Earlier this year, he was the slimily incestuous emperor in Gladiator. Now, he has two new films out, and two new personae on show. In James Gray's The Yards, he plays Willie Gutierrez, a Puerto Rican wideboy for whom racketeering on the New York subway offers a frail chance of social mobility. This will be followed by Philip Kaufman's Quills. Here, Phoenix is the tenderly idealistic Abbé de Coulmier, the cleric in charge of the asylum where the Marquis de Sade was confined, who finds himself tempted and corrupted by his prisoner's doctrine of sensual liberty.
On the way to the Dorchester for my interview with Phoenix, I passed a poster for The Yards. It makes him look like a fallen angel painted by Caravaggio, moodily engulfed by shadows. Upstairs, in one of the hotel's hospitality suites, surrounded by bottles of water which had lost their fizz and bowls choked with cigarette butts, I met the 26-year-old owner of that glowering, alluring image. There was not much resemblance between them. His hair had been slept in and his clothes - creased shirt, greasy jeans, scuffed trainers - belied his apprenticeship as a Prada model.
But once he began to talk, I understood the camera's infatuation with him. He is cinematic because he's so restlessly kinetic. The hotel armchair might have had hot bricks in it rather than cushions. His fingers anxiously shredded a scrap of paper, while his body twisted sideways like a corkscrew. The New Yorker's film critic Anthony Lane has said that Phoenix's face seems to have been squeezed in a vice; the rest of him is also pushed and pummelled by invisible forces. His slight frame houses a cyclone.
Describing a cinematic fight with Mark Wahlberg - the blood brother who betrays him in The Yards - Phoenix re-enacted the struggle in the hotel room, concussing the perfumed air. 'Mark and I blocked it out of ourselves. We wanted it to be an epic battle, falling down the stairs and out on to the street. We had elbow pads and knee pads, but on the first take Mark just grabbed me with his pinkie, flipped me into the air and I landed on my head. Man, did I have a bump. I was black and blue for days. But I sure as hell wasn't gonna do any fucking John Wayne-style punching. I wanted it to be sloppy and barbaric and painful, like I'm hugging the life out of this guy who's my friend while I'm pounding at him.'
He demonstrated on himself, pulling fistfuls of his hair and slamming the side of his skull. I remembered the astonishing scene in Gus Van Sant's To Die For in which Phoenix, a dim-witted slacker suborned by Nicole Kidman (who bribes him with blowjobs) to murder her husband, talks about vampires and turns himself into one, scratching at his own flesh as if it were anaesthetised, insentient, dead. The actor is someone who can replace his face at will. Phoenix, so frenetically physical, often seems to be trying to unscrew his own head.
He was able to treat me to a solo performance of the fight with Wahlberg because both characters were slugging it out inside him. James Gray originally offered him Wahlberg's role of Leo, a convict plaintively trying to go straight. Phoenix favoured Willie: 'I said, "I wanna play the charismatic one, the proactive guy", just to get away from the post-To Die For thing, where I was always the loser. But I agreed to take Leo; then, after I'd been being him in my head for a year, they offered me Willie instead. So I spent a month going back and forth between them, trying to decide. I chose Willie because he was the sorta guy I hadn't been before. And when I became him, that was kinda shocking to my family - that I could be so obnoxious and strut and swagger about, being so goddamn suave, as this guy who just thought he was the man.'
His family is Phoenix's touchstone of moral truth and emotional reality, and he endearingly explains the waywardness of Willie by saying: 'That kid had no secure parenting.' His parenting was secure, though unconventional. His mother and father were itinerant hippies, who happened to be disseminating the gospel of the Children of God in Puerto Rico when he was born. They named their offspring elementally or allegorically: the eldest was River (who overdosed on heroin and cocaine in 1993 and died on the asphalt of Sunset Boulevard while Joaquin, still a teenager, phoned for an ambulance in sobbing desperation), followed by Rain, Liberty and Summer. Joaquin felt that his own name (pronounced, significantly, Whack him) excluded him from the Aquarian tribe, and for a while experimentally called himself Leaf.
