Nick Robinson analysis: Plus ca change?
Imagine a brand new country.
One freed from the shackles of the past. A nation able to ignore Westminster's grubby compromises and whose people and Parliament could set out their own vision of the future.
What might this place be like?
It would, perhaps, have its own Head of State - perhaps an elected President like America or France or a more symbolic figurehead like Germany.
They would appear on the notes and coins of its new currency or, at least, on the back of the Euro (if, that is, this country was accepted as a member of the EU).
Switch on the TV and you'd be able to watch your own shows not just the latest imports from LA, New York or London.
This new country could design its own welfare system - changing the way benefits and pensions are currently paid.
Alongside that, a new debate could start about the right balance of public spending and taxes.
That, surely, is just the beginning of the list of what independence could mean.
Yet today Alex Salmond will unveil a blueprint for Scotland in which he promises to change everything whilst promising to change nothing much at all.
The new independent Scotland which he envisages will have the same Queen, the same old pound and pennies, the same hit shows - from EastEnders to Dr Who - and, yes, you've guessed it, pensions at the same level as now alongside public spending which will remain higher than it is in the rest of the UK.
It's not that this new country won't be any different from Scotland today.
It will, we're told, have more generous benefits as well as lower business taxes, lower energy bills, no "bedroom tax", as the SNP and other critics call it, and nuclear weapons will be scrapped.
In short, anything popular about Scotland today will be kept just as it is whilst it's promised that anything unpopular will change.
This is possible because today's document will not just set out the dry mechanics of how Scotland could leave the UK. It will also set out the ambitions of a Salmond-led SNP government.
Risks vs rewards
The SNP's critics will seek to prove that Salmond is aiming for what he simply cannot have.
They will point out that the rest of the UK may not agree to let Scotland use the pound - and have Scottish banks underwritten in London; that the EU will insist on fresh negotiations before Scotland becomes a member in its own right; that even the BBC may not make all its shows available to people paying a licence fee to some other broadcaster.
They will imply that an independent Scotland can have none of the things so many Scots like and take for granted.
Who is right? How big a change would independence represent? How serious are the risks? Those are the questions which will matter from now until the referendum.
Over the next few months voters will have to distinguish between what they might like to have, what they're guaranteed to get and what would depend on who they choose to elect - whether that's to the current Scottish parliament or the one that may govern a newly independent country.