It is hard to believe the Northern Ireland peace process may yet founder. Such a collapse would affront many histories of evolution from civil war to political peace all over the world. The process has come so far. Yet this, of course, is the very reason why, in the end game, the deal may not stick. The rejectionism that has sustained the war for 30 years resists the notion that the peace momentum must lead somewhere. The end is the time when it is put to the only test that counts. The closer this comes, the harder it gets. The two intransigencies on display here are no longer contesting power, still less, in any essential way, religion. Fundamentally, they're about attitudes to the prospect of mutual surrender. The surrenders that have got us this far have been substantial already. But there is just one more surrender to make, the decisive one, which really could liquidate, in the practical world, the violence of the decades. After the years of civil war, in which the ceaseless flow of calumnies and special pleading and implanted deviousness always confused the issue, two forms of real sincerity are now ranged against each other. That is why the challenge may defeat them.  On the republican side, there is a sincere belief that the war is over. The guns are silent, the Semtex is buried. Sinn Fein-IRA, the most disciplined political organisation in Europe, has embarked on a political track which its leaders, Gerry Adams and Martin McGuinness, know they can carry through. They have   taken the republicans very far. Even the IRA, when speaking solo - if namelessly - for itself, asserts that its commitment to the process is "total", and says it wants "a permanent peace".  Look at what is happening, says Mr Adams. Irish republicanism has given up its constitutional claim to the north. We have carried the terrorists a long way, as the IRA statement proves. We are sitting down and starting to run the country rather than destroying it. We talk with the hated British government. All this shows our renunciation of the past. It is a fantastic, constructive shift. We have chosen a different track, which we can sustain up to and through the deadline of May 22, even against forays by our dissident groups.  The credence to be given to this, moreover, is greater for the length of time over which we resisted it. When we do a U-turn, we are serious. The Good Friday agreement prescribes arms decommissioning by May, but that is not, at bottom, the point. Decommissioning, Mr Adams concedes, is achievable. But the point, he says, is that de facto the war has stopped. To disregard such progress towards an appointment with destiny in May would be to imperil what has been done under the shadow of the undecommissioned, but unused, gun. Let this objectively existing reality be sustained.  On the unionists' side one recognises the same brand of sincerity. By historic standards it is just as startling. The reality of peace has drawn them into credible   politics. They have accepted their republican enemies into power. They are starting to run the place together. They have surmounted the vast obstacles placed in the unionist psyche by memory and worse.  They are still goaded by their own hate-filled supporters, including bits of the London press, who have operated from the start in the hope that the deal will fail, and characterise it relentlessly as a blueprint for gangster rule. These play to the bloody inheritance which unionists believe they alone endured. But the leadership, courageously, has got past that. It sees further. The name is statesmanship. Along with the other partners in Good Friday -London, Dublin, Washington - David Trimble has manoeuvred round the easy negatives which history endorses and on which so many decades of fatalistic rumination have been lavished.   T o this state of mind, the republican analysis could seem quite attractive. It is, after all, true. The war seems to be over. The unionists have taken their own steps towards underwriting this happy development. They have lived with the procrasti nation over decommissioning. They will swallow most of the Patten report on the RUC. The hatreds simmer, and Mr Trimble's enemies gather. But on the unionist side, there have been the same successes as on Sinn Fein's, for realism over viscera. Why can't they take one more stride along this fruitful road - which already leads so far away from the dismal past - even though General de Chastelaine cannot yet report any decommissioning by the IRA?  To most outsiders, not steeped in the all-consuming obsessionalism of Ulster politics, this must be the way it seems. We don't diminish the importance of the arms. We read the agreement, and we know weapons have to start going. We can see the mistrust that has yet to be de-contaminated by the sincerity and the compromises already made. Having swallowed the camel, aren't unionists straining at the gnat? It is a tempting proposition. One more, final-final deadline in May - as against the possible ruination of a process that has already changed so much. When the unionists insist on Mr Trimble keeping his promise to resign if the gnat is not delivered, will the blood not be on their hands?  People say that at this delicate time, it is insensitive to be talking about blame. Republicans, pointing to the absence of war, are particularly prone to that opinion. Mr Adams's optimism, as I say, is sincere enough; and it is remarkable how swiftly his whole demeanour has   changed into that of a governing politician. But especially in this delicate end game, it is important not to mistake the matter. No amount of bluster, or axiomatic assertion, or small-print casuistry, or pseudo-statesmanship can obscure the truth that in the hour of crisis it is the republicans who are on trial.  Realpolitik has done us proud, but there is a limit to its virtues and we have reached it. Basking in the new-found success of Adams's strategy, Sinn Fein-IRA have to take their own small step and make a decisive - though entirely incomplete - surrender. The symbolic gesture, the token handover, is the substantively meaningless but politically crucial event now required if further credence is to be attached to the promises of peace. Only in the vocabulary of IRA self- regard, which demands that their arms and nobody else's are inalienable, does that appear unreasonable.  They say they are serious about peace. Let us believe they mean it, and will continue to deliver - even as they continue to hold, as everyone will know, a secret arsenal. Unfortunately, in the real world, it is not enough to make the promise. The unbearable discomfort of a necessary gesture is required, as proof that republicanism has really entered the world it chose some time ago to belong to.  Everything else, at this late stage, is bunker piety, which not only Ulster unionists will rightly curse.