Philip Seymour Hoffman: 'You're not going to watch The Master and find a lot out about Scientology'

It’s mid-afternoon, a Sunday, and Philip Seymour Hoffman looks beat up.

Spent, you might say. His breathing is heavy, as though he's just run up a flight of stairs. Maybe it's sheer emotional exhaustion or the weight of expectation. For finally, after years in development, The Master has arrived. One of the most anticipated films of the year, it's the latest offering from There Will Be Blood director Paul Thomas Anderson, in which Hoffman plays Lancaster Dodd, the charismatic leader of a religious movement known as "The Cause".

If you have heard anything about The Master, it's most likely one of two things. That Hoffman, along with his co-star Joaquin Phoenix, walked away from the Venice Film Festival with a share of the Best Actor prize. Or that it is about Scientology, the ever-controversial religion whose famous Hollywood followers include Tom Cruise, Hoffman's former co-star in Anderson's Magnolia and Mission: Impossible III.

But, while Dodd has been modelled on L Ron Hubbard, the founder of the Church of Scientology, Hoffman is adamant that The Master veers away from this. "It's quite clear that the movie is not about that," he says. "It's the groundwork. But it's not about it. You're not going to watch that movie and find a lot out about Scientology. We take a lot of liberties. I would not send somebody to this movie as a way of studying that."

Yet that has not stopped some elements of the media reporting various rumours – that Cruise walked out of a screening, that Scientologists planned to sabotage the US release of the film. It probably accounts for why Hoffman is in a testy mood. "No matter what we say, you want to still talk about it [as a film about Scientology]."

One of the finest actors of his generation, Hoffman is more than used to dealing with – or should that be "tolerating" – the press. A decade ago, when I met him for Punch-Drunk Love, another Anderson movie, one journalist asked him to "risk something" and talk about his private life. Aside from a spell in rehab for drug and alcohol abuse years ago, long before he was famous, there isn't much to tell. Together with costume designer Mimi O'Donnell since 1999, he has three kids – son Cooper (now nine), and daughters Tallulah (five) and Willa (four).

When I ask him about this later on, he remembers the incident. "Somebody wanted me to talk about my personal life. Talking about my personal life to a journalist is risky? It doesn't make any sense. That's just a choice. There's nothing risky in talking about your personal life. People do it all the time. That's not about risk. It's just about somebody wanting to talk about their personal life to the press. I'd rather not because my family doesn't have any choice. If I talk about them in the press, I'm giving them no choice. So I choose not to."

Today, sitting in the ballroom of a grand old Venetian hotel, he seems agitated, weary and wary. He looks light years away from the perfectly groomed Lancaster Dodd. Dressed in brown trousers and a short-sleeved shirt, the buttons straining a little against his belly, he's also wearing a green cap with the logo of the New York Rangers ice-hockey team on it, covering up his thatch of blond hair. His arms are covered in freckles and an unkempt sandy-white beard has sprouted across his face. If he won't be winning any GQ style awards, you sense that sartorial elegance is the last thing on his mind.

Hoffman is used to playing real-life people – most famously Truman Capote, for which he won an Oscar for Best Actor in Bennett Miller's Capote – though Dodd is a different beast. "Paul used elements of the birth of Scientology and L Ron Hubbard to fill in the story and the character," he says. "I didn't really because I wasn't really playing him. He's a fictitious character. So I tried to think of a lot of other things, in myself. I was very literal about it. I wasn't interested in playing L Ron Hubbard, because, ultimately, it wasn't his story, so I didn't want it to be confusing."

Certainly the central relationship – Dodd takes Freddy Quell (Phoenix), an unhinged Second World War veteran, into his fold – is fictitious. But set primarily in 1950 (the year Hubbard's book Dianetics was first published), the similarities between Dodd and Hubbard are clear. Both men love boats and motorcycles, both share a distrust of the American Medical Association and both are married to a Mary-Sue (the name reportedly given to Dodd's wife in early versions of the script, before it was changed to Peggy).

Hoffman refuses, however, to get drawn into a debate about whether Dodd runs a cult. "It's a movement," he says, his hand tugging at the tablecloth. "You can look at anything as a cult. Churches are cults in their own way. It's a movement that is extreme in nature. You can relate that to many religions that we have, too. I'm playing somebody who is heading one of these things, so I have to really support him and defend him. So I didn't really look at it from that point of view. It's a very cynical way to look at it. It's also, in the end, a film about a relationship between two men and how it can't work ultimately under the dynamics that they have together."

Whatever the relationship to Hubbard, the truth of the matter is that Hoffman has yet again delivered a virtuoso performance – powerful, mesmerising, unsettling. You can understand, somewhat, his ire with the reporter who asked him to take a risk. That's all he ever does on screen. Just think of that hideous scene in Happiness, where he is heavy-breathing down the phone-line to Lara Flynn Boyle. Or the drag-queen he played in Flawless. Or the grief-stricken character in Love Liza (a film written by his brother Gordy), who forms an addiction to huffing gasoline in the wake of his wife's suicide. People on the margins, spinning out of control.

The Master, however, represents his biggest collaboration to date with Anderson, who has cast Hoffman in five of his six films, more than any other actor. Their careers have almost gone in tandem. While Hoffman's early appearances included a role in Scent of a Woman opposite Al Pacino and Nobody's Fool (where he got punched by Paul Newman), it was as the garrulous craps player in Anderson's 1996 gambling debut Hard Eight that he began to gain notice. By the time of Boogie Nights, his portrayal of porn-movie gopher Scotty, a perfect encapsulation of awkward self-loathing, Hoffman was a fundamental part of Anderson's rep of actors.

