Spike Jonze’s latest film, “Her,” positions itself so self-consciously as a portrait of contemporary society that to watch the film is to witness a high-wire act in which the movie threatens to tumble into myopic presumption at every turn. A number of elements elevate the film, from a fully realized caricature world to a script that manages to implicate a facet of modern social living without passing judgment on it. Yet the key to “Her’s” success may ultimately rely on the film’s revealed truth about its star, that Joaquin Phoenix is not only the most captivating, least predictable and maybe just the best American actor working, period, but the one who best captures our current sense of cultural self. [Read Film.com's review of "Her" here].

Maybe it runs in the family. Phoenix’s brother River similarly epitomized the 1990s, representing the elevation to superstardom of those who disdained the concept and waste of fame. The elder Phoenix’s work and life illustrated Generation X’s contradictory impulse toward passionate activism and unfocused, uncertain idling, and his early, senseless death prefigured the slow collapse of the decade’s initial burst of creativity and hope. Joaquin Phoenix similarly reflects the Aughts: more intense and brooding than River, Phoenix imbues his roles with urgency and ambition. Compared to the slackerdom and rumination of Gen X, Phoenix has the drive of Millennials, but also their lingering doubt. His best roles find the actor playing people who either do not know what they want or do not know how to articulate, much less attain, what they do. In all cases, though, the characters feel the weight of time pressing up against them, the ever-shrinking window of opportunity to come up with a goal, much less pursue it.

Of course, Phoenix is no Millennial, yet in some ways he seems to exist across generations. The actor turned 39 this year, which comes as something of a surprise as he has seemed at or around that age practically for his whole adult career. This can be perhaps attributed to that distinctive face of his, the individual elements of which have never been in accord as to how old, exactly, he is. His crooked, bashful smile has an eternal youth to it, yet it is offset by the birthmark on his upper lip (not, as many assume, the scar of a repaired cleft) that gives him an aged and grizzled contrast. His eyes routinely light up in wonder, yet their their bright emerald hue can turn to dense quicksilver with shocking speed, a switch from exothermic warmth to endothermic heat absorption that can suck the joy right out of the frame. The trace baby fat that once rounded his face appears not so much to have fallen off but have hardened into gristle, sharpening his features while maintaining a veneer of childlike innocence.

Appropriately enough, Phoenix’s breakthrough came in the year 2000, with three roles that played to his contradictory, out-of-time presence. In “Quills,” he plays the benevolent priest who oversees the mental institution that houses the Marquis de Sade, comfortable enough with his vows to allow the libertine to continue writing his scandalous vulgarity as a means of therapy. Phoenix plays the Abbé with a wisdom beyond his years: though the priest’s commitment to chastity suffers mightily under the reciprocated affections for Kate Winslet’s maidservant, Phoenix never portrays the desire for physical love with the derangement of repression, though in forging a connection to the living world, he is driven to despair when that connection is lost. As with every other aspect of the film, Phoenix filters the past through the sensibilities of the present, though only he commits to any kind of plausible interiority for his character, wrestling with a priest’s convictions with a naturalism that has no business fitting as well with the absurdity of the rest of the film as it does.

Compare the beatific but worldly kindness shown in that film to the mad boy king who brings the only spark of life to Ridley Scott’s bloated, meandering revenge epic “Gladiator.” So obsessed with carving out his own legacy at court that he allows Rome to collapse around him, Phoenix’s Commodus is petulant, moping whenever Russell Crowe’s nemesis curries the favor of the mob and infusing threats of rape and torture with the tone of a spoiled child insisting that everyone play the games he wants to play. Phoenix’s eyes never again looked so beady as they do here, the eyes of a dimwit who fancies himself a master plotter. In retrospect, “Gladiator” may have marked not only Phoenix’s breakout performance but his first timely one, with Commodus, the disastrous heir of a beloved, or at the very least competent, leader now looking akin to an allegory for George W. Bush, another leader whose desire to live up to his father’s example resulted in social ruin.

