Philip Seymour Hoffman was the one great guarantee of modern American cinema

The day after the premiere of Paul Thomas Anderson's 2012 film The Master, I was interviewing the director in the upstairs ballroom of a Venice hotel when Philip Seymour Hoffman walked past our table. The windows were flung open and the place was bathed with light, and the big, rangy actor bounced by gracefully, like a golden lion walking on air. "Phil's actually a really good dancer," Anderson confided, referencing the parlour routine in the middle of The Master, when the title character performs a jig with his nubile acolytes. "You might not think that to look at him, but he seriously is."

I don't know why we should have been surprised. Every good actor possesses a peculiar grace. Even Philip Seymour Hoffman, an ostensibly foursquare American Job, could transform in an instant into a creature of beauty. His career took him a-roving from comedy to drama to tragedy, often in the same role, sometimes in the space of a single scene. He was lumpen and repulsive in Happiness and Before the Devil Knows You're Dead; limber and seductive in Almost Famous and The Master. He was at once the dancer and the dance, the artist and his clay.

Along the way he became, arguably, the one great guarantee of modern American cinema. Hoffman knew he didn't have the matinee-idol good looks of an A-list Hollywood actor, and yet he had made his peace with that and realised that his talents lay elsewhere. By the same token, few film-goers stumped up for a movie on the basis of his name; instead they stumbled upon him accidentally, like uncovering a diamond in the rough. Hoffman worked ceaselessly, cranking out film after film over a two-decade haul. And yet, try as I might, I can't think of one bad performance in all that time. He transcended his material, as Jimmy Stewart or Edward G Robinson did before him. He was invariably the best ingredient in a below-par production (Doubt, for instance, or Along Came Polly), while his presence alone made a great film sublime. I'm not even convinced the man was ever miscast. He possessed the uncanny knack of slipping inside the skin of every character that he played, and then waving his hands to make the wires disappear.

Does this make him sound like an effortless performer? Perhaps he was – but again there's a paradox. When we think of the defining Hoffman performances, hey presto, up comes a rogues' gallery of lonesome losers and white-collar disasters; of charmless boors and clammy masturbators. Films such as The Big Lebowski, Happiness and The Talented Mr Ripley established him as the poster-boy for square pegs and lost souls. His best-remembered characters are crippled by self-loathing. They are either shunned by their neighbours or treated as a joke. Hoffman may have portrayed these people brilliantly, but their desperate, clambering progress could be agony to watch.

"I didn't go out looking for negative characters," he once explained. "I went out looking for people who have a struggle and a fight to tackle. That's what interests me." In tackling these roles, Hoffman took thwarted, twisted humanity and ennobled it. "Be honest and unmerciful," was the advice of Lester Bangs, the renegade rock journalist portrayed by the actor in 2000's Almost Famous. And yet while Hoffman could be honest, he was never entirely without mercy.

Who knows how much of himself he poured into men like Lester Bangs or Truman Capote (the role that won Hoffman an Oscar); pathetic Allen in Happiness or depressive Caden Cotard in Charlie Kaufman's Synecdoche, New York. It's a moot point. Actors are actors because they pretend to be someone else. And human beings are a mystery, sometimes even to themselves. For all that, it seems safe to assume that Hoffman was prone to the same appetites, rages and frailties that threatened to derail the men he played. He had an addictive personality that he laboured to keep harnessed. Maybe the acting was his outlet. Perhaps it suddenly stopped working.

Philip Seymour Hoffman died from a suspected heroin overdose in the early hours of Sunday 2 February. Today, looking back over his career, I am still struggling to pick out the role I liked best. There are simply too many contenders, a whole two decades' worth of excellence. I love him when his guard is up, flashing that mortified rictus grin as the supine PA in The Big Lebowski, or fortifying himself with scotch and cynicism as an anti-terrorist agent in Anton Corbijn's forthcoming A Most Wanted Man. The trouble is that I also love him when he lets his defences come down. He was purely heartbreaking as the tortured artist in Synecdoche and the stoic angel in the marvellous Magnolia, sitting quietly at Jason Robards' deathbed as he tries to put the past to rest.

In The Master, tellingly, he plays a man whose guard keeps slipping. Anderson's film casts Hoffman as Lancaster Dodd, a honey-coated bamboozler, clearly based on L Ron Hubbard, who points the way to a blissful future. Dodd is authoritative and charming until he is challenged, at which point the mask slips, the rage erupts and we catch of a glimpse of the effort he's making to keep his fiction alive. Back in that hotel ballroom, Anderson told me that the casting was crucial and that his film hinged on the dynamic between Hoffman and his famously wonky co-star, Joaquin Phoenix. The director likened this tension to a tennis match between two top players with very different styles. Phoenix, in other words, was the free-styling John McEnroe, happy to let his demons lead him on a merry dance, whereas Hoffman was more akin to Ivan Lendl or Björn Borg: an intense, driven competitor, straining to hold himself in check. "Phil and Joaquin are pretty similar in some ways," Anderson reflected. "It's just that they go about things so differently."

I wonder if it was this sense of vulnerability that made Hoffman so special. If so, it might be the one common thread that stitches him in with the world's other great actors. Do we love performers such as Bette Davis, Spencer Tracy, Henry Fonda, Katharine Hepburn or James Stewart because they represent the glamorised ideal? Or because they manage to smuggle the base metal of humanity on to the silver screen? The best actors, it strikes me, are a curious mix of the inimitable and the universal, of prowess and fragility. Tacitly, they remind the audience that all their superhuman feats – the heroism, the horrors, the comedy pratfalls – are the work of a real person, not so different from us.

Even Cary Grant, routinely billed as the most glamorous movie star of the lot, was raised Archibald Leach on the back streets of Bristol. Grant didn't become successful in spite of his background, but precisely because of it; because his pedigree was what anchored him and made him real. "Cary Grant's romantic elegance is wrapped around the resilient, tough core of a mutt," Pauline Kael once wrote. "And Americans dream of thoroughbreds while identifying with mutts. So do movie-goers the world over."

I feel a similar way about Hoffman, who squared the circle in the opposite direction and still came away with the exact same result. In film after film he gave us the dreamy romantic in the guise of a mutt. In holding a mirror to the audience, he showed how our grubby urges and hopeless longings could be not just worthy of attention but sometimes actively glorious. We might idly dream of the A-list thoroughbreds. But we recognised Hoffman as one of our own.