PARADISE.<i> By Toni Morrison</i> .<i> Alfred A. Knopf: 324 pp., $25</i>

The vigilantes drive through predawn darkness to a decrepit mansion in the Oklahoma countryside. A tiny community of women, mostly black or of mixed blood, lives there, and rumors of weird and perverted practices have infuriated the right-thinking people of Ruby, the nearest town.

Equipped with rope, a palm-leaf cross, handcuffs, Mace, sunglasses and “clean handsome guns,” the men blast open the front door.

“They shoot the white girl first. With the rest they can take their time.”

Toni Morrison’s new novel, “Paradise,” begins with this brilliantly, unbearably described 1975 lynching. To read Morrison, though, is to advance upon an Olympic wrestling master. We draw confidently near, only to be hurled onto our backs and set in the opposite direction.

The nine members of the lynch posse are black. They are the leading citizens of a town founded a quarter-century earlier by 15 families whose enterprise, hard work and fierce religious values brought prosperity out of a remote stretch of Oklahoma wasteland.

Ruby, all black, lives in vigilant isolation. Typically, when three carloads of whites drive through, hooting obscenely at the local girls, two dozen men emerge from the well-tended houses and yards and silently surround them, their rifles pointed to the ground.

The isolation is not just a prideful and, for a while, a flourishing defense against the white world. It is directed against modern times in general and the changes that time and new generations bring with them. Ruby’s elders, particularly the two richest--Deacon and Steward Morgan--view these changes with desperate alarm: new sexual and moral values, women’s liberation, the youth culture, racial mixing and even the civil rights movement.

Throughout “Paradise” (the Ruby they struggle to maintain), the town’s obdurate and moving story alternates with the cloudier one of the young women in the mansion--formerly a convent and still called by that name--and the ultimately lethal threat they pose to each other.

If the term did not carry a faintly derogatory connotation (Why should it? Look at “War and Peace”), it would be right to call Morrison one of our three most formidable historical novelists. The other two--paradoxically in view of their vastly different styles--would be Thomas Pynchon and Don DeLillo.

Like them, Morrison has worked into a full historical focus over the last 10 years or so. “Beloved” and “Jazz,” whatever their other achievements, remain in the memory because of their rich and searing evocations of slavery and its consequences, in the first; and in the second, the black urban migration of the ‘20s and ‘30s.

The historical theme in “Paradise” seems more restricted, but only at first glance. The story of Ruby began long before the town was built. Deacon’s and Steward’s grandfather, Zechariah, was a Louisiana lieutenant-governor during Reconstruction before the white political classes reassumed their power.

Turned out and reduced to a field hand, Zechariah and other evicted black officeholders began a trek to the open lands of Oklahoma, eventually founding a town they named Haven. For decades, Haven prospered mightily; then, like other black trekkers’ towns in the territory, it declined into poverty.

After World War II, Deacon and Steward along with other veterans and their families began a new migration to the far western part of the state. Convinced that the downfall of Haven was caused by the influx of broader American influences, they chose total cultural, economic and racial autarchy with strict religious underpinnings.

It is a fascinating story, wonderfully detailed by Morrison’s shrewd and vivid portraits of Ruby’s citizens and forebears. But the author has done more than that. Her town is the stage for a profound and provocative debate--always personified and always searching--about black identity and destiny in America’s past and present.

The Ruby patriarchs--they call themselves the New Fathers, succeeding the Old Fathers who founded Haven--are magnificent, wrongheaded and doomed. (Those are easy words to throw about; Morrison doesn’t use them. She gives them such particular life that finally it is we who use them.)

After repeated white betrayals--slavery, the promise and deception of Reconstruction and a century of segregation--the notion of black exodus and isolation bears a somber righteousness. It recalls Moses; it recalls something more recent. Morrison is a master forger of history’s irony.

In their migrations and righteous seclusion, both the Old Fathers and the New suggest nothing so much as the 19th-century Boer Voortrekkers, whose heroic legend metastasized into brutal and sterile apartheid. Morrison goes on to spin the irony into a metallic lacework. On their original way west, the Old Fathers and their families, pure black, were turned away by mixed-blood Negro settlements. Now the patriarchs of Ruby treat the town’s lighter-skinned families as virtual second-class citizens.

The real war that is undermining the town’s dikes is not so much racial as generational. The young are rebellious; they hang about, eschew the industrious virtues, blast out pop music, get each other pregnant, flee to the cities. There is no escaping the outside world. The civil rights movement, opposed by the elders for its dangerous disorder, is taken up by the young, who turn aggressive and disrespectful. Morrison incarnates the argument in a splendid novelistic device: the town slogan, embossed in metal.

“Be the Furrow of His Brow,” it seems to read, but the older generation insists that four letters got rubbed off, making the original “Beware” the furrow, not “Be” it. The town founders preach humbling oneself before the anger of the Lord; their children want to embody the anger and use it.

Fear underlies the pain and anger of the older generation: the sense that it is unable to stand against time’s corrupting changes. Its anguish discharges upon the Convent. Originally a mansion, it was taken over around the turn of the century by a Catholic religious order as a shelter and school for Indian girls. When this collapsed, all the nuns left except one, who remained with her mixed-blood protege, Connie.

For years, Convent and town had lived peaceably if distantly. The townspeople regarded it as an oddity but traded supplies with it for pecans, pies and a special barbecue sauce. Then in the late ‘60s, four young women take refuge there, each a rebel fleeing a different form of abuse. When they come into town they scandalize with their miniskirts, see-through blouses and sexual unconventionality.

To the town’s leaders, the Convent comes to symbolize the invasive chaos of the outside world and a future that will dismantle their own. Rumors build up of witch-like practices, degenerate sex and general corruption. Finally comes the murderous assault that will disperse the interlopers but also signal Ruby’s destruction.

By contrast with the vital tensions, arguments, characters and stories in Ruby, the Convent episodes are frail and abstract. The old nun, Connie’s mentor, has an intriguing individuality; so does one of the four refugees: a woman who steals her brutal husband’s Cadillac, paints it magenta and flees. The others are not much more than chords in a mystical women’s harmony that Morrison propounds as the book goes along.

The touches of magical realism, which emerged in white-hot anguish in “Beloved,” here seem forced. The author is simultaneously sentimental and didactic in her conjuring of the ghostly but militant forces that prevail over the patriarchal assault. (It is not clear whether any of the victims were, in fact, killed, apart from Connie, and she in some ghostly fashion resurrects.) The Convent’s women are symbolic decorations of the feminine message. They are not enough to do it justice in the face of Ruby’s meaty, recalcitrant reality.