If we appear to seek the unattainable, it has been said, then let it be known that we do so to avoid the unimaginable.

– The Port Huron Statement, 1962

Participatory democracy – with its battle-cry "let the people decide" – was the call of 60-some young American activists who launched the Students for a Democratic Society (SDS), 50 years ago this week.

Our 25,000-word document became known as the Port Huron Statement, after the retreat center belonging to the United Auto Workers on the shores of Lake Huron. It was debated and adopted after five inspired days and nights, ending in the starry show of an aurora borealis, named for a goddess of dawn.

The Port Huron Statement resonates to this day – for example, in the 17 September manifesto of Occupy Wall Street, which called for a "direct and transparent participatory democracy". The thousands of nurses who recently marched in Chicago for a so-called Robin Hood Tax also declared their explicit commitment to participatory democracy – and economic democracy, too. The American historian Michael Kazin, a 1967 member of the Harvard SDS, recently wrote that it was "the most ambitious, the most specific, and the most eloquent manifesto in the history of the American left". And the longest, he added.

We drew on similar movements in Britain at the time, from the Campaign for Nuclear Disarmament [CND], which opposed the cold war nuclear arms race, to the intellectuals who gathered around the New Left Review. Few of us were inheritors of Marxist traditions, though as students, we all read and debated Marx, especially his humanist 1844 Manuscripts. Those few who grew up in Communist traditions were shocked and alienated by Nikita Khrushchev's 1956 revelations about Stalinist crimes, and by the Soviet Union's brutal crushing of Hungary's democratic uprising. Those who came from social-democratic traditions felt equally stranded by the apparent absorption of our elders into a labor bureaucracy that supported the escalating Vietnam war and had secret links with the CIA.

Most of those who founded SDS at Port Huron were more "new" than "left". We were homegrown American populists, many inspired by spiritual traditions like those that propelled Dr Martin Luther King. It was the year of reform in the Catholic Church, bringing the first stirrings of liberation theology. It was a moment when bearded young Cubans and South Korean students rose up against our dictators in their countries.

Intellectually, we were drawn more to Albert Camus' The Plague, C Wright Mills' The Power Elite than to Marx, Lenin or Trotsky. Some of us were touched by Doris Lessing. The chronology is important to bear in mind. This was all before the assassination of John F Kennedy, before the publication of Silent Spring, before The Feminine Mystique, before the Beatles, before black power, before LSD and, above all, before the decision to send American combat troops to Vietnam, in 1965. An old world was cracking open and we were the first to try defining what we called "an agenda for our generation".

More than anything else, we were inspired to stand in solidarity with the young black students taking direct action at segregated schools, registration offices, lunch counters, buses and trains in America's deep south. We drew theory from experience, not the other way around. Applying John Dewey's formula of "learning by doing" led us to the concept of participatory democracy.

Fifty years later, the concept keeps rejuvenating itself wherever two conditions are present: first, a deep common desire to take direct action against a moral injury; and, second, the absence of any meaningful remedy to that injustice from the formal institutions of power.

We agreed with Henry David Thoreau that it was not enough to simply cast a vote, though we took risks to make voting rights a reality. Thoreau also preached that a person must vote with their whole life, not a mere strip of paper. And John Dewey added that democracy was wider than a voting booth. We demanded more democratic relations in the patriarchal family, the remote-controlled religious sphere, the corporate-controlled workplace, the developer-controlled neighborhood, and the expert-controlled bureaucracy of war.

A strategic plan arose from acting in this spirit, which was to steadily displace the white southern Democrats from their segregated power base, empower blacks and students as catalytic new constituencies, and realign our government's policies away from the Vietnam war. If we had succeeded, it would have been a better world.

Why did we fail after such bright beginnings?

First, the archives show that JFK's assassination all but assured that Vietnam would escalate. Second, the turn towards war and away from the domestic agenda led to several years of racial rebellions and the formation of revolutionary groups like the Black Panthers, pushing droves of white voters into the Republican party. Third, the military draft led countless young people into resistance and disillusionment with the Port Huron vision of reform. Fourth, FBI and police counterintelligence programs were more than our fragile movements could bear.

Finally, we turned on ourselves in mad sectarian squabbles. Having once reached a membership of 100,000 with virtually no budget, SDS was finished as an organization just six years after it was born.

The lasting legacy, however, is participatory democracy, in both practice and theory – the only banner that might unify the rainbow of popular movements from generation to generation.