"People tend to think I'm sad," he drawls. "Like I'm some kind of miserable bastard - I guess because of the way my face is, or the way I talk. But I'm not. I'm a happy guy. Really." He could almost be reading a menu. Suddenly he frowns: "At least, until someone makes me unhappy."
The interviewer, suitably forewarned, puts on a cheerful face.
He's right, though: there are two Nicolas Cages. One is familiar enough - the scenery-chewing, hyper-kinetic star of Con Air and The Rock - and when he's good, in this incarnation, he's little short of phenomenal, one of the screen's great, larger-than-life characters.
Often, though, it's a question of direction: teamed with John Woo for Face/Off, or with the Coen Brothers for Raising Arizona, he achieved a kind of vivid mania, became his own Tex Avery cartoon. When he's bad, however - the first 15 minutes of Snake Eyes, for example, or the long- forgotten Zandalee - he can be little short of unbearable.
And then there's his quieter, more contemplative side - the actor rather than the performer. Occasionally this Nic Cage finds his way on to the screen, and he too can be either compelling or disastrous. He managed to invest Leaving Las Vegas with a tragic grandeur, gave the pop psychology of Birdy a heart; yet in City of Angels - that woolly-headed remake of Wim Wenders' ravishing Wings of Desire - his supposed sensitivity came off as mere solipsism; as an angel, he seemed more annoying than celestial.
He delivers a similarly muffled performance in his latest release, 8MM - in which he plays a private detective trying to find the makers of a snuff movie. He is a decent man drawn by small stages into the grubby underworld of hard-core porn, and into his own eventual corruption.
It's a strong premise, albeit reminiscent of Paul Schrader's Hardcore; however, given that its director, Joel Schumacher, was responsible for the camp farrago that was Batman & Robin, one cannot be altogether surprised that 8MM is not a particularly good or memorable film.
This is news to Cage, however, who seems utterly sincere when he says: "I think this movie, and Leaving Las Vegas, were the two that have pushed me hardest, that really took me to my limits. I went further this time, certainly in terms of the violent aspect of my personality, than I've ever gone before."
Certainly it's a project with which, at some deep interior level, he identifies. By his own admission, he feels oddly protective of the film - nervous, almost, that it be properly understood. A damning Variety review, published the day after its premiere at the Berlin Film Festival, so incensed him that he cut short his visit and returned to Los Angeles. Where, unfortunately, he was met by a string of American critiques that made the trade paper's seem tame by comparison.
You think he'd be tougher-skinned. No fragile newcomer, he started acting in his late teens. By day he auditioned, read, listened compulsively to music; nights, he worked serving popcorn at LA's Fairfax theatre. A nephew of Francis Ford Coppola, he also changed his name, taking his nom de travail from Marvel Comics superhero Luke Cage, Power Man.
"I was, without going into too much detail, a pretty wild guy. Angry, unfocused. I had a lot of rebellious energy and I didn't really have any idea where I was heading in my life. All I knew was, that energy had to go somewhere and, even though at the time I was really heavily into punk rock, I knew that I wanted it to go somewhere productive, not destructive."
Now 35, he admits to having mellowed somewhat in recent years: "Yeah, it's true. At the risk of sounding like a bore, I feel pretty calm these days. I mean, I'm a father now; I have a great relationship [with Patricia Arquette, another of Hollywood's most affectless voices]. Generally speaking, I enjoy my work. I no longer feel any need to be destructive."
I suggest his new-found peace might be simply part of getting older: just another example of a young firebrand mellowing into comfortable middle age, losing a little of their edge. Call it the Robin Williams syndrome.
At this, Cage half-smiles. "That happens all the time, sure. But I doubt very much that it'll happen to me. I don't think anyone could look at 8MM, for example, and suggest that I was making safer films. I mean, yes, I want the community to be a safe place for my kids, and yes, I like the idea of a cosy domestic life. All of that is very appealing. But that's where it ends. With my work, it's going to be just as dangerous and confronting as it ever was."
His role in 8MM is a complex one. At times, his exact motivation is unclear; his reasoning frequently seems suspect. As such, it attests to his preference for "characters that force me to really deeply analyse various aspects of the human psyche, both positive and negative". A noble ambition. Yet so many of his on-screen roles have involved extreme characterisations that you have to wonder: how will audiences respond to this more interior Nicolas Cage?
"Well, that's a good question. It's actually because for a long while I was so flamboyant, and I was acting in much more of a grand style, that I became really intrigued by the possibility of expressing myself in this other, more contained manner."
He pauses, considering his words. "I guess what I'm trying to say is I want to do a little of everything, and experience whatever range I have. I've done the larger-than-life stuff, I've been there. And I've set up this potential for risk, so hopefully people won't be too alienated by whatever I choose to do next."
"Next", as it happens, is Bringing Out the Dead, about an existential crisis faced by a New York paramedic, which he's just finished shooting for director Martin Scorsese. He describes it as being "a return to Taxi Driver territory, what with Paul Schrader writing the script and all". That should be bleak, I say. Cage looks unimpressed. "Whereas Taxi Driver was about going into the darkness, confronting your demons and losing yourself in the process, this one is much more about coming out into the light. It's more a spiritual journey than anything."
After that, he's set to re-team with producer Jerry Bruckheimer for yet another action flick, Gone in 60 Seconds, a remake of the 1973 smash-'em- up about a car thief with a penchant for destruction, once described in Time Out as "a rousing exercise in auto-snuff".
Somehow, though, it can't help but seem a cop-out. If, as he claims, the real challenge now is to act, rather than to perform - to command a film, rather than simply to dominate it - then his decision to make another mindless action flick seems faintly perverse, a comprehensive waste of time and talent. Why bother?
The suggestion seems to irritate him. He frowns, his stare narrowing. "Look," he says slowly, "it's just a big, dumb popcorn movie. Pure escapism. And sure, critics might not appreciate that, but I feel like I'm ready for it now. I've just done two very intense, very dark character studies in a row, and now I just want to enjoy myself. And I think I'm allowed to do that."
Oh dear, I've made him "unhappy". "Fundamentally," he continues, still prepared to try to convert me, "I think a good performance has a kind of resonance about it, a truth or honesty or whatever - and that holds true whether it's a comedy or a drama or some big-budget action movie. Working within a particular genre doesn't stop you from trying to do interesting work. Often it's what you can do within the boundaries of that style - how you can subvert it a little, or what you can bring to it - that makes for something really powerful." He's sticking to his story. I put on my happy face and leave.
`8MM' is released on 23 April