Since the end of World War II, when the U.S. emerged as an economic and military superpower, the English language has been punching way above its weight. Today 1.5 billion people speak English, fewer than 400 million of whom are native speakers. It is the language in which the Brazilians do business with the Dutch and the Japanese do business with the Italians. English is an official language of the United Nations, the World Trade Organization, the International Criminal Court and NATO. Political activists from North Africa to Myanmar tweet in it.

A growing number of multinational companies are adopting English as their official language, with significant consequences for their workers. In 2010, Japan’s largest online retailer, Rakuten, announced that all employees had to take an exam to demonstrate English proficiency within two years or risk being dismissed or demoted. The majority of Rakuten’s workforce couldn’t make the cut, and by 2018, 80% of the new engineers in its Tokyo offices were non-Japanese. Some of those who remained claimed they felt like “expats” in their own country.

Using a common language has undoubtedly facilitated teamwork and knowledge-sharing across countries. The Pfizer vaccine against Covid-19, the first to be rolled out in Europe and North America, was the product of a partnership between the U.S. pharmaceutical company Pfizer and the German biotech company BioNTech. Without the use of English as a common language, it might not have been developed with such unprecedented speed.

At the same time, relying solely on English inevitably limits the world’s collective knowledge base. Scientists and scholars who lack fluency in English are often frozen out of teaching, publication, speaking and networking opportunities essential to advancing their careers. The consequences for students are equally disturbing. Universities around the world use English to internationalize, improve their rankings and prepare students for the global economy.

Yet programs taught in English inevitably favor students from educated families who have benefited from years of high-level English instruction. To make higher education more accessible, Denmark cut back in 2018 on the number of courses taught in English, and the Netherlands is considering similar action.

For native English speakers, on the other hand, the world-wide spread of the language comes with many benefits. Travelers roam the globe with greater ease; political and business leaders can communicate directly; students can benefit from study-abroad programs. It’s easy for Americans, along with the British, Canadians, Australians and others, to conclude that learning another language isn’t worth the effort. If the world is speaking English, why bother?

This indifference or resistance to learning other languages is a recurring cause of finger-pointing in the English-language press and among globally aware policy makers. A century ago, 89% of four-year colleges in the U.S. required previous study of a language other than English for admission. By 2020, that number had dropped to 25%.

Some states have eliminated language requirements for high school students: In Oklahoma and Texas they can opt instead for computer coding, while in California they can choose visual and performing arts classes or technical education. One in five Americans speaks a language other than English at home, yet we have abandoned building our foreign language skills and ceded the advantages of being a multilingual country.

The idea that this is not a problem because “everyone speaks English” is far from the truth. Only a quarter of the world’s population is minimally competent in English, and even those who claim to have conversational skills often don’t operate at a very high level of proficiency. Monolingual English-speakers can’t effectively communicate with three-quarters of the world. That means they can’t tap into knowledge created in those languages or take advantage of business opportunities.

More disturbingly, they risk becoming politically and culturally isolated. English is the most popular language online, used by almost 26% of people on the internet, according to a January 2020 study. But Chinese isn’t far behind at 19%, and a substantial amount of internet communication takes place in Spanish and Arabic. While apps like Apple’s Gentle Reader make foreign language newspapers and magazines instantly available in English on computers and iPhones, the end product is only an imperfect facsimile of what speakers of the original language are absorbing.

Translating spontaneous communication in real time still eludes current technology. Human interpreters are often required in situations that demand on-the-spot decisions, like healthcare and national security, where relying on a machine could prove risky or strategically unfeasible. The global price to be paid for a misinterpreted phrase can be extraordinarily high, causing financial loss and reputational harm for individuals, companies and even countries. The current health crisis has especially revealed the limitations of machine translation and the false sense of comfort with English monolingualism that technology has created.

In the long term, another language may push English aside as the world’s lingua franca, but we can only speculate about which one. French is unlikely to make much headway beyond France’s former colonies. Mandarin Chinese is often mentioned as a likely successor, but China’s repressive policies are dimming its appeal in many parts of the world. Spanish, which is spoken on five continents, might prove the most viable candidate; it is already the second most common language in the U.S.

For now, policy makers around the world have to deal with the opportunities and dangers of English. As the global economy reconfigures in a post-pandemic world and countries rethink their transnational alliances, language skills will be essential to achieving a shared vision of the future. Sans doute, English can’t do it all.

Corrections & Amplifications
A significant number of Spanish speakers are present on five continents but not on Australia and Antarctica. An earlier version of this article incorrectly referred to “all five continents.” (Corrected on Dec.1)