Robert Downey Jr. is ungoverned by traditional laws of cellular and cultural decay. Examine the evidence on his face. He’s 49 years old, a veteran of the penitentiary system and enough stimulant and sedative abuse to weather the most youthful countenance. Yet few visible signs of age exist.

At a time when even the most handsome movie stars turn craggy or plasticine, Downey looks increasingly like a young Al Pacino. A decade after his career was fitted for a casket, Forbes named him “Highest Paid Actor” for the second straight year. That’s an estimated $75 million per annum, or enough to buy 10 of Tony Stark’s translucent oceanfront palaces.

Here’s Iron Man, Sherlock Holmes, Charlie Chaplin, the “poster boy for birth control” (don’t you remember “Back to School”?) reclining on a couch at the Four Seasons in Beverly Hills. The occasion is what he’d call “the selling of soap” for “The Judge,” the new film in which Downey plays an arrogant Chicago trial attorney forced to defend his estranged and ailing father (played by Robert Duvall) from murder charges in rural Indiana. The drama is the first picture from Team Downey, a partnership between Downey and “the missus,” the producer Susan Levin.

“The continual need for confidence approval eventually ran dry. It might be fun in your 20s, but now I’m confident what I’m capable of,” Downey says, crossing his legs and vainly attempting to trace the provenance of a preternatural gift. “What I’m capable of isn’t that special, but I know how to work it.”

This is intentional understatement. Downey has charmed too many audiences and directors for too long to believe that there isn’t something rare in his charisma and theatrical chops. His Twitter bio more accurately states the obvious: “You know who I am.”

Robert Altman once said about Downey, “There isn’t a better actor in America.” The late Sir Richard Attenborough, who directed “Chaplin,” once said, “the little bugger can sing, act, dance, play the piano and compose like an angel. And, as if that wasn’t enough, he’s got a photographic memory.”

His latest collaborator, David Dobkin, who directed and co-produced “The Judge,” lavished similarly effusive praise.

“A lot of times comedians can do drama and vice-versa, but it’s not what you want to see them do. You want to see Downey do both. No one’s more versatile,” says Dobkin, whose directing credits include “Wedding Crashers” and “Shanghai Noon.”

“You can’t quantify what makes a great actor become a movie star. It’s just something you feel,” Dobkin continues. “[Downey] is one of these people. He’s open about who he is as a person, but there’s that mystery and extra magnetism. You feel like you’re learning something new about him all the time.”

Downey is too convincing of an actor to not possess a mildly slippery quality. In conversation, he’ll call you by name and lock eyes in a way that suggests you’ve been friends for decades. In the next breath, he’ll grow distant, as though immured in memories best left off the record. As on-screen, his brown irises dart with astonishing velocity and expressiveness. It’s not hard to see why he’s held in such high regard. Common sense tells you everything is a performance, albeit a heartfelt one, but whatever he’s selling or telling, you want to believe in.

“When [Downey] acts, you feel like you can enter his frame,” Vincent D’Onofrio replies, when asked about what makes Downey singular. The Brooklyn native plays Downey’s brother in “The Judge.” “He has the ability to reach through the shot and make an uncanny connection with the audience.”

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At a press junket for “The Judge,” the other cast members arrive dressed casually, but Downey wears a gray suit with soft tasteful pinstripes, a burgundy tie and a floral pocket square. He’s clean-shaven, sporting gilded designer high tops and a meticulously trimmed thatch of black hair. Back when “swag” was merely “style,” Downey acquired a comically expensive ascot collection to seemingly prove Oscar Wilde’s adage that “a well-knotted cravat is the first serious step in a man’s life.”

Despite the flamboyance and excess, Downey retained the subversive ethos imparted by his father and namesake, a revered experimental filmmaker famed for the 1969 social satire “Putney Swope.”

“I was raised in this environment where ‘we don’t work for the man’ and we’re always reaching for something and we might self destruct before we get there and it will be all lovely and tragic,” Downey reflects on an upbringing split among the bohemian corners of Greenwich Village, London and Los Angeles. “But the truth is that in the reach, there’s salvation.”

The concept of salvation frequently emerges from conversations surrounding Downey. Everyone loves a good comeback story, but his practically mirrors a fable of divine intervention.

“In whatever character you’re playing, there has to be some of you in it to get your best work out there, and Downey brings the most entertaining and interesting part of himself to his roles,” says Billy Bob Thornton, who plays a rival attorney in “The Judge.”

