In a multilingual context, as the Swiss one, the immigration of foreign language users and the increasing predominance of English - especially in leading positions - introduce a new debate: Should one introduce a unique lingua franca, despite of the multiligual tradition of Switzerland or should immigrants rather be encouraged to learn the language of the region where they decide to stay? This is the subjet of an article by Georges Lüdi, DYLAN researcher and deputy coordinator, published in the Swiss newspaper "Le Temps". Here you will find the complete version of this article.