The positions of Sinn Fein and the Ulster Unionist Party are oddly similar. Both will have to swallow some bitter pills along with the spoonfuls of sugar in the Northern Ireland Agreement.

The scale of the philosophical recasting of Irish nationalism in the document is breathtaking in its ambition. The territorial basis is essentially being thrown out, and the claim to unity will now be a matter of argument and persuasion, not doctrine.

The sleeping dogma that underlay the old Articles 2 and 3 of Bunreacht na hEireann was a "given" of Irish life, south of the Border at least. This is being junked in favour of real, practical, hands-on, day-to-day engagement between the two parts of the island.

Not everyone will be comfortable with the change, as is evident from the results of this week's poll in The Irish Times. There will no longer be the consolation of knowing that, whatever might be happening on the ground, basic ideological cornerstones remain in place.

Articles 2 and 3 were originally in part a formula to permit militant republicans to square their consciences with participation in the institutions of a State they had tried to strangle at birth.

They were also an implicit guarantee to Northern nationalists, but many of these - including some Sinn Fein members - appear to have placed very little practical value on them over the years.

It was only when unionists began to make an issue of the Articles that nationalists, and the Dublin administration in particular, woke up to the fact that this rusting vehicle in the constitutional garage might be a tradable commodity rather than a candidate for the scrapyard.

Nevertheless, amending them in the form suggested represents a major change in the nationalist and republican mindset. It is not something republicans can come to terms with overnight, and for that reason we are unlikely to see any dramatic decisions at this weekend's Sinn Fein ardfheis in the RDS.

Nevertheless, the pressure is there for Sinn Fein to take a straightforward pro- or anti- position on the agreement. There is little or no room for cherry-picking or sitting on the fence.

If Sinn Fein opposes the agreement or takes a limp-wristed position on the sideline, there is a possibility the deal could be defeated or else fail to secure a convincing majority. Dublin, London and Washington are watching and waiting.

There seems to be no way out and no space for the party to fudge or seek "clarification" as it did on the Downing Street Declaration. Mr Gerry Adams and his friends can play for time, but not much.

There has been talk of a special ardfheis to consider the document in a fortnight. By that stage, the pressure will be almost unbearable, and there are hints that a special session could take place within a week.

The prospect of some members falling away and joining the irredentist 32-County Sovereignty Committee or Republican Sinn Fein is very real. There are no indications yet that members of the leadership are about to splinter off. The cadre which has steered the Provisional movement over the years appears to be holding firm.

Mr Adams has described the recent talks as a phase in the struggle and has asked his followers to look at the "big picture". The comparison with Michael Collins and his stepping stones to freedom has been drawn.

Another similarity with the Collins group is that few of the dissidents and their supporters are known to have the same track record of republican activity that the Adams leadership has established over the decades.

One crucial difference between the Adams and Collins leaderships is that Collins established a conservative, middle-class State, whereas the group currently leading Sinn Fein has sought to put itself at the head of the Northern nationalist drive for equality and social progress.

WE are likely to hear very little rhapsodising about the agreement from Sinn Fein delegates this weekend. There is lingering suspicion that elements which are promised may not be delivered, and any approval of the agreement is certain to be conditional and with many reservations.

If the North-South bodies had a wider remit and if the policing reform was "nailed down" better, this document would be easier for the Sinn Fein leadership to sell to its members. At the same time there is a sense in Sinn Fein circles that if the party rejects the document outright it will be playing into the hands of the unionists.

The issue of whether the new northern Assembly is a truly partitionist institution or not may surface this weekend. Given the safeguards for the minority and the link with the North-South Ministerial Council, there is an argument that this is a fundamentally different institution from the old Stormont.

Some Sinn Fein members feel the North-South bodies will never be more than token institutions unless the party is represented on them.

But to do so Sinn Fein must stand for the Assembly, take its seats and overcome the decommissioning obstacle to becoming ministers. These are major issues which are unlikely to be fully teased out in the RDS.

Even if the referendums pass, or perhaps especially if they pass, we will see further violence. But the Adams group seems to be keeping a firm grip on its support base in the republican ghettos and heartlands of the North. That's the importance of the "equality agenda", the release of prisoners and the reforms in policing which are promised in the agreement.

Life "on the ground" must improve for ordinary nationalists who have less interest in theory and dogma and the finer points of voting procedures in the Assembly or the rules pertaining to North-South bodies.

When traditional militarist republicanism fused with the social grievances of Northern nationalists, with the civil rights movement as the catalyst, the consequences were explosive in every sense of the word.

Now we are seeing a divergence of the ways, with the bread-and-butter concerns of nationalists and the political structures necessary to accommodate them taking precedence over the bomb and the bullet.

But the old methods still have their adherents, and there will probably always be some form of guerrilla activity in Northern Ireland for the foreseeable future. The question is what the scale of it will be.

We seem to be seeing the development of a Catalan-style nationalism in the North where the vast majority support political activity and the exploitation of new structures while the paramilitary path is chosen only by a few. But only time will tell.