Ed Miliband needs the Union more than most.

This is, of course, an elementary fact of political life. The further south you travel, the harsher the climate becomes for Labour, with few signs that the weather is improving. Mr Miliband needs the protection of his Scottish voters.

This ought to make him ruthlessly pragmatic, prepared to say or do whatever it takes to keep the Union intact. No-one would be too surprised; some would call it common sense. Instead, the Labour leader has decided to attempt a thoughtful approach to the future of the United Kingdom.

Loading article content

He has a point, or rather two points. First, no-one is going to "save the Union" unless they work out what it is they are trying to save. Secondly, there are too many people on Mr Miliband's side of the argument who act as though the case for the UK is self-evident, and barely worth stating. Then they wonder why sceptics become irritated.

The stand-off has become almost comical. Not a week passes without another speech or article proclaiming that the time has come to make "a positive case for the Union". Then the rest of us are left drumming metaphorical fingers when this famous statement of virtue fails to materialise. In its place, instead, come the usual predictions of disaster and doom. Some of those are pretty comical too.

What's their problem? Why can people – a few of them clever people – be so passionately convinced by an argument and yet incapable of spelling it out in simple words? Others manage the trick all the time. "This treaty/reform/vacuum cleaner is a historic achievement because ..." Instead, Unionists lapse into untested assertions: "Stronger together than apart." Ask for the why or the how and another assertion follows: because the alternative is catastrophe.

Mr Miliband lapsed into this sort of talk often enough in a speech in London's Royal Festival Hall on Thursday. He also seemed to show that the history of these islands isn't widely taught at Oxford or the LSE. Inadvertently, nevertheless, he might have touched on an important point. Most of the talk of Britishness is woolly because Britain was always a fudge. The Union worked, if it worked, because the details were skipped, the contradictions ignored.

Mr Miliband was thinking aloud, therefore, about things that have been left unsaid, south of the Border at any rate, for generations. Some of it was foolish. The claim that Scots will cease to be British if they vote to end the Union misunderstood history, geography, politics and, as it happens, the Union itself. If Britain is defined as the UK – bang goes the historical record, though – then the people of England will also "cease to be British" if the UK is dissolved.

We share the island, versions of its languages and a good deal of its culture. Mr Miliband also shares the place with Alex Salmond and the SNP. Politically, our ultra-conciliatory First Minister is far ahead of the Labour leader in this argument. So wedded is Mr Salmond to a continuing social union – plus the monarchy, the pound, the Bank of England and much else besides – some of us have begun to wonder where independence is supposed to begin.

In simple terms, Britishness, whatever it is, is not Mr Miliband's to grant or refuse. One national community's right to self- determination beyond the political muddle of the UK does not, in Mr Salmond's version, negate a host of other relationships. Since Labour's leader claimed to be defending those very relationships he was wading in a morass. That's where talk of Britishness leads on a multi-cultural and constitutionally muddled island.

You can't blame Mr Miliband for trying, however. Unlike other Unionists, he was at least trying to think things through. He was most impressive when he tried to introduce another tricky concept that the UK's defenders prefer to ignore. What becomes of Englishness in all of this?

As a tactic, this was brave. There are plenty of Conservatives below the Border – not to mention Jeremy Clarkson, St George's unlikely stand-in – who would happily see the back of the ungrateful Scots. They hanker for an England restored. They dislike being told that the country they occupy should not be confused with Britain, far less with the UK. And they would happily fight a chauvinist war with Mr Miliband. They think it would be a walk-over.

Given recent election results, they might be right. They discern an England that is "naturally Tory". If they ever pay attention, they notice first and last that their party has not prospered in Scotland for a generation. That is, they say, fine by them. Mr Miliband's claim that a "progressive Englishness" survives will not impress this faction much. Nor will they bother to wonder how their English nostalgia and modern Scottish attitudes can still be welded into something called British.

Mr Miliband understands the challenge from the right. English identity, he said "has tended to be a closed book of late. People have been nervous that it would undermine the UK, but also because it connected to a nationalism that left people ill at ease". He maintained, nevertheless: "If we stay silent, the case for the United Kingdom in England will go by default."

So where is Britishness in all this? It counts, it seems, as a kind of overarching compromise underpinned by what Mr Miliband believes are shared progressive values, values that recognise no borders. Labour's numerous failures in England and the strange fate of English identity suggest that this is wishful thinking. The compromise doesn't work – hence devolution, far less the campaign for independence – and the values diverge increasingly.

Still, if this was the start of the campaign for a no vote, it was a better effort than many would have predicted. Who are these peoples who find themselves in dispute, good-natured or otherwise? Who do they think they are? Mr Miliband pushed his luck somewhat by suggesting that the people of England must be part of the "debate" over the Union. He seemed to say that they should be part of the decision. But if he only meant to invite English folk to begin to think about their place in the world, one response would be: about time.

There probably is no coherent case that can be made for Britishness. It was born from propaganda and patronage in an effort to cement a political Union. It puzzles people because it was an effort to obscure genuine differences beneath the appearance of unity, and to do so – the tricky part – within the terms of a treaty that supposedly guaranteed the distinctiveness of nations.

Mr Miliband needs to work on his terms. He also needs to explain why the dual identity bestowed so often on Scots, desired or not, seems not to apply to England. He might even attempt again to say what he means by identity. The answer to that puzzle eludes many in Scotland, far less those to the south. A choice, an inheritance, an accident of history? Some odd mixture of all three?

Unionists count the notion blasphemy, but the word worth discarding now is British. Two nations, one principality and one province in a political and economic union: who's in and who's out? They can decide and they can vote. The rest is an old, intractable mystery.