(As is more befitting the arc of the public at the turn of the century, subsequent early-aughts films starring Phoenix show him in a much more conservative light. This is most evident in 2004’s “Ladder 49,” a straightforward paean to firefighters, and in M. Night Shyamalan’s 2002 “Signs,” in which an alien invasion stands in for post-9/11 anxieties. In it, Phoenix portrays not a generation so much as America itself, the physically atrophied foil to Mel Gibson’s spiritually adrift protagonist. If Shyamalan’s film otherwise serves to buck up the idea of America’s resilience to attack, including its revitalization of Phoenix’s has-been baseball player into an alien-smacking machine, Phoenix plays his goofy meathead with a touch of weariness that emphasizes how exhausting it is to be the swaggering jock all the time.)

The best of the actor’s 2000 work is the least-known yet most crucial of the three, kicking off an as-yet unbroken string of collaborations with James Gray. “The Yards,” like Gray and Phoenix’s subsequent 2007 film “We Own the Night,” shades Phoenix in generic terms, as low-level crooks deepened by their torn loyalties to crime bosses and loved ones. Gray’s films are characterized by a blend of baroque classicism on the scale of Francis Ford Coppola and Michael Cimino at their most epic with an intimately observed focus on naturalistic but expressive acting worthy of the best and most exciting independent cinema, and Phoenix is a significant reason for the success of that balancing act. In “The Yards,” Harris Savides’ cinematography routinely shadows Phoenix’s narrowed eyes in a noirish signifier of evil, but there’s nothing so composed about the fight his Willie has with Mark Wahlberg’s Leo when he fears the latter will rat to the cops, a sloppy mess of a brawl in which he grabs Wahlberg in as much of a hug as a chokehold, the clumsy fighting of a dumb, heartbroken animal who has been driven insensible by the feeling of being wronged and just wants to inflict damage as much as he wants to make amends.

“We Own the Night” expands the scale of this role, swapping Willie’s conflict between friend and boss for a family vs. Family story of a club owner whose devotion to a Russian mobster is torn asunder when the gangster orders hits on his cop father and brother. Gray favors medium and long shots, but Phoenix fills the space as if in close-up with a jerky physicality of a man coming undone by his incompatible affections, not only between his biological and chosen families but the girlfriend (Eva Mendes) who objects to being made to follow his lead as he shatters their life. The arc of Phoenix’s performance, from cocky braggadocio to paranoia to dutiful heroism, could stretch most actors too far, but Phoenix plays each stage of Bobby’s journey with such immediacy, such barely contained emotion just behind his veneer of cool, that the film actually lives up to the operatic ambitions of its maker.

Gray’s films, with their modernist acting and Golden Age framing, often seem to attain a universality outside time and space, even despite their precise settings. Yet it is the director’s third collaboration with Phoenix, “Two Lovers,” that truly puts Phoenix forward as a prime candidate for the quintessential actor of Millennial angst. Phoenix plays Leonard, a suicidally depressed man who still lives with his parents in a New York apartment. The latter detail is sometimes rendered comically, as when Leonard yells at his mother while conversing with a woman in his room, but Phoenix upends the trend of stunted man-children; Leonard may be socially awkward and perhaps too forthright for his own good, but he is an intelligent and talented man with an endearing sense of humor. And as his complex, frustrated but loving interactions with his parents make plain, the traditional sensibilities of his immigrant family are as much at the heart of his continued residence with them as his mental illness and idle. There is a give-and-take to Phoenix’s depiction of the baby bird that never leaves the next, an acknowledgement of personal hang-ups but a nonjudgmental views of the internal and external forces that can keep an adult with his parents past the time most would move on.

