Boxing at its best is beastly.

If that assumption holds no appeal, then you cannot relish the stirring and horrid spectacle of Roberto Duran's public assault on Sugar Ray Leonard here on Friday.

Boxing is about pain. It is a night out for the carnivore in us, the hidden beast who is hungry.

Few men have ever become world champion without facing that dark side of their game; Leonard was one.

Leonard might even have arrived in this cosmopolitan city to defend his WBC welterweight crown still believing, at 24, that his profession was a sport rather than a disturbing, paradoxical arena where vice and virture sometimes exchange roles once they enter the ring.

Duran, who has been the quintessential creature of the ring in his time, acquainted Leonard with the true facts about his business.

After a lifetime of hard work but almost effortless success inside the ropes, Leonard finally came face to face with the core of boxing: suffering. He passed the test of personal courage but, because he was so intent on that examination of character, he neglected the tactics of his art and lost a crown.

Someday, if the '80s turn out to be a decade of Leonard evolution, this fight -- called "le face a face historique" -- may prove to be historic because it brought a great young fighter face to face with fear.

Duran, only the third man ever to be both lightweight and welterweight champion, won a unanimous decision over Leonard by a slim and controversial margin.

Leonard won a unanimous and incontrovertible decision over fear. This defeat was his letter of credit to a doubting world that thought him a likeable boxer, but not necessarily a heroic fighter.

Few nights in history, certainly very few in the last 20 years, have met boxing's highest and most dubious standard of greatness: the constant, relentless and mutual inflicting of the maximum tolerable amount of pain.

By that measure, the Leonard-Duran conflagration was worth every penny of the $30 million that it probably will gross. No one who is fascinated by watching men under extreme duress was cheated.

Duran, given his choice, would fight 15 rounds in a telephone booth without any intermissions. Only the Panamanian brawler, among current fighters, can monopolize 399 square feet of a 400-square-foot ring. Duran's victims sometimes wonder if they have room to fall.

That was the case for the first five and last five rounds of Friday night's classic, which was as riveting as boxing can be without knockdowns or copious blood.

Experts will argue interminably over why Leonard fought what appeared to be a brave but hopelessly stupid fight. Why didn't he jab? Why didn't he dance? Why didn't he circle? Why didn't he slide when Duran tried to cut the ring? Why didn't he clinch or push off more to avoid the in-fighting? Why did he stand toe to toe countless times and exchange hooks to the head and uppercut digs to the gut?

Only Leonard had the absolute and unarguable answer.

"I had no other alternative," he said.

Early in the fight, when Duran was fresh, and late in the fight, when Leonard was tired, Duran made certain that the fight would be conducted only one way -- his way.

Wherever Leonard was, there was Duran -- less than arm's reach away and throwing leather without surcease. In such circumstance, no man can dance, or jab or slide. Once Duran is within the parameters of an opponent's defense, and both his hands of stone are moving, a fighter has only one choice: exchange punches or call for mama.

The tone of a brutal and elemental evening was established quickly when prelim lightweight Cleveland Denny was carried out unconscious in convulsive paroxysms so strong that doctors could not get the mouthpiece out of his clenched jaw. Denny is in intensive care.

For any in the crowd of 46,317 -- the once-a-year boxing fans like Jack Nicklaus -- who might doubt, that twitching body on the stretcher was a declaration of boxing's basic nature.

When Gaetan Hart, the man who knocked out Denny, was told that his last punch hardly seemed powerful enough for such damage, he was offended. His last opponent left the right in a coma and required eight hours of brain surgery, so Hart, with his matted hair, tattoos and rearranged features, is proud of his punch. In his life, it is what he has.

"When I hit Denny with the right hand," explained Hart, "his eyes go around backwards like this."

And Hart twirled his forefingers as though illustrating how the cherries on a slot machine revolve.

That is boxing. And Duran, the man who, in the ring, has the hands and the heart of stone, knows it better than any fighter of his generation.

Other boxing eras would not have found Duran unique. His personality type would have seemed comfortably familiar: a fatherless street urchin who stole to feed his brothers and sisters, dropped out of school in the third grade at the age of 13, turned pro at 16, became the athletic pet of a Latin military dictator, won a world title at age 21, and now has a fleet of gaudy cars and a 680-pound pet lion which he walks on a leash.

In any period, Duran would have stood out. But in the '60s and '70s, when Muhammad Ali brought footwork, defense, an unmarked face and poetry to fighting, Duran seemed almost an embarrassing anachronism, a stage in boxing's evolution that the game seemed anxious to act as though it had passed.

Duran, with his 71-1 record, seldom got his due. Or if he did, it was done with a shudder as though Heathcliff were being introduced in polite society and might smash the china in a rage.

But boxing never changes. One central truth lies at its heart and it never alters: pain is the most powerful and tangible force in life.

The threat of torture, for instance, is stronger than the threat of death. Execution can be faced, but pain is corrosive, like an acid eating at the personality.

Pain, as anyone with a tootache knows, drives out all other emotions and sensations before it. Pain is priority. It may even be man's strongest and most undeniable reality.

And that is why the fight game stirs us, even as it repels us.

For at least 10 of their 15 rounds, Leonard and Duran set as intense a pace as any fan could wish -- they looked like Ali and Smokin' Joe Frazier in the first round in Manila but, because they weigh only 147 pounds, their speed and frequency of violence did not dwindle nearly so much as the fight wore on.

"He threw his best, I threw my best," said Leonard.

What landed? he was asked.

"Everything," said Leonard.

In the early rounds, there was defense, slipping and blocking of the fiercest punches. In the late rounds, when the blows still carried pain but insufficient force for a blessed unconsciousness, every third swing seemed to land flush.

