My advice is: don’t trust anyone who claims the movie is hogwash. And don’t trust Stone either. Movies are, almost by definition, a demagogic art form: they can emotionally persuade you of just about anything, which is precisely why Stone’s movie will be dissected with vehemence. An entire generation of filmgoers is hereafter going to look at these events through Stone’s prism. If history is a battlefield, “JFK” has to be seen as a bold attempt to seize the turf for future debate.

It is also “just” a movie, and one that for three hours and eight minutes of dense, almost dizzying detail, is capable of holding the audience rapt in its grip. If Stone was just a clumsy hack “JFK” could be as easily dismissed as Hollywood’s first, long-forgotten conspiracy movie, “Executive Action” (1973). But Stone’s work is, on many levels, stunning. Using as a base Jim Garrison’s “On the Trail of the Assassins” and Jim Marrs’s “Crossfire,” Stone and coscenarist Zachary Sklar structure their film as a thriller, with New Orleans D.A. Garrison (Kevin Costner) as the beleaguered investigator who stumbles upon links between Oswald (Gary Oldman) and local rightwing, anti-Castro zealots that implicate those in the highest corridors of power. It is, quite deliberately, a “Mr. Smith Goes to the Assassination,” complete with a climactic courtroom peroration that is a 90-proof Capraesque barn raiser, down to the Jimmy Stewart catch in Costner’s throat.

At this, a lot of people are going to cry foul. By turning Jim Garrison–a troubling, shoot-from-the-hip prosecutor whose credibility has been seriously questioned–into a mild-mannered, foursquare Mr. Clean, Stone is asking for trouble. “JFK’s” Garrison is perhaps best viewed more as a movie convention than as a real man. Stone has always required a hero to worship, and he turns the D.A. into his own alter ego, a true believer tenaciously seeking higher truth. He equally idealizes Kennedy, seen as a shining symbol of hope and change, dedicated to pulling out of Vietnam and to ending the cold war.

But it is possible to remain skeptical of “JFK’s” Edenic notions of its heroes and still find this movie a remarkable, necessary provocation. Real political discourse has all but vanished from Hollywood filmmaking; above and beyond whether Stone’s take on the assassination is right his film is a powerful, radical vision of America’s drift toward covert government. What other filmmaker is even thinking about the uses and abuses of power? The first footage we see is Eisenhower’s farewell address in 1961, in which he presciently warned the nation to guard against the growing threat of the military-industrial complex, and everything that follows is an illustration of that thesis. That “JFK” comes out in the reign of our first ex-CIA president is an irony that hangs unstated over the movie.

Anyone who’s ever dipped into the contradictions of the assassination knows what a spellbinding, crazy-making story it is–and Stone does it justice. He manages to pack in an astonishing amount of information while maintaining suspense and narrative clarity. Quasi documentary in style, “JFK” shifts between color and black and white, fact and speculation, newsreel and staged recreation, so that you can’t always tell what’s real footage and what’s not, never mind what’s true and what’s not.

Charged as Stone’s style is, he mercifully discards the strong-arm tactics of “Born on the Fourth of July.” Costner’s understated integrity gives the film a steady anchor. He’s playing an icon and he plays him with unfussy grace. The flamboyant roles go to the villains, a fascinating gallery of shady characters, none more bizarre than Joe Pesci’s David Ferrie, the hairless, chain-smoking mercenary pilot whose untimely death crippled Garrison’s case. Tommy Lee Jones is a powerful, if too overtly sinister, presence as Clay Shaw, and Kevin Bacon shines as the fascist hustler/convict (a composite character) who claimed to be privy to Shaw and Ferrie’s plotting. (That all three are homosexual has made the gay community understandably nervous, but the film itself shouldn’t be charged with homophobia.)

The cast, studded with star cameos (Garrison himself pops up, ironically, as Earl Warren), is too huge to single out. But mention must be made of Oldman’s creepy Oswald, and Donald Sutherland’s mesmerizing turn as the mysterious X (based on L. Fletcher Prouty, former aide to the Joint Chiefs of Staff and an adviser on the film) who functions as the film’s Deep Throat.

What X tells us may be more than many people can, or want, to swallow. No one should take “JFK” at face value: it’s a compellingly argued case, but not to be confused with proof. But my hat is off to the filmmaker–and Warner Bros.–for the reckless chutzpah of the attempt. Make no mistake: this is one very incendiary Hollywood entertainment. Two cheers for Mr. Stone, a troublemaker for our times.