The Taoiseach last night issued an appeal to unionists to accept the Government's bona fides in the new arrangements under the Belfast Agreement.
Mr Ahern said that while some of those opposing the agreement could never say Yes to anything, there were others whose doubts and fears he respected.
Speaking at a party meeting in Galway, he said it was clear that the greatest uncertainty lay within the unionist community. He wanted to address this honestly and straightforwardly - "as a friend and, I hope, a future partner".
It was true that the agreement meant fundamental change within Northern Ireland. The prospect of an equal partnership between nationalists and unionists, and the acceptance of the legitimacy of the nationalist tradition and aspiration, would demand flexibility and generosity from unionists.
"But which kind of Northern Ireland - the old or the new - is more likely to live at ease with itself? In any society, real stability comes from all of the people feeling that they have a stake in its success and a share in its institutions. It is that kind of stability which this agreement offers."
The most difficult aspects of the agreement for some people related to the immediate consequences of the conflict, including the release of prisoners, decommissioning and Sinn Fein's role in an executive. He assured unionists that the only basis on which the Government was proceeding was that IRA and mainstream loyalist violence was "definitively at an end". There could be no each-way bets and no dual strategies, he said.
While the accelerated release of prisoners had caused hurt and anguish, it was the correct course of action to take in the context of the agreement.
Mr Ahern again deplored the "triumphalism which accompanied the appearance of prisoners at recent political rallies". Much of what some unionists seemed to fear in the agreement - such as prisoner releases - would be occurring in any event. It was "far better" that it took place as part of a binding peace agreement.
The agreement offered the people of Northern Ireland the right to determine their own constitutional destiny, the power to govern themselves, and responsibility for developing co-operation and partnership with the rest of the people on the island.
"If the agreement were to fail, on the other hand, Northern Ireland's constitutional position would remain a matter of dispute; the people of Northern Ireland would continue to have no direct input into their own government; and co-operation between North and South and between Britain and Ireland would remain the exclusive responsibility of the two governments under the Anglo-Irish Agreement, without the direct involvement of the people of Northern Ireland."
Earlier yesterday, speaking in Dublin at the closing press conference of the campaign for a Yes vote in the referendums on the Belfast Agreement and the Amsterdam Treaty, Mr Ahern issued a blunt warning to paramilitary groups which intended to continue to wage a campaign of violence. He declared that "further violent challenges" would be stamped out.
"Let me make it clear that the Irish and British governments will not allow anyone to wreck a properly endorsed agreement or to overturn the clearly expressed will of the greater number. It is time for any remaining paramilitary activity to stop and for the organisations concerned to accept what I believe will be the overwhelming will of the people", Mr Ahern said.
Nevertheless, if there should be any further violent challenge from any quarter, the Government would "know what has to be done to uphold the rule of law".
Asked if this meant introducing internment in certain circumstances, Mr Ahern replied: "No." He repeated that the Government would know what had to be done to uphold the rule of law.
The Government would not allow a few dozen people to "damage the name of this country and inflict terror and torture on people", Mr Ahern added. "We will stamp out that kind of violence."