There can be little doubt that dealing with the past is the most difficult issue facing former US State Department mandarin Richard Haass. Who did what to whom and why during the more than 30 years of bombings and shootings are two questions which, if left unaddressed, have the potential to block and even reverse Northern Ireland's journey into a more tranquil and congenial future.
Dr Haass has been asked to unravel a Gordian knot that has defied the best efforts of many others and there is no disguising the obstacles in his path.
Two stand out – one created by the British Government, the other by the erstwhile leadership of the Provisional IRA. Unless they are removed, Dr Haass's mission is doomed.
Northern Ireland Secretary Theresa Villiers put the British hurdle in place at a recent meeting of the British-Irish Association, where she said that any mechanism for dealing with the past would need to be consistent with the rule of law. The Government, she added, "will never put those who uphold the law on the same footing as those who seek to destroy it". Translated, that means the British reserve the right to jail people for offences committed between 1968 and 1998 and will not participate in a truth recovery process that regards the misbehaviour of British security forces as contributing to the Troubles.
If Ms Villiers's statement represents the final British word, then it is really a veto on Dr Haass's work.
Her logic is that the British regard themselves as still at "war" with the IRA and do not wish to see the past properly dealt with. Her statement is the antithesis of what the peace process means.
Here is the reasoning for that claim. The IRA fought its "war" against the British mostly by killing, or trying to kill, soldiers and policemen and by planting bombs, while the British fought the IRA mostly by trying to put its activists behind bars.
As a result of the peace process, the IRA has stopped killing and bombing, so its "war" is over; but the British still want to put IRA members in jail. Ergo, the British are still fighting the "war". And, as long as this is so, who could blame IRA leaders and activists for not wanting to come forward to tell the truth about the past?
As for British security force responsibility for the three decades and more of violence, the record of unlawful killings, collusion, torture of detainees, intimidation of lawyers and failure to properly investigate killings carried out by its forces speaks for itself.
If the British government insists that any mechanism for dealing with the past must involve pursuing and jailing alleged paramilitary wrongdoers from the Troubles, while its own misdeeds escape scrutiny, then Northern Ireland will never be able to put its past behind it. Dr Haass's mission will fail.
But the British are not the only ones at fault. The two most prominent leaders of the Provisional IRA during the Troubles, Gerry Adams and Martin McGuinness, continue to deny, or minimise, their involvement in directing the IRA's campaign. Mr Adams maintains that he was never in the IRA, much less its most influential leader, while Mr McGuinness claims he left the organisation in 1974.
Neither assertion is at all credible and the problem for them, for Richard Haass and for Northern Ireland is that the level of cynicism about the two men's denials is now so caustic that any attempt to deal with the past emerging from Dr Haass's efforts that leaves these fictions intact will not only fail, but deserves to fail.
Throughout many years reporting on the IRA, I have never been given a satisfactory explanation why Gerry Adams chose to actively deny his membership, rather than do what all his predecessors did, which was to fudge his answer.
He first adopted the outright denial approach back in the late-1970s and I can only imagine that he did not then think he would ever be propelled to his current prominence and so claiming non-involvement may not have seemed such a big deal at the time.
But it has become a big deal; so much so that one must wonder if Gerry Adams himself regrets it. He was without doubt a military strategist of exceptional talent during the 1970s and was pragmatic and courageous – some would add ruthless – enough to later lead the Provisionals out of war and into dizzying political success.
Yet he will not be remembered for this remarkable life story, but for his denial of what everyone knows to be the truth.
And it has been a self-destructive deception. There is no doubt in my mind that his denial of their shared lives prompted both Brendan Hughes and Dolours Price to spill the beans on him, with allegations that pursue him everywhere.
At this point, Gerry Adams could be forgiven for feeling trapped by his years of dissembling; for feeling that, if he now admitted the truth, he would only make things worse.
But to believe that may be to misjudge the hunger for real peace in Ireland. If he was to come clean and apologise for the years of deception, it is just as likely his honesty would receive the warmest of welcomes and be greeted by sympathy, hope and relief.
Such a move could have a liberating impact on himself and help slice through the past's Gordian knot, pressurising all the other parties – not least Ms Villiers – to respond with generosity.
It would remove at a stroke the most potent weapon wielded by his opponents in the Dail and guarantee his place in Irish history.
It remains to be seen whether Adams has the courage, imagination and foresight to take such a step. But one thing is certain: no mechanism to deal with past can have any credibility as long as leaders like him continue to deny the defining part of their lives during the Troubles. No more than if Ms Villiers's mean-spirited approach were also to prevail.