At one point in a relentlessly fatuous career, Margaret Thatcher dismissed

Nelson Mandela as ''a terrorist''. Dick Cheney, currently an unreliable heartbeat away from the presidency of the United States, once also voted, in his own country's Congress, against any attempt to liberate the father of the South African nation from incarceration on hellish Robben Island. How times do change.

As arguments go, the neo-con case back then was almost theological. The Thatcher who encouraged the sinking of the Argentine vessel Belgrano might yet, in many basic interpretations of international law, have a moral case to answer. Cheney, as architect and instrument of America's latest war on Iraq, could well do a star turn, one of these days, at a war crimes tribunal. But in the 1970s and 1980s they took Mandela's measure without hesitation. He was a terrorist. So who, and why, are they to talk?

A few years back, in Dublin, I had a long conversation with a distinguished Irish educationalist. The topic was the Belfast middle class and their fixation with A-level results. The professor was very firm about the wastage in young talent in Northern Irish housing schemes, a loss caused by the obsession with testing, standards and job possibilities. Then he did what I took to be his party piece. ''So who's the best education minister Northern Ireland has ever had?'' he asked, teasing.

The distinguished chap, with no whiff of armed republicanism around him, supplied own his answer. The best, most astute, most adventurous and most eager minister for education the province of Northern Ireland had ever possessed, the prof said - and

there was a real relish in the hyperbole - was Mr Martin McGuinness, ''former terrorist godfather''.

The prof was right, as people of all persuasions in Belfast, Derry and elsewhere in Northern Ireland were later happy to concede. McGuinness once controlled the Belfast battalion of the Provos: of that there is no serious doubt. Once upon a time, he commanded people who killed other people, generally without a hint of mercy, for political ends. Yet there he was, suddenly a modest but talented regional education minister, doing the dull stuff and doing it well.

It tends to be the fate of terrorists, or at least the fate of those who survive their shabby trade. Sometimes they wind up as heads of government. Sometimes they grow old and pompous in their dotage What is persistently clear,

nevertheless, is that yesterday's

psychopaths/freedom fighters have a tendency to be the people with whom, one day, elected governments have to do business.

This demonstrable historical fact presents us with both a problem and an idea. The problem is simple. It is summarised in the litany offered by the democracies of the west when they face political violence: can you, should you, ever negotiate with the practioners of terrorism? Reverse the paradox and it amounts to a much better question: why not?

At the human and simplistic level, you can spell it out easily: two female Italian aid workers escaped kidnap, or worse, in Iraq recently because their government cut a squalid deal and paid a ransom for their release. In contrast - and there is no pretty way of putting this - Ken Bigley was killed because Her Majesty's government does not, allegedly, cut such deals.

But why not? In most circles, the question qualifies as stupid. You do not deal with terrorists because, clearly, it only encourages them. As with any form of blackmail, it is suicidal (in this case, literally so) to succumb to a criminal's demands. Put aside the fact that two Italian women happen to be alive and Mr Bigley happens to be dead: what does a resolute refusal actually achieve? The theory of conflict resolution is neither new nor complicated. It turns on the simple idea that everyone has, to some degree, a point of view. It may not be pleasing to imagine that the killers of Ken Bigley have a decent opinion, a sincere credo or a cause about which any decent person should give a damn. It may even be intolerable to pretend that such individuals can ever occupy our rational universe. They exist, nevertheless, and they have grievances. Do we deal with them or do we, as current British

and American foreign policy seems to suggest, simply kill them all?

The International Criminal Court is an idea the Bush presidency has attempted to destroy. Perhaps concerned at the thought of personal culpability, the incumbent and his White House have scorned the possibility that they, or their subordinates, might be judged by their global peers. Yet as the ''war on terror'' unravels unpredictably, endlessly, it begins to seem obvious that what the world truly needs is a forum in which sheer, bloody and vicious hatred can be addressed.

South Africa, after apartheid, made the attempt with its Truth and Reconciliation Commission. What the world needs now is a larger arena, controlled by the United Nations, in which anyone who needs to can bring a case against any interest - governmental, personal or economic - they feel has done them harm. This would involve ''sitting down with terrorists''. It would also necessitate the oxygen of publicity being given to some disagreeable people. But it would be better, by far, than the slow, bloody wars which beset the planet.

Granted, a Palestinian petition against the state of Israel would involve a lot of windy rhetoric and some nasty language. Accepted, equally, that Ken Bigley's killers would not mount much of a case, coherently, against the unseating of Saddam and the occupation of Iraq. The central point remains, nevertheless, that the people we call terrorists have not taken up cruelty as a mere hobby. They have an argument, a history and, sometimes, a point.

Clearly, the great powers will be less than keen to lend an ear to those who devised 9/11, Bali or Madrid. Britain once said that it would never sit down with those who bombed Brighton. On the terrorist side, equally, there is probably no appetite for talking

to imperialists, Zionists, or ''the Great Satan''. But that only

makes the need for a global

forum more urgent.

It becomes, with luck, a form of reverse psychology. The terrorist who refuses the opportunity to make his case in the court of international opinion forfeits his credibility. The government, equally, that cannot explain an Abu Ghraib to the world without propaganda and spin passes judgment on itself. In either case, the point is to bring the propagandists and zealots together with no risk to either party.

The point to realise, always, is that terrorism, bloody and grim, is itself a form of negotiation. An act of terror is the means by which the weak gain leverage. No Iraqi insurgent is about to destroy the United States of America. Endless bombs inflicted on GIs could, nevertheless, sicken the American people. Why not oblige both parties to argue instead? It might not satisfy all concerned, but it will keep them alive for a while longer.

Convene a court, in Switzerland or Swaziland. Give it the imprimatur of the international community, under the protection of a binding treaty. Let everyone

with a grievance bring it forth. It couldn't be worse, could it, than endless war?

Do you agree that we should

negotiate with terrorists. E-mail features@theherald.co.uk with your address and we will publish a selection next week with the The Big Debate.