All this was known a year ago. It was Tony Blair's recognition that disarmament could not be made a condition of Sinn Fein serving in a devolved Northern Ireland government which made the Good Friday Agreement possible. And yet Mr Adams signed up to an agreement which set a two-year deadline for the complete disarmament of all the terrorist groups indirectly represented at Stormont a year ago.
It was an extraordinary event, which should appeal above all to students of semiotics: it was the triumph of words over weaponry. At the last minute, on the afternoon of Good Friday last year, the Prime Minister finally secured the assent of the Unionists led by David Trimble by dashing off a letter with a form of words saying essentially that he would really, really try to get the IRA to disarm before Mr Adams would be allowed a post in the devolved administration.
Mr Adams later declared: "The war is over." He said IRA weapons had been "taken out of commission" because they had not been used. Yesterday Mr Adams talked of "removing the causes of conflict" in the next year "so that either disarmament becomes possible, or it becomes irrelevant". Which could mean anything or nothing and, in a situation where ambiguity provides the only space in which progress can be made, we should be grateful for that.
As any semiotician would say, the realm of words is as real as that of guns, timing devices, detonators and explosives. The old American gun lobby slogan is that it is not guns that kill, but the people who use them. It contains a grain of truth: in Northern Ireland, it is not the weapons that kill but the ideology and language used to justify them.
But there is only so much stretching that even the English language can do. In the end, some kind of verifiable disarmament, on both the republican and loyalist sides, must take place, in return for their representation on the Northern Ireland executive. If it cannot be made a condition of their taking their seats at the top table, the trick must be to devise what Mr Blair and the Irish Prime Minister called "sequences of events" that would link representation to disarmament.
It will take all of the two prime ministers' skills to solve this conundrum, and any ideas should be welcomed, however outlandish they seem, like that of offering cash inducements for handing over weapons. And the offer of help from Senator George Mitchell, the honest American broker who did the spadework on the Good Friday Agreement, should be eagerly accepted.
The next step can be made, but it requires further bravery from Mr Trimble and Mr Adams. The Unionists have to share power with Sinn Fein on the executive, while Sinn Fein has to deliver more than mere words to persuade the Unionists that the ceasefire is permanent.