It is, as the Prime Minister noted yesterday, an agreement which paves the way for the "biggest question of all". After years of nationalist agitation, and months of political hardball over the mechanics of a ballot, a referendum on Scottish independence will now be held in the autumn of 2014. Given the public appetite for a vote, it can only be welcome that the formal process has finally begun. But to support the right to choose is not necessarily to support all choices, and it is this newspaper's view that Scotland's interests remain firmly with the Union.
First, there is the economics; and that, to a considerable degree, means oil. Nationalists claim that an independent Scotland's newly enhanced North Sea income would be more than sufficient to keep the country in the style to which it has become accustomed. But the glib parallels with similar-sized, oil-rich Norway are misleading. If – and it is a big if – Edinburgh keeps the lion's share of hydrocarbon revenues, it might indeed feel no immediate loss from the withdrawal of Westminster's subsidies. But the newly independent nation would be left dangerously exposed to the vicissitudes of the global commodities market; and with North Sea hydrocarbon supplies already markedly dwindling, they cannot be relied upon for long.
Sterling or the euro?
Then there is the small matter of currency. Alex Salmond, the Scottish National Party leader and Scotland's First Minister, has ruled out joining the euro, at least straight away. Yet a Scotland that retains the use of sterling – and is therefore at the mercy of fiscal and monetary policy decisions made in London – is hardly the sovereign state that Mr Salmond so loudly desires. Such a set-up also looks disquietingly like the one that has caused such problems for the euro.
Meanwhile, a Scotland without the benefit of either the British Government's triple-A credit rating or its long-established bond market could expect to see borrowing costs rise. With shallower pockets and dearer debt, the risk of economic shocks (from misbehaving banks, say) also multiplies. And with Scotland's biggest market – England – now a separate country, subject to a separate regulatory regime, there is also a drag on trade to consider.
When it comes to politics, the questions are no easier to answer. A sovereign Scotland would not only need to re-apply to the EU, it would also lose the influence that comes with membership of Nato, a seat on the United Nations Security Council and a global (albeit shrinking) network of embassies and consulates.
Meanwhile, for all the attention to the UK's loss of the Faslane submarine base, independence also brings tricky military questions for Scotland itself. Mr Salmond's ready references to a £2bn defence budget and the takeover of existing British military resources underestimate both the costs involved and the reluctance of London to accede to demands the Defence Secretary has described as "laughable".
Autonomy at home
Neither are the prospective gains over domestic policy all that the nationalist lobby might make out. Holyrood already has autonomy over swathes of public policy, including education and the health service. What would change, however, would be Scotland's ability to pay for the more generous state services, such as free university education, that are currently provided. Indeed, recent talk from Mr Salmond about a post-independence Scottish broadcasting corporation, complete with licence fee, is just a glimpse of the breadth of services the country would now need to provide for itself.
The ties that bind
So much for practicalities. The case for retaining the Union is not only a balance sheet of tangible pros and cons. There are indeed, as the pro-independence lobby claims, some things that have no price. But for all that Mr Salmond picked a referendum date coinciding with the 700th anniversary of the Battle of Bannockburn to stir up anti-English fervour, the reality of the Union is 300 years of shared history, shared values and, to a large extent, mutually advantageous co-operation. Nor are the ties that bind purely historical ones. In an increasingly competitive, uncertain and interconnected world, the benefits of standing together outweigh emotive nationalist rhetoric more clearly than ever before.
Yesterday's historic deal was quite a compromise, extending the ballot to 16- and 17-year-olds (as Mr Salmond wanted), in exchange for dropping the option of "devolution max" (which he did not). It was a trade-off worth making to leave a simple choice of "in" or "out" that can be conclusively answered. To make the case against independence is not to suggest that Scotland cannot go it alone; it can, of course. But it would be a different country – poorer, more isolated, less secure. The question for Scottish voters is whether that is what they want.