Those who knew the artist -- some of them his friends -- described him variously as "devil," "whore," "one of the world’s leading alcoholics," "bilious ogre," "sacred monster" and "a drunken, faded sodomite swaying nocturnally through the lowest dives and gambling dens of Soho." Bacon was no kinder: He called himself a "grinding machine" and "rotten to the core." This hasn’t stopped admirers and critics alike from proclaiming him "the greatest painter in the world," "the best. . . since Turner." Never one to spare hyperbole, Robert Hughes wrote, "This painter of buggery, sadism, dread, and death-vomit has emerged as the toughest, the most implacable, lyric artist in late-20th-century England, perhaps in all the world."

For me, Bacon -- who may be the only artist sharing a name with one of his main subjects, meat -- has always been more of a cartoonist. He’s an illustrator of exaggerated, ultimately empty angst. His early accomplishments are undeniable, and the Met’s survey of 66 paintings and a cache of never-before-seen source material is peppered with high points, especially the signature paintings of the ‘40s and ‘50s: Canvases with twisted masses of faceless flesh and otherworldly homunculi, creatures of the id posed in living-room wastelands and Stygian prisons. The best of this work shrouds you in a sulfuric gloom where strange powers transform human souls into delirious monsters. These paintings make audiences stare as if they were looking at animals in a zoo, trying to come to terms with these merciless inhuman presences. You’ll see this at the Met: people blankly gaping in wonder.

To understand Bacon’s impact, look no further than the young Brits emulating him. Jake and Dinos Chapman place tortured figures in glass cases; Jenny Saville’s contorted Gargantuas are direct descendants of Bacon’s golems; Tracey Emin works with blood and guts; Sarah Lucas gives us spooks and deformities. Damien Hirst not only makes vitrines straight out of Bacon -- he puts meat and carcasses in them. Like Dalí and Munch, Bacon is an artist we love when young. Tantalized by the urgency, angst, weirdness, blood, sex and bodies, we think, That’s me! That’s how I feel!

You might have reconsidered feeling like Bacon if you’d lived in his skin. His love life is a study in emotional privation and degradation. "We are meat," he often remarked -- understandable, given his adolescence. Bacon, who was given morphine as a child for his asthma (the ailment that contributed to his death in 1992), always knew which way his erotic compass pointed, which is not to say that he approved of its inclination: He called his homosexuality "a defect" and a "limp." And no wonder. When Bacon was 16, his father -- the artist derisively called him "a failed horse-trainer" -- caught the boy wearing his mother’s underwear. ("Fishnet stockings were an essential part of the artist’s wardrobe for most of his life," one biographer notes.) As punishment, the father had him horsewhipped by the stable hands, whom, Bacon later claimed, he then had affairs with. Bacon Sr. asked a family friend to "straighten the boy out" by taking him to Berlin. The man complied -- and subsequently bedded the younger Bacon, then abandoned him in the city that W.?H. Auden called "a bugger’s daydream."

Endless liaisons with rent boys and society types followed, until Bacon’s predator-prey notion of love and his "desire to suffer" reached new heights, in 1952. At the age of 43, he met a former RAF pilot, Peter Lacy, in London’s Soho. They spent a lot of time in Tangier, a refuge for gay men looking for freedom. "I’d never really fallen in love with anyone until then," Bacon said. "Of course, it was the most total disaster from the start." Bacon couldn’t live with or without him: "Being in love in that extreme way," he said, "being totally obsessed by someone, is like having some dreadful disease. I wouldn’t wish it on my worst enemy." They experimented with the far reaches of S&M. The end was horrid, too. On the day before his first Tate retrospective opened, in May 1962, Bacon learned Lacy had been found dead, almost surely from drinking.

Less than two years later, Bacon met George Dyer --reportedly when Dyer broke into his studio to rob him. For the next seven years the relationship rocketed up and down, then history repeated itself. On Oct. 25, 1971, the day before Bacon’s retrospective at the Grand Palais in Paris opened, Dyer overdosed and died in their Paris hotel room. Bacon, then 61, was again devastated. No wonder he talked about "the destruction" of love.

All this manifested itself in his art, which rattled the cage of English painting like nothing before it. Compared with the prevailing emphasis on the literary and the anecdotal (the sappy Victorian painter George Frederic Watts is considered "England’s Michelangelo"), Bacon came out of nowhere. His unfinished surfaces, saturated color, and nonstories make him a near anomaly in the history of his country’s painting. He never attended art school -- he was entirely self-taught -- but he devoured art history, and you can easily spot his influences: Cubism, Romanticism, Expressionism, Surrealism, Chaim Soutine, Goya’s late paintings and the figures of Michelangelo.

