My seven-year-old, starting school in New York, mentioned to his class that he spoke Irish as well as English. When the teacher asked who else spoke a second language, a forest of hands shot up. Some - the biggest group - spoke Spanish, some Portuguese, some French. One kid spoke Ibo, another, as he proudly announced, "Jamaican patois".
Later that day, when we discovered that our other son's French teacher is Russian, I began to sense for the first time what it means to live in a truly multi-cultural society.
To live in New York is to be immersed in daily contact with people from, literally, all over the world. The barber who cut my hair last week is from Tashkent in Uzbekistan. The driver who drove me from the airport is from Jordan. The last two babysitters we hired are from Morocco and Kenya. To take the lift in our apartment block, to go into a subway carriage, to ride in the cable car that joins Roosevelt Island, where we live, to Manhattan, is to enter a linguistic confluence where the languages of diverse continents feed into a babbling stream of human sound.
And there is, in this, an enormous sense of relief. If you come from a society as homogeneous, as ethnically paranoid as Ireland, you feel liberated. You savour the variety, the richness, the sheer abundance of this great human array. You enjoy the range of food, of music, of cultural events that it generates.
And you learn things about yourself. You become aware of the markers of identity you usually take for granted - your skin colour, your speech patterns, your assumptions, your points of reference. You don't lose yourself in the crowd - you find yourself, see your own cultural distinctiveness more clearly by way of contrast.
At school, both of my sons are in classes in which the majority of the pupils are black or Hispanic. You quickly realise, of course, what a crude measure skin colour is - some of the black kids are native New Yorkers, some are West Indian, some African. They have different first languages. It makes about as much sense to categorise them together as it would to file Australians and Russians as members of the same ethnic group.
But you also realise how good it is for Irish kids to get some sense of what it means to belong to a racial minority. And how good it is when the majority is open, tolerant and accepting.
Walking down the street the other day, we met a group of black kids standing around on some steps, nattering away. As we passed them by, a few of them beamed at my eldest, translucently white, son and called out "Hi, Sam". Those two syllables lifted my heart. And the pleasure they gave me brought to the surface the unspoken fears that had just been dispelled.
What if they shun my kids? What if they're subjected to racial taunts? How easy would it be, even without any explicit threat or insult, to send out signals of exclusion? And how much misery could those small signals trigger in the mind of a child?
Maybe, in Dublin or Cork or Shannon, an African or a Romanian kid would be treated with the same kind of easy-going acceptance. Maybe their parents would have their fears calmed in the same way. Maybe those little, silent arrows of contempt and exclusion wouldn't be in the air. Maybe - but maybe not.
If they are not there, it's small thanks to officialdom or to some sections of the Irish media. Could anyone watching the recent treatment of refugees and migrants in Dublin, forced to queue for hours in the rain outside the Department of Justice, be surprised if Irish children were picking up bad vibrations about the strangers in their midst?
In the course of moving to New York in recent months, I've encountered my fair share of US bureaucracy. I've learned about immigration laws. I've been warned of the dangers of being deported for minor, even inadvertent breaches of regulations. I've experienced the delays, the seeming indifference of the system, the frustration, the sense of absolute powerlessness.
And I've been aware that I've experienced all of this in a position of immense privilege. I'm not fleeing from poverty or repression. I have a home to return to. I know the language. I had a Washington lawyer working on my behalf, paid for by my prospective employers. And whenever people in Dublin asked me about how I was getting on with the immigration authorities, and I explained my problems, they were sympathetic. How can these bureaucrats behave like this? How can those right-wing politicians in Congress pass all these laws without thinking of their effect on ordinary people?
The absolute assumption was that an Irish person should have a right to go and work in the US. Yet it's not an assumption we always apply to other people coming to Ireland.
One of the reasons we don't do so is that immigration is so often defined, even by those who are sympathetic to outsiders, as a problem. Good news is hardly news at all, so "the problem of immigration" is defined by tensions, illegalities, hostilities. How often do we reflect on the ordinary, everyday norm - that immigration is not a problem but a blessing?
How often do we hear about, for example, the way the influx of Ugandan Asians to the English midlands in the 1970s rescued a city like Leicester from what seemed to be terminal decline and turned dying inner cities into thriving communities? How often do we remember that without wave after wave of immigrants, a great city like New York would in all probability be no more than a provincial backwater?
Slowly, inevitably, Ireland will in the coming decades evolve into a multi-ethnic and multi-cultural society. Like every other country that has joined the small club of the developed world, it will attract people from elsewhere looking for a better life. This should make us proud. But whether we greet it with pride or hostility, it will certainly happen.
Our attitude to these changes will, however, shape the way they happen. If we continue to treat immigration only as a problem, then we will experience it as a problem. If we become defensive, surly and grudging in our attitudes to outsiders, then we will generate exactly the kind of tensions we purport to fear. No one would deny that immigration, like any other social change, needs to be managed and prepared for. No one would suggest that there is no need for laws, processes and policies. But underlying those policies must be a memory of the experience of Irish people over the generations.
Millions of us have found, in the cities of Britain and the US, that cultural diversity is one of the great pleasures of modern urban life. Millions have been glad to live in cities where their own presence is seen as a welcome addition to the rich weave of society.
Millions have been proud of the fact that, by their presence, they have enriched the economies of the places they have come to. In this one respect at least, New York, in part an Irish creation, really does offer the sense of a future that works.