The film’s romantic entanglements are handled with a similarly refreshing honesty, capturing the sweetness and the pitfalls of navigating the contradictory, uncertain impulses of one’s heart. Vinessa Shaw and Gwyneth Paltrow play characters who flirt with their own reductive types—Shaw as the stable, career-oriented woman improbably attracted to a guy like Leonard, Paltrow as someone even more addled and confused than Leonard, a potential Manic Pixie Dream Girl who elevates him through her own self-destruction—and sidestep their pitfalls in complex interplays with Phoenix, who responds to each of their virtues and drawbacks in such a way that Leonard’s seeming emotional stagnation is revealed to be the result of too much feeling, not enough. “Two Lovers” is a loose adaptation of a Dostoevsky short story, and the actor’s inchoate passion, overflowing but haphazardly directed, in danger of being consumed by his own need for love. Near the end of the film, he shares a moment with Isabella Rossellini, who plays Leonard’s overprotective but patient and empathetic mother, in which he tells her “You don’t need to worry about me” in an exhausted tone that justifies her 30-plus years of worry. Though Phoenix is slightly too old, and too reluctant to use technology like cell phones, he crystallizes a portrait of the new generation, informed by tradition but faced with a world fully unshackled from it, so full of possibility that one runs the risk of regressing in the face of that freedom.

Phoenix’s work since “Two Lovers” has only added further dimension to this encapsulation of millennial life, starting with his ostensible retirement from acting. “I’m Still Here,” Casey Affleck’s overhyped mockumentary that makes its winking falsity obvious to anyone not sufficiently hoodwinked by its marketing strategy. Phoenix’s commitment to the bit is about as much praise as can be spared for what is otherwise a tedious exercise in irony, but that it is such an exercise at all aligns Phoenix’s performance art joke with an unfortunate tendency in contemporary culture, that of the ironic posture taking precedence over earnestness. Focus also on the genre of music Phoenix decides to “pursue,” his ostensible adoption of hip-hop an appropriative affectation of the successful white artist looking to branch out; many wondered at the time why Phoenix did not try to parlay his “Walk the Line” work into a country career, but how timely could that have been? Misfire that the picture is, its attempt to comment on a media culture that simplifies artists but also makes them complicit in their attempt to maintain celebrity is merely the fulfillment of Phoenix’s long-simmering hatred of that culture. It all goes back to what may have been his true breakthrough, not a film but the recording of his frantic 911 call as a 19-year-old watching his brother convulsing to death, an eerie precursor to a society in which young people increasingly live out in the open for potentially millions to see and judge.

Phoenix’s “return” to acting continued to build on his increasing embodiment of modern America. Though “The Master” generally situates his Freddie even further back in time from Generation Y, it nevertheless presents the actor with a raw showcase that constantly suggests his character is as relevant today as in a postwar landscape that left more disturbed and aimless young men than nostalgia would like us to believe. Freddie is first seen living out a bacchanal of his own making on a beach as WWII comes to a close, making swill out of any liquid he can get, forming makeshift women out of sand and masturbating in plain view. Never mind regressing to the Greatest Generation; Phoenix threatens to take us back to cavemen days.

In regressing to a state of total primitivism, however, Phoenix lends Freddie a rawness that makes him feel of the present. Indeed, Paul Thomas Anderson’s script sets the character up with conflicts that feel modern: Freddie, cleary riddled with hang-ups that have existed for a long time, has been further altered by war, and he seeks some path in life outside the almost hyperbolic portrait of normalcy that his job as a family photographer represents. His quest for self-actualization through Philip Seymour Hoffman’s cult is a stand-in for any attempt to understand life when one has been broken from the norm and views society as fundamentally incompatible to one’s life. Anderson’s film is often made murky by its attempt to exist across time periods, but it is never clearer than when staring head-on at Phoenix’s animalistic behavior: his alcohol-slacked face moaning out words from the one corner of his mouth that still functions, the wild expressiveness of physical gestures ranging from a hug that turns into a childlike wrestle to leaping up into the underbelly of a suspended bed to punctuate his anger. He is the unvarnished id that rages at Big Lies, be it the catastrophe of war or, more recently, the collapse of late capitalism.

