The Hillsborough declaration of last Thursday has the potential to destroy the Belfast Agreement and convince militant republicans that the "unarmed struggle" of Gerry Adams can never succeed. Unless in private talks the Sinn Fein leadership has given signals on decommissioning to the two prime ministers - signals that are entirely at odds with what that leadership has been saying in public - it is difficult to understand how Tony Blair and Bertie Ahern could have got it so badly wrong.
The core of the "peace process" that brought about the 1994 ceasefire and the involvement of Sinn Fein in the talks since then has been the alliance of Sinn Fein with the SDLP and the Dublin Government in the pursuit of nationalist objectives. Now, for the first time since this started, Sinn Fein is isolated, abandoned by both the SDLP and the Dublin Government.
The 1998 agreement avoided making the decommissioning of IRA arms a precondition to Sinn Fein's participation in government. This occurred despite demands by the Ulster Unionist Party that it be done, because Sinn Fein insisted that if such a precondition were to be part of the agreement, the whole would be rejected by the republican movement.
In other words, Sinn Fein won on the decommissioning issue in the Belfast Agreement but lost on the issue that is fundamental to its republican ideology: Sinn Fein agreed that the constitutional future of Northern Ireland would be determined by the people of Northern Ireland, not by the people of Ireland as a whole.
Now the Hillsborough declaration reverses the Belfast Agreement on decommissioning. While protesting that decommissioning is not a precondition to Sinn Fein's participation in the new executive, it makes it a precondition to Sinn Fein's participation. And the reality is that if this precondition sticks, Sinn Fein's participation in the new executive becomes impossible, because there will be no decommissioning.
This means either that the executive goes ahead without Sinn Fein participation (it is hard to see how the SDLP could reverse all its commitments on Sinn Fein's participation to allow this to happen, but one never knows) or the Belfast Agreement is "parked" or abandoned.
If the executive goes ahead without Sinn Fein, what argument would there be against those in the republican movement who have argued that the "unarmed struggle" will get nowhere because one can never trust the British government, the Dublin Government or the SDLP? What is the point, they may reasonably say, of entering into political agreements when the parties to such agreements simply disregard them when the heat comes on from the ever-combustible unionist camp?
All this treachery even when the republican movement, in the interests of reaching an accommodation with unionism, abandons the fundamental of its ideology: that only the people of Ireland as a whole have a right to determine the constitutional future of Ireland?
Tony Blair and Bertie Ahern seem well satisfied with their work at Hillsborough. It seems astonishing that they are, given the signals coming from Sinn Fein. It is true that on last Thursday night the Sinn Fein spokespersons, Mitchel McLaughlin and Barbara de Brun, sought valiantly to put a positive spin on the outcome to the Hillsborough talks, but that has worn thin in the last few days as, at cemeteries around the country on Sunday, the real response of the republican movement became evident.
At Glasnevin, Gerry Adams said that the agreement was "clearly in crisis". He said "no one can impose obligations or commitments [on the parties] beyond what was collectively agreed on Good Friday in 1998". And he reiterated: "Sinn Fein has . . . made it clear, both privately and publicly, that we cannot deliver the demand for IRA weapons, no matter how this is presented".
Martin McGuinness said the Hillsborough declaration was at attempt to rewrite the Belfast Agreement. He said there was "an unrealisable and unrealistic demand for a surrender by the IRA". an Brian Keenan, another senior republican, said there would be no surrender of IRA arms and at Milltown Cemetery in Belfast the emollient Mitchel McLaughlin spoke of the agreement being "in crisis".
Having made this blunder in trying to rewrite the Belfast Agreement by making decommissioning a precondition of Sinn Fein's participation in the executive, the two prime ministers will probably be forced to retract what they said at Hillsborough and, inevitably, this will further infuriate the unionists.
David Trimble, speaking about the impasse on the implementation of the agreement, said: "I think we have cracked it now." He and Ken Maginnis were jubilant that the two prime ministers and the SDLP had seemed to back their interpretation of the agreement on decommissioning. Their position will be very much more difficult within their own party should the prime ministers change tack again.
So what is to be done? In his introduction to Ken Maginnis's interesting pamphlet on disarmament, David Trimble correctly observes that a fundamental assumption of the "peace process" has been that the republican movement was willing to abandon violence if offered a political outlet.
He acknowledged: "We realise that the transition from violence to peace is not always clearcut. The paramilitaries may be genuinely seeking peace or they may be operating tactically to gain what they can from a peaceful posture before returning to `what they know best'. Or they may start out with the latter aim and be compelled by circumstances to embrace peace. We have such a political sense to know that such a situation has to be tested. Decommissioning of terrorists' weapons is one such test."
He is right in asserting that decommissioning is a test of the genuineness of the republican movement's commitment to peace. But it is also right that it is "one such test", one of several that could be applied.
The most important is the silence of IRA guns. Apart from very limited and very occasional (albeit shockingly murderous) outbreaks of violence from February 1996 to July 1997, IRA guns have been silent for nearly five years now. The IRA's armed struggle has been over effectively since August 1994. That is an important reassurance, although it would be understandable if David Trimble and his party did not think it was adequate.
A further reassurance would be an unequivocal declaration on the part of Gerry Adams that the war was over for good, done with, a thing of the past. He almost said this in September last year. He could now say it without the equivocation (he said then he "hoped" this was so). Of course, if the IRA said this itself, it would offer even more reassurance.
But one way or another, what was done at Hillsborough last week was a serious reverse, and we would know all about the Taoiseach's part in that blunder had John Bruton, rather than Bertie Ahern, been Taoiseach.