Nick Nolte lies, forgets, gets confused and makes mistakes. He tries and fails and then he tries again. The actor admits to all of it, and there is a vulnerability about him that makes this valiant. He exists in the space between having insight into why he does what he does, and actually doing something about it. It is a space that is heavy with consequences.It is early afternoon and I am being escorted from sound stage 6 to sound stage 12. The members of the press who have been junketed in to promote Nolte's latest movie, Hulk, have been strategically manoeuvred by an army of publicists through the desert that is Universal Studios in Los Angeles.

We have been bused, fed, handed schedules and instructions. And, as in most military operations, numerous things have gone awry. The round-table interviews, which started at 7am, have run late and now it's past lunchtime; my one-on-one interview will be delayed. I am told that there's a chance I won't have the full hour. Clipboards are consulted. Cars are rescheduled. All I can think is: Nick Nolte has been up since 7am answering questions. Great.

The cavernous sound stage has a tiny door, and I trail behind the publicist across the barren space to an area that has been sectioned off with a thick black drape. Behind it is a claustrophobic science-theme setting: primary-coloured props from the film, including a yellow gamma sphere, orange and blue tubes in the shape of double helixes and glass beakers on makeshift shelves, and, in the middle of all this, a large, round table with 12 empty chairs.

A spotlight with a red scrim heats the room. Everything is fake - the lighting, the air, the atmosphere. I want to open a window but there isn't one. Eventually, footsteps approach and the drape is pulled back. Nolte appears, accompanied by a small group. He is graceful, rumpled, holding out his hand, apologising for the delay. His presence is gentle but wary. Seconds later, just the two of us, seated and facing each other. A few feet away, he exhales. In front of him, a bottle of water and a pack of Winston cigarettes.

'You mind if I smoke?' he asks. I shake my head. He lights up. 'I know it's insane - it's crazy. I've tried to quit but doing press causes me stress.'He is wearing a crumpled, lavender-coloured long-sleeved linen shirt and silky violet pants. He's into purple now, all shades of it, because it's soothing. His clothes seem lived in, like Nolte himself. His hair is a muted golden colour and hangs down over his eyes, which are blue and intense - challenging, gleaming - as he leans his 6ft 1in frame back in the chair.

Contradictions play out everywhere. His face: ravaged yet at the same time still taut and remarkably youthful. His manner is affirming - head frequently bobbing up and down with a gravel-voiced 'Yeah, yeah.' But still there is a distance. He's here, not here. There is an intelligence in his speech because he is thoughtful, but there is also an undercurrent of menacing amusement. I'm never sure whether what he is saying is real. You soon realise that with Nolte this uncertainty is the point. None of it is real. 'We're all liars,' he says.

Some of the stories he's told the press include how he left his dead father's artificial leg in a bar... How he had a testicle tuck... He lived in a Mexican brothel... He couldn't read until his mid-twenties. But fiction is a refuge, and Nolte seizes the chance - any chance - to hide.

What Nolte doesn't hide from are his mistakes. The characters he plays are often tormented, introspective men and Nolte gives their rage a powerful, physical beauty and depth, whether he's playing a Vietnam veteran in Who'll Stop the Rain, a ruthless officer from The Thin Red Line, a racist killer in Q&A, or a beaten-down son in Affliction. His characters tend to be men in crisis, and his range is staggering. The challenge, he says, is when the time comes to let the characters go.

'You have to slowly wind out of it,' he drawls. 'When you come out of it, there's depression first. Then sadness. You don't know what to do. Not quite sure who you are, or where to go. I used to try and drink my way out of it. I'd drink until the next film. That was highly destructive behaviour. The only place I ever felt comfortable in life was on stage. When I got on stage, I was home. I'm not comfortable out here. There's too much coming at me. At least on stage, I can be what I am and explore what I know. Same when I go on a film, when I walk into a trailer. Some people hate trailers - I love 'em. Because when I walk into that trailer, all time ceases to exist. All outside responsibilities fall away. I have one responsibility - and that's my commitment to the role.' He compares the feeling of everyday life falling away to having an affair. 'Everything becomes more. More sex, more holding, more touching - you become addicted because it doesn't last. It can't be sustained. It releases too many chemicals that keep this heightened state of feeling going. But you can't stay there for ever.'

Whereas most people - especially actors - are careful about what they say, Nolte's filter is missing. Some of his thoughts link together, others are seemingly coming out of nowhere, but they all, eventually, round out to make a point.

'I stopped drinking when I was 48, stayed sober 10 years and then picked it up again in 1998 - only this time,' he pauses, 'it wasn't alcohol.'