“The Master” approaches the modern through allegory, but “Her” attacks it directly. Boiled down to the pitch of “Man falls in love with Siri,” “Her” sets up its story with a world effectively taken over by Apple. All technology has been homogenized with the same sleek design, and even sociality takes on the same oversimplified tone, in which the difficulty of introduction and interaction are streamlined by technology and overdetermined lives. Theodore Twombly (Phoenix) takes this one step further, purchasing a new, artificially intelligent OS, selecting a woman’s voice for its interface and slowly falling in love with the ideal partner the software programs itself to be. The setup leaves the film dangerously open to settling into a simplistic tract about People These Days and our overreliance on technology, but it is Phoenix above all who prevents the film from lapsing into easy commentary and instead positions it as a thoughtfully considered look at shifting social landscapes.

As Theodore, Phoenix never takes shelter in the facile reserve of the “spectrum” to which seemingly all characters of his socially maladjusted persuasion have been resigned of late. Instead, his fumbling romantic plays, which always break out of fissures in his otherwise controlled interactions, are the result of inexperience, an otherwise normal person who has become so accustomed to everything about the world being convenient that he does not know what to do when he must stretch contend with someone with their own interests and thoughts. On a date, he proves a fine company: funny, not too concerned with himself. When a window opens to let the date continue back at her place, however, Theodore hesitates for just a second too long, leading to a disaster he cannot comprehend and makes worse for trying to stabilize. Small wonder he prefers the programmed companionship of “Samantha,” in which common interests, topics of conversation and the pressure of knowing the “right moment” are rendered moot. The film’s final act brings out some of Theodore’s desperation as the A.I. starts to grow out of its designed role, but his primary expression throughout the film after getting Samantha is one of relief, of having the last big variable of his life made a constant.

Calling for a far more restrained lead performance than “The Master’s” barbaric yawp, “Her” nevertheless proves as useful in displaying Phoenix’s best attributes. With his birthmark hidden under a mustache, the actor seems to shed a full decade in age, yet the high-waisted pants that inform the fashion of Spike Jonze’s near-future offset that youthfulness with a geriatric touch that fits with the actor’s ability to look every age but his actual one. Wide-eyed and carefree once Samantha enters Theodore’s life, Phoenix sheds the baggage of his more intense work, and his light humor and sociable talk with his phone practically float for their lack of worry. When Samantha begins to evolve, though, Phoenix shakes up Theodore’s calm with panic, and when even his idealized romance starts to buckle with the need to actually grow and contribute, Phoenix looks more lost than he does as the peripatetic Freddie. Through it all, however, Phoenix never plays Theodore’s desire for a false, “perfect” woman over the complexities of the real thing for mocking satire. There is always a warm understanding of the man’s predicament and his solipsistic flaws, a sympathy for those who have become so used to a world they can build around their tastes that the unpredictability of another person renders them catatonic. Jonze’s script crucially never confines the happiness of a preset companion to just Theodore, but it is the expansiveness of Phoenix’s performance, with its slow crawl toward responsible human interaction, that truly gives the film its sense of humanity, critiquing a person it nonetheless renders lovingly.

Next up for Phoenix is the belated release of “The Immigrant” and another teaming with Paul Thomas Anderson in the adaptation of Thomas Pynchon’s “Inherent Vice,” projects that should be of interest to, well, everyone. The range of the two movies, one a period piece by our greatest contemporary classicist, the other an adaptation of one of America’s finest postmodernists, suggests Phoenix is still pushing himself, not to mention that 2014 is guaranteed at least two top-notch acting performances. The actor has largely retreated from the fully commercial starring vehicles afforded to him in the wake of “Gladiator” and again after “Walk the Line,” yet he still works in mostly mainstream film, which is a gift to multiplexes starved for anything even interesting, much less masterful. As Hollywood struggles to adapt their storytelling formulas to the altered exchanges of digital life, Phoenix has, in movies that rarely even feature technology, embodied these shifts with such rich expression that a movie like “Her” suggests that only the most clever American filmmakers are just now catching up to where he’s been for years. Wherever he goes next, it will be a pleasure to see how intuitively he reflects our present, and how he drags the rest of the industry forward as they try to keep up.