The most mind-boggling paradox about the impasse over the Northern Ireland backstop is that if it leads to a no-deal Brexit there would be nerve-wracking uncertainty about whether the 300-mile border between NI and the Republic would and could be kept open - which is precisely what the backstop is designed to prevent.
If that led to anxiety about a resurgence of gangsterism and terrorism along the border, everyone would lose. But playing the cynical game of political calculation, which all leaders do however much they protest their high moral standards, who would lose most?
This is a desperately difficult judgement. What is clear to me is that the PM and her Cabinet are split on this.
In refusing to countenance a backstop that would keep just NI in the single market and customs union, or one that kept the whole UK in the customs union without defined termination date, or one that extended the UK’s status in transition as a non-voting member of the EU till such time as a permanent solution to the border problem could be found (longer than a few months), Brexiter ministers are calculating that such resolve (or inflexibility, if you prefer) would be rewarded by a strengthening of the union between Great Britain and Northern Ireland.
They take the position of Northern Ireland’s DUP, which by coincidence keeps their minority government in office with the remunerated loan of their votes. Many ministers assume that a majority of Northern Ireland and British voters would cheer for a Westminster government that prioritised ties with GB above openness to the EU.
This assumption is moot.
By contrast, the PM seems less wedded to hard formulae in the talks - even if her rhetoric would suggest otherwise.
Her relative elasticity in Brexit talks - when represented by her official Olly Robbins rather than her minister Dominic Raab - presumably stems from her awareness of a challenging reality: EU negotiators and government heads look at the uneasy historic relationship between Dublin and Westminster and figure that the Irish government under Leo Varadkar could reap a popularity boost at home if the cause of a failure to agree Brexit terms were their and his perceived steadfastness in standing by the Good Friday Agreement (the momentous UK/Ireland pact that formally and actually brought peace).
They also look at Northern Ireland’s 56% vote to Remain in the EU and believe that even in Northern Ireland there would be a propensity to see the collapse of Brexit talks as more the fault of Westminster than Brussels and Dublin (which may be wishful thinking).
Theresa May may be most troubled by something else too: one feature of the EU’s no-deal preparations would be a package provided by the EU26 to Dublin to cushion Ireland from the economic shock of a temporary or prolonged increase in the costs for Irish businesses of selling to Britain.
To put it another way, in the fraught circumstances of a Brexit they hate and never sought, EU governments will rally round to protect one of their loyal ilk, the Republic of Ireland.
All of which is to say that when push comes to shove, and the hardest and most chaotic of no-deal Brexits could be just days away, don’t assume that the gravity of the Irish issue will see London, Brussels and Dublin suddenly and miraculously coalesce around a compromise that averts the worst.