In 1927, a year after he was banished from home, Bacon went to Paris, where he saw a survey of over 100 Picasso drawings. The show tattooed itself on his brain and left him thinking that Picasso had come closer than anyone in the century to "the core of what feeling is about." He became "the reason I paint," Bacon said, "the father figure." Tellingly, the show consisted mainly of Picasso’s classical drawings; no Cubist works were on hand. Thus Bacon’s rendezvous with modernism was fairly un-modern. Like Balthus, another insider-outsider type, he’s an artist who never went abstract or painted in the visual idiom of his time.

In 1929, back in London, he set himself up creating furniture and rugs based on modern French design. He tentatively showed a few paintings in his own home, but it wasn’t until April 1933, when he was 24, that Bacon exhibited his first painting, at the Mayor Gallery in London’s West End. Interest was immediate and word spread. Within months, a painting of his was reproduced opposite a recent Picasso in art historian Herbert Read’s book Art Now.

That work, Crucifixion (1933), which vibrates off the walls at the Met, Bacon claimed to have finished "in about a fortnight when I was in a bad mood of drinking." It’s a haunted little thing, with no sense of devotion to anything except painting -- an ectoplasmic alien shape with phosphorescent wings and outstretched arms standing in a murky monochromatic ground demarcated by lines forming invisible planes. The macabre work was influenced by the almost unknown Catholic Australian painter Roy de Maistre (Bacon’s mentor and lover) and owes much to Soutine and archaic altarpiece painting. Yet it also epitomized Bacon’s astonishing description of what a painting should be: "a snail leaving a trail of the human presence." Crucifixion radiates what Deleuze called "cosmic dissipation."

But just as it appeared that he would take the English art world by storm, Bacon’s trail dissipated. He exhibited works the following year, to little attention and bad reviews. Stung, he destroyed every painting from the show. By the late ‘30s, he had quit painting. He "abandoned himself with a vengeance to drifting, from bar to bar, from person to person. . . setting up a series of private -- and totally illegal -- gambling clubs," says his biographer Michael Peppiatt.

Then came the "night of the world": the Second World War. In April 1945 -- a month of simultaneous relief and unimagined horror -- Mussolini was hanged upside-down, Hitler committed suicide, Roosevelt died, and the nightmares at Buchenwald and Bergen-Belsen were revealed. And Bacon, then 35, exhibited a painting that still induces shudders. Three Studies for Figures at the Base of a Crucifixion is a triptych depicting howling, deformed, harpy-like goblins. There are intimations of real space, but these raving underworld visitants mostly exist in a universe of animal instinct. A lamentation for the dead and living, a retaliation for his personal traumas, the painting exudes venomous visionary force. Reviewers were shocked and awed: "Images so unrelievedly awful that the mind snaps shut," wrote John Russell after first seeing Three Studies. "We had no name for them, no name for what we felt about them." (Years later, in 1953, the Tate had to be persuaded to accept the painting as a gift.)

Bacon had broached a new door, and to his enormous credit, he kept doing that for fifteen years. Painting, from 1946 (bought by the Museum of Modern Art in 1948 for £280), was an even bigger breakthrough. In this coagulated masterpiece, a grinning or grimacing man -- only the bottom of whose face is seen -- is jammed between splayed cow carcasses and what looks like a witness stand. An umbrella is over his head. Here, Bacon hits on many of the themes, techniques and formal concerns that occupied him for the rest of his life: Man, animal and meat merge. There is no narrative, just a conjuration of some malevolent force. As with countless subsequent figures, Bacon isolates this one within an enclosure in the middle of the canvas. The space feels hallucinatory, menacing, sullen, shallow. Best of all, the paint is physical and visceral -- clotted, smeared, wiped off, applied with rags and fingers and brushes or straight from the tubes. Intense lilacs, pinks and magentas multiply the effect. Within a few years, Bacon was applying great unbroken fields of orange, apricot and red. Some of this color is so intense and modern it keeps even the worst of his oeuvre alive.

By the ‘50s, Bacon had hit his stride, painting what he called "figures. . . [in] moments of crisis. . . [with] acute awareness of their mortality. . . of their animal nature" -- truths hauntingly self-evident in his large pictures of naked beefy men crouching in transparent cases, making love with or attacking one another; dogs cowering on dark streets; sphinxes; businessmen; and howling monkeys. Adding to this symphony of hatred, longing and pain are his many portraits of popes.

This period of Bacon’s paintings was revolutionary for two reasons, both hard to see now. First, an openly gay man was painting gay subjects at a time when homosexuality was a punishable crime in Great Britain. (Sodomy laws remained in effect there until 1967, and sentencing could involve hard labor.) Introducing overtly queer subject matter into grand painting without dressing it up in classicism or coy kitsch was as unheard-of as it was dangerous, and not just in England. One of Bacon’s first solo exhibitions in New York in the ‘50s included a painting of two naked men grappling on a bed. It had to be installed out of the way, on the gallery’s upper floor, in case of a police raid.

