All sides seem to agree that the Occupy London Stock Exchange protesters are leaving undefeated. The cathedral authorities stress that although 'tents and camping equipment' have been removed from the vicinity of St Paul's, 'ideas and protests' are still welcome. One protester described the eviction as 'an opportunity for us to move sideways and be innovative and creative'.

But in London, as elsewhere, as the campers have had to move sideways, Occupy will have to find another way forward. It isn't the kind of protest in which an achievable goal is linked to a symbolic nuisance, so that when the authorities see reason everyone can go home. Its demands have been much bigger, and they've been backed by the continuing physical presence of people obstinately taking up space. In this respect it's much more like the Greenham Common peace camps, or Brian Haw’s one-man encampment in Parliament Square, than a traditional demonstration or sit-in. Their current position recalls the experiences of the Situationist International, a group the Occupy movement has often been compared to, not least by Adbusters, which issued the original call to occupy Wall Street last July.

Founded in 1957, the SI didn't seek converts; situationists didn't have an 'ism', any more than violinists or physicists. A situationist was someone who contributed to the construction of situations: a deceptively bland phrase which stood for a revolutionary transformation of society and everyday life, uniting Marxism with Surrealism and taking them onto the streets. Initially working in art, architecture and film as well as political theory, in 1961 the Situationists took a decisive political turn, ruling that art could only be anti-situationist, and that the path to the construction of situations lay through wildcat strikes and workplace occupations.

After May 1968, and the only wildcat general strike in history, the situationists hit difficulties. Political work had been favoured on the grounds that situationist artists had merely contributed to the spectacle of artistic radicalism. But if the only revolution worth working for would be carried out by workers transforming their own daily lives, and if the workers had just been defeated and gone back to work, then what? Oppositional activism would simply contribute to the spectacle of political radicalism – a criticism that has been levelled at Adbusters too.

If both radical art practice and radical political activism are irredeemably compromised, what can be done? Sometimes, perhaps, the answer is not much. Guy Debord, the only Situationist present at both the group's founding and its dissolution in 1972, wrote in 1967 that revolutionary critique must ‘work among the irreconcilable enemies of the spectacle, and admit that without them it is nothing’; in between times, it ‘must know how to wait’.

And how we would know the enemies of the spectacle when they reappeared? Essentially, by their negativity. In 1979 Debord wrote that the workers of Italy

can be held up as an example to their comrades in all countries for their absenteeism, their wildcat strikes that no particular concession can manage to appease, their lucid refusal of work, and their contempt for the law and for all statist parties.

Debord identified the keynotes of the long wave of protest that traversed Italy in the 1970s, peaking in 1977: intransigent physical presence (or recalcitrant absence), refusal to identify with any established political party, protests with no single demand. Putting forward 'ideas and protests' wasn't the point; the Italian 1977, like May 1968, was a fertile source of slogans and publications, but that wasn't what the movement was for. The point was to be there: to assert the identity of the movement and its opposition to the status quo by the force of physical presence.

Cutting away the ground from beneath Occupy is a real blow, and it won't be redressed by reasserting the movement's ideas in less confrontational ways: indeed, this would tend to return it to the much more manageable world of the pressure group. Occupy wristband, anyone? The movement's enemies may have understood its strengths better than it does itself.