Their friendship, he says, is not like the Master's relationship with Freddie (to begin with, the 45-year-old Hoffman is three years older than Anderson). There is no mentor-pupil equation. "It's different to that," he says. "It's more of a mutual friendship. When we're working together, then the status can change, because he's directing, but there is so much time we spend together where it's just the two of us." They'd spend hours talking about Dodd, across the course of three or four years, Hoffman allowing the character to percolate "in my mind".

The conversation takes an interesting turn when we start to talk about therapy. Some of The Master's most powerful scenes come when Dodd takes his young charge through some intense sessions designed to access his unconscious and root out his traumas. "I think therapy is a helpful thing," says Hoffman. "I think everyone knows it. You do it for your life, you do it for yourself, because you want to explore some things, and get at the bottom of some things. It's about your life, the quality of your life. [It brings out] a lot of humility, I think."

What makes Hoffman such an honest actor, so truthful, is just how knife-edge he can be. In the past, he's talked about wanting "to really show what it meant to have such doubt about yourself, such fear", to explore the difficulty of making connections, our own feelings of inadequacy. "It's hard," he says, of acting. "The job isn't difficult. Doing it well is difficult. To act really well takes sharp, sharp focus. Making the choices and focusing in such a way that you can be living moment to moment… it's tough, it's tough."

Born in Fairport, New York, Hoffman grew up in the suburb of Rochester – an existence he has described as somewhere between "white trash and affluence". Raised with two sisters and an older brother, Hoffman saw his parents split when he was nine. His father, who worked for Xerox and "travelled a lot", walked out of the family home, leaving his mother to bring up their four children. A civil-rights activist and lawyer who later became a judge, Marilyn O'Connor was also a staunch feminist – and an intelligent, optimistic, artistic soul, by all accounts.

Hoffman was entirely under her spell as a teenager. Just look back to his Oscar acceptance speech. "Her passions became my passions," he told the world. As a youngster, Hoffman was introduced to both the theatre and to sport by his mother. A burly teen, he was more taken with the latter: baseball, American football and wrestling. All his friends were "jocks", he says. But then a neck injury, sustained in wrestling practice, put paid to any thoughts he had of taking it further. "You have to do something else to fill your time." His mind turned to the stage.

"I'd been going to the theatre since I was 10 or 12. I always loved the theatre. I got into plays in high school then I ended up going to college for it. So it was around then that I thought it was something I wanted to do."

His "lightning bolt" moment came when he saw Arthur Miller's All My Sons for the first time. He studied drama at New York University's Tisch School of the Arts, soaking up the art-form. He still does. He's been heavily involved with the New York-based LAByrinth Theater Company for years, spending more than a decade as its co-artistic director.

It was his time in a production of Jack Goes Boating that later inspired him to turn it into his modest 2010 directorial debut. And it's tempting, if mischievous, to look at his role as Caden Cotard in Charlie Kaufman's 2008 film Synecdoche, New York – a theatre director riddled with anxiety and neuroses – as some sort of warped self- portrait. He claims he never wanted to be a screen star, just to ride his bike to his local theatre. "All of a sudden somebody stares at you in a restaurant and you think they don't like you or they want to fight you or you know them and you forgot their name. Then you realise they saw your movie and they know you. And that's shocking."

While he's not one to bang the drug for politicians, he voted for radical candidate Ralph Nader in the 2000 presidential elections, and even fronted a documentary, Last Party 2000, filmed over the final six months of the campaign at the Republican and Democratic National Conventions. Having excelled as a campaign manager in George Clooney's The Ides of March, I ask how he feels about all the hoopla in an election year in the US. "There's more attention put on it because it's a longer process," he says. With the celebrity backers and televised debates, it feels like showbiz. "Well, that's the media," he replies, the disdain in his voice returning.

The chances are, he will be venturing into Hollywood's own popularity contest over the winter months, with an Oscar nomination almost certain for The Master. He's been there before, of course. Other than his win for Capote, he has been nominated twice in the Best Supporting Actor category – for his accused priest in Doubt and his CIA operative in Charlie Wilson's War. Winning was terrifying, he says. "Getting up in front of 100 million people… you can't imagine the fear! You don't get up there in joy. You get up there in absolute terror. Like I'm going to say something really stupid and everyone in the world will hear!"

Currently shooting Anton Corbijn's political thriller A Most Wanted Man, he already has musician tale A Late Quartet in the can and there's talk he will direct again – a supernatural drama called Ezekiel Moss. But, most intriguingly, he's about to star in Catching Fire, the sequel to The Hunger Games. Based on the hit books by Suzanne Collins, in which teenagers in a totalitarian society are forced to fight to the death for mass entertainment, Hoffman will play Plutarch Heavensbee, the politically astute head gamemaker, who organises the tournament.

"I wasn't aware of the books until the film came out and people made me aware of them," he says. "I'm in the middle of reading the last one now; they're very special.

"She's written these books for teenagers about fascism and they overthrow fascism, and then what overthrows fascism is as bad as the fascist government. It's so smart." Does he think teens get the political subtext? "I can't see how they couldn't. She's very clear." So does this mean he's about to become a teen idol? "I don't think that will happen!" And he smiles – a rare ray of sunshine across a cloudy face.

'The Master' (15) is out in cinemas on Friday