Inception

"Once an idea has taken hold in the brain it is almost impossible to eradicate," says Dom Cobb (Leonardo DiCaprio).

He should know. After all, he is an 'eradicator' – an industrial spy whose work involves infiltrating people's brains when they are in a vulnerable dream state and stealing their innermost secrets. His latest assignment is even more challenging – an 'inception', which involves not taking an old idea away, but implanting an entirely new one, without the subject, in this case corporate heir Robert Fischer (Cillian Murphy), ever suspecting that the idea was anyone's but his own in the first place.

Cobb's right-hand man Arthur (Joseph Gordon-Levitt) suggests that inception is impossible, but Cobb himself insists he has done it once before. "You just," he says, "have to go deep enough" – and Cobb proves willing to go to any depth, once powerful client Saito (Ken Watanabe) has promised in return to enable the international fugitive at last to return home to his beloved children.

So a specialist crew is assembled for the high-concept heist – Cobb, Arthur, fledgling 'architect' Ariadne (Elliot Page), experienced 'forger' Eames (Tom Hardy) and experimental chemist Yusuf (Dileep Rao), with Saito along for the ride – but as they play off their elaborately layered dream-within-a-dream-within-a-dream sting operation, they must face not only the armed-and-dangerous projections of Robert Fischer's own mental defenses, but also the far more treacherously unpredictable psychic detritus of Cobb's unresolved feelings towards a past, half-real, half-dreamt, with his former wife Mal (Marion Cotillard).

If philosophers from Descartes on have discussed the difficulty, if not impossibility, for an experiencing subject to distinguish dreams from reality, then cinema, with its all-encompassing dramas of sight and sound, is perfectly suited to giving vivid, vital form to this thorny problem. For it is in cinema that suspension of disbelief sits happily with patent fictions, so that seeing both is, and is not, believing. It is this sort of paradox on which Inception depends – indeed 'paradox' is a recurrent word in the film.

The events on screen are repeatedly exposed as little more than swindle, masquerade and trickery, even as we find ourselves so involved in the characters' emotional journeys that we positively will ourselves to follow them deeper and deeper into the web of illusion, in search of some sort of transcendent, albeit well-guarded, truth that we want to believe is there, as the object of and justification for our own 'leap of faith' (another key phrase in Inception).

Writer/director Christopher Nolan is at pains to remind his viewers that they are in a cinema, watching a film woven from the stuff of other films. By making all his film's dream scenarios – and some of its 'real' scenarios – resemble distorted set-pieces from Bond and Bourne movies (chases through narrow North African alleyways, rendez-vous in swanky hotels, gunplay on ski-slopes, etc), he prompts us to recognise worlds constructed of a decidedly cinematic texture. By having Cobb's team use the song 'Non, je ne regrette rien' as an important trigger within their dreamscapes, he is going out of his way to remind us that the self-same Cotillard who plays Cobb's ex-wife has also – in her Oscar-winning performance for La Vie En Rose (2007) – played the very woman who made that song famous. And by casting DiCaprio as a noirish agent haunted by a traumatic past and forced to choose between fantasy and reality, he is virtually insisting that we compare and contrast the actor's similar role in Martin Scorsese's similarly metacinematic Shutter Island (2010), and then lose ourselves even further in the intertextual crosstalk between two films that are labyrinthine enough individually.

In his own version of inception, Nolan uses what Eames calls 'very subtle art' to insinuate in the viewer's mind an idea, itself almost impossible to eradicate, that what we are seeing may not be real at any level, on either side of the screen. He then leaves us to find our own way back home from his Escher-like 'infinite stairwells', his corridors of the subconscious and his windmills of the mind, as Cobb's totemic spinning top, used to distinguish reality from illusion, continues tracing its revolution in the head long after the film itself is over. Nolan elaborates seductive layer upon layer of narrative to trap us, much like Fischer, into placing our own image in a hall of mirrors, supplementing this floating world with our own very real hopes and fears.

There is not much more that one can ask from a movie – but Inception also delivers thoroughly believable performances in its many (purposefully) less than believable scenarios, and matches the gymnastics through which it puts the mind with a kaleidoscope of awe-inspiringly idiosyncratic imagery, as though all the tropes of a conventional thriller were being both defamiliarised and trumped before our eyes. You will no doubt need to see Inception more than once to appreciate every nuance of Nolan's carefully balanced ambiguities – but, more importantly, you will also want to. This is a film that people will be watching, rewatching and cherishing for years to come, in pursuit of answers that only they can in fact provide, as they choose to connect their own brains to Cobb's dreams. Worming its way into our consciousness with more ideas than a year's worth of blockbusters, Inception is a triumph of cerebral cinema.