It was another substance: gamma-hydroxybutyrate (GHB), commonly known as the 'date rape' drug. It gives a euphoric effect while lowering the degree of consciousness. Nolte, who got it from scientist friends, explains that it is part of the Gaba system, the part of the brain that regulates neurotransmissions. He tells me, very matter-of-factly, that he drank it in liquid form, morning to night. 'It overstimulates, so you feel intoxicated almost immediately. You have to be careful because if you take a little too much, it will operate as an anaesthetic. Then you go into a deep REM sleep for about four hours and a lot of people don't think you're alive, but it contains a natural oxidiser, so it does keep you breathing.'

He had quit all drugs, but when he was doing some research into the genetics of addiction, he says he 'ran into' some scientists. He discovered that GHB functions as an absolute mood elevator - immediately. It was faster than alcohol. 'You stayed high for longer. There was no hangover, no side effect. I was the only person who has ever been in rehab who drank this stuff daily for four years. They didn't know what to do.'

GHB clears from the body fairly quickly, so it's often hard to detect when patients go to emergency rooms. At lower doses, it can relieve anxiety and promote relaxation and euphoria; at higher doses, the sedative effects can result in sleep, coma, unconsciousness and rambling speech. When it's combined with alcohol, the effects can be lethal.

Being an addict, Nolte says, is a genetic problem and he dignifies the damage by exploring it. He has had his DNA examined, and his brain and body Pet-scanned; he has studied the receptor sites of his brain - the suspicious sites such as D1 and D2, the dopamine-receptor sites that the addicted brain has a lack of. He has discovered that he has no satiation point. This, it seems, is the thread that both holds together and regularly unravels his life. He is a man on the verge, seeking satiation the way others seek sleep.

Nolte believes that it is impossible for him to experience enough of anything, because his brain is always trying to get more dopamine and this pushes him to extremes. 'To get more dopamine, you can run, but you'll have to run till your legs are bloody and your knees don't work. You can have sex - but you'll have sex far past the other person ...'

He breaks off and smiles, mischievously. 'Look, after an orgasm, you're supposed to then be satiated and relaxed, right?' I nod. 'And one of the tests is: do you fall asleep after orgasm, or do you get up and do things? If you get up and do things - you got a problem.' He takes a drag on his cigarette and exhales a long line of smoke.

'All the dopamine has been fired off - it's depleted - but if you don't have enough receptor sites, the brain doesn't sense satiation. It's enjoyable, it's ecstatic, it's wonderful - and now, let's build a house.' He is smiling. There is something distinctly non-sexual about the conversation, like an erotic chemistry lesson. He is sharing knowledge. He looks right at me. 'The push - the drive - of testosterone is creating more sperm than can possibly be held. It's later that you begin to learn that a male has to learn a lot of things about his body.

'For instance, in the east it's called milk and water; 2% is milk, 98% is water. It's created by the prostate. The prostate has to orgasm to create that water. If you can find that, you can continually be in this ecstatic state. But if the milk comes, the man turns over and disconnects. That's because it takes tremendous body nutrients to rebuild the sperm and it disconnects him.'

He is fiddling with the button on his cuffs. His hands tremble slightly and I have a sudden urge to reach out and help him, but I don't. Slowly, methodically, he rolls up his sleeve and continues.

'I've always wondered why, one second ago, I was totally, universally connected and now... ' He shrugs: ' What's that about? It's in the nature of the orgasm itself. But there is a way to avoid that and still be extremely ecstatic. You have to learn technical subtleties. You have to learn where the prostate is and the pelvic muscles, how to breathe, chakras and things like that - and use sexual energy to energise the whole body.'

Portrayed as a modern-day Ponce de Le-n, Nolte has gained notoriety for his odd experiments. It's been reported that he has a laboratory at his home and he mixes up hormonal potions and vitamin brews, injecting them into his body to stave off the ageing process. This motive, though, is suspicious. Why would someone with a propensity to escape reality seek to prolong it?

'I've been accused of trying to achieve immortality. The purists don't believe you should mess with hormones. Eat good food. Meditate, make peace with God. Well, there's a quality of life - a standard - that I want to maintain. And that means doing certain things.'

He grows all his own organic fruit and vegetables at his estate in Malibu. 'In America, nothing tastes like anything because of all the genetic alterations. I've been collecting Mexican maize... ' And he is off. For the next 10 minutes he talks about corn. It is a rhapsody. He speaks with such lyricism and attention to detail on how and why there's no decent corn in the supermarket, I begin to wonder if I'm under a weird spell. Why am I finding corn this compelling?

