In an era when many young people are said to be turned off by politics, the World Social Forum, which has just been held in Porto Alegre, Brazil, bucks the trend. Founded three years ago by Brazilian progressives as an alternative to the World Economic Forum in Davos, which meets at the same time, this chaotic gathering has turned into a Mecca for members of international civil society.
This year, the gathering included 100,000 activists, NGO campaigners, academics and trade unionists from more than 130 countries and 5,000 organisations. There is some ultra-left utopianism - grandstanding speeches calling for everything from the abolition of armies to the end of world trade - but most of all the forum is a giant teach-in, where people from the north and south share ideas on how to campaign, protest, influence and cajole governments to win greater rights for the people they seek to represent.
Take one of those at the forum: Omana Imani from San Francisco, the daughter of a single parent. She learnt her politics from her mother, who was on welfare, then joined People Organised to Win Employment Rights (Power), which mobilised low-wage workfare mothers to win greater rights from the city government. Her message to mainstream political parties is harsh, if simplistic: "They're the elite. The majority aren't for the working class, the poor, people of colour. They have the capitalist mentality."
Raw in their politics they may be, but the young people who attended the forum are serious. They did not go just to party, but to learn. The forum offered workshops on everything from the politics of Aids, through agrarian reform and renewable energy, to the transformative political effects of hip-hop. The banner at Porto Alegre declared: "Another world is possible"; but what world is it that the activists are trying to create?
There is as yet no coherent alternative. The "big tent" politics of Porto Alegre are unimaginably big, and proudly so. Its founding principles declare that the forum is a process of debate not a representative body. Nevertheless, it is possible to discern an overlapping and perhaps maturing consensus. This has become known as the anti-globalisation movement, and while much of the forum was devoted to excoriating the trade and other practices of western countries and multinationals, there was an acknowledgement that the right kind of trade and globalisation can have benefits.
As a leading article in the conference's daily newspaper put it: "Let's not forget how much we have benefited from some of the by-products of globalisation - improvements in communication technology and travel. Can you imagine organising the WSF without the internet?"
The organisers are explicit that this annual forum is not designed for parties or governments, although this has not stopped the attendance of some party and elected representatives from around the world. The ultimate irony of the anti-institutional ethos of Porto Alegre is that Lula, Brazil's new president, is one of its political mentors. Some even said he should not have been allowed to address the forum this year, as he now holds elected office. He eventually did so - but only because he was the "host".
Despite their determination to stick to the politics of protest, not the politics of power, those gathered at Porto Alegre do represent a challenge and a lesson. The challenge is to international institutions and national governments, which have far more to do to answer the searching questions that people at the forum ask about fairness in trade, environmental sustainability, poverty and other issues facing all the world's countries.
The lesson comes from the dynamism, energy and commitment of the young people who attended. There was a thirst to participate and to learn.
Empowerment is an overused word, but whether or not you agree with the forum's ideas, Porto Alegre convinces people that, in a world of big forces that are often beyond their control, they can make a difference. It links community involvement to an analysis of society and a bigger picture of the world.
For those of us who try to enthuse people about our politics, that is a lesson we would do well to remember.
Edward Miliband, on leave from the Treasury, where he is special adviser to Gordon Brown, Chancellor of the Exchequer, is visiting scholar at the Centre for European Studies, Harvard (email@example.com)