Behind the wheel of his Rolls-Royce, tooling north on a two-lane highway in southern Michigan, Muhammad Ali was heading home to Berrien Springs one December afternoon in 1991 when all at once he crunched the brakes and swerved to the shoulder, raising a bloom of dust from the road. Turning hard to the left, he did a quick U-turn across the highway and slowly drove back about 200 yards to where a small party of college students, like mourners at a wake, stood solemnly around the raised hood of their car. Parking in front of them, Ali climbed out and walked unsteadily to the rear of his Rolls. Back in the 1970s, when Ali was trotting the globe, there were whole countries that couldn't pick Jimmy Carter out of a lineup but recognized Ali at a glance. His face was the most familiar on earth, and wherever he went the whispers always went up—"Ali...Ali..."—as crowds moiled around him in rural villages and city streets, and the world's children, trying to get a foothold on his lap, clambered up him as if on a backyard oak.

Now he was turning 50, and while age and Parkinson's syndrome had stolen the graceful swank and unending banter of old, the moon-cheeked visage was still as familiar and seductive as ever. "Isn't that...?" whispered a wide-eyed young female student. Her companion rolled his eyes. Moments later, after fishing around in his trunk, Ali was observed standing on the side of the road trying to untangle a set of jumper cables. Honking trucks and cars roared by. Hands waved yoo-hoo from passing windows. A car in the far lane skidded to a stop and backed up to where Ali was; four white faces appeared, pumpkinlike, in two windows and said, "Ali, we love you! You are the greatest!"

And there was the three-time heavyweight champion of the world holding the cables in his left hand while blowing kisses to the pumpkins with his right.

Ali fought professionally for more than 20 years, from 1960 to 1981, and his life was so brassy and daring, so filled with wonders and adventure, and so enlarged by the magic of his personality and the play of his mind that no one remotely like him has ever been seen on the sporting scene. Dancer, poet, fighter, mime, he was sui generis—the most gifted and unforgettable athlete-performer of his time. He inspired the era of globally televised megabuck fights, but no stage was ever large enough for his range of expression.

"I'm bigger than boxing," he used to say, and he was. Ali came of age during a period of social upheaval growing out of the civil-rights movement and the Vietnam War, and he not only came to personify the turbulent '60s but also became one of the decade's most hated figures. In 1964, as the world's new heavyweight champion, he broke from the nation's Judeo-Christian tradition by joining the Nation of Islam and changing his name from Cassius Clay; and then, in 1967, he stirred the country's patriotic gore by refusing induction into the armed forces on the grounds that he was a Muslim minister. "I ain't got nothing against them Viet Congs," Ali said.

As punishment, at the age of 25 he was stripped by boxing authorities of his title and consigned to a 43-month exile from which, in some ways, he never recovered. The ban divided his boxing career into halves. In the first, during which he whipped Sonny Liston for the title in 1964 and then toyed with the likes of Cleveland Williams and Zora Folley, he was a 210-pound man who moved around the ring like a lightweight, with darting hands and the quickest feet ever owned by a big fighter. In fact, young Ali was rarely punished for having failed to learn the most fundamental ring skills. Instead of bobbing under hooks and slipping straight punches, he used his reflexes to escape punches by moving or leaning backward—sins for which ordinary mortals would have paid heavily.

By his return from exile, however, he was 28, and his idleness had stolen those surpassing legs and left him a slower, more vulnerable target. The intriguing irony of his career is that his two most inspired, memorable triumphs—his eight-round knockout of George Foreman in Kinshasa, Zaire, on Oct. 30, 1974, to regain the title stolen from him in 1967, and his 14-round war with Joe Frazier 11 months later in Manila—came years after he had lost his best stuff. Surely nothing else that Ali ever did inside the ropes was quite as spectacular as his dismemberment of Foreman, who had arrived in Africa with a menacing glower and a ring history that had Ali followers fearing for their man's life.

Fearing no one, Ali alone was unmoved. He had been promising for weeks to pull off the greatest miracle since "the resurrection of Christ," and Hugh McIlvanney, in his column for The Observer of London, expressed most eloquently the stunning turn of events in that Sunday's newspaper, writing, "We should have known that Muhammad Ali would not settle for any ordinary old resurrection. His had to have an additional flourish. So, having rolled away the rock, he hit George Foreman on the head with it."

His skills, though, grew ever more diminished through time and trial. Even in his other signature fight, the Thrilla in Manila, Ali took 440 blows from Frazier, many of them murderous left hooks. Two of Ali's greatest virtues as a fighter, the depth of his bravery and the strength of his chin, worked their wickedness on him in the end. He took some terrible punishment, and that bravery and that chin kept him standing there, lolling wearily on the ropes, long after the rest of him had vanished.

If Ali was not the greatest of all time—and a more persuasive case can be made for him than for any other prizefighter—he is certainly the most important figure that the game has ever produced and its largest, most charismatic performer. Today, navigating the sweet land of liberty and religious freedom, he is as loved and embraced as he was once scorned and despised. Now they gather round him in airports. Now they wave to him from passing cars. Now they stand back watching him untangle jumper cables.

He never did get that car started, but he gave two students a lift back to campus. As he was about to leave, the wide-eyed student approached him hesitantly, in a whisper. Standing by his car, Ali took out a pamphlet on Islam, signed it and handed it to her. Then he leaned forward and pointed to his left cheek. Cautiously, she leaned forward and kissed it. Opening his arms, he swooned grandly and fell back against the car, as if in a faint; little wide-eyes stepped back with a startled laugh. Ali had fooled 'em all again. Coming to, he grinned. And winked.