Next week, Scotland goes to the polls to decide whether it wants to be an independent country or remain part of the United Kingdom. It is clear that, whatever the result, we are already two separate countries: over the last eighteen months, Scotland has been animated by debates over this referendum; people everywhere have been discussing finer points of constitutional law, the ethics of border controls, the value of an independent nuclear deterrent, membership of the EU and NATO, Devo Max, dual citizenship and currency substitution. In England, these debates are silent, or confined to think tanks and universities. For the English it is as though nothing is happening.

Until this weekend, when one poll showed, for the first time, that the Yes campaign had crept into the lead. With less than two weeks to go, the pro-Union political class have creaked into action. Cue more fear-mongering, more negativity. We're 'sleepwalking to tragedy', declared Boris Johnson. Everywhere the pro-Union Press (which, in England, means 'The Press') announce that we have only ten days to 'save the Union'. In fact, they had eighteen months to save the Union but they did nothing about it.

Why? Arrogance, for one thing. Most people believed No would win easily. Of course they did. You don't put Alistair Darling at the front of a campaign that actually needs to win something. Labour has always considered the SNP an upstart and it seems has refused to engage with the ideas. Part of me thinks it was so confident that they would lose, they just contemptuously thought it was an opportunity to clip the SNP's wings. But also ideology: when people use fear and misinformation as the main strategies in a campaign, they are trying to hide something. And what they have been hiding from us is the idea of change.

Change is infectious. It really is. Look what just happened. Panicked by the polling and the sudden discovery that, against the odds, Project Fear is not working, the British political class has announced a set of devolved powers to Scotland's Parliament to be handed over in the event of a No vote. There's also a timetable, agreed across the three major pro-Union parties. That was yesterday; this morning, on the Today Programme, I heard for the first time people seriously discussing whether we should extend this kind of federal system across England too. Suddenly, the problem of Britain's Londoncentricity becomes something to discuss. What kind of country do we want? How do we arrest the decline of our common citizenship? Suddenly the country seems not something we're stuck with, but something we can change. Change is infectious.

And this is why I am excited about the prospect of a Yes on 18 September. It's Scotland's decision, of course. But I'm not talking to Scotland; they're well ahead of us on these debates. I'm talking to England. Some on the left have worried that an independent Scotland, with its 50 years of solidly voting for left-wing parties, would consign a rump England to eternal Tory rule. But, as I've argued before, there's not much evidence that Scottish votes often sway General Election results. (Indeed, that is surely one of the strongest arguments that a Scottish voter would have for voting yes. If Scottish votes were constantly foisting left-wing governments on Britain, I'm sure there'd be a lot less wind in the Yes Campaign's sails)

I've heard some poor arguments from England. One is that since Scottish independence would change the nature of the United Kingdom, everyone should have a vote. Try googling the phrase 'national self determination' people. Second, this really annoying phrase, that we would 'lose Scotland'. As far as I know, Alex Salmond does not intend to unhook Scotland and let it float away. It will still be there. Probably a lot more settled and happy, less angry about its relationship with Britain, flourishing and comfortable. Scotland is great and it could be even greater and we, its closest neighbours, will still 'have' it - to visit, to cherish, to work in, to read the books that come out from it, to continue to allow it to enrich our culture as it always has.

Let's also say that to expect Scottish voters to vote No purely to save English left-wingers from Tory rule is to suggest that they should put our political happiness before theirs, which seems a perverse thing to expect. Imagine Scotland were independent already; would we expect Scotland to voluntarily absorb itself into Britain just to help the British left? No. So we can't expect them not to want to go the other way. If we keep voting Tory, that's our fault and we shouldn't gerrymander the vote by demanding Scotland stay.

As it happens, I think this is why the economic argument against independence is irrelevant. Various economic experts have claimed that Scotland would be seriously damaged by becoming independent. Now, first, economics is not a precise science. If it were, we wouldn't be only now struggling our way out of a catastrophic worldwide recession. Truthfully, nobody knows anything (and there have been plenty of economists arguing for the benefits of independence too). But even if Scotland were to be a bit worse off as an independent country, that's their choice. The effects of such a change are simply unpredictable and no honest economist would deny this. If Scotland were independent already, it would be absurd to urge them to absorb themselves into Britain for economic reasons. By the same argument, Britain should absorb itself into China.

If Scotland votes yes, it will be the biggest shock to the identity of this country for almost a century. In the short term, I will be anxious, anxious that the immediate response will be massive hostility and intransigence on the part of the established political order - and indeed from the little Englanders who seem to be driving right-wing policy right now. It might push the country further towards UKIP and the kind of bullet-headed refusal to accept that change is good, that change is always an opportunity, that we can use change, its dynamic, its energy and power, and we can become better people. In the short term, I fear the British left will be in retreat.

But in the medium and long term, imagine it. A successful social democratic state, right next door. While we scrabble around finding a place to keep Trident, they'll have nuclear disarmament. While our prescription charges go up, theirs have been cancelled. While university fees go sky high, next door they're free. It will be a standing refutation of the ideological myth of the Right that There Is No Alternative. It will be an inspiration, a rallying cry, something to point to whenever we are told by the so-called realists that neoliberal market capitalism freed from government intervention is the only game in town. Because there will be another game in town just over the border. An independent Scotland will be an amazing thing for the British left. If we let the future be what it could be, it will be a chance to rethink the nature of Britain, the relationship between the capital and the regions, the nature of community, local government, devolution. What if the West Country had its own tax-raising powers? A parliament for every region? What if we had genuine, local, street-level representation that was responsive, vigorous, imaginative and funded? What if we, the majority, the non-rich decided we wanted to rebuild the NHS, invest in education, let the arts flourish nationally and not just in a few metropolitan centres? And we decided we wanted to pay for it? And force the rich to pay their fair share? Scottish independence, makes Britain independent too.

And if that doesn't work, fuck it, we can just go live there.