Good old Hume, but what exactly does he stand for?

John Hume is the great postwar leader of Irish nationalism. In an age of anger and frustration, he has consistently and effectively opposed violence to achieve nationalist ends. Not only has he forsaken killing, he has also steered clear of the violent language and crude populism that is the currency of politicaldebate in Northern Ireland. Yesterday, as he ruled out an electoral pact between the SDLP and Sinn Fein unless there is an IRA cease-fire, Mr Hume once more established his credentials as a leader who sets strict limits on the methods nationalism may employ.

But try to nail down Mr Hume on where else he stands and you're in trouble. You will be swept up in a whirlwind of dizzying, elliptical language that leaves you little the wiser about his ultimate political aims, beyond talking, reaching agreement and making change with consent. He may be clear on violence, but he is steadfastly unclear about what limits he draws on the ambitions of nationalism. A united Ireland is certainly not ruled out.

Such a vague style is understandable for one seeking to persuade the paramilitaries to lay down their arms. It's best not to dwell too explicitly on how little can be achieved through peaceful politics, for fear that the men of violence will be scared off.

But for a man who seeks to win over Unionism, the vagueness of Mr Hume's agenda is disastrous. The lack of detail in what he eventually seeks creates a vacuum which is rapidly filled from the fertile imaginings of Unionist paranoia. The fact that Mr Hume is even considering an electoral pact with Sinn Fein only fuels such fears.

The chief Unionist fear is cultural obliteration. And, so far, no one has ruled that out in the long run. The Protestants in Northern Ireland have merely been guaranteed the right to stay within the UK as long as the majority in Northern Ireland desires to do so. In short, the Unionists have been promised jam only for today. Meanwhile, those who want a united Ireland have been offered jam some time in the future, when demographics put Unionists in the minority. This apparently democratic formula, part of every Anglo-Irish agreement since Sunningdale in 1973, has failed to produce a meaningful dialogue. Unionists fight a rearguard as they await their demise and Catholics breed for a revolution.

Breaking this paralysis requires a new type of nationalist leader in Northern Ireland, who will explicitly abandon not just violence but all hope of a united Ireland. The next great leader of Irish nationalism must fashion an ideology which meets the need for Ulster Catholics to be Irish, enjoy justice and play an equal role in the running of Northern Ireland, without destroying the Union.

Such a notion may seem fanciful. It sounds as though I am arguing that nationalists should give up being nationalists. I'm not. I am merely saying that nationalists must formally abandon their territorial revanchism. Unless they do so, there is little possibility of coaxing Unionists out of their laager.

A formula for doing so is available, thanks to the Opsahl Commission, which consulted widely in Northern Ireland, before reporting in 1993 on options for a political settlement. It proposed that Catholics should be given equal power with Protestants in today's Northern Ireland. The quid pro quo would be that Protestants would enjoy the same right if they became the minority. And there would be a united Ireland only if a majority of both Protestants and Catholics agreed. In other words, probably never.

For this concession, those desiring to be considered Irish in Northern Ireland would be entitled to enjoy the same advantages and privileges as those terming themselves British.

These recommendations are consistent with the development of nationalist politics in Northern Ireland. John Hume has been a key figure in making that state work for Catholics, rather than merely hoping against hope that one day a united Ireland will be achieved. His leadership of the civil rights movement was crucial in beginning to make Northern Ireland a place where Catholics could feel more at home. And agreements between the British and Irish governments - with their emphasis on consent - have all tended to put off the possibility of a united Ireland in the short term. Everyone with any political nous - even in the IRA - knows that today's real task is to make Northern Ireland function properly for everyone.

So far, however, no one on the nationalist side has had the leadership abilities to abandon explicitly long-term territorial ambitions. Some perhaps are afraid, as Charles Haughey, the former Irish prime minister was, of leaving the IRA alone to bear the torch of unity. At the moment - particularly after the summer marches in Drumcree, when the RUC gave in to loyalist threats of violence - few Catholics have the confidence in a Northern Ireland state to abandon the possibility of a more benign government run from Dublin.

But a genuine settlement between Unionism and nationalism requires a nationalist leap of imagination. It will come sooner or later. Listen to the speeches of Mary Robinson, the Irish President, who travels the world speaking to the diaspora, as she defines an Irish identity that extends beyond the boundaries of the Irish Sea. Like her, the post-millennial Irish nationalist will be explicitly working to establish a way of living, not a new state.