The basic contour, the shape of the story: that is clear. The Corbyn upsurge has unleashed an energy and excitement on the scale of the Scottish Yes campaign. It has sucked in tens of thousands of people – young, old, trade unionists, campaigners of all kinds – who had thought the parliamentary system simply wasn’t interested in them any more.

Now, in victory, it proposes a radical shift of direction for the Labour Party, in terms of public ownership, foreign policy, the redistribution of wealth, Trident, Nato – you name it. The history of the Blair-Brown years, with all their successes, compromises and obvious failures, is to be expunged. Listening to some Corbynites, you get the impression that Tony Blair, apparently the Labour prime minister for some period, is a bigger enemy than the Conservatives. At any rate, they propose as big a break with the past as the Bennite revolt against Callaghan-Healey which was beaten back (just) in 1981.

On the other side we had Continuity Labour candidates of various positions, ranging from Blairite (Liz Kendall) to Brownite (Yvette Cooper and Andy Burnham). Continuity Labour was hammered – not just beaten or defeated, but hammered.

But seen from the outside, both positions looked problematic. I don’t share the belief that Jeremy Corbyn would always, under any circumstances, be unelectable by the general electorate. Nor, clearly, do leading Tories, and for good reason.

By 2020 we could have had another global economic crash (pencil in 2018, I’m told), plunging our public finances into a new crisis and introducing hitherto undreamt-of austerity proposals; and the Conservative Party might have returned to its favourite occupation of the internal civil war over ­Europe. We might be out of it. Scotland could have gone through another referendum and said “yes”. Here and now, in 2015, we know diddly-squat.

Nevertheless, reading the book rather than looking into the crystal ball produces some uncomfortable facts for the left. It was rammed home again in this year’s general election that the fulcrum of the electorate is currently to the right of where anybody in the Labour Party would like to believe. This year, some 11.3 million people voted Tory and 9.4 million Labour. Compare that difference with the half a million people drawn into the admittedly impressive Labour leadership vote. Just to begin to have an effect on real voting, each of the new £3 members would have to go out and persuade three or four Tory or other non-Labour voters to back Jeremy Corbyn . . . And then, of course, actually to vote.

That is not, I suppose, impossible but it means that the upsurge of activity to get him into the Labour leadership needs to be followed and multiplied, year by year, in communities up and down the country, by persuaders working far below the radar of the national media, restlessly and repeatedly. It’s not about tweeting. It’s not about attending meetings. It’s far harder than comfortable-ism.

Our electoral system gives peculiar power to relatively small groups of swing voters in certain seats in Middle Britain – in the bellwethers around London, through the Midlands and into parts of the north-west. An upsurge of enthusiasm among younger, left-wing voters in central London, around the universities and in some industrial cities, doesn’t really count against the quiet, imperturbable conservatism of those Middle English who don’t march but do vote where it matters. What happens if life goes on much as it is at the moment – if there are no sudden collapses, if things hold together and the economy improves? Then, to put it gently, assuming that Middle England will swing sharply left in five years’ time is a huge risk.

Indeed, talking to bruised Labour MPs recalling doorstep conversations, and looking at some of the recent polling (I know, I know) on issues such as welfare, taxes and immigration, it seems the real Labour nightmare is that even in Labour areas and among Labour voters there has been a swing to the right – the new welfare scepticism. So, that’s the gamble Labour has taken with

Jeremy Corbyn.

Then again, he and his supporters could turn these arguments right around. Where precisely is the evidence that a modulated, probably watered-down form of Blair-Brown politics is going to get the country voting Labour again? Newspapers highlight polls showing just how few people say they would vote for a Corbyn-led Labour Party; they usually shove the data further down that shows the other contenders were almost as unpopular, and in some cases more so. Even for those terminally turned off Blairism by the Iraq war, the combined chancellorship and then prime ­ministerial record of Gordon Brown was given two tries at the polls – under the man himself in 2010 and then again under Ed Miliband this year. It didn’t go tremendously well.

And then, because of what happened in Scotland, Yvette Cooper, Andy Burnham or Liz Kendall would have had to achieve a far more dramatic turnaround than anyone before, even TB himself. There are Blair supporters who argue that if the party shifted decisively to the right, mimicking the Conservatives on, for instance, welfare cuts and tax rates, and pursuing an aggressively anti-immigration policy, the country might be shocked into giving Labour another look. Well, maybe so. But the chances of the ­Labour Party itself swallowing another U-turn on that scale and in that direction are fractionally less than zero. Anyway, what’s the point of having not one but two neoliberal parties? In these circumstances – the Corbyn camp would argue – perhaps the energising effect of a swing to the radical left isn’t such a crazy gamble after all. Already they are changing some of the terms of political debate in Britain. Even if they lose, isn’t it better to go down arguing than to go down half asleep?