Their parents fed them on tofu sandwiches and, when signing the toddlers up with a talent agency, specified that they would not do commercials for Coke, McDonald's, meat or milk. Engaged by Prada, Joaquin declined to wear leather shoes. He isvegan, though I wonder how his intake of cigarettes and his proud ownership of a yellow, '72 Le Mans sports car accord with these dietary and ecological dogmas.
Although he claims not to have suffered from his vagabond, hand-to-mouth upbringing, it's remarkable how many of his characters are waifs, mentally precocious but emotionally vulnerable. In Ron Howard's Parenthood, aged only 15, he carried round a paper-bag full of porn flicks; he even described Commodus in Gladiator to me as 'a lost kid. Yeah, I discovered the child in him. He was only 19 when he became emperor. You know, the guy's father ran the Roman Empire, which is like the biggest multinational ever, and Commodus just hates the fucking suit and tie they make him wear!'
By encouraging self-expression, the elder Phoenixes turned their children into instinctive actors. 'I'm not technical,' Joaquin said, his arms flailing, when I asked him about a scene near the end of The Yards in which, in an excruciating close-up, we watch a tear slowly form in the eye of the anguished thug. 'I don't have something I can just turn on. I sit there for hours in my trailer, hoping I can get into the mind of the guy I'm supposed to be. I don't think too much. I try to let go and suddenly [he flung his arms wide, like Leonardo DiCaprio riding the breeze on the prow of the Titanic] it's time to feel.'
On Gladiator, Richard Harris helped him to liquefy by pouring booze into him. But eventually, he found his own way into Commodus. 'About two weeks in, I had an epiphany. I'd shot the beginning, with me arriving at the German camp, and I had some days off. So one morning I was studying the script, and lightning struck. I thought, "Fuck ya! I geddit!" I went out and cut my hair and added some weight. To start with, I was toned. But I made him flabbier, to show how this scrawny prince had kinda ripened into an emperor. It all happened because... no, I don't think I want to say what the epiphany was.'
Self-expression for Phoenix entails self-denudation. Hence the borrowed, inherited garments shed by Commodus: 'We never see people pulling off their clothes in period films. But I though he'd be uncomfortable with those strangling collars and heavy cuffs. So why not take his shirt off?'
Phoenix tore at his own shirt and exposed an unironed vest. The psychological striptease went even further as he remembered and re-enacted the abbé's crazed, quixotic effort to rescue Kate Winslet in Quills, discarding piety and propriety as he races to save her from flagellation. 'He sheds his armour, which is his cassock, and he runs through the rain with his shirt open, his chest bare.' By now, Phoenix had worked himself into a frenzy, ripping off clothes he wasn't actually wearing. And the end of the process was the revelation of naked, puny inadequacy. 'This guy thinks he's being so heroic, and we're going, "You arsehole". The joke of the movie is that there is no heroism in that world.'
The Yards is already being compared to On the Waterfront, with Phoenix as a latterday Brando. But there is an earlier and, perhaps, more telling augury in To Die For. His character is called Jimmy; Kidman flatters him by calling him James, which reminds us that his mother called him after James Dean. Phoenix was modestly shifty when I made the comparison between their styles (or, if you like, their shared Method), and created a diversion by fumbling with a cigarette. 'Yeah, I guess I saw some of East of Eden when I was a kid. But only about 10 minutes of it and I couldn't see why everyone thought he was so amazing.'
He paused, puffed meditatively, then decided to risk a further admission. 'Then I watched Rebel Without a Cause not so long ago.' Again he stopped, wistfully unreeling Dean's great, intimate, raw-nerved performance in his head. 'As a matter of fact,' he tentatively added, 'that was while I was on Gladiator.' He dragged on the cigarette, exhaled, and disappeared behind a thick grey cloud. When the fog cleared, I noticed that he was staring directly into my eyes, while a knowing grin sealed lips which were not prepared to say any more on the matter.
But his smile confirmed my suspicion: he had told me, not in so many words, about his epiphany.