The nightly meetings of the General Assembly at occupied Liberty Plaza (officially, Zuccotti Park) in New York have been treated by the media mainly as a quaint footnote to the mass arrests and alleged police brutality attendant to the occupation. In fact, though, the open, non-hierarchical assembly has been at the center of the movement. Starting with the planning meetings that took place in parks around the city prior to September 17, it was instrumental to bringing the #OCCUPYWALLSTREET Internet meme created in July by Adbusters magazine into real life. And as the occupation movement has caught on and spread from city to city, open assemblies have been spreading alongside.

Participating in the assembly process can take some getting used to. “It took me a while to figure it out,” a gentleman from Brooklyn confessed to me one day. A TV cameraman by trade, he had already made several impressive speeches to the GA at Liberty Plaza, to the effect that the occupation needed to send a clear, relevant message if it was to reach urban black people like himself. All this sitting around in meetings, he was saying, wouldn’t do. But now he’d changed his mind a bit. “I realized that this isn’t just about making some point out loud,” he said. “It’s about learning how to go back to your own community and organize there.” I heard almost exactly the same thing from a Nordic-looking college student an hour later—and again, and again.

Each night at Liberty Plaza since the occupation began, a few hundred people have clustered in loose, semicircular rows to attend the GA. The meetings always begin with a primer — amplified, like every other public pronouncement at the plaza, through the “people’s mic,” in which those who are nearby echo the speaker’s short phrases so those further away can hear. (The police officers who perpetually surround the plaza have arrested occupiers for using megaphones.) One of the facilitators explains the hand signals: flutter your fingers upward for applause, and downward for discontent; touch your index fingers and thumbs in a diamond for a point-of-order; hold up an index finger for a point-of-information. New signals can be added or old ones changed, as needed.

The meetings proceed with oral reports from the occupation’s various committees (Food, Direct Action, Sanitation, Arts & Culture, and more, with new ones invented daily), then general announcements of a minute or two each, then agenda items and proposals, which cover topics from schedule changes to public declarations. Throughout, someone takes “stack” — a list of those who wish to speak — and adjusts its order if necessary, to favor those representing traditionally marginalized races, genders, and ages, as well as those who haven’t spoken yet. When someone makes a proposal, others can counter with questions, amendments, concerns, and, finally and most seriously, “blocks” — vetoes, essentially. In the absence of a serious concern or a block, the assembly reaches consensus (or close to it, if necessary), and the proposal passes. Then the human amphitheater typically bursts into applause and perhaps a chant, effervescent that hundreds of people have just reached agreement. The GA usually lasts a couple of hours, but it could as easily go on all night.

While the occupiers take their time, the outside world keeps wondering why the “one demand” Adbusters called for hasn’t materialized yet, and whether it ever will. “This is not about the demands,” said facilitator Amin Husain at a recent Liberty Plaza GA. “The demands will come. It’s about the beautiful thing we’re doing here.” The demand, for now, is in process, and the process isn’t easy. It takes practice to work well, not to mention time, which is why duration is a crucial feature of the occupation: it’s not only a sign of commitment, but a practical necessity.

Open assemblies like the GA have roots in classical anarchism, Native American tribal councils, Quakerism, and the post–World War II feminist, civil-rights, and anti-nuclear movements. Ask those who have been at Liberty Plaza since the beginning, and you’ll probably hear about the influence of the assembly-based May 15 movement in Spain, which a few members of Occupy Wall Street witnessed or participated in. In turn, several Spaniards have been helping out at the plaza, especially at the media center — watching, offering advice, and reaching out to assembly movements around the world.

The General Assembly’s most direct antecedent in the United States, though, is probably the “spokescouncil” model used in the mobilization against the 1999 WTO talks in Seattle. Marina Sitrin, a lawyer and activist who facilitated the inaugural GA of Occupy Wall Street, first encountered the process there. She went on to edit an oral history, Horizontalism, about the assemblies that formed in factories, neighborhoods, and occupied spaces after the 2001 economic collapse in Argentina. These assemblies scrupulously rejected the hierarchies that had helped lead to the crash, and they became — and in some cases, remain — a significant political force in the country.

In an alluringly titled book, Freedom Is an Endless Meeting, sociologist Francesca Polletta argues that movements adopt assemblies not simply out of principle but because they’re effective and efficient methods of managing a diverse grassroots organization. Their egalitarianism fosters individual initiative, she writes, while their emphasis on consensus helps to secure everyone’s full commitment, especially when the risk of arrest or injury is present. Assemblies are also flexible, allowing for division into independent but potentially politically cohesive assemblies of assemblies — as with, say, the congregationalist model that prevails among American churches. And they’re resistant to being co-opted by charismatic individuals or sold out to moneyed interests — unlike, say, the Tea Party movement.

The General Assembly has thus far held together Liberty Plaza’s world-unto-itself, with its food for all, incessant music, and celebrity drop-ins. But the occupation’s fate will likely be akin to the “temporary autonomous zone” imagined by the anarchist author Hakim Bey. “The TAZ,” he writes, “is a guerilla operation which liberates an area (of land, of time, of imagination) and then dissolves itself to re-form elsewhere/elsewhen.” Even now, as the occupation movement disperses, grows, and spreads, the assembly process is having to adapt. “It’s untenable, especially with so many new people, to have both real consensus and the possibility of a block,” Marina Sitrin told me. Monica Lopez, who had been traveling back and forth between Liberty Plaza and her home in Madrid, cringed and smiled as she watched Americans repeat the same trial-and-error process the May 15 movement went through. Even the beloved people’s mic, she prophesied, will get old before long and need to be replaced somehow.

In the first few days of Occupy Wall Street, those gathered would sometimes chant, “This is just a practice!” Three weeks on, with assembly-driven occupations beginning in cities and towns all over the country, many more people seem determined to get the hang of it.