The university is not doing this to attract foreign students. It is doing it mainly for its own students who speak Italian as a first language, but must make their living in a global economy where the players come from everywhere - and they all speak English as a lingua franca.
Many other European universities, especially in Germany, the Low Countries and Scandinavia, have taken the same decision, and the phenomenon is now spreading to Asia. There is a huge shift under way, and it has become extremely rare to meet a scientific researcher or international businessperson who cannot speak fluent English. How else would Peruvians communicate with Chinese?
But wait a minute. Peruvians speak Spanish, the world's second-biggest language, and Chinese has the largest number of native speakers of any language. Why don't they just learn each other's languages?
Because neither language is much use for talking to anybody else. Chinese won't get you very far in Europe, Africa or the Americas - or, indeed, in most of Asia. The same goes for Spanish almost anywhere outside Latin America. Since few people have the time to learn more than one or two foreign languages, we need a single lingua franca that everybody can use with everybody else.
The choice has fallen on English not because it is more beautiful or more expressive, but just because it is already more widespread than any of the other potential candidates.
Mandarin Chinese has been the biggest language by number of speakers for at least the last thousand years, and is now used by close to a billion people, but it has never spread beyond China in any significant way. Spanish, like English, has grown explosively in the past two centuries: each now has over 400 million speakers. But Spanish remains essentially confined to Central and South America and Spain, while English is everywhere.
There is a major power that uses English in every continent except South America: the US in North America, the United Kingdom in Europe, South Africa in Africa, India in Asia, and of course Australia (where the entire continent speaks it). All of that is due to the British empire, which once ruled one-quarter of the world's people. For the same reason, there are several dozen other countries where English is an official language.
Of course, the British empire went into a steep decline almost a century ago, but the superpower that took Britain's place was the United States, another English-speaking country. After another century during which everybody dealing in international business and diplomacy - indeed, any independent traveller who went very far from home - simply had to learn English, the die was cast. English had become the first worldwide lingua franca.
There have been few languages in world history that were spoken by more people as a second language than as a first; English has had that distinction for several decades already. Never before has any language had more people learning it in a given year than it has native speakers; English has probably now broken that record as well.
Most of those learners will never become fully fluent in English, but over the years some hundreds of millions will, including the entire global elite. And the amount of effort that is being invested in learning English is so great that it virtually guarantees that this reality will persist for generations to come.
No other language is threatened by this predominance of English.
Italians are not going to stop speaking Italian to one another, even if they have attended the Politecnico di Milano, and no force on Earth could stop the Chinese or the Arabs from speaking their own language among themselves.
But they will all speak English to foreigners.
