On 11 March over a million people will march to Atocha railway station in Madrid to commemorate the 191 people who died in the bomb attacks of 2004. And in the three days before the anniversary the city will be hosting a gathering of current and former world leaders, academics, policy wonks, journalists, NGO representatives and others, there to discuss and agree on the Madrid Agenda - a set of principles and practices which democracies can adopt in order to counter terrorism. The International Summit on Democracy, Terrorism and Security, as it is properly called, is being organised by the Club de Madrid, a group of former world leaders that includes Vaclav Havel, Mary Robinson, Helmut Kohl, Mikhail Gorbachev, Kim Campbell, who was Prime Minister of Canada and chairs the Club de Madrid, our own John Major, and of course the ubiquitous Bill Clinton.

As you would expect from such a summit, most of the organising is taking place in a few closed committees where powerful people make serious decisions, although they are getting ideas and support from a couple of hundred of the world's best known experts on terrorism. It's a good idea, but not what most of us would call full public consultation.

Fortunately the organisers are aware that they must come up with proposals that can command popular support — ideas that the rest of the world sees as making sense. So they have asked openDemocracy, the UK–based online magazine of world politics and culture, to make sure the summit engages with people around the world.

Since January we have been running a debate on openDemocracy featuring a wide range of experts and analysts on the topic of terror and democracy, trying to flush out the core issues and disagreements ahead of the summit. As should be expected with such an issue there is a need to build common ground where none currently exists. According to research carried out in five Arab countries by Fares Braizat of the Opinion Polling Unit at the University of Jordan, there is a huge gulf between what the US administration defines as terrorism and what the Arab public feel is criminal violence.

We might have expected that Hamas and Islamic Jihad — both on the State Department list of terror organisations — would be considered 'legitimate resistance organisations' by large percentages of the Arab public, but what do we make of the fact that 41 per cent of the Egyptian sample viewed al Qaida as legitimate? As Fred Halliday suggested in a major essay last year ('Terrorism in Historical Context') the old adage that one man's terrorist is another man's freedom fighter still holds true. Unless we try and understand the subtleties and the motives of those who believe they have every reason to despise 'the west', Halliday warns, we will never be able to deal effectively with this newly globalised terror.

Other fundamental disagreements have emerged in relation to the causes of terrorism. Karin Von Hippel, an expert in failed states, argues in her 'Five steps for Defeating Terrorism' that the first priority should be addressing global poverty, which acts as the Petri dish for developing future terrorists. In a fierce response, eminent English philosopher Roger Scruton counters that terrorism is caused by evil resentful people, influenced by a flawed form of Islamic belief that fails to teach that hatred is a 'sin'. Again the gulf this summit needs to span is shown to be wide indeed.

Beneath the arguments about what counts as terrorism, and what causes it, are the crucial debates about how far democracies can go in the fight against terror before they sacrifice the very principles which define them as democracies. Veteran reporter Isabel Hilton, in her contribution, argues that it is essential that democracies, and the free media which defines and supposedly protects them, do not inflate the threat of terrorism, do not sacrifice the moral highground — through aberrations like Guantánamo — and do not rely solely on the security services for information or political guidance. Such arguments sit alongside those by figures like John Hulsman of the Heritage Foundation in Washington, who says Europe has a responsibility to get real, and do whatever it takes to rid the world of the growing ranks of ruthless terrorist, bent on the destruction of the west.

As frequently occurs in online debates, readers have scrutinised all these arguments and challenged them in the public forums. But for Madrid we have gone a step further and built a special stand–alone website solely devoted to the discussion of this issue.

Since late last year ordinary citizens from around the world have been engaging with the experts at www.safe–democracy.org, and many of the hundreds of insightful and stimulating contributions will be fed back to the summit organisers.

In a brave attempt to pull people in at an emotional level as well as getting them involved in the intellectual debate, people are being asked to hold their own, small, meetings on 11 March, where they can sit down with friends, family or colleagues to remember those who died or were injured in terrorist attacks at Atocha and elsewhere, and discuss the core issues being addressed in Madrid.

Most of the meetings will be informal, private gatherings, although some will be larger events. They will give people around the world a chance to reflect on democracy and terrorism, to decide how they want their leaders to behave and to explore ways of holding them to account.

After the meetings openDemocracy will seek everyone's views through email and a special section of the summit website. We will then present those views to the Club de Madrid as part of the process of refining the Madrid Agenda. If it works it will make it clear to political leaders that the Madrid process matters and that the principles expressed have to be taken seriously.

This is an exciting initiative, an experiment in mobilising global civil society in a format which allows for constructive debate rather than simple protest.

So far over five hundred people have signed up and said they will host a meeting, but these need to be confirmed and guided and there will inevitably be a high dropout rate. As well as registrations from across Europe and North America, they have come in from Bangladesh, Nigeria, Iraq, Jordan, Venezuela, Malaysia, India, Argentina, Chile, Ghana, Turkey, Kenya, Australia, Thailand, Syria, South Africa and Saudi Arabia, among others.

The significance of the meetings on 11 March goes far beyond the simple achievement of persuading thousands of people that it's a good idea to remember Atocha and consider how democracies should respond to terrorism. We believe it could be the starting point for a new form of political engagement, one that sits outside existing structures.

It is similar in intent to the free and open source software movement (FOSS), the relatively unstructured groups of programmers who created the Linux computer operating system, the Firefox web browser and many of the other programmes we are increasingly using every day.

Their way of working can be seen as an attempt to out–compete large corporations by doing well something that they also do well — produce useful, reliable and supportable software — through a system which does not carry with it the downsides of post–industrial capitalism.

What is more, FOSS has shown that there are many different ways of writing software, and some work better than others. The movement encourages experimentation, rapid evolution of processes and practice, and learning from experience. It also delivers usable outcomes, in the form of running code.

With the meetings on 11 March, openDemocracy is starting to do the same thing for political parties that FOSS is trying to do for the software industry.

While political parties are very good at aggregating power and forming governments that can make decisions efficiently, they often make bad decisions, or decisions that fail to respect the interests of all. Our meetings are one way of looking for something to replace that form of organisation, something that could be equally good at aggregating power and equally effective at making decisions but which does not carry the downsides of the party system.

If we can get people to sit down and talk, and get those with political power to listen to what they say, then we have a new way of engaging in politics that does not rely on existing structures, even if change will still happen through those structures for the time being. Perhaps in our experimentation around the meetings on 11 March — and other meetings in future — we will uncover ways of making a difference to local, national and global political expression that do not rely on discredited parties, unrepresentative governments or ill–informed leaders.

Of course, in order for this to be possible we must ensure that the first meetings happen, that the structures we create persist beyond 11 March and that we have a way of reaching out to more people over time. The chief goal for openDemocracy is therefore to work with the summit organisers to get at least five hundred meetings around the world — if that is accomplished then other things can follow.

Few international political events of the scale of the Madrid Summit seem willing even to attempt to engage online, with all the risks that come from inviting comments and trying to organise events around the world. It's a brave move which might just ensure that governments take notice of what gets said in Madrid and elsewhere. And it could also mark the beginning of a new form of network–enabled activism.

The debate site is at http://madrid.opendemocracy.net/ and the main summit site is at http://www.safe–democracy.org/ . Sign up for your own meeting on 11 March and help make a difference yourself!