Director Danny Boyle has never been one to repeat himself, from Trainspotting to 28 Days Later. But the leap in subject matter that he made from his award-winning Slumdog Millionaire to 127 Hours is as prodigious as any move the new film’s protagonist makes.

Well, except for cutting off his own arm.

Slumdog was as urban as a film gets; in my memory the screen was always overflowing with humanity, color, and motion, while 127 Hours’ hero Aron Ralston (James Franco) is mostly alone on screen, except in his fantasies. And, again, apart from his fantasies, he doesn’t get around much, because, as you no doubt know, he was trapped in the bottom of a very narrow Utah canyon, his right arm pinned under a boulder.

On the face of it, Ralston’s true-life story seems like it could be the inspiration for a Jack London short story, but hardly for a film. In fact, part of the film’s appeal comes from wondering how Boyle and Franco will make a story about being stuck in a narrow space cinematic.

But the nimble pair meet the challenge so fully that they give the surely false impression that making the film was a breeze. Boyle handles the filmmaking chores with utter confidence. He makes full use of stark desert beauty and his subject’s hallucinations, so that the film is in fact constantly in motion. There’s lightness to his touch, and an exhilaration to much of his imagery (especially during a desert thunderstorm) that, in theory at least, threatens to turn Ralston’s grim tale into a joyride.

But Boyle doesn’t cross that line. Given the nature of the story, I’d say he makes the audience suffer just enough. When the time comes, his camera doesn’t flinch from Ralston’s self-inflicted carnage, but it doesn’t revel in the gore either.

Franco’s accomplishment here might be even more impressive. He’s never really convinced me that he was his character before, but he thoroughly inhabits Ralston, and makes a memorable and even important character out of him. This could be a career-defining performance.

Why important?

The film makes much of Ralston’s blithe sense of self-reliance. When he sets out for the desert, he never tells anyone where he’s going; he never leaves a note, just in case. He took his own invulnerability for granted. Franco’s Ralston ultimately comes to represent some essential strands in the American character. A rugged individualist, Ralston is an updated Western hero, living the unattached life that his kind of heroism requires (he’s a regular rescue-mission volunteer).

The film makes it clear that it’s the essential selfishness of this archetypical character that gets him into trouble, and it’s a self-centeredness that Ralston comes to bitterly regret.

Watching Franco’s Ralston struggle for his life, I couldn’t help but think about the Chilean miners’ saga, which was a triumphant story about social groups and cooperation. I wondered if Boyle intended here a critique of the American exaltation of self-reliance, of our go-it-alone, “cowboy” ways, as the rest of the world sees them, which has led us to our own desert difficulties in recent years.

On the other hand, Ralston does save his own life through extreme self-reliance, so which is the ultimate message?

To my surprise, 127 Hours turns out to be a thought-provoking film that also provokes thrills, and, together with The Social Network, which it reflects in interesting ways, is the film of the year so far.