It is, said one close observer, about quantum: which I initially took to be a posh version of the block grant, the system by which Scottish public spending is capped, presently lacking borrowing powers or a usable tax system.
But think on. Perhaps John Swinney, Scotland's Finance Secretary, is currently subject to a Holyrood version of Heisenberg's uncertainty principle.
If he does a deal on his budget with one party, he cannot be sure that the very content of that deal is not simultaneously deterring another lot.
Mr Swinney believes he has one fixed point: that the Greens will vote against his budget, leaving him two votes down.
(The SNP and others calculate that the Green position - demanding higher taxation - is partly owing to their desire to hold on to Patrick Harvie's seat in Glasgow in the face of sundry challenges from the Left.)
Mr Swinney had further talks with opposition party finance leaders today.
Still no deal - but that is not surprising since it is vital to tie up all elements before finalising an agreement. Think quantum. Think Heisenberg.
Mr Swinney will be hoping that he can, once again, reach an agreement with the Conservatives.
He will be hoping that he can count upon Margo MacDonald. But, as I have noted previously, that is not enough.
It would leave the chamber tied at 64/64 if all the others voted agin.
The presiding officer would be obliged to declare that the budget had not carried.
Again, think quantum.
Mr Swinney must calculate what level of concession would placate, say, the LibDems without deterring, say, the rival Tories.
Numerically, Labour are the largest opposition party - but, politically, would the SNP want to give the most substantial concessions to their largest rival?
Yes, if it secures the budget. But, no, if the altered version is no longer perceived as an SNP programme.
Mr Swinney feels the opposition parties could usefully start by suggesting ways of plugging the £30m gap left by the defeated large retail levy.
They caused the gap, he argues. In collective spirit, they can close it.
If a deal is to emerge, a spirit of co-operation will need to emerge behind the scenes in tandem with the upfront ethos of confronation.
That latter was well to the fore in questions to the first minister.
Labour's Iain Gray pursued the issue of short sentences - with some good points re the availability (or otherwise) of community alternatives.
Alex Salmond rebutted successfully, pointing out with vigour that recorded crime was at a thirty year low - owing, he argued, to extra police recruitment, opposed by Labour.
For the Conservatives, Annabel Goldie seemed rather discomfited that Mr Gray had pre-empted her planned topic.
She even had the same newspaper headline ready to brandish.
By the time she did so, the audience members were shifting a little uncertainly in their seats like a concert audience in the village church about to be subjected to the second rendition of a doleful ditty.
Mr Salmond contrasted her views with those of Ken Clarke (Con.) In vain did she protest that she was responsible for Scottish policy.
Mr Salmond noted that she had been only too content the previous week to seek to contrast Scottish practice with that in England. A points victory to the FM on this one.
For the LibDems, Tavish Scott suggested that proposals to transfer elements of social care to the NHS was creating uncertainty for local authority staff.
After an initial counter-attack, the FM responded reasonably - I stress, reasonably - emolliently.
Perhaps he was reflecting that, in financial matters, his government will need chums to acquire a quantum of solace.
PS: The committee at Holyrood which is scrutinising the Scotland Bill broke with precedent today and opened with a series of detailed questions about . . . the Scotland Bill.
Dropping the satirical note for a moment, this was a notably successful committee session, taking evidence from the Scottish Secretary Michael Moore and David Gauke from the Treasury among others.
The mnisters were pursued on the extent of new borrowing powers and continuing Treasury supervision.
Mr Gauke indicated that the proposed capital borrowing level might be open to review in the light of events and the passage of time.
Serious issues, sensibly pursued by all members of the committee.
PPS: The FM is not pleased at suggestions from Mr Moore, highlighted by others, that his government has failed to provide chapter and verse to the committee re fiscal autonomy.
Mr Salmond is writing to the Prime Minister to protest, detailing the extent of his government's engagement with the issue.