You ask what, specifically, is wrong with this statement.

One thing about it is right. Summers is writing about the future of American universities, not about the entire educational system. In that context, it is true that teaching foreign languages from scratch to eighteen-to-twenty-two-year-olds is costly and not very efficient. A far better investment would be to teach foreign languages to eight-to-twelve-year-olds—they learn faster, and their teachers don’t have professional salaries. But one thing is pure sleight of rhetorical hand. “The fragmentation of languages” following “emergence” and “progress” makes it sound as though linguistic diversity is getting worse. There is no evidence whatever that this is so. Linguistic diversity is as old as language itself.

The second sentence presupposes that at present or at some recent time it is or was essential to master a language in order to do business in Asia, to treat patients in Africa, or to resolve the situation in the Middle East. The presupposition is fantastical. Over the past century, far too few American or European adventurers, administrators, and peacemakers were, or are, sufficiently competent in Chinese, Vietnamese, Japanese, Wolof, Hausa, Swahili, Arabic, or Ivrit to have any real clue as to what their interlocutors wanted or needed. The only real point Summers is making, one that is widely shared by the ignorant, is that English is enough, because everybody is now learning English. That is where it gets interesting. Allow me to expand on this, since I was in Geneva recently talking to interpreters and teachers of translation at the E.T.I. [the University of Geneva’s School of Translation and Interpretation] about this very problem:

English speakers are now a relatively small minority among global users of English. However, the majority of users of English do not write or speak “English” but, rather, a vehicular tongue called I.E. (International English) which is highly inflected by the (very diverse) native languages of its users. The effect is that it is often easier to translate a piece of I.E. into a third language if you know the native language of the user—and sometimes it is positively necessary. I.E. is not designed to carry nuance, and for that reason it is often ambiguous and of uncertain meaning. Non-native users of it are perfectly aware of this. All users of I.E. are fluent/native speakers of another language, which they can (and do) use for more important, personal, or subtle kinds of communication (such as inevitably arise in business, diplomacy, and treating the sick). The only people disenfranchised by recourse to I.E. are those native speakers of English who do not have another idiom for side-channel consultation. Hoping that the “imperfect” English used by a large part of the world for functional communication will one day come to resemble “real” English is quite futile. It will diverge more and more, and its dialectal variations are likely to become increasingly distinct.

You ask why learning a foreign language is critical to our educational system.

Where to begin? Maybe with the Romans, who insisted on teaching Greek to all their highborn citizens. Or with the Russian Empire, which taught its élite to speak French. Or the French, who until very recently made everyone learn Latin. Mastery of a foreign language has been a required skill in every Western civilization since time immemorial. Columbus, Descartes, Newton, Euler—find me an important Western thinker in any field, and you’ll find someone who spoke and wrote in at least two languages. Why should we think of abandoning the fountainhead of Western culture? The real impact of this long tradition is, however, not in the field of business or diplomacy or mathematics or exploration; it is because mastery of a foreign language is a prerequisite for understanding how to use your own. That’s why we teach it.

You ask what makes the substantial investment necessary worthwhile.

No great investment is really necessary. Teach it young and it gets learned fast. But no amount of teaching can supply motivation, which is a far more effective pedagogical tool. Motivation can come only from the real world. That’s why it is so important for people with clout, like Larry Summers, to shut up. Many American youngsters are inspired to learn Japanese because they are fans of manga and anime. In my own, now ancient, generation, many British adolescents fell in love with French because of Sartre and Camus. Others got the Russian bug from the excitement caused by Yuri Gagarin and Laika. Language teachers are to some extent prisoners of what’s “hot,” but it’s also their job to find sources of excitement in foreign cultures that will make youngsters want to learn the language.

You ask what would be lost if foreign languages continue to be dropped from the curriculum.

Full command of spoken and written English: to be able to understand what is specific about your own language is a huge advantage if you want to manipulate it with subtlety and effect. International clout: monolingual academic, businessman, diplomat, or taxi-driver is not going to be taken seriously in Tallinn, Mumbai, or Beijing. Or Paris, Frankfurt, or Dubai. Everything else.

You ask when I took up French and why.

In preadolescent depression, around the age of twelve, I realized I was no good at mathematics, art, music, or sport, and as I had a very nice teacher of French I decided, in a rather arbitrary way, that I just had to be good at something. It turned out that I was rather good at French, and so I also learned Latin and German and Russian (the last not very well). Most of what I know properly I learned before I left secondary school. I’ve lived off it for half a century. What continues to engage me is the possibility of sharing this kind of knowledge with young people and seeing them (or at least, some of them) blossom into open-minded and curious global citizens.