'And you have to get corn into the pot within five minutes for the sugar to remain, otherwise it's... starch.' He says the word with repulsion. 'Sweet corn is only sweet for a period of five minutes.' A perfect metaphor.

The subject of corn exhausted, we return to relationships. Nolte has been married three times. All his relationships, he says, have been accidental. 'There's a certain kind of attraction. I can tell immediately. The other person feels it too. It's not something I plot. I've never dated. I wouldn't know what to do on a date. It's chemical. It's across the room. You feel it - and you go right to that person. But you have to be in situations where that can happen and I have a tendency to be very reclusive. But I've always just run into it. I don't go looking. Your antenna is up but you're not deliberately going to certain places because if you do, all you'll find there is a bunch of f---mates.' Right now he is alone, and he misses being in a relationship. 'But, you know, it's heartbreak. It's tragic when there's someone you can be with, but you can't.' He looks away for the first time. 'How do you remain your individual self and be in a relationship? It's very difficult. It's kicked off by the nature of the connection - the matching of the chemistry. There are extremely passionate relationships but they can't be sustained. It hurts too much. It's the impulse. I have a tendency to go to the one that hurts the most, has the deepest pain. Because I identify - I can feel it.'

Nolte is haunted by past relationships. They have all been long-term, passionate and combustible. He was sued in a bitter palimony suit by an ex-girlfriend and he has been married three times. He was divorced from his third wife, Rebecca Linger, in 1994, and they share custody of their son, Brawley King Nolte, 17. He lives with his father most of the time, but his mother lives right up the street and he has made up his own mind about where he stays since he was 12.

Does Nolte want to get remarried? He lets out a long, meandering sigh. 'There's so much negotiation that has to go on. I was with a woman once who said, 'You know, you never clean the dishes.' So I said, 'All right, I'll clean the dishes.' So I did. And Jeez, it was fun. I really enjoyed it because it kind of reminded me where I grew up in Iowa, on farms. And then I notice - she never washed a single dish. And I said, 'What the hell is this!'' Laughing, he recognises it was a test. 'But once I felt tested... ' He looks down. And when he looks up, he appears glum. 'I can't follow your instructions any more. Tell me the right things. Don't tell me the wrong things.'Nolte is a notorious fabulist. And the last lie he told? 'Oh, a lot today. But my cop-out is, I'm being honest, I tell you that I lie. I started that to deal with journalists. So that I could have the freedom to say anything I wanted. I just said, 'I'm a liar.' Brando calls it 'lying for a living'.'

But the last real lie?

His voice lowers into a deep, self-righteous tone. 'I'm not doing any drugs,' he says, grinning.But he already told me that.

'Yes.'

At the beginning of the interview.

'Yes.' I stare at him. He stares back. 'Well, I'm not doing any drugs.'

But that's a lie.

'It's not a lie. The last time I really did lie was when I said, 'I'm not doing any drugs,' and it was obvious. I was sleeping in inappropriate places. I would fall asleep on the lawn with the dog. I'd fall asleep in Union Square in San Francisco. I'd fall asleep in a bookstore.'

It is not startling that this would happen, since he is indifferent to the public's perception of him. When he falters, the results often end up on display. But living, as he does, in his reclusive world, the gossip literally doesn't get to him.

'I overheard a couple once. We were sitting in a restaurant out in Malibu and I had on what they thought were pyjamas and a long cashmere coat, which looked like a bathrobe to a lot of people. So this lady at the next table says, 'Why does he do that? It's disgusting.' And the man with her says, 'He thinks he can get away with anything.''

He did nothing. It confused him. But then again, the press has been commenting on what he wears for a long time. Pyjamas - outdoors! And doctors' scrubs - yet he's not a doctor!

'I went along with it for a while and said, 'Yeah, they're pyjamas.' But then there was this really snippety journalist... ' He wrinkles his nose and twists his voice into a pinched, nasal tone. ''Why do you wear pyjamas?' And finally I got fed up. I said, 'Look. These pants are made by Calvin Klein. They're called leisure wear. And this isn't a bathrobe: it's afghan cashmere. Take a feel.''

Over Nolte's shoulder, I see the small group loitering by the drape. A woman is hesitant, but steps forward. She's signalling time is up. Nolte leans in. 'Go on. It's all right. I don't think I have to be on time.' He reassures me we aren't done. I mention I should probably ask him about the film. He shrugs it off. 'You don't have to.'

But the film is something he's pleased with. The director Ang Lee has created a moody, unusually poignant portrait, and Hulk is about transformation. Nolte's character - the father - wrestles with conscious good, unconscious darkness, right and wrong, anger, destiny and the effects of gamma radiation. It's no wonder he felt a connection to the material.

