Kevin McGuigan murder: Sinn Fein has to show that it's prepared to defend the peace
The Short Strand shooting has echoes of the period around the killing of Robert McCartney, when the IRA was threatening to resume violence as the peace process seemed to unravel
It wasn't his intention, but I suspect that decommissioning witness Harold Good raised doubts about the project with a story he told on the Nolan Show recently.
He said that while he and the Redemptorist priest Alex Reid were following General De Chastelain, the decommissioning commissioner, around the various dumps where weapons were to be dealt with, they were accompanied by a man with a rifle on his shoulder.
You have to wonder why he was there. Was he a guard to see off any ambush on them by loyalists or dissidents or whoever?
At the completion of the process, General De Chastelain was rounding off their work when the man with the rifle stepped forward to remind them that there was still one more gun to be dealt with, his own.
Harold Good, a good man and a former head of the Methodist Church in Ireland, saw this volunteering of the final weapon as evidence of the completion of his mission, an assurance of the totality of the IRA's commitment to ridding itself of guns.
The more cynical won't like the story at all. It smacks too much of a contrived drama, a perfect little piece of pre-scripted propaganda.
The Provos were always good at the dramatic flourish.
If the decommissioning process was embellished with dramatic touches to impress the naive, then one has to wonder how dependable any part of it was.
Afterwards, Harold Good visited Ian Paisley and met his scepticism by reciting the story of Doubting Thomas to him and calling on him to be among those who have not seen, yet have believed.
On such foundations was the DUP commitment to power-sharing with Sinn Fein built, that and the later endorsement of policing.
In effect, Paisley had made the call that an acceptance of the police by Sinn Fein was more important, a higher hurdle for republicans to get over and the only one that could be tested.
For there was no way to prove that the IRA had got rid of all its guns.
That simply wasn't realistic, and the architects of the peace process knew that.
After the first ceasefire 21 years ago, the unionists would have insisted that the IRA surrender its armouries. The Secretary of State, Sir Patrick Mayhew, was more realistic. He conceded that the IRA and other paramilitaries would deal with the guns themselves. Decommissioning, later reviled as a humiliating demand, was actually a concession to the IRA to help it into negotiations.
Mayhew said it had only to agree to put its gear beyond use and demonstrate its willingness to proceed by agreeing a mechanism for doing so and using that mechanism once. But republicans procrastinated throughout the process.
When George Mitchell set out the Mitchell principles, which affirmed the need for decommissioning, the IRA went back to the armed campaign, accusing Prime Minister John Major of having "ditched the Mitchell principles", when it was in fact itself who could not live with them.
Eventually, Blair let Sinn Fein into talks on the understanding that decommissioning would come later. The Good Friday Agreement allowed for it to happen within two years.
Some in the SDLP argued that changing mindsets was more important than getting rid of guns, for people with changed mindsets wouldn't use those guns.
And, when Blair's emissary Jonathan Powell visited Martin McGuinness in Derry to ask when decommissioning might start, McGuinness told him that it would not be happening at all, and that Sinn Fein's endorsement of the Agreement had no binding effect on the IRA, which was a different organisation.
The fact that the IRA dug in so adamantly in its refusal to part with its weapons has to create a doubt that it would ever have wholly dismantled its stocks of them.
We know also that republicans were continuing to import new weapons from the United States, even while they were stringing the governments and the unionists along on decommissioning. Yet the declared aspiration of the Sinn Fein leaders at the start of the peace process was "to take the gun out of Irish politics".
There had been precedents for the IRA morphing into a political party. Fianna Fail was one such. The Workers Party was another; but there had been no precedent for a republican paramilitary army being fully disarmed, and it was perhaps always a vain hope that one ever would be.
There are precedents of the republican political wing eschewing former violent comrades and changing its mindset so radically that it is willing to crush them.
De Valera's 10-year journey from civil war to the office of Taoiseach matches the decade since the IRA conceded decommissioning in 2005.
This is a moment to gauge whether Adams and McGuinness can confront the restive gunmen of the IRA with De Valeran resolve. He went as far as to intern them.
On Wednesday night, Kevin McGuigan was shot dead in Short Strand. The immediate suspicion is that he was killed by a Provo in retaliation for the murder of a Provo, Gerard 'Jock' Davison. Ironically, the IRA had once been willing to shoot Davison itself.
That was when it was trying to manage a protest by the sisters and partner of Robert McCartney, who blamed Davison for the murder of Robert.
There is an echo of that ambiguous allegiance in Davison's own dealings with McGuigan, for they too are said to have been allies who fell out, McGuigan having been given a punishment shooting on the orders of Davison.
Wednesday night's shooting has other echoes of the period around the killing of Robert McCartney, when the IRA was threatening to resume violence as the peace process seemed to unravel.
It was sliding back and Adams had a clear decision to make and he made it, to meet the demand for decommissioning, however imperfectly, and break a deadlock.
If Sinn Fein let guns slip through the net to threaten the peace again, it is its peace too, and it will have to defend it.
When dissidents killed, Martin McGuinness stood beside the Chief Constable of the day and damned them as traitors.
He is going to have to do that again, or something very like it.
The guns may not all have gone, but the republican mindset has to be radically different from how it was.