Bong Joon-Ho’s Snowpiercer has been praised for its action-movie spectacle and its message of class struggle. It exceeds expectations on both counts. Amid tightly-paced sequences that eschew standard-issue Hollywood pyrotechnics, it evokes some of the thorniest dilemmas of socialism and revolution, in the twentieth century and today.

This is a science-fiction adventure set entirely on a train. Or rather, the train, which forever zooms around the planet carrying the last remnants of humanity because the outside world has been rendered uninhabitable. The class hierarchy within the train is expressed physically: the closer you are to the front of the train, the more opulent and leisurely your existence.

The script, written by Bong and Kelly Masterson, takes the central conceit of the train from a decades-old French graphic novel of the same name, though the plots of the two stories are quite different.

Most of the movie’s story focuses on the figures of Curtis and his mentor Gilliam (wonderfully portrayed by John Hurt). They lead a proletarian revolution, touched off by a police raid that seizes several working-class children and takes them away for reasons unknown. They are fighting to make it to the front car and confront the mysterious Wilford, who controls the train and whose corporate emblems appear throughout it.

Curtis makes the stakes plain in an early conversation with Gilliam. “If we control the engine, we control the world,” he says. “Without that, we have nothing. All past revolutions have failed because they couldn’t take the engine.” Not exactly subtle.

As they struggle forward, the revolutionaries confront various representatives of the existing order. Tilda Swinton gives a gleefully wicked portrayal of the sorts of imperious and yet timid figures who serve the ruling class without quite being a part of it. Alison Pill, best known as the sullen indie rock drummer in Scott Pilgrim vs. the World , appears as a prim schoolteacher cheerfully indoctrinating the young ruling class in the ways of self-assured domination and patrician condescension.

Along the way, the band of rebels also breaks out a prisoner named Namgoong Minsu, who once designed the locks dividing the train cars. He and his daughter grudgingly agree to join the revolutionary forces as they continue inexorably toward the front.

It adds up to an exciting and well-constructed action movie, with more interesting characters and more legible cinematography than the chaotic visual gibberish of CGI and explosions that comprise most contemporary American blockbusters. Bong does great things with the cramped and linear environment of the train, from the grim fight scenes in the back to the surreal opulence of the front cars.

And while the excessive length of big Hollywood movies is another of their consistently irritating qualities, I only occasionally found this movie’s two hours overlong. I certainly trust Bong to make editing choices over Harvey Weinstein, who wanted to cut twenty minutes out of the film and add superfluous voiceovers. As it is, Snowpiercer is an enjoyable spectacle whether you care about its political message or not.

But this is also a story with genuinely subversive and radical themes. If Snowpiercer had merely told the tale of an oppressed working class rising up to seize power from an evil overlord, it would already have been an improvement over most of the political messages in mainstream cinema. There are all sorts of nice touches in its portrayal of a declining capitalism that can maintain its ideological legitimacy even when it literally has no more bullets in its guns.

But the story Bong tells goes beyond that. It’s about the limitations of a revolution which merely takes over the existing social machinery rather than attempting to transcend it. And it’s all the more effective because the heart of that critique comes as a late surprise, from a character we might not expect.

The allegory is perhaps too general to root in any specific theory. But it evokes a tradition of critiques that grappled with the limitations of both reformist social democracy and Soviet Communism, which attempted to seize power and to ameliorate exploitation without really challenging capitalist labor as a system of alienation and domination.

This has taken forms ranging from Moishe Postone’s Frankfurt School-derived critique Time, Labor and Social Domination , to Jacques Camatte’s journey from left communism to primitivism, to Kathi Weeks’ post-work leftism, to Paolo Virno’s adoption of the biblical language of Exodus in his call for a collective “defection from the state bond, from certain forms of waged work, from consumerism.”

It’s impossible to say how fully this is intended, and whether Bong is familiar with any of the work in this tradition. But while the theoretical wellsprings may be ambiguous, Bong’s leftist commitments are not. He has talked about his past as a student activist and affirmed his membership in South Korea’s socialist New Progressive Party, albeit with the petit-bourgeois reservation that “whatever the party or organization, it isn’t possible to exceed the power of one passionate individual.”

