The recent Occupy and Indignados movements around the world have shown the extent of the backlash against the injustice generated by the ongoing crisis of capitalism and the difficulty in articulating a co-ordinated alternative, and as such have been a source of abundant political commentary.

One rarely commented-upon aspect is the way intellectuals have responded to them. During the Zucotti Park occupation in New York in autumn 2011, acclaimed critical intellectuals – among them Slavoj Žižek, Judith Butler and Cornel West – came to support the occupiers, and to give speeches in front of them, aired through the "human microphone". A weird law in New York forbids the use of electric microphones in public space so the only way for the speaker's voices to get through was for the front rows of the crowd to loudly repeat each of their sentences. The resulting litany resembled a kind of postmodern ritual. These speeches were then rapidly posted on YouTube.

This of course is not the first time committed intellectuals have spoken in support of a movement of occupation. The Zucotti Park scene recalls a famous speech given by French philosopher Jean-Paul Sartre at the Renault automobile plant, at Boulogne-Billancourt near Paris, in 1970. Perched on a cask, Sartre addresses the workers on strike, and tells them that the alliance between intellectuals and the working class that once existed should be rebuilt. These were times of revolutionary upheaval, in France and elsewhere, and intellectuals were urged to take sides.

Despite visual similarities, these two scenes, separated by more than 40 years, are in fact very different. For one thing, Sartre used an electric microphone – modernity had not yet become postmodernity. Sartre also wore a fur coat that only militant hipsters would dare to wear these days.

More seriously though: Sartre spoke in front of automobile, ie industrial, workers, whereas Žižek, Butler and West addressed a more indeterminate audience. The exact sociology of the current global movements is still up for debate. A more "middle class" recruitment than the worker's movement of the 19th and 20th century, with higher "cultural capital", seems indisputable, though important sectors of the working classes are also involved. Žižek, Butler and West, moreover, spoke not in front of an occupied factory, as Sartre did, but in a public place. The occupation of public places is a trademark of these new movements, and the difference is crucial. If occupying public spaces is a matter of "reclaiming the street", or of demanding a "right to the city", then it is simultaneously a symptom of their not knowing what else to occupy.

There is a second crucial difference between the two scenes. Sartre was never actually a member of a working class organisation but his political and intellectual universe was organised around their existence, and they structured the political field in which he spoke when he addressed the workers. What about Žižek, Butler and West? It may be a good thing or not, but today's critical intellectuals, no matter how committed they may be, are "free-floating" and not organically linked to any kind of organisation.

A final difference between these two scenes is that Sartre was not an academic. He was so distrustful of bourgeois institutions that he refused the Nobel prize for literature in 1964 (as Guy Debord said at the time, refusing the Nobel prize is nothing, the problem is having deserved it). Sartre was very successful as a novelist and a philosopher, which permitted such "aristocratic" dismissal of all things vulgarly bourgeois. Žižek, Butler and West, on the other hand, are academics, as are most, if not all, critical thinkers today. Exceptions may be found, such as Bolivian vice-president Alvaro Garcia Linera, who is one of Latin America's finest philosophers and sociologists. But today, the production of influential critical ideas is more and more the monopoly of academics.

Universities have changed considerably since the end of the 19th century, transformed from small, elitist institutions to mass learning ones. However, the political and intellectual fields have grown more and more apart since the second part of the 20th century, to the point that non-academic intellectuals (even among fiction writers) are a species virtually extinct.

For the Italian Marxist Antonio Gramsci, the purpose of a political party of the working classes is not only to organise collective action, but also to organise collective thought and knowledge. And such serious thinking takes time. It requires permanent organisation, and not only "temporary autonomous zones", to quote a widespread slogan in today's movements. It also requires "mediating" institutions that permit theory and political practice to interact. What else has been the purpose of the worker's daily paper, the cadre training school, the radical publishing house, or the theoretical journal?

Each epoch comes up with its own forms of collective intellectuality, its own original mediating institutions. What will these look like in the 21st century? This is a question of utmost strategic importance. In the nascent field of so-called "distance education", universities have a considerable advantage, but the international left has to catch up. However deep the current crisis of capitalism, the majority of the people will not be convinced to participate in grand-scale social transformation processes unless the "where next?" question is answered – and these mediating institutions are precisely the place where it should be tackled.

One should start by acknowledging that, despite all the fuss about the internet, Facebook, Twitter, and "horizontality", all recent interesting ideas coming from the left have been elaborated in rather old-fashioned journals, such The New Left Review, the Socialist Register, Historical Materialism and their equivalents in other countries. These now come with websites and social media accounts. But this has in no way altered the content and style (for instance, the length) of their articles. The same can be said about books written by critical thinkers. Alain Badiou, Butler, Žižek, Antonio Negri, Leo Panitch or Donna Haraway write books that are no less substantial than the ones published by previous generations of critical intellectuals.

This doesn't mean that the left shouldn't use new media, of course. These were abundantly taken advantage of, for instance during the Arab spring, to mobilise and organise. But when it comes to elaborating relevant ideas by way of the new media, much remains to be done. One pioneering initiative has been that of David Harvey, the British radical geographer based in New York, who recorded his classes about Marx's Capital and posted them on his website, where they have been seen by thousands around the world. More of this is needed.

This is not to say that the teaching only goes one way. The ongoing social movements have produced and will produce in the years to come innovative knowledge and political knowhow. One striking example is the question of "gratuity" – the claim for free access to public services, such as parks in Turkey or public transportation in Brazil, has been central to these movements. Yet there exists no serious theory of gratuity in critical theories today, which would provide a history of this demand, or analyse its anti-capitalist potential. Hence, more than ever, intellectuals should learn from the movements from below. This means not only supporting them "from outside" once they have occurred, as many have done, but conceiving of one's intellectual activity as part and parcel of a collective intellectuality. Only then will the monopoly of academics on the production of influential critical theories be broken.