By rejecting the Lisbon Treaty, Ireland's voters may have thrown the European Union into cri sis, but in a more profound way I am optim istic about Europe. A while ago, I took the train from Paris to Brussels for a meeting at the headquarters of the European Commission. The train was full of people my age - the late thirties - going to Brussels to participate in various EU projects.

I started chatting with my neighbours. Most of the people I spoke with came from more than one cultural background, with two or more nationalities in the family. All of us were at least bilingual, many trilingual or more. My neighbours epitomised the deep cultural change now taking place in Europe. A new generation has grown up, of people born more than a quarter of a century after the end of the Second World War and now moving around Europe to study and work - meeting, dating, marrying and having children with people from other European countries and doing so as a matter of course.

More and more European children are growing up multilingual. They are unlike immigrants born in one culture and having to grow up in another. They are unlike children growing up in a monolingual, monocultural family that happens to be located in a wider multicultural en vironment. For these children, cultural and linguistic diversity is not just a part of the society at large, it is a part of themselves, a novel kind of identity. Multilingualism is becoming an existential condition in Europe, good news for a continent in which national identities have been so powerful and have caused so much tragedy and pain in the past.

This condition also affects our cognitive life. Recent research in developmental psychology shows that bilingual children are quicker to develop an ability to understand the mental states of others. A likely interpretation of these findings is that bilingual children have a more fine-grained ability to understand their social environment and, in particular, a greater awareness that different people may represent reality in different ways. My bilingual six-year-old son makes mistakes in French and Italian but never confuses contexts in which it is more appropriate to use one language than the other.

I believe that European multilingualism will help produce a new generation of children whose tolerance of diverse cultures will be built from within, not learned as a social norm.

All this may be wishful thinking, projecting my own personal trajectory on the future of Europe. But I can't help thinking that being multilingual is the best and cheapest antidote to cultural intolerance, as well as a way of going beyond the empty label of multiculturalism by experiencing a plural culture from within. And, of course, this is not just a European issue.

Gloria Origgi is an Italian philosopher based in Paris. Taken from "What Are You Optimistic About?" (edited by John Brockman, Pocket Books)