Rebuilding the arc
It is a truth universally acknowledged that the best form of defence is robust attack.
Certainly, that appears to be the strategy here at the SNP conference in Perth.
It has been suggested, not least by the prime minister, that the economic crisis and the UK Government's response presents a challenge to the SNP.
How, asked Mr Brown, would an independent Scotland have mustered the resources to rescue RBS and HBOS?
Further, what now for Alex Salmond's "arc of prosperity", comprising Iceland, Ireland and Norway?
Mr Salmond, naturally, declines to enter the debate on terms set by his opponents.
Rather, he says that the PM has shattered any lingering consensus over the economic situation.
He says further that he is now entitled to respond in kind.
Consequently, opening the conference, Mr Salmond spoke of a "Downing Street downturn", blaming Gordon Brown directly for the circumstances, including banking regulation, which led to the crisis.
Intriguingly, David Cameron has now made pretty much the same case in a speech in London.
Here in Perth, we can expect to hear this argument amplified by John Swinney when he addresses delegates.
Right now, Mr Brown is being hailed as a hero.
That mood seems unlikely to last, particularly as the economy slows and unemployment rises.
Given that, it is reasonable for the PM's opponents to seek to hasten the process of applying that longer-term scrutiny.
However, I also believe that the PM's words will have left at the very least a seed of doubt in the minds of those in Scotland who might be asked to cast a vote in any subsequent referendum on independence.
To that degree, I hold to the view that the first minister needs to find a revised and updated narrative for his vision: one that takes account of the economic developments and at least addresses the arguments advanced by Mr Brown.
It is, perhaps, asking too much for that to emerge this weekend, here in Perth.
We are all still at the stage of absorbing these cataclysmic events.
Understandably, the allocation of blame has now begun.
But a reshaped narrative will still be needed at some point.