Politics requires many virtues - organisation, ideas, resolution, luck. But chief among them is the hardest to define: that elusive sense of being in tune with the times. Political parties succeed when they join their values to deep economic, social and cultural trends. I am convinced that a fourth election victory, and fundamental changes to the landscape of Britain, are possible precisely because a more demanding, educated, savvy population want the power and control that modern progressive politics can offer. I believe the opportunity is as great as at any time in the past 60 years.
In the years after 1945, people said: "I need . . ." I need the basics of a civilised life: good insurance against pain and economic misfortune, a decent education and housing. The Labour Party understood that mood, shared it and enacted policy to make it real.
The fit was both philosophical and administrative. Labour's governing ideas of community and fraternity were perfectly suited to a society that had lived through the most binding of all common experiences, a war against an aggressor. Labour's strategy - the state as the provider of social goods such as healthcare and education - was no more than a continuation of the evident success of the wartime economy. Millions of lives were made better as a result.
In the 1980s, "I need" was replaced as the dominant philosophy by the politics of "I want". A political philosophy emerged which, again in its ideology and its methods, understood the times. The Thatcher government licensed this materialism, encouraged aspirations and captured a new constituency. Its method was simple: get out of the way. The revolution was never completed. The state actually grew in size.
Millions of people, every bit as aspirant as those who had been rewarded, were left behind. Some communities missed out altogether.
The government stood by. The helping hand of the state had been scorned, replaced by the invisible hand of the market. We are still living with some of the consequences of those times: the families struggling to get on the housing ladder; the young people outside education, training or work, unsure of their futures. The politics of "I want" collapsed under its own weight. In the end, no society can be the sum total of individual desires.
Since 1997, Britain has changed in some ways more fundamentally than new Labour promised. It is a different country - richer, fairer, more confident. I also think it is being driven forward by a new spirit. I call it the politics of "I can". The era of "I can" is the culmination of the long decline of deference and automatic authority. It is the late flowering of individual autonomy and control. It is, in other words, one of the founding ideas of left-of-centre politics: to put power in the hands of the people.
In the "I can" era, people want to be players, not just spectators. They want to be contributors, not just consumers. Technology is enabling these aspirations to be fulfilled and new institutional models to emerge. In South Korea, the online newspaper Ohmynews has, as its motto, "every citizen is a reporter". It is the first "paper" in the world where the majority of the content is written by freelance contributors who are mostly ordinary citizens. YouTube and MySpace enable citizens to create and distribute content, shifting power from traditional broadcasters and record companies to citizens and small groups.
Politics cannot stand apart from these changes. A generation is coming to political maturity that expects not just high standards of provision, delivered quickly to specification, but also real control.
David Cameron is groping for this when he talks about social responsibility. But it is not enough to say that the world would be a better place if people showed social responsibility. This soon becomes a new code for malign neglect, the old Tory idea in fancier dress.
An "I can" society asks new things of citizens, and demands that they acquire new skills. But it also requires very different government institutions. That is why social and economic change today require government leadership and profes sional innovation, as well as mass mobilisation.
In the battle against climate change, an "I can" society enables citizens to become producers as well as consumers of energy. Within ten years, all new homes will need to sell energy back to the national grid, with citizens getting a fair price for their electricity. The power stations of the future will draw energy from a million roofs, rather than just a central generator.
"I can" must be combined with a sense of "we can" - the belief that there is a shared willingness within each community that individuals' actions will be reciprocated by others. The best way of getting citizens to invest in energy-efficiency measures is not just to appeal on the basis of individual self-interest, but to target a whole street or ward and make citizens feel part of a wider drive to tackle climate change. That is why energy policy in future must be a matter for local government as well as national government.
In public services, an "I can" service will continually ask: how can we devolve power, funding and control to the lowest appropriate level, while maintaining high national minimum standards? Can teachers and children inject more creativity into what is learnt, where and how? Can communities manage public spaces, from parks to community centres? Can the criminal justice system become more connected to the communities it serves, with courts based within communities, and citizens able to have influence over sentencing (as happens in the pioneering Liverpool experiment that Charlie Falconer described to the cabinet two weeks ago)?
This is not a zero-sum game between government power and citizen power; it is a genuine partnership that breaks down the divide between producer and consumer.
In the economy, "I can" companies and public sector organisations will inspire their employees to go the extra mile and apply their creativity in the workplace. Employees will be offered more power, responsibility and autonomy, from options to buy a stake in the company to the opportunity for further training.
These changes must be underpinned by changes in the way we govern. Strong local government in cities such as Manchester, Sheffield and Exeter has been the heartbeat of economic growth and social inclusion. But, in truth, new Labour has been better at strong national leadership than at nurturing strong local institutions of self-government. Yet look at our membership cards: they say clearly that we are pledged to put power, as well as wealth and opportunity, in the hands of the many not the few.
The concentration of power in Westminster is as antithetical to our ambitions of a more equal society as is the concentration of power in the private sector.
Creating institutions closer to citizens, open and accountable to their communities, able to reconcile conflicts and competing demands, is the way to tackle the sense of powerlessness that can seem pervasive. That means we need to fight the instinct of bureaucracies and political parties to hold on to power. One hundred towns and cities with the leadership, confidence and power to lead British economic, social and cultural renewal should be our aim.
New Labour has joined together the twin drives to meet needs and to fulfil aspirations. The next phase will be to capture the politics of a people who can now do so much more. That is a project that should excite everyone for the years ahead.
David Miliband is Environment Secretary. His blog is at http://www.davidmiliband.defra.gov.uk