The blurry snapshot catches Leon Trotsky in mid-sentence, in Frida Kahlo’s house sometime in 1937. To the left of the frame is Natalia Sedova, Trotsky’s wife. To the right is Kahlo and, half hidden behind her, a young woman listening intently: Trotsky’s secretary Raya Dunayevskaya.

We don’t know what the argument is about but we can be sure of the premise on which it is being conducted: everybody in the photograph is a Marxist. Their ideas about politics, economics, morality and art were shaped by the writings of a man born in Germany 200 years ago.

Trotsky would be assassinated in 1940, and Sedova would rage against the Soviet machine thereafter. Kahlo would become one of the most formidable female artists of the 20th century. But it is Dunayevskaya who provides the link between classic Marxism and the only form in which it can be relevant today. “Marxism,” she would insist, “is radical humanism.”

As we reach the 200th anniversary of Marx’s birth, the struggle over his ideas shows no sign of stopping. The American alt-right marched through Charlottesville claiming that the town had succumbed to “cultural Marxism”. The Bank of England governor Mark Carney has warned that Marxism could make a comeback due to the impacts of automation on jobs and inequality. Meanwhile, in China, a decidedly uncultural form of Marxism has been revived as the new state doctrine of Xi Jinping. To understand what can survive of Marxism and what cannot, we must ask what its teachings might mean in the radically different conditions of today.

By July 1850, Karl Marx was already a theorist of defeat. He had written in The Communist Manifesto (1848) that the destiny of the working class was to abolish private property and bring communism, but now he understood it was going to take some time. After two years of trying to push the democratic revolutions in France and Germany in the direction of social justice, Marx had admitted failure and fled to London.

Yet in the upstairs room of a Soho pub, over a pint, Marx assured fellow exile Wilhelm Liebknecht there was hope. He had just seen the prototype of an electric train on display in Regent Street: the age of steam would soon be over and the age of the electric spark would begin. Liebknecht records:

Marx, all flushed and excited, told me… “Now the problem is solved – the consequences are indefinable. In the wake of the economic revolution the political must necessarily follow, for the latter is only the expression of the former.”

From left: Natalia Sedova, Leon Trotsky, Raya Dunayevskaya and Frida Kahlo in Mexico, 1937

Amid the tobacco smoke, Marx had outlined a simple version of the materialist conception of history. A more complicated version would follow. In his preface to A Contribution to the Critique of Political Economy (1859) Marx explained social change as the result of a clash between two layers of reality created by human beings: the forces of production – technology and the expertise needed to deploy it – and the social relations of production: the economic model required to bring the technology to life.

Together, said Marx, the technology and the economic model form a “base” on which the “superstructure” of laws, political institutions, cultures and ideologies are founded in any given system. Revolutions happen when the economic system begins to retard technological progress.

After the 1848 revolutions failed, Marx devoted his life to two complementary projects: forming and educating stable working-class parties to defend workers’ interests and prepare them for power; and analysing the dynamics of industrial capitalism.

Only once, in a notebook that lay unpublished for more than a hundred years, did Marx hazard a guess at the form that the techno-economic revolution might take. In the “Fragment on Machines”, written in 1858, he imagined a time when machines do most of the work and in which knowledge becomes “social”, embodied in what he called a “general intellect”. Since capitalism is based on profits generated by workers, it could not survive a level of technological advance that eradicated the need for work. The clash between private property and shared social knowledge, he said, would blow the foundations of capitalism “sky high”. This prophecy, so obviously relevant to our time of robots and networked knowledge, lay in the archives, unread until the 1960s.

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In the 50 years after Marx’s death in 1883, his ideas suffered three reinterpretations. First, his collaborator, Frederick Engels, tried to systematise Marx’s ideas into a theory of everything in the universe, encompassing no longer just history but physics, astronomy and ethnography. This was the Marxism that the leaders of the early socialist parties learned; but they added a second revision: claiming that Marx’s theories justified peaceful parliamentary socialism, not revolution. Then, starting around 1899, there emerged a Marxism of confrontation and class struggle, elevating human willpower and organisational elan above concepts of historical inevitability or fixed stages of development.

