The Facebook boss Mark Zuckerberg made headlines when he said earlier this year that the social media giant wants to bring together communities and help people “find a sense of purpose and support”. As a film-maker, I know that cinema is an ideal medium for opening minds and, in Zuckerberg’s words, “expanding our horizons”. Films are not designed to serve as schools or teach lessons. They are spectacles. Even so, those spectacles can have profoundly political dimensions. Through cinema, distant countries have got to know one another and powerful taboos have been overcome.

Politicians rightly fear and respect these powers. This is why authoritarians have always sought to subjugate them. History shows us that fascists and Stalinists have little patience for dissenting views – especially when those views are immortalised in the form of a book, a painting, a play or a film.

Everyone who cares about culture should take an interest in this week’s appointment of a director-general

The most straightforward way of determining whether a government is democratic is to ask: does it allow cultural life to proceed independently, or does it seek to bend culture to its own purposes?

These same impulses towards control extend to the business world. Corporations tell us not just what we should think about them, but how we should see the world around us. They sponsor art and culture that serves their purposes. The rise of new media channels should mean more freedom, but the fundamental constraint – funding – remains.

Film-makers have always been subject to monetary constraints, with producers and financiers demanding changes to scripts or casting. Often, film-makers have no choice but to censor themselves so their work can see the light of day. But film-makers are not alone in confronting this challenge. All those who seek to produce culture must answer the fundamental question of how to pay for it.

This is why the promotion of culture – free, independent, unshackled by state censorship or corporate sponsorship and accessible to all – is vital. Culture is not something we can take for granted; it requires a constant state of struggle. This is not a struggle for any one country to pursue on its own. This is why we have Unesco, the United Nations Educational, Scientific and Cultural Organisation. The organisation’s mission is a vital one: to “build peace in the minds of men and women” and “create the conditions for dialogue among civilisations, cultures and peoples, based upon respect for commonly shared values”. That means fostering quality education for all, putting science to work for sustainable development, and celebrating cultural diversity.

In the 1960s and 70s, the organisation had the intellectual heft to serve as an incontrovertible reference point for the world of culture. Unfortunately, Unesco has lost much of its credibility and prestige since then. But it remains the only global body with the legitimacy to take positions not only on cultural and artistic matters, but also intellectual and scientific ones. Unesco’s word still carries great weight: its reports and warnings not only signal threats to our collective heritage but also help shape the path of culture and science across the globe.

That is why everyone who cares about culture should take an interest in this week’s appointment of a director-general to replace Irina Bokova, who will step down in November.

Interview: Costa Gavras Read more

I believe Audrey Azoulay, who was France’s culture minister until earlier this year and is one of the candidates, would be perfect, as I have seen her approach her work not with the mindset of a politician or a bureaucrat, but instead with the vision of an artist.

Our great global cultural institutions, Unesco among them, have failed to keep up with the way culture has changed in our globalised world. Azoulay understands how the internet and digitisation have changed the arts. To fulfil its mission in this new era, Unesco needs to embrace these technological changes and stop seeing our present and future challenges through the lens of the past.

Were they to look beyond their business interests, businessmen such as Zuckerberg could be incredibly helpful in meeting these challenges. Social media networks are incredible tools for building bridges across borders, but cannot create the cultural touchstones that bring disparate peoples together. Indeed, we have too often seen them having the effect of driving neighbours apart.

If our shared objective is to heal divides, we must work together to protect our shared global heritage, while educating our children to preserve it when we are gone.

• Costa-Gavras is an Oscar-winning director and screenwriter. He is president of the Cinémathèque Française in Paris