***

Thus, tens of thousands of Labour supporters were caught in an impossible position, queasily swinging between hope and terror. What’s the best way to think about this, looking forward?

We have to start with the fundamentals, what we know. The all-dissolving dynamism of global markets, anatomised by a certain exiled, hirsute German philosopher some time back, remains the overwhelming reality of our time. The rate of change, the accelerating pace of its impact on individuals and families, is like nothing humanity has faced before.

Open world markets, hooped together by freight jets and satellites, have helped global populations, with new medicines and a greater variety of foods, to grow very fast and have enabled huge increases in material wealth, from urban China to parts of Africa. But in the old industrialised world, for the majority of people, they have brought, first and foremost, disruption – new products and new industrial centres wiping out old industries; fast mass migrations; wild swings in the pricing of everything from raw materials and housing to currencies and stocks; new kinds of non-state security threats; and the dissolution of top-down forms of media once believed to shape public opinion. “All fixed, fast-frozen relations, with their train of ancient and venerable prejudices and opinions, are swept away, all new-formed ones become antiquated before they can ossify,” Karl Marx and Friedrich Engels wrote in 1848. “All that is solid melts into air . . .”

These are the big realities around which any political project has to be based. Playing 20th-century politics in today’s circumstances – a piece of gently ameliorative legislation here, a royal commission there, a fiddle to a tax credit, a bold speech to the Press Gallery – is like trying to play cat’s cradle on a storm-whipped mountain in the middle of an avalanche. Politicians claim they can control migration. They can’t. Politicians promise economic stability. Until Westminster controls market sentiment in Shanghai, phooey. British politics has been unable to house enough people in a reasonable and affordable way. In most parts of the country, it has been unable so far to formulate industrial policies that create new industries to replace vanished ones, or even reverse our woeful record on productivity.

And the trouble is that folk have noticed. If we are beginning to live through a politics of protest and disruption – which includes the new populisms of right and left almost everywhere on the European continent; the pugilistic rhetoric of Donald Trump; and even, in a way, Putinist nationalism – then we don’t have to look far for the reasons. People don’t feel safe. They don’t feel calm.

This is an age of radical instability; politics is merely catching up. Conventional wisdom thought that the SNP was way too far to the left to be a credible force. Oops. And indeed the new challenge in Scotland is coming from further left, not further right, with the new independence movement Rise. Although Ukip was buried under the Tory landslide, the number of second and third places it achieved suggests that story isn’t over, either.

How ought social democrats to start to think about all of this? I’d suggest that the crucial question is what you think about the global markets. There are two distinct, almost alternative, approaches. The first is to regard the disruptive force as so great that you make yourself its enemy in every way you can: you oppose all further international trade treaties, you want to pull out of international bodies of all kinds, from Nato to the EU, you nationalise and regulate your own economy, probably without compensating shareholders. You impose completely different values on shareholder-fixated companies. You end up with something quite close to the politics of the Bennite economic strategy. Isn’t that where John McDonnell is heading?

In current circumstances, that is a revolutionary stance. To work, it would need massive and steely popular support, sustained for decades. To give it a chance of success you need to forget the committed believers, the marchers, the new movement and think very hard indeed about the vast majority, lurking silent and sceptical in their homes.

The second approach is to say that, for all its disruptive power, capitalism remains a remarkable creator of wealth and spreader of possibility that, however, leads to vast inequalities, international disruption and a horrible mess. The job of social democrats, and government generally, therefore, is to act to soften the inequality, minimise as much of the disruption as possible through agreements with like-minded powers, and to clear up the mess. That would produce a programme based on redistributive taxation, including taxation of wealth; a clear and principled policy on immigration, of the kind that Angela Merkel has been trying to forge; an aggressive “thus far and no further” defence of the role of the state; low tolerance for extremism; and an outward-looking

international profile, starting with the EU and a revitalised environmental agenda.

Now, I know that lists such as that are pretty puny in themselves – the pabulum of the well-meaning political herbivore – but, shaped by a clear and forthright description of the world as it is, such a programme might serve. Thus far, the old “New Labour” people have given Britain neither a coherent description nor a detailed economic strategy clearly enough distinguished from the right. Meanwhile, the first thing the new Corbyn movement has to decide is whether it is revolutionary or reformist. Perhaps, bizarrely, right now, we don’t really know.