This was the Marxism that both Trotsky and Sedova had learned in the Russian underground, and which brought them together as exiles in Paris in 1902. It said: Russia could only become democratic under the leadership of the working class; the task was to organise workers into a party as confrontational, secretive and hierarchical as the states run by the tsars and kaisers that they were to overthrow. Mass strikes and barricades, not elections and socialist choral societies, were their chosen weapons.

By now Marxism also contained a theory of the working class that was diametrically opposed to that of Marx. For Marx, the revolutions of 1848 had failed because capitalism was not ready to be overthrown. For Lenin, by 1902 it was the workers who were not ready – and never would be without the cattle prod of an elite, underground “vanguard party” to make them move.

The entire skilled workforce of the developed world had been bought off by the proceeds of imperialism, Lenin said: revolution would be a job for the unskilled workers in the West, and for the peoples of the less developed world. From around 1910 the nationalist revolts and land wars unfolding in Mexico, China, Ireland and ultimately Russia seemed to confirm this prediction.

Trotsky and Sedova had at least seen this new, revolutionary Marxism evolve. For Kahlo and Dunayevskaya’s generation it was the only one they had ever known.

Dunayevskaya was born to Jewish parents in today’s Ukraine in 1910 and emigrated with them to Chicago in 1922. She joined the Communist Party at the age of 14, during a school strike. She left it four years later, after having been thrown down a staircase for questioning Trotsky’s expulsion from the Comintern.

Trotsky had helped to lead the revolution in 1917. He then took part in the abolition of workers’ control in factories and the suppression of left-wing opposition movements. But faced with the rise of a new bureaucratic elite he launched, from 1923, his own left opposition. By the 1930s he had concluded that Stalinism and fascism were “twins” separated only by their differing economic basis.

Dunayevskaya’s job in the beleaguered Trotskyist movement was to run, from an office in New York, the Russian-language bulletin they were trying to distribute in the USSR. She arrived in Mexico in July 1937 to work as Trotsky’s stenographer and translator – just as the Great Purge began to roll up their underground networks.

Kahlo had joined Mexico’s communist youth movement in 1928, aged 21. “I am a communist being…” she would write later. For the generation of young intellectuals attracted to Mexican communism, this state of communist being involved not only sexual and artistic experiment, but deep engagement with the indigenous cultures of Mexico and enthusiasm for the peasant wars begun by Emiliano Zapata.

If we list the common assumptions of the people in the photograph, they would be: that revolutions usually happen in backward countries; that they involve mobile warfare, peasant land seizures and ruthless repression of the rich; that a Marxist party has to stand aloof from the conservatism of the Western working class and instead defend indigenous peoples and the racially oppressed; and that the working class is the “revolutionary subject” intrinsically at war with capitalism, though misled.

These were self-sacrificing people, prepared to use manipulation and violence for the greater good. But each was, in their own way, struggling to preserve Marxism with a human face: to resist the organised lying, mass murder and suppression of artistic freedom that Stalinism had unleashed.

The tragedy is that none of them understood how thoroughly humanist Marxism had been at its conception – and only Dunayevskaya ever would.

Self Portrait with Stalin by Frida Kahlo, 1954

Marx disdained philosophy, writing that “philosophers have only interpreted the world; the point is to change it”. The Economic and Philosophic Manuscripts – written in Paris in 1844 but not published in Moscow until 1932 – show how he came to that conclusion: through a critique of Enlightenment philosophy that is thoroughly imbued with humanism and firmly descended from a concept of human nature traceable to Aristotle, via St Augustine and Hegel.

The purpose of human beings, says the Marx of 1844, is to set themselves free. They are enslaved not just by capitalism, nor by any specific form of class society, but by a problem arising from their social nature, which obliges them to work in groups and to collaborate via language, not simply instinct.

