Phoenix, 40, is never easy - in person or on screen. The same reticent and enigmatic behaviour that makes him look like a hostage on the red carpet renders him a natural for the messed-up, hard-to-play roles that would flatten most of his Hollywood peers.

Minutes after irritating his previous interviewer, Phoenix welcomes me with a big, overzealous hug. It's a standard greeting in Hollywood, yet unnerving coming from him. "You haven't changed a day," he effuses, referring to our last interview more than 15 years ago.

Did I mention he's unpredictable?

"OK, I'm kidding," he says, breaking character, his bubbly demeanour giving way to a more familiar coolness. "I don't remember our interview at all. She reminded me," he says, indicating his long-time publicist. "But it was probably hard, right?"

In the aptly titled , Phoenix plays a jaded philosophy professor who's lived through enough tragedy to know that life will yield little joy from here on out. Abe drinks and recites Kierkegaard by day, drinks and sleeps with his much younger student by night (the latter plot now a queasily familiar dynamic in many Allen films). But even the adoring company of Jill (Emma Stone) isn't enough to make him truly feel again. He's searching for anything that will validate his life, even if it means taking someone else's.

"I've been very fortunate where I've only made movies recently - except for one - where I felt like I had to do it," says Phoenix of the quirky roles he's taken since returning from a self-imposed acting hiatus a few years ago. "It wasn't 'I want to do this film'. It was 'I'll do anything for this. I'll battle anybody. Give me a shot.' I want to experience it more, and reading it isn't enough. I want to magnify that and see the full expanse of that feeling, how much of it there can be."

It's with that passion that the former child actor has brought countless tortured souls to life over the past two decades, such as the hapless teen murderer in , the dark and conflicted Johnny Cash in and the lonely writer who falls for a computer operating system in .

"Everything you give him to do or say becomes interesting because of this complexity he naturally projects," Allen has said of the actor. "There's something going on in there all the time."

Phoenix contends there's no real methodology to the roles he chooses - or the parts he's chosen for. "I think a majority of my career has been luck. I'm available, and the other guys aren't. It's like 'Thank God Christian Bale isn't working; thank God Leonardo's working on something else.'"

Wearing worn Converse sneakers, jeans and T-shirt, Phoenix in every way seems to say, "I'm relaxed", though he's cautious about making too much eye contact. The more we talk about Allen, however, the more animated he becomes.

"I've always admired him, but I don't think people appreciate Woody as an actor," says Phoenix, who reels off the names of various Allen films before referring to a particularly difficult scene in . "Most actors would play that scene wearing so much regret on their faces, trying to show, 'Hey, I'm a sympathetic character.' He plays it sincere and straight.

"I feel I'm guilty of trying too hard to make sure you understand. That's the thing I hate most in acting - my acting."

Ironically, Phoenix is that rare talent who conveys so much without saying a word. At the same time, he's able to keep audiences guessing about what's underneath that troubled exterior. It's a combination that has been exhausting (the 2009 David Letterman interview) yet intriguing enough to lend a unique longevity to his career.

Phoenix, of course, doesn't see it. And why would he, since he says he barely, if ever, watches the films he's in? "Not too long ago I was flipping through the movie channels and there was a movie [I was in] that I'd never seen," he says. "I watched it, and I was garbage. It just felt like I was working. I saw so much acting. I was really embarrassed by it."

The first and last movie of his that he deliberately saw in the past decade is 2012's , and only because director Paul Thomas Anderson told him to "man up", recalls Phoenix with a laugh. "It was so crushing. I was like, 'OK, you're right. I should be able to watch it and not be a … coward and just go, 'Oh, that did or didn't work.' I manned up for a little bit," he says, "and then I didn't have the courage to finish it. I turned it off."

Phoenix was born in Puerto Rico, then moved around South America with his family, which was part of the religious group the Children of God. His parents left the group in the late '70s and moved to California to pursue acting careers for the children. There he eventually began to land small roles along with his siblings River, Rain, Summer and Liberty. (Joaquin once went by the name Leaf.)

Phoenix's childhood film roles include and Ron Howard's . A teenage Joaquin was with his older brother River when he overdosed and died in 1993. Joaquin's 911 call was replayed by the press in the weeks that followed, marking the beginning of his tense relationship with the media and fame.

His critical breakthrough came in Gus Van Sant's 1995 movie , when Phoenix masterfully played a stoned, working-class teen seduced by the local TV weather presenter (Nicole Kidman). He then became an acclaimed performer in such blockbusters as and .

But it was Phoenix's behaviour in the interview with Letterman that revealed yet another side of the actor. He mumbled non-sequitur answers from behind sunglasses and a shaggy Unabomber beard. (Phoenix later said he was in character for the mockumentary , directed by his brother-in-law, Casey Affleck.)

Phoenix became the butt of several late-night jokes before going on his short hiatus from acting, though he contends it was a breakthrough moment for him. "That experience is definitely in the top five - or maybe the best acting experience - I ever had," he said. "I learnt to let go, partly because there was no time to make a choice."

Planning and deliberation, however, played a large part in how Phoenix approached his role as Abe in . He is not a stand-in for Allen, as other leading men in Allen's films have clearly been.

Phoenix knows audiences will likely be looking to glean insight into who he is through his role as Abe. But by now, he's used to it. "I don't know why people try to analyse me through my roles … or maybe I do," he says. "I've seen performances where I'm like, 'Whoa! I wonder what [that unfortunate actor] went through'. However you want to think about it is up you, but I'm not sticking around to listen to it."

Los Angeles Times

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