The small group has returned. This time they are insistent that we stop. 'You know,' Nolte says, politely twisting his torso around to face them, 'this is probably gonna go on for a long time - can we afford to do that?'

He is told that there are other people waiting but if I'm willing to hang out, we can continue afterwards. During the break I hang out with Nolte's British friend, Matt, 33, a musician who works with him and lives on the compound in Malibu, a secluded six-acre estate with several houses. They met a few years ago in London when Matt was hired to tutor Nolte's son, Brawley. There are others who live there: Big John, a retired teamster; Nolte's nephew, Eric, a screenwriter; Matt Polish, whose brothers Nolte made a film with; Gerardo, who takes care of things. The place functions as a sort of Boystown.

For instance, one of Brawley's friends was into glass-blowing - and now there's a glass-blowing studio at the house. Matt comments on Nolte's breadth of knowledge in philosophy, photography and science. And something interesting nobody would expect? He thinks for a second. 'He's a fan of Godspeed You! Black Emperor.' That's a 10-piece Canadian collective of anarchist musicians. When Nolte and I settle in for part two, he brings two packs of Winston cigarettes. He lights up. 'I was discussing with my psychiatrist about normal - how someone could change their patterns and attractions and all of that - and he basically said, 'You can't trust your first instinct.''

Does he believe that?

'No, I don't think so,' he replies. 'I don't think that you can change who you're attracted to, because that's chemical. This is my problem - all the feelings I have. I can feel everything - that's what I put into my work. It's problematic for a man, you know, to over-feel.'

Perhaps the problem is not that Nolte is over-feeling but that the majority of people are under-feeling or insensitive.

'It may be that, I don't know. I can't climb inside your consciousness and you can't crawl into mine, but we can communicate and cross feelings. I don't know what level of sensitivity is normal - I just know that I found some work where it's a requirement to be emotional.' He adds: 'Have you ever had this feeling - it's a beautiful feeling, a sad, sweet loveliness, but it's got a tone of sadness, kind of melancholy?...'

I'm not sure what he's referring to.

'Looking out at a view - it's too beautiful for me sometimes. It's too, too... It will cause me to go into tears. I can look out my window and the trees and the green and the way it is - it gets too much.'

There are things he does to relax. He blows glass. And he plays the Theremin, an instrument that can be played without being touched. It creates a spooky sound, like from the old Vincent Price movies; one hand controls the pitch and the other controls the volume.

There are benefits to making mistakes, such as regrowth. And Nolte always learns. 'I do. You always learn from your failures. With success, all you do is get fat.'

And the biggest failure he's learnt from? Silence. Then he says: 'Avoiding pain. Trying to cut myself off from pain. By running from it. Using things that shut me off emotionally. Because you can become soulless when you're not feeling your feelings.'Responding to how he functions in that pain, he looks uncomfortable. He shifts around. Begins to slowly, meticulously, unroll the shirtsleeves that earlier he had rolled up. 'Uh, not well, not well. But you can learn. And it has kind of a wonderful process - like loss.'

One of the biggest losses he has suffered was the death of his mother three years ago. To deal with the pain of that, he went to yet another extreme. 'I blew the heads of my calves off and ripped the plantar fascia,' he says. 'I have no feeling in the bottom of this foot.'

Why?

'Because my mother was dying. That's what I did to myself. The plantar fascia, it goes across the arch.' He leans down and elegantly sweeps his finger across the sole of his foot. 'I ripped it.'

The plantar fascia is the strongest and longest ligament in the foot, the one that holds all the other tendons in place. He tells me that he was trying to push a 4,000lb machine over with his hands, on his toes.

'Four thousand pounds. And when I had it almost over... ' He jumps up to demonstrate, leaning forward on one leg, his arms up in front of him, hands in the air.

'I couldn't quite get it over - I was pushing - I almost had it tipped over and I reached up with this foot, thinking I could hold 4,000lb with one foot and push off it - and the heel slammed down and the plantar fascia gave way and bullooom! Both calves blew. Muscles ripped apart.

'And you know that white light people say that you should go after? I saw that light and it knocked me flat out. I woke up six hours later.'

Did he think he did that intentionally? 'I know I did. I know I did. I was running from the loss.

'When my mother died, I knew it was coming. It feels like it happened for a purpose. When I got to my mother I had powerful pain medication for my leg that would kill her pain. When I got to her, I called her on a Sunday and I said, 'I'll be there on Friday,' and she said, 'Oh, that long?' And I turned to Matt and I said, 'We gotta go now.' It was an hour's flight to Phoenix, where she lived. She always told us as kids, 'I'm going to die in my own home.' When I got to her...'

