How to pay for Scotland's schools and hospitals? Not to run them - but to build them in the first place.
The issue, rather topical at the moment, arises again from a report by Holyrood's finance committee.
To varying degree, there is something for everyone in the report - although majority opinion, reflecting parliamentary numbers, tends towards criticism of the Scottish Government's approach.
Ministers, however, can live relatively comfortably with a report which, rather than excoriating a single approach, picks faults with each of the capital spending options on offer.
Most attention has focused on criticism of the Scottish Futures Trust - although, in practice, all that is said is that the SFT remains "unproven".
The committee advises that no project should be delayed while Scotland waits . . . and waits for the SFT to swing into what passes for action.
Myself, I was more intrigued by two other findings. One re statistics (sorry, but I'm like that; I was hideously keen on sums as a youth.)
The other re borrowing powers.
On stats, the committee gripes, entirely understandably, that it is extremely difficult to compare the lifelong cost of various funding methods, owing to the lack of consistency in data.
That is a point regularly made by Audit Scotland.
On borrowing, the committee notes the quite exceptional constraints upon the Scottish Government, even by comparison with local authorities.
That is something being examined within the ambit of the Calman Commission.
More immediately, it is a source of frustration to the Scottish Government, both ministers and senior civil servants.