requested that they not look up answers. “But,” he writes, “most of the surveys were filled out quickly, scarcely allowing time to research answers. The overall results—which often show a shockingly low state of public knowledge—argue against cheating being much of a factor.” (For readers who want to know if they’re “smarter than …,” most of the book’s chapters include sample questions.)

The book is divided into three parts: the Dunning-Kruger effect, the knowledge premium, and strategies for a culturally illiterate world.

From the section on the Dunning-Kruger effect (which, if you don’t know, says that “those most lacking in knowledge and skills are least able to appreciate that lack”) I’ve selected one example of the consequences of ignorance, which also showcases Poundstone’s style. In 2014, as Russians were entering Crimea, three political scientists ran a survey asking Americans to locate Ukraine on a world map. Only one in six clicked within Ukraine’s borders.

Head in the Cloud: Why Knowing Things Still Matters When Facts Are So Easy to Look UpOther guesses were, literally, all over the map. There were clicks in every populated continent, with a cluster in Greenland and a few within the continental United States. There were a few clicks in the world’s oceans. They weren’t on an island. Either the clickers imagined Ukraine to be some lost Atlantis or they couldn’t tell which part of a world map was water and which was land.

Here’s the upshot. The researchers found that, the farther a person’s guess was from the actual location of Ukraine, the more likely it was that that person supported a US military intervention in Ukraine.

There’s a reason why war rooms have maps. Geography helps determine whether a military occupation is essential to national security or immaterial to it; feasible or ruinously costly. A decision about sending troops to war in Ukraine ought to be informed by wonkish details such as whether Ukraine is in the United States or is a foreign country and whether Ukraine is on land or under water.

Okay, people are often frightfully ignorant, but, one might ask, so what? We’re not going to name someone who doesn’t know where Ukraine is secretary of defense. (Although we’ve had and continue to have our fair share of political candidates whose knowledge of the world is, shall we say, somewhat deficient.)

Poundstone found that there is a strong correlation between income and performance on quizzes of general knowledge and some correlations between income and specialized areas of knowledge. (If you want to know what you can skip learning about and not have your income suffer, try grammar, slang, sex, and religion.) And “general factual knowledge has an effect above and beyond educational level in predicting income.”

As is usually the case, the section of the book on strategies for dealing with ignorance is the weakest. But it’s a critically important issue to confront. In one of the starkest examples, Poundstone asked his panelists whether they would push a button that made them a billionaire but killed a random stranger, assuming no one knew they were responsible for the death. “Nearly one in five Americans said they’d push that button. Those who scored low on a general-knowledge quiz were more likely to push the button, and yes answers were almost twice as common (36 percent) among those who couldn’t name the year of the 9/11 World Trade Center attacks.” If you were that random stranger, wouldn’t you want the person with the button to have broad general knowledge? Think about it the next time you say, “I don’t have to know x or y, I can just look it up.”