One sign of a modern society might be its ability to generate its own thoughtful critics. North America has them by the bucket loads; it used to be Malcolm X, Angela Davis, Woody Guthrie and Bob Dylan. Now it’s Naomi Klein, Michael Moore, Oliver Stone and of course the irrepressible Noam Chomsky. The Indian subcontinent has the equally irrepressible Arundhati Roy and the Anglo-Indian author, Salman Rushdie. Australasia, still something of a colonial outpost in both politics and cultural attitudes, has its highly combatant John Pilger.

Britain has its George Monbiot, Poly Toynbee, and Gary Younge amongst its many competent journalists; daring politicians like Caroline Lucas, Jeremy Corbyn and John McDonnell; cutting-edge musicians like Linton Kwesi Johnson and of course its stand-out playwrights and film makers like Mike Leigh, Dennis Potter, Alan Bennett and Ken Loach. The African continent, both at home and in the African diaspora, has produced and continues to produce a rich seam of critics and activists, not least the revolutionary leaders of the post-colonial struggles and of course those wonderful reggae artists like Cliff, Tosh and Winston Rodney. But in the far-East, and in China in particular, the only name that comes readily to mind to the Eurocentric media, is that of Ai Weiwei.

The almost certain reality is that there are thousands of activists like Ai Weiwei scattered across Asia’s sprawling cities and towns, many of whom are forced to operate primarily in the blogosphere. Similarly, it is almost certain that the Indian subcontinent has produced thousands of its own courageous and critical artists and activists. Certainly, Ms Roy would not stand alone in this respect. But Roy and Ai Weiwei stand out from the pack in particular because of their global vision, their uncompromising internationalism and above all their essential humanism. It is one thing to be a fierce critic of local, regional and national injustice, but quite another to take that campaigning to an international dimension. In his latest artistic endeavour, that is precisely what Ai Weiwei has done. His documentary, Human Flow, speaks to every nation, every citizen and in an indisputable sense, to every moment of history. That is no mean feat.

Documenting the waves of migration that humans have been too often forced to make, Ai Weiwei reminds us that they are us, that we should resist thinking of migrants as the other to be feared and despised, but rather to embrace them as part of our shared humanity. Of course, the people that make the effort to watch this wonderful documentary are probably the ones who already embrace this philosophy. Will the powerful work ever make mainstream? I very much doubt it. Every school and college would do well to get a copy, but they probably won’t. I think this is Ai Weiwei’s most explicit political work to date and it certainly elevates him to the status of global spokesman for a more rational, more humane world order.

But his path, coming as he does from booming China, is a perilous road. The Chinese Communist Party is literally dragging hundreds of millions of Chinese citizens out of rural poverty but what they are dragging them into is highly questionable. China is replacing both Europe and America as the workshop of the world but for the millions of its newly urbanised workforce, the reality will be grim indeed. Long and punishing factory hours, cramped and unsatisfactory living conditions and precious little space for cultural and political expression. Should dissidents like Ai Weiwei seek to reform and humanise the system or advocate its revolutionary overthrow? And what would take its place? Gangster capitalism along the lines of post- Soviet Russia most likely.

In one sense, Ai Weiwei might have more impact on the Chinese system by becoming a global spokesperson against injustice and tyranny. Human Flow speaks to a global audience whilst pointing a condemnatory finger at his own local tyrants. Taking on the Communist Party head on will only result in ever lengthening imprisonment with little gained. But as China increasingly takes its place on the world stage, so it will inevitably produce its own plethora of dissident authors, artists, film producers and playwrights. They too should strut the world stage. Ai Weiwei should be seen as part of the advanced guard. Others will surely follow.

As the walls and barbed wire are erected around the capitalist citadels, Ai Weiwei pleads for empathy for those escaping poverty, war and injustice. The ability to empathise with other people’s misfortune is, after all, a key component of our humanity but one that can easily fall victim to economic insecurity and an ugly national tribalism. Ai Weiwei’s work is invariably challenging and Human Flow is the ultimate challenge: embrace the other as part of the single human tribe.