“He can do different characters and doesn’t just play himself,” Thornton adds. “Without question, he’ll be remembered as one of the best actors of his generation. To find a comparison, you’d have to take a lot of pieces from different people. A little Chaplin, part Peter Sellers, maybe some Humphrey Bogart. You can’t put him in a box.”

These aren’t just hollow encomiums from co-stars eager to sell the product. Even subjected to the numbing battery of oft-repeated questions, Downey radiates the tangled electricity of a man who could make an emotional connection with a lamppost.

It’s why he first landed on the short list of best actors of his generation in 1987, only a half-decade after dropping out of Santa Monica High. But his role as Julian, the tragic junkie in “Less Than Zero,” ultimately became a matter of life imitating art and hastened Downey’s descent into substance abuse.

“I’d never done half the stuff that Julian did, but I came from that culture,” Downey says. “But I certainly didn’t come from money, so when I’m suddenly driving an Avanti and wearing $2,500 worth of clothes at 10 a.m, the writing was on the wall.”

He unlocks a brown leather satchel and pops pills from two bottles. Herbs or vitamin supplements. Maybe some active ingredient in these natural remedies betrays the key to his Lestat-like invincibility.

“The ’80s was a well-put-together period piece, and I was in the right place,” Downey continues. “When I came here, I already exhibited depraved behavior, but everyone was like don’t worry about that, it’s fine, we make movies, too.”

Since his best actor Oscar nomination for “Chaplin” in 1992, Downey’s averaged nearly two films a year. Some have been good (“Wonder Boys,” “Short Cuts,” “A Scanner Darkly”) some forgettable (“The Shaggy Dog,” “Friends and Lovers,” “U.S. Marshals”), some iconic and iron-suited.

You probably remember his career interruptions from tabloid headlines. In 1996, cops found cocaine, crack, heroin and an unloaded .357 Magnum in his black Ford Explorer. There was the “Goldilocks Incident,” where a drug fugue caused Downey to walk into the Malibu home of strangers and fall asleep alone in the bed of an 11-year-old girl. He later served six months in Los Angeles County jail and nearly a year at the California Substance Abuse Treatment Facility and State Prison, Corcoran.

The narcotic turbulence ceased on an afternoon in 2003 when Downey chucked his remaining drugs into the ocean outside of a Malibu Burger King. For the last decade, he’s been happily married and sober.

“It’s basically just illness. How long does it take before your cancer goes into remission?” is how he summarizes his struggles with addiction, clearly weary of being asked. “Sometimes people will show me interviews of myself at half my age, and it’s like an anthropological exhibit. I want to say that I know that guy and understand the angst that he had, but it’s hard to identify.”

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You’re familiar with his third act. “Iron Man.” “Sherlock Holmes.” “The Avengers.” “Tropic Thunder.” (The last one netted him a deserved best supporting actor nomination.) He’s entering the legacy era of his career, the time when superstars switch franchises in search of a championship.

He’s too savvy to admit that “The Judge” is a play toward award season returns, but its fall release date, heavy themes and estimable cast hint at an Oscar hunt. Reviews have attacked the plot’s cliches, but predictably, Downey’s self-assured restlessness has won raves.

Back in the baroque conference room of the Four Seasons, the actor invokes Team Downey’s future slate: a Perry Mason reboot set in Depression-era Los Angeles; a live-action Pinocchio adaptation starring Downey as Geppetto; and “Yucatan,” a Mayan treasure yarn adapted from a never-made Steve McQueen project. There’s also a daughter coming soon — his second child with Levin.

“My career is this broad, fun thing, but my life is actually very managed and small,” Downey says, returning to the four walls of the present.

It feels like a disappointment, but not quite a surprise. The man could make a directional request to Siri seem like spilling the depths of his soul but still leaves you feeling as though he’s withholding the secret that would allow you to solve the mystery.

Or maybe the mystery is that elementary. Maybe to get here, he had to figure out how to rein himself in — how to learn to work within boundaries that he was born to break. After all, even the most extraordinary sometimes have to learn simplicity to survive.

“When we’re done today, I’m going to pack up and go home, unwind, take a bath with the kid, and probably watch the American Heroes channel,” Downey adds. “I think ‘World War I’s Greatest Raids’ is coming on.”