I am not a member of Sinn Fein, nor ever have been, but I can still harbour hopes that they will make moves that would be good for us all. I criticise them from outside and yet I can understand why they, within their own terms, would find some things difficult. I imagine myself sitting in an ard comhairle meeting, urging them to allow their MPs to take their Westminster seats, and I can anticipate the arguments for and against.
The 'for' argument would be that they might be able to swing a vote against the immediate triggering of Article 50, which will set the timetable for the UK's departure from the European Union. Theresa May seems likely to be told by the Supreme Court that she cannot act on Royal Prerogative, but that she must put a Bill before parliament.
Parliament seems unlikely to rally adequate forces against actual Brexit, but it might insist on an amendment or two to the Bill, setting down limits to how comprehensive the final exit might be.
Even now, Labour and the DUP and others are saying that they will not oppose the Bill, not even having read it yet. As far as they are concerned, the Supreme Court will have secured their right to an opinion and they will have waived it.
Only the SDLP and the SNP, as far as I can tell, will be there to oppose Brexit altogether. And Labour doesn't seem to have copped on yet that there is a middle way, amending the Bill and forcing May to come back with something better. Maybe they will. Maybe Sinn Fein should be using its long friendship with Jeremy Corbyn to tip the party in that direction.
While it doesn't look now as if Sinn Fein's four MPs could tilt the balance, that occasion may arise if Labour stiffens its resolve a bit. Might it even be tempted to do so for the prize of having four Sinn Fein MPs on the benches to support them on other issues?
The argument against Sinn Fein entering Westminster by taking an oath of allegiance to the Queen is that it would be throwing away a foundational principle. That principle is that there is one legitimate parliament in Ireland and that is the first Dail, established by the general election of 1918, in which Sinn Fein got a majority and declared Ireland an independent nation.
There isn't a lot left of that principle. It was compromised by the decision to fight for - and take - seats in the Dail.
It has also been made irrelevant by Sinn Fein running a devolved administration in Northern Ireland and thereby deferring to the right of the British parliament to delegate power to it.
The other component of that principle is that taking seats in Westminster would involve swearing an oath of allegiance to the monarch. Yet, other republicans did that in the past, including British republicans and Republican Labour MP Gerry Fitt, as did De Valera, when he entered the Dail in 1927, declaring it "an empty political formula".
A pragmatic political activist would not allow the way forward to be blocked by such trivia, knowing that the oath would not bind him or her to anything of substance. Indeed, in recent years Sinn Fein has framed its objection to taking seats at Westminster in different terms. It has said that it has always been able to achieve more through direct negotiation with prime ministers than the SDLP has achieved through joining debates and asking questions.
This is the pragmatic defence of abstention. But it would fall apart if negotiations didn't prove as fruitful as debating and voting might. Take the scenario in which Theresa May puts forward a Bill to allow her to trigger Brexit and fails to pass it, because she refuses to accept amendments prosed by Labour. The SDLP has entered the debate with the determination to oppose Brexit.
May would then call a general election. The SDLP would campaign for more support on the grounds that it would be turning up for the fight. Abstention would not then look like an attractive selling-point for Sinn Fein.
And the fact that Sinn Fein has been defending abstention on the pragmatic argument, rather than the old principles, suggests that they know that the voters want what works. They are not ready to make sacrifices to defend the legitimacy of the first Dail - an argument that Sinn Fein has already given away.
And they will wonder what's so important about not taking the oath when Martin McGuinness is starting to look like the most eager monarchist among us, shaking the Queen's hand at every opportunity and even posing proudly beside her portrait. The abstention policy has been hugely important in the past, but it has also been overturned by those who were previously most committed to it.
In 1970, the IRA split over it. The Provisional IRA was formed in assertion of the refusal to recognise the Dail. But what was really going on then? The north had been ignited and the real difference between the two wings of the IRA was the question of whether to escalate. They called it "defending the Catholic community".
Sixteen years later, Gerry Adams drove through a change in Sinn Fein policy on the grounds that the Provisional IRA had already decided in favour of them taking seats in the Dail. That split the movement again, though the old purists were in a small minority and their Republican Sinn Fein is now a negligible force in Irish politics.
Surely, the greatest lesson of republican history is that those who preserve the pure flame warm their hands by it alone. And modern Sinn Fein wants to grow and wants to take power and has already swallowed other shibboleths for the sake of it.
Well, they now have a chance to be part of the biggest row in decades. Or they can stand aside and watch the SDLP and the SNP fight for the rights of devolved regions who voted against Brexit.
They may not have much prospect of winning in that fight - but when did that ever stop them?
Political reputations will be made in the coming months and years as nationalists from Scotland and Northern Ireland defy the right of England to make decisions for the rest of us. Isn't that what Sinn Fein was created to do?
The alternative is that we will rely on the schizophrenic partnership of Martin McGuinness and Arlene Foster to impress on Theresa May the need to get the best deal for Northern Ireland, each of them hobbled by the need to hold together.
And this while Nicola Sturgeon and Mark Durkan are on the battlements shouting in unison: No Surrender.