When the largest guerrilla army in Europe, which has carried on a war of attrition for a generation, sends in its resignation letter you would expect that the news would dramatically alter the political landscape. Sadly, that has not been the case.

What is historic is that Sinn Fein made it clear last week that it will use its influence to bring about decommissioning when the Good Friday agreement is implemented. When Sinn Fein makes such an offer, as it did for two cease-fires, it is eminently bankable, as the two governments realise.

The speculation now about an IRA statement on imminent decommissioning is misplaced. Insiders say any statement would likely just reiterate support for Sinn Fein's handling of the peace process.

What is now clear is that the implementation of the Good Friday agreement, voted for by 71 per cent of the people in Northern Ireland, will result in the most significant step in Irish republicanism since the birth of Sinn Fein in 1906.

The only way it can fail is if the governments fail to realise that there are two communities taking a leap of faith. Assurances to unionism cannot undermine the agreement and its fail-safes for both sides.

You would expect that the unionist community, the target of much of the IRA campaign, would exhale a deep sigh of relief at recent developments and feel a mixture of vindication and relief.

Yet the unionists continue to suffer from cognitive dissonance, a condition where, all evidence considered, you know you have been wrong in your assessment of a situation but continue to insist you are right.

Mr Ken Maginnis, of the UUP, told the BBC that the deal was bad for unionism because "we have been asked literally to jump on to glass in our bare feet and because the IRA have not agreed to give up their guns, They're being given a free run".

Any objective reading of what occurred last week would come to the opposite conclusion. The governments and Gen John de Chastelain believe that the republican movement can now commit to the banishment for ever of their guns from Irish politics.

Yet instead of understanding this historic step, much of the media and unionism seems locked in a freeze frame, unable to respond to the new reality.

The media say the deal is in danger from unionist objections to the timing of the weapons hand-over. Suddenly the IRA move out of the shadow-lands, signalled by Sinn Fein's commitment last week, is devalued because unionists have problems over whether it should begin immediately or within months.

Some commentators have even attempted to equate Mr David Trimble's dilemma in accepting a formula for decommissioning with the republican movement's extraordinary decision to bring it about under the terms of the Good Friday agreement.

That is a scenario worthy of a absurdist play, one where unionists have shown all the subtlety of an elephant performing a ballet dance in responding to events.

Sinn Fein in government conjures up monsters of the most wicked kind for some unionists and, even if all the IRA arms are decommissioned, they are unwilling to accept it.

Writing in the Daily Telegraph last week, Boris Johnson, a unionist sympathiser, envisages one such scenario. "There are many possible nightmares, [Martin] McGuinness, the schools minister, could propound some mandatory teaching of the Irish tongue which is then forced on teachers in unionist schools by the overt or covert threat of the gun."

They are being indulged in this nonsense by elements in the media. They say, in shocked tones, that the latest developments give the IRA a stranglehold over political development.

Perhaps they should cast a backward glance and see where the decommissioning issue came from. It was the unionists and Sir Patrick Mayhew who decided to give the IRA the veto over the political process when they first invented decommissioning as a ne plus ultra for the peace process.

There has also been an unfortunate tendency by unionists and the media to pocket Sinn Fein concessions over the years and to assume that, however high the hill, those redoubtable climbers, Mr Adams and Mr McGuinness, would surmount it. We are seeing it again in the aftermath of their latest step.

However, this decommissioning move is different, so far beyond any recognisable peak conquered before as to make it Everest-like territory. It is a step so bold that it has unsettling consequences for many republicans.

Mr Adams stated it best when he compared their new position to a piece of elastic stretched to its limits.

It is also about a powerful symbolism in the way that Drumcree is about symbolism for unionism. Despite their hurly-burly, we know that the Orange marchers will never again have the full run of the queen's highways in the North.

Similarly, the creation myth of an IRA ready to defeat the British army or to defend an entire nationalist community has hugely symbolic importance for many republicans who recall the bad old days. They are prepared to jettison that for the reality and the uncertainty and hard slog of democratic politics. It is as if for unionists the Orange Order had decided to disband.

I can only imagine how difficult a sell the new dispensation will be to the republican constituency. There will be many who will refuse to let go of the old certainties. Anyone needing a primer on what these constitute can look at the Republican Sinn Fein commemoration speeches at Bodenstown recently.

Republicanism has reached a place where unionists have still to go and which they appear reluctant to approach as long as they can march (over 3,000 this summer alone) and put off the reality of their changing circumstances and blame Sinn Fein for every shortcoming they feel.

Unionism must also examine its creation myths, the battle long ago at the Boyne, the sectarian aspect of the Orange Order, the need to have the "croppies lie down" as posters in Drumcree in 1998 proclaimed. Unlike republicanism, they have only nibbled at the edges of them. Sinn Fein may have crossed the Rubicon, but unionists are still rooted to the river bed of the Boyne.

They have, for instance, proclaimed a need for absolute certainty in their dealings with republicans and the peace process, and they say the words of presidents and prime ministers are not enough for them.

The only certainty they need comes from the reality that if Sinn Fein is in government and the Good Friday agreement is implemented and there is IRA violence, or a refusal to do as agreed with weapons, then the Sinn Fein position becomes untenable, not just to unionists but to the watching world.

Unionists need to trust themselves and their own capabilities a lot more. It is a hard-won belief in their ability to manage change that has sustained this remarkable era of Sinn Fein progress. Unionists need to display some of it now.

Niall O'Dowd is founding publisher of the Irish Voice in New York