Only in the middle rounds, starting late in the fifth, when Leonard finally landed enough consecutive punches to make Duran back off for the first time, and extending through the 10th, did Leonard achieve a painless modus-vivendi .

Then, Leonard still had his speed and Duran had his doubts. The Sugar Man struck and escaped, dealt fire for fire, then had breathing time to regroup.

After those early rounds of perplexity bordering on fear, Leonard gradually gained conference -- more's the pity for him -- until, by the 11th, he thought he was Duran's better. He thought he could reach into the furnace and save the crown that he saw melting there.

The 11th round was meant for the film archives. Everything that gives boxing undeniable dimension and emotional authority was wrought to white heat then.

Money, glory or the search for identity may get a man into the ring, but only facing and surmounting pain can keep him there. Only that act of creating a brutal art in the presence of suffering can bring nobility to man's oldest and most visceral competition.

Boxing has the cleanest line, the fewest rules and the most self-evident objective of any endeavor that people gather to watch.

When shabbily done, like the third meeting of their careers between Denny and Hart -- a pair of lifelong plodders -- few things are so worthless and destructive. Life and death on the undercard is as depressing as the sporting life gets.

However, at certain heights of skill and will, fighters like Duran and Leonard begin to carry with them a symbolic nimbus. They seem a distillation of their backgrounds, their time and place and the people out of which they sprang.

Only when Duran is seen in this way does that 11th round, and what he did after it, seem inevitable.

Here in Montreal, this town of boutiques and glass-and-neon malls where an obsession with the latest imported European fashion is everywhere, Duran's fans and followers have looked as alien as Martians.

In swanky hotels like the Meridien, the Regency and the Bonaventure, these people who chant "Cholo" -- the word for a Panamanian of Indian descent -- and talk constantly with animated delight are distinguished by more than their old, clean, one-suit-per-lifetime clothes.

Their hands and faces, like Duran's, have been weathered by eternal forces -- the erosion of work, age and the rub of stubborn necessities.

In Olympic Stadium on a cool Canadian night, with salsa music in the upper deck, Duran's people -- his true kin or those here who have adopted him -- cheered with raw conviction.

Out of our pestilential sump holes of social unconsciousness rise up a few strong, if lopsided personalities, who create much of our public collective mythology. Duran is a sample of that up-from-under caste that seems simple, unified and forceful.

In the 11th, that absence of complexity proved useful.

Leonard had mustered both his confidence and his resolve.

"Sugar Ray is like the rain," said Leonard's sparring partner Mike James before the fight. "Once he gets started, you can't make him stop."

Leonard had clouded up and was in full thunderclap. Just as Duran had had Leonard deeply worried and near trouble in his second-round blitz, Leonard now was sure he was going for a kill. "I hit Duran some tremendous shots with left hooks, right hooks and overhand rights," said Leonard.

Instead of covering up, Duran met the pain directly, almost welcomed it. The more his head was battered from side to side, the more his fists flew in return. By midround, Leonard was so arm weary from punching that his gloves slipped to his waist. Duran took the initiative in the assault and battery until, by round's end, Leonard was in another desperate retaliatory rage, storming down punches on Duran after the bell sounded.

The net effect of this sustained firestorm was not a new balance of terror, but merely a change in exhaustion levels. Leonard had gambled and lost.The fight reverted to its early-round syndrome with Duran boring inside against a gam but stationary Leonard.

Had Leonard resisted the impulse to knock out this taunter, had he stayed with his midround style as long as his energy lasted, those ever-so-close judges' cards (146-144, 145-144 and 148 -- 147) might have been reversed.

It is appropriate that in such a morally ambiguous sport, one of boxing's great fights should leave beind it a mood of nagging paradox.

A view of the world -- usually unspoken -- often hangs around the edges of major sports. Certainly it always has with boxing.

The notion that life is a fight is inescapable in this subculture of leather and liniment. The search for glory through taking advantage, the constant pursuit of getting the better of someone are percepts so ingrained that no one would think to preach them.

As a consequence, those who tend to see the world that way are drawn here: politicians, mobsters, business millionairs, junkies of all persuasions, entertainers, athletes and journalists.

It is a night for those who have sharp teeth, or think they do; vegetarians and saints need not apply.

However, this shark ethic may have been carried further -- reduced really to the absurd -- in boxing than in any other corner of our culture. The big eating the little is gospel.

That is why Leonard entered this scene as such as refreshing anomoly. Essentially, he was a world champion who had none of boxing's shabby back-room entanglements.

It was no accident that this fight could gross more money ($30 million predicted) and bring more to the fighters themselves (at least $8 to Leonard and $1.5 million to Duran) than any fight in history.

Leonard's lawyer, Mike Trainer, set a precedent of squeezing out middlemen and promoters, keeping the financial books above board and making no private deals.

But as soon as this beastly good fight ended, the big sharks of boxing began circling.

Duran as devoid of duende -- that indefinable Latin mixture of style and class -- out of the ring as he is chocked with it inside the ropes, sat beside his boxing godfather Don King, the promoter.

As Duran attacked an orange -- spitting seeds and rind in any direction as he held a surly, gloating, graceless press conference -- King, his hair electrified and his vanity in full bloom, took out a hugh roll of big bills.

With great pretense, King began slapping the money in Duran's palm of stone as the photographers clicked.

Not only Sugar Ray Leonard had been beaten, but Sugar Ray Leonard Inc., too. That great perennial enemy of boxing -- an honest fighter -- had been removed from the game's top rung.

And that, on one of boxing's best nights, was a beastly development, indeed.