The other striking invention is his use of photography. Unlike his contemporaries, he didn’t project (or paste) photos onto canvas, and he freely admitted his hatred for working from life. His visions came mostly from stacks of photos he kept for decades: images from radiography textbooks; Muybridge pictures; Sergei Eisenstein’s Battleship Potemkin; Grünewald paintings; pictures of Nazis, athletes, friends, lovers and his own face, which he claimed to loathe.

In 1957, while going through one of his tumults with Peter Lacy and with the pressure of an imminent solo show building, Bacon, who in his own words was in a "bad way mentally and physically" and was trying to avoid a crackdown on homosexuality in Tangier, tried to make a move in his work. This, for all practical purposes, was the last time he’d attempt to break from predictability. He painted a series "at high speed," based on Van Gogh’s The Painter on the Road to Tarascon, experimenting with more viscous surfaces and strident light. The color is flamboyant and brassy; space is flatter, less reliant on perspective; subjects are outdoors. In the one Van Gogh painting at the Met -- a stunner -- you can see him giving up his tricks, breaking out of his style to fantastic effect. But when the series first appeared, some of his most ardent supporters turned away. Russell called them "clamorous," "hectic," "perhaps the weakest" he ever did; Lawrence Alloway dismissed the series as "an outburst from a gypsy violin."

I believe the Van Gogh series marks the beginning of the end for Bacon. It’s true that he painted for another 35 years, and that in the ‘60s and ‘70s he produced arresting triptychs of bloody figures -- in fact, it’s doubtful that Bacon would be nearly as famous without them. Bernardo Bertolucci based scenes in Last Tango in Paris on them. A so-so 1976 example sold in 2008 for $86.3 million, setting an auction record.

But the Metropolitan’s retrospective, like most Bacon shows, makes it clear that he kept working his theme until it became a gimmick. The calculated pictorial repetitiousness and lack of formal development wear thin. Except for a number of fabulous portrait heads and the astounding Jet of Water -- made in 1988, just four years before his death, featuring an enormous streak of blue paint across an interior -- Bacon’s formula had grown stagnant by 1965.

Once you’re aware of this point, it becomes all you see. He has no idea what to do with the edges of his paintings. Everything that happens in Bacon’s work happens in the middle of the canvas; at times you don’t have to look anywhere else. The bottoms of his paintings are always the same, too—a receding plane curves up at the sides, like you’re looking through a fish-eye lens or from inside someone’s eye sockets. He neutralized his paintings further by insisting they be framed behind glass. ("I even like Rembrandts under glass," he once said.)

Last fall, when I saw this Bacon retrospective at the Tate, it ran concurrently with a Mark Rothko show. Rothko and Bacon were virtually the same age; both worked away from Paris and took "anguish" as their subject. Yet compared with Rothko’s glowing blank Buddhist television sets, Bacon’s work seems mannered, conservative, simplistic. Bacon said that "only by going too far can you go far enough," yet in giving up all the conventions of painting, Rothko went further. When I saw the Bacon show again at the Prado this past winter -- near the galleries full of Velázquez masterpieces -- Bacon’s work seemed dead and canned. His supporters often refer to the rousing chaos of his studio (Cecil Beaton noted its "discarded paintings, rags, newspapers, and every sort of rubbish"). If only his late work had some of that anarchy.

What’s especially poignant about Bacon is that he knew he’d built his own prison. As early as 1963, he referred to "my rigidness." He talked about the "drawback" of his style and how he used painterly tics as a "device." In 1970, drama turned to tragicomedy when Dyer falsely accused Bacon of marijuana possession. A police raid was followed by arrest, public humiliation, and trial and acquittal. By then Bacon and his work were becoming parodies of themselves. You can see this at the Met; the bright chalky color in his work is vibrantly alive, but everything else is flat. And he seems to have recognized that. He’d sealed himself off from the art of his time. "I stay here in my cage," he said. Bacon disliked abstract art, saying it was "too weak to convey anything, and had "nothing to do with the avant-garde."

When you watch the 1985 BBC film of Bacon being interviewed in that grubby studio and hear him spout bromides he’d repeated for decades (he was "an optimist about nothing," he said again and again), one of his self-assessments seems apt: "I am the most artificial person you’ll ever meet." The more one looks at his long career -- especially the last 25 years of it -- the more Bacon strikes you not as an artist unafraid of the darkest within himself but as an artist who didn’t go to that source enough. Bacon wanted to "remake the violence of reality itself," and for a time he succeeded. But in the end, he seems less a modern painter than the last of a breed of Romantics -- one who, in his final interview, plaintively stated, "I painted to be loved."

"Francis Bacon: A Centenary Retrospective," May 20-Aug. 16, 2009, at the Metropolitan Museum of Art, 1000 Fifth Avenue, New York, N.Y. 10028

JERRY SALTZ is art critic for New York magazine, where a slightly shorter version of this essay first appeared. He can be reached at jerry_saltz@nymag.com.