Ireland may be an invention, but the Easter Rising was powerful theatre

I know Dublin only from flying visits. Each visit has the quality of a night of dreams. One scene rapidly overlays another, and the words of a succession of vivid men and women - experienced so fast that I am often left wondering who on earth they were - ring around my head as I wake up.

Last week's visit took the best of two spring days, full of wind, sun and rushing cloud-shadows. But at one moment, I recognised the scene of a real dream which had come to me a few nights before. We were on a low bluff in Phoenix Park, looking across the Liffey towards the Dublin hills, and suddenly the scene was familiar.

For some reason, I dream persistently about a city I have never seen and which has five names. This time I was on a low bluff overlooking this majestic Lwow-Lviv-Lvov-Lemberg-Leopolis, whose river ran among trees between me and the dark hills beyond. To my astonishment, I heard my own voice grandly announcing: "My friend Mendelevich, who has an engineering degree from Chicago, is prepared to construct for our city a gas-powered tramway system..."

And here I stood again. This was Ireland, not Ukraine, and Dublin's traffic congestion will not be cured by anything as Victorian as gas-powered trams. But the reflection of my dream was there, all the same. It was not just in the shape of this view across a river and a city to hills. It was there in the big-headed impatience, in the energy for change, that I felt all around me in Dublin.

The first thing that is changing is the past. That sounds metaphysical. But it is often a process you can touch and see. I was standing above the Liffey because my host had wanted to show me something on the other bank of the river. This was the war memorial, designed by Lutyens, to the Irish dead of the First World War. There is a tall tapering cross, a wall of memory and two domed pavilions which used to contain written rolls of honour, all set in gardens.

Once, explained my host, this place had been overgrown and neglected. Independent Ireland had declared its descent from the 1916 Easter Rising against the British, just 80 years ago this month. As a result, the memory - the reality - of the tens of thousands of Irishmen who fought and died under the flag of Britain and its Empire in the war of 1914-18 became an embarrassing discord. The Lutyens park decayed.

Now it has been restored and cleaned, and put back on the city's mental map. "Ireland is coming to terms with its history," my host said. The day before, he had driven me straight from the airport to another garden of remembrance, in the graveyard behind Arbour Hill jail, where a wall bears the words of the 1916 Proclamation of Independence in English and Gaelic. Under the wall, there are names cut in a stone kerb: the names of those who signed the Proclamation and died for it, whose bodies were cast into quicklime here.

They were so few. At the time, many of the Irish soldiers in the trenches thought that the men and women of the Easter Rising were traitors in German pay. Yet, only a few years later, the new official mythology of independent Ireland was suggesting that German money had been cleaner than British money. The shrine of Irish patriotism in those early decades was not totally exclusive. But those who entered it were requested to keep their voices down, when discussing certain episodes in the past.

Nobody requests that now. For nearly 10 years - certainly since Roy Foster published his Modern Ireland in 1988 - the shrine has been echoing with impious voices. They challenge the old Republican version of Irish liberation, and they laugh at the idea that the centuries of British rule were a "foreign occupation". But the arrival of the "Revisionists" is already an old story. Now they have been put on their mettle by the "Re-Inventers".

These are intellectuals, born out of the world of "cultural studies" and deconstruction, for whom history is not so much a matter of truth or falsehood as a theatre production, a tale to be reviewed for its creative skills and power to convince. Declan Kiberd's brilliant new book, Inventing Ireland, is an example. For him, Ireland is a work of imagination. No process of natural development, no law of self-determination, brought that movement and its victory about. Instead, a small group of clever people persuaded a great number of their fellow countrymen that they were a nation with a destiny. Yeats, Douglas Hyde (promoter of Gaelic), Patrick Pearse, even Wilde and Joyce were among these inventors.

The study of nationalism is now big university business, and students are taught that nations are "imagined communities" which construct their own myths and pasts to justify their existence. That certainly happened in Ireland, as it did all over Europe. But are these forged nations therefore in some way invalid? Not at all, says Kiberd (and I agree with him). Macbeth is not "invalid" because Shakespeare invented it. The Irish nation may have started as a script composed by Yeats, Pearse & Co - but there it is, real enough to fall over.

The Re-Inventers have, in fact, brought back to life a very 19th-century approach to history. If nations are works of art, then artists and intellectuals are more important makers of history than politicians. This is how Czech or Hungarian writers saw their role under the Habsburgs.

And, as far as Ireland is concerned, "re-invention" gives the old Republican myth a new lease of life. The point is no longer whether Ireland really was a passive colony, or whether Ireland really does - in the words of the Easter Proclamation - derive her tradition of nationhood from "dead generations". Never mind how few people actually backed the Volunteers in 1916; the Easter Rising was fantastic street theatre which seized its audience and ran and ran.

But it was fun, this time in Dublin, to find so many confident theories of Ireland wrestling for supremacy. The heroic version of the Liberation Struggle is no longer an orthodoxy, but one toy among others. Everyone has his or her model train - or gas-tram - to push along the rails.

Yet there survives another Ireland which is not a "discourse" but a darkness. While I was in Dublin, the papers and television pictured a very old lady called Sister Xaviera. She had ruled orphanages for half a century; now, generations of grown children were rising up to allege that she had treated them with dreadful physical and mental cruelty, some of which claims she admitted.

Such stories have been coming out of Ireland all my life. Now they are becoming a torrent, as if (I hope) to drain some ancient ulcer. They are about the Catholic Church's endemic temptation to abuse its power. They are about people, mostly young women and children, whose own sense of worthlessness made them accept profound degradation in silence. (And they should remind us, in Britain, that the existence of single mothers who can survive on their own without orphanage or workhouse is not a "problem" but a proud social achievement.)

Like a good tourist, I snatched a look at Jonathan Swift's tomb in St Patrick's to read his epitaph. There he lies, "ubi saeva indignatio" - "where furious outrage can no longer lacerate his heart".

Sister Xaviera comes straight out of Swift's Ireland, which still lays siege to sprightly, thriving Ireland-in-Europe. But if the Revisionists and the Re-Inventors can still find "saeva indignatio" on behalf of living pain as well as of dead imaginings, that siege will fail.