What exactly do we celebrate on Saint Patrick's Day? The obvious things of course: the arrival of spring, the pleasure of a day off, the timeless Celtic ritual of jeering good-naturedly at the high school marching band from Minnesota or Delaware, the goodness of the holy man who gave us an annual excuse for a knees-up.
But there are other things as well and one of them is the right to emigrate. Saint Patrick's Day is, above all, an emigrant festival. As such, it has always had a slight edge to it. This week, with Bertie Ahern's descent into the territory of Jean-Marie Le Pen and Jorg Haider, that edge is keener than ever.
The only reason that Saint Patrick's Day became more significant than Saint David's, Saint Andrew's or Saint George's was that, for a society that sent out large numbers of migrants, it was important to have a day on which you declared your presence on foreign soil and asserted your right to be there. The first play with the title Saint Patrick's Day goes all the way back to the 1770s.
Written by the Irish playwright Richard Brinsley Sheridan, it is set in England. Though suitably merry and festive, it is also self-consciously defiant. Its Irish hero overcomes the prejudices of a thick-headed English justice of the peace with a particular loathing for the Irish.
In American cities, the Saint Patrick's Day parade, which had begun in the 1820s as a small-scale celebration, became a mass event in the 1850s as a direct riposte to the Le Pens and Haiders of the day, who frequently described the Irish as "the mongrel mass of ignorance and crime and superstition" who were "utterly unfit for the common courtesies and decencies of life".
The parade itself was often construed in the press as an example of this kind of barbarity. As I write, I'm looking at a cartoon from Harper's Weekly in 1867. Headed "Saint Patrick's Day 1867", it has the words "Rum" and "Blood" imprinted in alternate corners. Within the main frame, ape-like Irishmen and boys in green sashes are assaulting handsome American policemen with their boots and shillelaghs.
This element of defiant pride meant that in some circumstances the parade could be used to express similar feelings by other groups who had been abused and oppressed. In the 1980s, for example, the black population of the island of Montserrat in the West Indies turned their Saint Patrick's Day into a six-day festival commemorating a revolt by slaves against their Irish masters whom they tried to overthrow on Saint Patrick's Day 1768. As the island's government declared: "When we celebrate Saint Patrick's Day we think not only of the Irish patron saint but more importantly of those first Montserratians - Negro slaves - who fought for the freedom of our people."
How bitterly ironic, then, that if any those Montserratians, whose island has recently been devastated by a volcano, sought refuge here now they would be met by a Taoiseach who wants to incarcerate refugees in prison camps and a Minister for Justice who wants to put them on ships.
Bertie Ahern's repeated effusions of admiration for the Australian system of incarcerating asylum-seekers in privately run prisons and John O'Donoghue's hints about what would be, in effect, floating prisons are the exact contemporary equivalents of the anti-Irish abuse of the 19th century. As John Bruton pointed out, both men are using thinly-veiled codes to suggest that refugees are unclean, dangerous creatures unfit to mix in ordinary Irish society.
And as Ruairi Quinn said, both have engaged in the most brazen dishonesty concerning Ireland's international obligations under UN agreements. John O'Donoghue claimed in 1997 that the United Nations High Commission for Refugees had described Ireland's system for dealing with asylum-seekers as a model for other states, a claim that was wildly untrue. Now this week Bertie Ahern has claimed from Australia that the UNHCR believed that the Irish system was too liberal.
Were it not so reminiscent of John O'Donoghue's previous falsehood, this extraordinary statement could be put down to the effects of jet lag. Instead, it seems to be part of a deliberate policy of undermining the notion that Ireland has international obligations to live up to.
The truth is that the UN's Human Rights Committee has found the Australian practice of effectively treating asylum-seekers as criminals - the practice which Bertie Ahern so admires - to be a breach of international law. Mandatory detention of asylum-seekers is simply a euphemism for imprisonment without trial for people who may be fleeing from torture, violence and abuse. It is, in other words, internment.
The notion that we in Ireland would similarly intern asylum-seekers - many of them, let us remember, vulnerable children - is so cruelly outlandish that it can only be seen as a cynical attempt to exploit the kind of racism and xenophobia that have been so electorally successful in much of Europe. I don't believe for a moment that Bertie Ahern is actually thinking of carrying out such a policy, or that Irish public morality has degenerated to a point where this kind of system would be tolerable. But by suggesting that he might do it, the Taoiseach is pandering to what may soon emerge as the racist vote.
It's probably just as well then that almost all of the members of the Government are out of the State today. Watching them celebrate a festival whose roots are in the defiance of prejudice and the honouring of migrants while they line up with history's Know Nothings and the scrawlers of "No Irish Need Apply" signs would be some spectacle.
Listening to hypocritical cant about the joys of Diaspora and the achievements of exile would be more sick-making than a gallon of green beer. We can thank Saint Patrick, indeed, that at least for today, most of the snakes have been driven out of Ireland.
He, meanwhile, can say a prayer of thanks that Bertie Ahern and John O'Donoghue weren't around in 432 when a bedraggled former slave arrived on our shores seeking to make a life among us. Then again, seeing how little impact his Christianity now has on our public culture, he might as well not have bothered.