The website io9 conducted a revealing interview with Bong in which he clarifies his political intentions with Snowpiercer . He says that “the science fiction genre lends itself perfectly to questions about class struggle, and different types of revolution.” And what his latest production has to say about class struggle and revolution is complex and powerful, far more so than you’ll get from most ostensibly left-wing filmmakers — or many Marxist theoreticians, for that matter.

The film will inevitably be read as a fable of ecological catastrophe as well, with the inhospitable cold of the world outside the train arising as an unintended consequence of attempts to reverse global warming. But this is something of a red herring (or a green herring, as it were). The cold, brought about by a mysterious substance perhaps inspired by Kurt Vonnegut’s “ice-nine,” has no real narrative purpose other than to restrict the remains of humanity, and the film’s story, to the interior of the train.

In his io9 interview, Bong makes explicit that “it’s not humans per se, but capitalism that’s destroying the environment.” And clearly it’s capitalism that’s at the heart of his allegory. Or, to be a bit more precise, an industrial logic that has defined the history of capitalism, but that was taken up by many of the anti-capitalist state-building projects of the twentieth century.

The train symbolizes that system, which subordinates everyone to logics of domination through labor while convincing them that no other world is possible — that only death awaits them outside the machine.

If Curtis’ journey represents a revolutionary class struggle, his final encounter with train-leader Wilford expresses the limitations of the main twentieth-century revolutionary projects. For it turns out that he is only capable of perpetuating the train’s oppressive logic, albeit perhaps with a new figurehead in charge. Wilford even suggests that the whole “revolution” was a charade he concocted — if not in collusion with Gilliam, than at least with his service as a useful idiot.

Were that the endpoint, we’d be left with a nihilistic trope familiar from anti-revolutionary liberalism: Meet the new boss, same as the old. For something more radical, we have to look elsewhere: to Nam, the former system insider turned renegade.

The narrative hides Nam’s significance for most of its length. It seems not coincidental, in his first movie for English-speaking audiences, that Bong makes this character one of the only prominent non-Westerners in the movie. He is played by Song Kang Ho, a regular in Bong’s Korean work, and speaks no English lines.

The Curtis character, meanwhile, misdirects the audience into seeing him as the film’s protagonist, right until he meets his pathetic dead end. He is played by Chris Evans, who is not just a handsome young slice of white beefcake, but literally Captain America.

Yet it’s the surly Korean who turns out to be the real hero. At a climactic moment, he tries to warn Curtis away from a confrontation with Wilford that will prove disastrous. Instead, he suggests that the whole premise of the train is a lie — that the conditions have ripened to make life outside the train finally possible. He offers, to put it in Marx’s words, the possibility of a realm of freedom beyond the train’s implacable world of necessity.

Once again, Bong’s sympathies seem unmistakable. In the io9 interview, he asks whether it is “more revolutionary to want to take control of the society that’s oppressed you, or to try and escape from that system altogether?” Of Nam, he says only that his ideas of class struggle are “above” anything Curtis can conceive.

Making a break for freedom brings with it great risks, of course, and Snowpiercer doesn’t shy from this, either. The political scientist Adam Przeworski once proposed that the transition out of capitalism might inevitably entail an intermediate period of great hardship: “To reach higher peaks one must traverse a valley.”

And one can’t know for sure that the higher peaks will ever be attained; catastrophe is also a possibility, the common ruin of the contending classes. The conclusion of Snowpiercer resembles such an apocalypse, albeit with some hope for the future. But even then, it’s not clear whether this was the only possibility, or whether the catastrophe was only a result of Curtis and his comrades’ inability to see where the real revolutionary road lay.

All too often, explicitly political art fails as both art and politics. Socialists shouldn’t put up with half-assed imitations of popular genres, nor with political messages denuded of anything but the lowest common denominator.