The three films made by Jafar Panahi after he was forbidden by the Iranian government from making more films form an intriguing little symbolic arc. 2011's This Is Not a Film is all clastrophobic realism, a barely-fictionalised diary of Panahi's own life under house arrest, the director playing himself and his apartment playing itself and the whole "story", if such a deeply plotless meander can be accused of having one, is about the boredom and fear that trade spaces in the life of a man insistently making a film-like object with the meager resources available in a single space, well aware that if he's caught, his life and career are terminally fucked. 2013's Closed Curtain starts to add multiple people and more of a narrative scenario to the same ingredients, expanding the world of Panahi's exile while still trapped inside a single house. And now we come to Taxi, winner of the Golden Bear at the 2015 Berlinale, which leaves the claustrophobia of the director's last two films behind, to enter the wider world and a panoply of characters.

Albeit a heavily circumscribed version of the wider world. As you can perhaps guess from the title, Taxi takes place in its entirety within a taxi cab. The action is filmed from two dashboard cameras and one handheld DSLR, and while they are frequently pointed out the windows of the vehicle, they are never permitted to leave it. Conspicuously so - at one point the DSLR user exits the car while filming, and the shot cuts away at the last minute, if not indeed the last frame, before the camera leaves what we would confidently define as the interior of the cab.

Like This Is Not a Film (and unlike Closed Curtain, which was completely fictional), Taxi is a weird sort of docufiction hybrid, clearly scripted and acted, but also in some ways indistinguishable from what the rigorously nonfiction version of the same material would have turned out to be. As in that film, our protagonist is Panahi himself, inhabiting the role of a cab driver. Or maybe it would be clearer to say that he's inhabiting the role of film director Jafar Panahi inhabiting the role of a cab driver. Panahi - both of him - can't bear the thought of not making a movie, so he has staged the taxi driver job as a way to capture footage of the wide variety of life in Tehran without being detected. And that's really it. The fleeting movie (just 82 minutes) watches with rapt attention as various colorful figures pile in and out of the back seat, going through the day; it sometimes watches Panahi watching his fares, or gazing at the city streets passing by; sometimes the camera is itself sharing in that outward gaze. Nothing so leading happens as "and those passengers end up forming a metaphorical cross-section of modern Iranian life!" - though the film was scripted and the characters all played by anonymous amateurs (to avoid implicating anyone but Panahi in his lawbreaking), the illusion that this is a pure documentary is damned convincing.

Certainly, the filmmaking is completely visible in the fashion of a documentary: various passengers notice the camera, or recognise that the great Panahi is their driver, or in some cases have conversations about the very film in which they now find themselves appearing. The reason for this, at first blush, seems to be exactly the same as the similar meta-layers of This Is Not a Film: Panahi's filmmaking has by necessity and by rhetorical strategy turned into filmmaking about his filmmaking as a process, since no matter how interesting or not this film or either of its predecessors might be, it's not as interesting as the fact that Panahi made it. And no matter what political content, the existence of the film per se is a greater act of defiance than anything said or done onscreen.

All of that is true. But Taxi goes beyond that model (I do think it is distinctly the best of the director's three post-ban films), in great part thanks to its dynamism: this is an unabashed love letter to the physical city of Tehran and the personalities of the people living in it. The interplay between the passengers and Panahi, or the passengers between themselves, is lively and consistently (also surprisingly) spiked with wry comedy that is already enough to give Taxi a strong sense of self, one that This Is Not a Film and Closed Curtain arguably lacked. It's more limber, the tone more slippery and wide-ranging; freer in a sense, albeit a freedom that is viscerally constrained by the setting. Taxi is driven by a paradox: the constantly shifting backdrop of Tehran, whether glimpsed over a passenger's shoulder, or lingered on in a long unblinking take through the windshield, gives the film an expansive feeling, like the whole world is right there for the plucking. But it's also a movie whose limitations are constantly stressed by the visuals and even the characters: the meager number of angles permitted by the small array of cameras, and the closeness of the taxi interior, tamp down hard on the visual dynamism of the movie, and no matter how much vibrant life passes through the cab and in front of the lens, we are always keenly aware that this whole movie is being made under horribly compromised conditions, a desperate attempt at gathering whatever images are possible under reigned-in circumstances.

By making Panahi-in-the-film so closely aligned but, crucially, not identical to Panahi-outside-the-film, (that is, by making him a character) Taxi manages to make these issues part of the film's text rather than its super-text, much to its benefit as a movie to watch rather than an object to parse. There's still plenty of parsing that must go on: the function of the film as a documentary on its own creation is dauntingly self-aware and requires us to overlook distinctions between "real" and "scripted" that we mostly cling to as sacrosanct elements of the documentary form. Like both of the director's last two films, it's a referendum on his filmmaking process, and like them leaves unasked and unanswered the question of why he's so driven to keep working in defiance of the government; the possibility of not making films seems to have totally escaped his consciousness. It is, one might say, a treatise on the inevitability of cinema: it insists on existing, no matter what form it must take.

The film is both easier to watch and harder to fully explicate than Panahi's other post-ban movies: it reminds me most of Abbas Kiarostami's 1997 Taste of Cherry, another Iranian film about a driver having conversations with his passengers (though Kiarostami's 2002 cab-bound Ten is the film Panahi has openly mentioned as an influence), specifically that film's contentious final scene, in which we suddenly shift into watching a film about the making of the film we're watching, something that Taxi extends to feature length, without making it any easier to unpack. The politics behind Panahi's film leads us more than in either of Kiarostami's; conversations that lumpily turn towards detailing exactly what Panahi is doing and why, or a curiously unsatisfying ending that suddenly transforms things into a wholly fictional political thriller (though one of a particularly minor sort). It's not perfect, admitting that I don't know what a "perfect" version of a self-aware movie about the limitations of filming inside a cab while one is hiding from the government would look like in the first place.

In lieu of being perfect, though, it's challenging and exciting: a movie that doesn't let us sit as passive observers but demands that we think about what how films are made and why films are made and what we (as artist or as audience) expect for films to "do". It is thick with the outrage of a lover of humanity wondering why other people don't share that love, and it's also frequently laugh-out-loud hilarious; it is about film as an esoteric and mystifyingly complex Art that also presents filmmaking as a collection of accidents whereby you just kind of point the camera and hope that interesting stuff happens. It's an exciting movie - I had far more energy leaving the theater than walking into it - and one that doesn't resemble anything else out there. How could it? Nobody in the world is making films like Jafar Panahi, literally. And that is as much as reason as the film's thoughtfulness about its own form and its appealing rendering of a wide range of human behaviors why Taxi is one of the greatest pieces of cinema I've seen in all of 2015.