When humans make things, or discover a new idea, we tend to embody our concept of “self” in the new object or idea – a process Marx calls self-estrangement or “alienation”. We then allow our products, mental and physical, to exercise power over us, whether in the form of religions or superstitions, or by fetishising consumer goods, or by mindlessly obeying routines and disciplines that we have created for ourselves. To overcome alienation, Marx argued that humanity has to rid itself of all hierarchies and class divisions – which means abolishing both private property and the state.

The 1844 manuscripts contain an idea lost to Marxism: the concept of communism as “radical humanism”. Communism, said Marx, is not simply the abolition of private property but the “appropriation of the human essence by and for man… the complete return of man to himself as a social (ie, human) being”. But, says Marx, communism is not the goal of human history. It is simply the form in which society will emerge after 40,000 years of hierarchical organisation. The real goal of human history is individual freedom and self-realisation.

When they published these notebooks in 1932, Soviet academics treated them as an embarrassing mistake. To do otherwise would be to admit that the whole materialist conception of history – classes, modes of production, technology versus economics – was underpinned by a profound humanism, with moral implications.

Dunayevskaya, who got hold of a Russian version of the Paris Manuscripts in the 1940s, spent nearly a decade hawking her English translation around, before publishing them herself in the mid 1950s.

She understood the Paris Manuscripts were a challenge to all previous interpretations of Marx. For the Soviet bureaucracy, the contrast between Marx’s idea of freedom and their own drab, oppressive reality was obvious. For Western Marxism, which had become obsessed with the study of permanent structures, here was a Marx arguing not for impersonal forces but for a clear and almost Aristotelian concept of human nature, autonomy and well-being. Could it be, Dunayevskaya asked, that all the disasters that had befallen the Marxist left were traceable to the rigid theories propagated by Engels? Could it be that the ruthlessness of the Bolshevik tradition, always justified by the goal of working-class power, was unjustified when compared to the goal of communism outlined by Marx? Could it be that Marxism was not, after all, a break with the philosophical humanism of the Enlightenment, but its most complete expression?

These were the conclusions Dunayevskaya drew. And from them she outlined new practical priorities. All left-wing politics in the future had to be based on the experience of individual human beings and their search for freedom. In 1950s America this meant not only joining the struggle for workers’ control on the factory floor, but also advocating feminism, black civil rights, the rights of indigenous people – and supporting anti-imperialist struggles in the global south. It meant, when the revolts against Stalinism began in Germany (1953) and then Hungary (1956), supporting them without equivocation.

When researchers eventually discovered and published Marx’s “Fragment on Machines” in the late 1960s, Dunayevskaya understood it was the last piece of the puzzle. This was not an account of capitalist economic breakdown due to the falling profit rate, it was a theory of technological liberation. Freed from work by the advance of automation, Marx had foreseen how humanity would use its leisure time: for the “free development of the individual”, not some collectivist utopia.

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Frida Kahlo took a different path. Her last painting shows her seated beneath a portrait of Joseph Stalin. Kahlo had conducted a love affair with Trotsky, seen him assassinated in her own house, and practised a form of surrealism that Trotsky praised and Moscow labelled degenerate. So why did she end up lionising the man who had ordered Trotsky’s murder?

Kahlo’s art was, though she could not know it, a lifelong riff on the Marxist concept of self-estrangement. She clearly regarded the self as the site on which human liberation would be achieved; she explored through her paintings the alienation of her gender, sexuality, disability and ethnicity. Her unflinching portrayals of unhappiness and isolation have made her, since the 1970s, the artistic patron saint of feminism.

Yet it is clear that she regarded her most famous paintings as un-Marxist and anti-political. She once described them as “small and unimportant, with the same personal subjects that only appeal to myself and nobody else”. Political paintings were what her husband, Diego Rivera, did; the concept of the personal as political was alien to her generation.

