Seventeen years have passed since his last fight, and nearly 20 since he last won one, but the mythic figure known as Muhammad Ali continues to enjoy periodic revivals around the globe. Just the other night, for instance, the BBC devoted an entire evening to Ali in its run-up to the European television premier of When We Were Kings, Leon Gast's long dormant account of Ali's improbable victory over George Foreman in their 1974 "Rumble in the Jungle" in Kinshasha. For most viewers on the other side of the Atlantic this represented Ali's first trip back into the spotlight since that memorable evening two summers ago when he ascended the final steps of Atlanta's Olympic Stadium and, with trembling hands, ignited the torch to inaugurate the 1996 Games.

Then, as now, otherwise well-intentioned people greet these rude reminders of what Ali has become with misplaced expressions of pity. At the same time, the spectre of Ali, circa 1998, serves as ammunition for the anti-boxing lobby, which continually reminds parents that if the sport is not outlawed, their sons in gymnasiums around the world could "turn out like Muhammad Ali," and, on the face of the evidence, rational discourse on the subject has become all but impossible.

Ali is undeniably afflicted with Parkinson's Syndrome, in all probability as a result of his boxing activities. There are those who would argue otherwise, pointing out that there are men suffering from the same malady who never laced on a pair of gloves. I would disagree with them, as would Ali himself, who has admitted that "boxing probably did this to me."

At the same time, Lonnie Ali, his devoted fourth and final wife, reminds friends "Don't feel sorry for Muhammad. He's as happy as any man on earth and he's at peace with himself."

Imagining what Ali would have become without boxing is to contemplate the life of Sinatra had he never sung a note. It may have diminished some of his physical faculties at 55 years of age, but it also gave him the platform from which he continues to reign. Still the most recognisable figure on the face of the earth, he may speak in mumbled whispers, but those whispers have forestalled wars, freed hostages, and brokered truces no politician had been able to achieve.

The well-intentioned folk who view Ali as a pitiable figure often confuse his state with puglistica dementia, the punch-drunk syndrome which often afflicts elderly former boxers, but the truth of the matter is that he can still be as sharp as a tack.

A few years ago I found myself at a picnic lunch the city of New York was hosting in Ali's honour. Among the 200-odd guests milling about on the lawn of Gracie Mansion, the mayor's residence on the East River, I chanced to run into Chuck Wepner, who was in the process of attacking the buffet table.

(Glancing at the latter, I could not help noting to myself, "Leave it to a politician to invite the world's most famous Muslim for lunch and then serve ham sandwiches.")

Chuck Wepner's boxing career was more or less defined by one fight, his 1975 encounter with Ali in a basketball arena outside Cleveland. Although he lost, Wepner, through a fluke, managed to become one of four men ever be credited with having knocked Ali off his feet. That he actually tripped him by stepping on his shoe as he threw a punch was apparent to nearly everyone present save the referee, Tony Perez, but the act not only preserved Wepner's place in history, but made him the real-life model for the character "Rocky" in Sylvester Stallone's film the following year.

Once his boxing days were over, Wepner fell upon hard times, and has only recently been released from prison after attempting to supplement his income by selling a rather large quantity of drugs to a man who turned out to be a federal agent. A decade and a half on, the Ali fight remained the most important moment in his life, and as we stood chatting, a doddering Ali emerged from the mayor's mansion, guided down the stairs and across the lawn by a pair of minders.

His eyes seemingly fixed on the ground, Ali slowly shuffled his way through the crowd, and I watched Wepner as he attempted to place himself in the champion's path, hoping against hope that he might be spotted and recognised by a man he had not seen in 16 years. As Ali drew abreast of his one-time adversary and kept right on going, a forlorn look began to spread across Wepner's countenance, but at the last instant, Ali stopped, whirled, and planted his right shoe atop Wepner's.

"You stepped on my foot," he softly whispered. "You didn't knock me down, sucker!"

A smile sneaked across his face and his eyes twinkled, and soon the old rivals were locked in an embrace.

"His mind is as clear as ever," says Tom Hauser, his friend and biographer, but, truth be known, his physical condition can fluctuate greatly, depending in many cases on whether he has taken the medication prescribed to control the effects of Parkinson's. The medication evidently has unpleasant side effects, and there are times when Ali would prefer to skip it altogether.

I happened to be present on one such occasion, and it wasn't pretty. A couple of years ago Ali had come to Boston to accept another of his many honorary university degrees. By appointment, another friend and I dropped by to visit him in his hotel suite the night before, and spent an hour in near-silence with Muhammad, Lonnie, and Ali's best friend, the photographer Howard Bingham, who frequently accompanies him on such journeys.

As we made ready to say our good-byes, Ali attempted to struggle out of the armchair in which he was sitting. I motioned for him to stay put and crossed the room to give him a hug, and as I did so I was shocked to see that the great man was drooling.

Lonnie couldn't help but note the look of horror that had spread across my face at that moment, and as we walked toward the door she stopped and told me: "He didn't take his medicine today."

Bingham walked us to the lift.

"Howard," I told him, "I've known for some time that he has good days and bad days, but until this moment I never knew just how bad the bad days could be. Are you sure he'll be all right tomorrow?"

"He'll be fine," promised Bingham, and he was. Ali was brilliant in his appearance at the college, and later broke up the audience by challenging and then shadow-boxing with Peter McNeeley. From the evidence on display, you'd still have liked Ali in that fight.

Although it had become obvious within minutes of our arrival that anything resembling an interview would be impossible, I had wanted to collect Ali's thoughts on another matter. His old rival Foreman was about to fight for the heavyweight championship, and while he would knock out Michael Moorer in the 10th round to regain the title he had lost to Ali 20 years earlier, most people, including the "experts," believed that, at 45, he should not be fighting at all.

I had watched Ali's sorry performance against Larry Holmes in 1980, and a year later I had been there in the Bahamas for his final fight, a pathetic loss to Trevor Berbick on a baseball field outside Nassau. No one had bothered to procure a proper bell with which to signal the rounds, but somebody had rounded up a cow bell to serve in its stead. It also developed that there were only two pairs of boxing gloves to be found on the island, so the cornermen in the supporting bouts were instructed not to cut the gloves off. The same pair of increasingly sweaty and waterlogged gloves were passed on from fight to fight until they finally wound up on the hands of Berbick and Ali. It was an inglorious end to a magnificent career, but the question had always dogged me: What would have been the proper ending?

That evening I had finally put the question to Ali himself: "If you had it all to do it over again, what would your last fight have been?"

He gave the matter some thought, and then beckoned me to lean over.

"Probably," he whispered in my ear, "George Foreman."

Had the end of his career coincided with the end of When We Were Kings, of course, there would have been no "Thrilla in Manila." There would have been no third fight against Ken Norton at Yankee Stadium; Ali would never have lost or regained his title in his two fights with Leon Spinks. He would never have indulged in his buffoonish antics by "fighting" the Japanese wrestler Antonio Inoki. (Who, by crawling around on the floor attempting to scissor-kick Ali, did earn his own place in boxing history: even though he went there of his own volition, Inoki was the last man ever on the canvas against Muhammad Ali.) And, of course, he'd never have fought poor Chuck Wepner at all.

If Ali had gone out then, would the legend have been more, or less, complete? It's a question we are all left to ponder. If he'd never boxed at all, be might be a healthier specimen now, but if he'd never boxed at all, he wouldn't have been Muhammad Ali.