The art gods cooked up something special for James Ensor. This avant-garde painter’s decisive moment came in a salon show in Brussels in 1887 (the same year the gods had Van Gogh meet Gauguin). Ensor was a co-founder of a group called "the Twenty," living with his mother at 27, and doing all right in his native Belgium. That year, he exhibited a breakthrough series of large, smoky drawings of Christ in modern-day settings. As fate had it, they were installed near Georges Seurat’s epic, world-changing A Sunday on La Grande Jatte. Reactions to Ensor’s work were mixed at best. Many critics and viewers, including his artist friends, enamored of Seurat’s ideas and methods, found Ensor’s religious subject matter and murky drawings "fatally retrograde." (The criticism set him off; he referred to "bizarre Pointillists operating behind the scenes," of being "surrounded by hostility" and "mean vile attacks." He condemned Impressionists as "superficial daubers suffused with traditional recipes.")

Today, Ensor is still squaring off against the master of speckles. The Los Angeles Times critic Christopher Knight calls him "the anti-Seurat." Ensor’s swirling surfaces, kaleidoscopic color, corkscrewing space, fluttery fevered touch, and fiendish feel for facial features and fanfare make him, with El Greco, one of the great weird painters of all time. At the Museum of Modern Art’s diligent, disciplined Ensor retrospective, you can see that he was better than just about anyone at painting crowds, clowns, contempt, and cacophony. Despite the flushed grandstanding in many of his paintings, his perfect storm of inflated self-esteem, angry viewpoint, and perverse inner landscape combine to make him one of art history’s visionaries.

A visual hysteric and geographer of fin de siècle pathologies, Ensor gives us kings defecating on citizens, himself urinating on a wall that reads ensor est un fou ("Ensor is a nut"), skeletons fighting over a pickled herring, waiters serving human heads on platters, flesh-eating ghouls, vomiting comics, and cavorting demons. Even if you find his visions flaky, he’s the advance man for practically everything twentieth-century, including Expressionism and Surrealism. He presages artists as diverse as Miró, Florine Stettheimer, Henry Darger, Cy Twombly, and Verne Dawson.

Not all his work is up to that lofty level. His obsession with artistic revenge and local politics often traps him in the cul-de-sac of satire. As seen in the show’s final galleries, his scathing visions of doctors, lawyers, and politicians (not to mention Wagner) feel dated; it’s hard to say what he’s on about. Except for a few tumultuous years at art school in Brussels, he lived his entire 89 years in the Belgian seaside resort of Ostend, overcoming the Seurat throwdown and becoming, in his last four decades, an art star. He had grown famous, but -- then and now -- was often relegated to what he himself described as "the outskirts of painting."

Even at his deepest, and unlike his northern contemporary Munch, Ensor isn’t a tragedian, seizer of mental moods, or wizard of spatial pauses and spiritual vacuums. He’s more about the sprawling human comedy and the fragile, febrile release from pain and misery that comes from laughter and fantasy. The surfaces of his best work are far more experimental and fun to experience than Munch’s, or most late-19th-century artists’. He’s Toulouse-Lautrec aflame, without Paris. Rather than peering into the psychic darkness of pre-Cubist Picasso, he takes you further out. He was there at the first signs of the fractures -- in urban life, social structures, irony, morbidity, the landscape of dreams, fiction, fact, the grotesque, and phantasmagoria -- that would come to define the 20th century.

Rather than celebrate Ensor’s weirdness, the curator, Anna Swinbourne, has given us a studious, careful show, tracing the artist’s development from Tachist painter of sketchy brushstrokes and earth tones to someone obviously influenced by Courbet and Manet, a painter who finally let color, light, line and dreaming guide him to his own supreme style. I’d rather have seen more of Ensor at his most painterly flamboyant and unrestrained. Stressing his development and grouping things by theme waters the show down and interrupts the optical intensity, which is his best quality. Sadder still, Swinbourne follows the long-standing view of Ensor’s career, ending this show around 1900. It’s true that by then he was often repeating himself, riffing on his own older works. But if the few examples here are any proof (one interior from 1900 is proto-Matisse), it’s time to let audiences make up their own minds. I suspect there’s a lot more there to see.

There’s also an unavoidable giant crater in this show. Citing the painting’s fragility, the Getty declined to lend Ensor’s fantastical 1888 masterpiece Christ’s Entry Into Brussels in 1889, a gigantic lurid vision depicting the artist as Jesus astride a donkey surrounded by a sea of crazy faces. The late art historian Robert Rosenblum rightly dubbed this psychological cyclone "the best painting in America, west of La Grande Jatte." (D’oh: Seurat again!)

There are almost a dozen retina-tickling works here. (The large drawings, too, are a revelation.) Most are from the ten years starting around 1885, when he was a creative fireball. My favorite, and one of the most radical in early modernism, is MoMA’s own Tribulations of Saint Anthony (1887). The work features a hooded holy man inundated by Boschian creatures floating in swampy skies -- devils and demons who fart on him and defecate. But the subject matter, wild as it is, is nothing next to the delirious, worked-up way it’s painted. We see lush, jittery brushstrokes, viscous paint doubling as clouds, mountains, forests, and thought-balloons. This painting has been a door for a thousand artists; seen in this context, it can be a door to a thousand more. In the much flatter and blocky Fireworks, an abstract plume of fire or an erupting volcano or a flaming palm tree explodes from the bottom of the painting, towering above tiny onlookers. Across the gallery, Adam and Eve Expelled from Paradise (also 1887), however muddled, looks like Monet and Turner on hallucinogens.

Because of the effusiveness of his paint, his visual inventiveness, and his flickering, heavenly touch, Ensor has a special purchase on our imagination. Now that we’re in our own fin-de-binge moment of starting over, stepping out, digging deep, and working hard, he is a necessary artist for other artists to see. Ensor clearly tells us that there are more things in heaven and earth than are dreamt of in our philosophies.

"James Ensor," June 28-Sept. 21, 2009, at the Museum of Modern Art, 11 West 53rd Street, New York, N.Y. 10019.

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.