During the Cold War, as the world divided into “camps”, Kahlo made the same choice that many leftists did: she rejoined the Mexican Communist Party and denounced Trotsky. Her paintings changed, too. She began to attempt big social allegories, such as Marxism Will Give Health to the Sick (1954), from which the layers of mysticism and metaphor found in her earlier work are stripped. This was not a choice of a political dilettante. In 1952 she wrote in her diary: “I was never a Trotskyite… I understand very clearly the material dialectics of Marx, Engels, Lenin, Stalin and Mao Tse. I love them as the pillars of the new communist world.”

Kahlo’s political trajectory is a case study of what happens to a Marxism devoid of humanism. She had to keep her artistic engagement with psychological trauma and sexual freedom separate from the ideology she understood as “material dialectics”. Her focus on the defenceless self, on the beauty of the oppressed person, on the inescapable power of the natural world, were all products of her engagement with the same idea of freedom that Marx had expressed in 1844. But she just couldn’t reconcile it with the Marxism of the Moscow textbooks, and the textbooks won.

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What’s left of Marxism in our era of techno-euphoria and environmental doom? Not its class narrative: despite the doubling of the global workforce, the workers of the developing world are as encaged in bourgeois society as their white, male, manual counterparts became in the 20th century. Workplace unrest will continue but capitalism has worked out how to quarantine it away from revolution.

That’s only a tragedy if you have never read the Paris Manuscripts. The Marx of 1844 theorised communism first, and the workers’ role in bringing it about second. He saw communism not as the end point of history but, as he once put it poetically, the end of prehistory. And for the Marx of these early writings, the workers’ role in bringing communism lies in their propensity to self-educate and to create co-operative associations – not as blind automata, driven purely by their material interests.

In the early 1960s the pro-Kremlin French sociologist Louis Althusser “solved” the problem of the Paris Manuscripts by declaring them to be un-Marxist. They contained, Althusser argued, the “Marx furthest from Marx” – a humanist philosophy that should be “driven back into the darkness”. Yet he recognised their publication as a “theoretical event” – and anybody who calls themselves left-wing is still living with the consequences of that event.

Once the Paris Manuscripts were brought to light, the dilemma was clear: either Marxism is about the liberation of individual human beings or it is about impersonal forces and structures, which can be studied but very rarely escaped. Either there is a “human essence”, which we can rediscover by abolishing property and class, or we are a sack of bones conditioned by our surroundings and our DNA. Either people make history, as Marx had said, or history makes history.

During the past 50 years, much of left-wing academic thought has followed the anti-humanist path Althusser laid out. Dunayevskaya, like most other people who had embraced humanism in the aftermath of war and genocide, was revered but treated like a crank.

However, the Marx she helped to rediscover is highly relevant to the future we face. If we are to defend human rights against authoritarian populism we must have a concept of humanity to defend – as we must if we insist that human beings should have the power to limit and suppress the activities of thinking machines.

If the Marx of 1844 is correct, the ideal of human liberation and communism can survive the atomisation and dispersal of the class that was supposed to bring it. As the revolts of 2011 showed, large masses of people now possess the capacity for autonomous action, self-education and collaboration that Marx admired in the Parisian working class of the 1840s.

As Dunayevskaya understood, the impulse towards freedom is created by more than just exploitation: it is triggered by alienation, the suppression of desire, the humiliation experienced by people on the receiving end of systemic racism, sexism and homophobia. Everywhere capitalism follows anti-human priorities it stirs revolt – and it’s all around us. In the coming century, just as Marx predicted, it is likely that automation coupled with the socialisation of knowledge will present us with the opportunity to liberate ourselves from work. That, as he said, will blow capitalism “sky high”. The economic system that replaces it will have to be shaped around the goal he outlined in 1844: ending alienation and liberating the individual.

If I could speak across time to the people frozen in that photograph I would say, after congratulating them for their magnificent lives of resistance and suffering: “That inner desire you are suppressing, for Marxism to be humanistic? That impulse towards individual liberation? It’s already there in Marx, just waiting to be discovered. So paint what you want, love whom you want. Fuck the vanguard party. The revolutionary subject is the self.”

Paul Mason is a New Statesman contributing writer and author of “PostCapitalism: a Guide to Our Future” (Penguin)