'I hate to interrupt...' There is a young, tanned man with questions about what to do about the car. There are others waiting; should he let it go? I say yes. The young man goes away.

Nolte continues without hesitation. 'I walked into the room and saw her; she was holding onto her collarbone. Her right foot - the same foot that I injured - was black, it was gangrene. What was keeping her alive was the pain - she couldn't let go. So... I got out one of my pills and I was too scared to do the right thing right away, so I cut it in half and I said, 'This will take your pain away.' I took a walk - said I didn't do that right - and I crushed up more, put a little alcohol in there, and I said, 'Just sip this. After about 15 to 20 minutes your pain will go away.' Then I got the hospice in there and I negotiated a deal. You have to negotiate these things because when you die in the United States and you call 911, they'll take you to the hospital even if you're 90 years old and they'll bring you back to life.'

The publicist in charge of the car appears and this time she is insisting, urgently: 'They've got to go.' I tell her that's fine; I'll take a cab. Matt, who's standing behind her offers me their car. 'Yeah,' Nolte says. 'You can have our car after we go to the hotel.' Problem solved, we continue.

In September 2002 he was arrested for driving under the influence on the Pacific Coast Highway (PCH) in California. A photo taken at the time showed him looking dazed, a one-dimensional snapshot of distress. This was the last time he surprised himself. The arrest was, he recalls, deliberate.

'I couldn't get out from under the substance I was on. I wanted to - in fact, that morning, I went to an AA meeting, and I got there early and I was sitting in the parking lot and people began to show up. I got out of the car and I started to walk up there and thought, 'I can't do this. I'm too fed up,' and I got back in the car. Now, I always drive on the back roads because I don't have to go on the main highway, which is a particularly controlled highway - they write a lot of tickets on the PCH. But for some reason, I went right down on the highway and I was only three blocks from my turn-off, but I drove way past my exit. I was in and out of consciousness. And when the lights went off, I said, 'The jig is up.' I wasn't at all upset I got arrested. But I was surprised that I had to go that far.

'That's a very dangerous distance to go, because I'm in a car - and I'm falling asleep.'

GHB was found in Nolte's bloodstream and he would later plead 'No contest' before going to rehab in Connecticut. 'I was tremendously relieved. The monkey was off my back. Remember, it's a relatively new substance. It's in every cell of our body. And it just so happens there are only two places in the world that test for it: New York and Los Angeles.

'I honestly didn't think they wouldn't test for it. They've got me in the police station and I'm feeling no pain. I'm in a rather elated mood because I had just come from the stage of anaesthesia. I mean, they wrote things like 'He was drooling,' and I'm sure I was. I remember it all. There was a guy holding a camera over the fence, shooting photographs of me from the trailer park near the station - paparazzi.'

Most people would feel humiliated, but then most people don't explore their dysfunction to the extent that Nolte does.

'I had deeper problems,' he says. Namely, concern for his son. 'He was afraid. When it goes that far, and I have to go away for a month, that I was in jeopardy of dying. But I talked to him at length about it, you know. And I said, 'Brawley - I couldn't stop. It had so many health benefits.' I know people who take it today - they're in their eighties and they use it for pain. It's much better than any opiate.

'He's seen me in most states. Right now, it's a sober house. At first he was afraid I'd relapse. He'd say, 'Are you still sober?' and I'd say, 'Yeah.''

It's stressful, this world. And Nolte navigates through it the best that he can. He shoots massive amounts of vitamin B12 once a week, but when stressed, he doubles the dose. And is he stressed now? 'Yeah - I've had to talk to a lot of journalists. I'm going to suffer for this. I've talked too much about myself. You know when that happens. You feel mournful. Kind of a disgust with yourself.'

He stretches out. 'What time is it?' He doesn't wear a watch; he owns one and it's sitting in a box.

We end the interview and I follow him out of the darkened sound stage into the light. It is early evening. He puts on his sunglasses and there is a childish sweetness about him, a bounce in his step, like he's been let out of detention. Matt is waiting inside the car and as Nolte climbs in he exclaims: 'Hey, look who's joining us! We have a new friend!'

On the way to the hotel, he tells me that when he was in the hospital, he liked the bed so much, he brought it home. 'I was lying in this bed and it was so fantastic, I just bought it. It adjusts for burn patients, so any time you move it automatically adjusts.'

We're almost at his hotel but I have a question - a big one - that I'm not sure that I have the time to ask. Worn out, he says: 'Go ahead.'

Okay: how does he handle life not being fair? He laughs and replies: 'Moment by moment, man.'