Slowly but inexorably, the coalition government is backing into a Scottish trap. But in the end it's a benevolent trap. If it clangs shut, the nations of the United Kingdom – England as well as Scotland – may emerge transformed into a wiser, modernised relationship in which they can cope with their own problems without illusions.

Everything depends on getting the famous "second question" into the referendum. This is the option for "devolution plus" or "devo max". It's the choice that Scotland should acquire full control over taxation and other "reserved matters" while staying – for the present – within the United Kingdom which would keep authority over foreign policy and defence. In other words, complete internal autonomy – as practised in several European multinational states. Spain, for instance, grants full internal self-government, including taxation powers, to the Basque country and Catalonia.

So far, the powers in London and Edinburgh won't admit that any such option should stand on the ballot paper. David Cameron and Ed Miliband, queasily supported by the Liberal Democrats, demand the single question: yes or no to full sovereign independence. Alex Salmond, first minister and leader of the SNP, doesn't shut the door on that second question. But he continues to insist that by 2014 the Scottish people will be ready to return a solid majority vote for independence.

Does he really believe it? In an article published in Friday's Herald, Salmond scathingly derided the panicky efforts of Westminster to impose its own terms and date for the referendum, which he claims are merely hardening support for "independence, nothing less". He did not even mention the "second question". But everyone knows that it's on his mind.

There's a gross contrast between the muddled uproar in the Westminster village and the sardonic calm north of the border. The Scots have heard all this stuff many times in the past half-century, especially the bedraggled old threat that uncertainty about the constitutional future is driving business away from Scotland (the evidence for it is still zero). They are entertained and stimulated by the fuss. But they are waiting to see if anyone is going to make the Scots an offer resembling what most people want.

Scotland is a deeply conservative country – with a small "c". The colossal uprootings and transformations of the industrial and agrarian revolutions left the Scots with a heavy distrust of social experiment. Politics has become a matter of drastic steps to preserve older securities. In that sense, paradoxically, the SNP can be seen as the most "British" of parties. Its social programme is to preserve and fortify what's left of the old British welfare state consensus, building a new Hadrian's Wall against the neoliberal tsunami that has weakened social justice and cohesion in England from Thatcher through Blair and Brown to Cameron. Ironically, this resistance is also the programme of the Scottish Labour party, brutally traumatised by the experience of Blairism and New Labour. On almost all policy save constitutional matters, the two parties agree. But they hate each other too much to say so.

In the same way, Scottish views about how their nation should be governed show a stolid consistency across generations. For most of my working life, the polls have shown the wish for independence drifting up and down between 20 and 30%. Nothing , not even the years of hating Mrs Thatcher, seemed to change that significantly. Some polls taken in the present crisis show the figure rising slightly over that 30%. It's still a minority, and – unless something outrageous happens – it's almost impossible to imagine that Alex Salmond could create his clear majority for independence by 2014. And that cunning man – "sleekit" is a good Scottish word for him – must know that in his heart.

Many Scottish politicians, starting with John Smith and Donald Dewar, have talked about "the settled will of the Scottish people". Few have taken that will to its full conclusion. But, as a matter of fact, it has been broadly clear for about 40 years. It's really quite simple. The Scots want to run their own country as other small nations do. Most of them want to stay in the Union. They want a Scottish government that is not bossed about by London, and especially not by English politicians in parties most Scots did not vote for. As David – now Lord – Steel said a few years ago: "No self-respecting parliament can exist permanently on a grant from another parliament."

This preference has been around for much longer than people realise. Oddly, it was a main reason for Scottish Labour's initial hostility to devolution in the 1970s. This assembly would just be a talking shop, or so ran their line. They felt that if it had real powers to change the lives of working people in Scotland, that would be a different matter. Many non-political Scots agreed with that. They also saw that devolution had been invented to "dish the Nats" and not because Harold Wilson thought it was a good thing in itself. Those old anti-devolution campaigners predicted – rightly, as it turned out – that a Scottish Parliament, far from dishing the SNP, would eventually unlock the doors of power for them.

That proposal failed in 1979. Tony Blair revived devolution for Scotland and Wales and the Scottish referendum in 1997 produced a strong "yes". But the new Scottish Parliament, wonderfully open and democratic in its procedures, was still financed by a block grant from London and lacked control over some important areas – immigration, broadcasting, the coastal seabed among them. Within a year, public mutters began to suggest the Parliament needed wider powers if it was to command real respect. Slowly, the politicians responded. Wendy Alexander, for Scottish Labour, suggested a transfer of tax powers. In 2006, the Scottish Liberal Democrats called for "fiscal federalism" allowing Holyrood to raise and vary most taxes, perhaps even corporation and income taxes.

Then things began to move fast. The SNP formed a minority government in 2007, and won a crushing overall victory in May 2011. In response, the Westminster government drafted a new Scotland bill whose minor concessions, including control of airgun licences and speed limits, some borrowing powers, a right to modify some income tax, were already far behind the curve when they were published. The SNP retorted by demanding far higher borrowing rights, full control of taxes (including corporation tax), devolution of the Crown Estate (inshore seabed) and broadcasting.

This is what's now known as devo max. Its idea of "fiscal autonomy" means that Holyrood would set, raise and keep all taxes – remitting to London Scotland's share of common costs on foreign affairs and defence. As soon as this plan was published, it became widely popular. Why not? For the first time, somebody had put forward a scheme coming close to that long-standing, patient wish – "to run our own affairs as other nations do".

Today, the polls suggest that this version of devo max is supported by some 70% of Scottish voters. But the coalition parties and the Labour opposition in London are determined to keep it off the ballot paper. The SNP government will let it in by the back door in their referendum consultation document, due in 10 days' time.

And how does devo max fit with that persistence preference to stay within the Union? And what happens if the two wishes converge? If the majority's preference for full "federal" autonomy is blocked by London, won't independence appear in a quite different light – as a reluctant necessity, as the only means to reach that full self-government? That has to be one of the scenarios revolving in the Big Eck brain. Another, given Salmond's rare sense of political process, must be that devo max can also be seen as verging on "Independence Lite", which – given some predictable wrangles with London – can easily slide into independence full strength.

This weekend, an independent campaign was being organised in Edinburgh to fight for the "second question" – the one which so obviously corresponds to what most Scots want. By denying it and concentrating on the "Independence: Yes or No" choice, the coalition and the Unionist camp are backing into the trap. If Salmond runs his own consultative referendum including that second question, there would be a huge majority for sweeping change. If the coalition tries to impose its own referendum, Salmond could call for a boycott and render it meaningless – except as a poisonous abscess of mistrust between the two countries.

Independence means not being dependent. "Max-devolved" or sovereign, a new Scotland responsible for its own resources – and blunders – would be a far better partner for England. And the English would at last have to face their own problems: a decent nation grotesquely dominated by the interests of the rich south-east and the City of London. Giving the Scots what most of them want can also mean "England Arise!" This referendum is a historic chance for change – and not just for Scotland.

• This correction was published on 22 January 2012:

A Comment piece said: "Spain, for instance, grants full internal self-government, including taxation powers, to the Basque country and Catalonia." Catalonia relies on funds from the Spanish government as it does not have its own tax system ("If Scotland becomes a sovereign, mature nation, England gains too").