THERE ARE LOTS of ways to start a column about Muhammad Ali. There is, for instance, a beginning that would mention how striking he is in person - how he is bigger than you would have imagined and broader and how there is a power in him that you can sense through street clothes. That's a beginning of sorts but it has nothing to do with getting old.

There were other things to say. There is the notice you have to take of how he had once been a punk kid named Cassius Clay, a kid with the gift of fast hands and a faster mouth and how he took out Sonny Liston in seven rounds. He left him bloody, his arm in a sling, and the next morning, in an interview, he called Liston an "old man." Ali was then 22 and he was never going to get old.

You have to say something, too, about his convictions. He said he was a Muslim and that his name was Muhammad Ali and people just laughed. He had to be kidding. Fighters did not have convictions and they did not have political beliefs - certainly not unpopular ones. So the sports writers, most of them, ignored him and so did the boxing establishment and everyone continued to call him Cassius Clay.

When it became clear that he was serious, Floyd patterson, once the champ himself, offered to fight Ali for nothing. He would rescue the crown for Christianity, the flag and God knows what else. There was a time in this country, when Muhammad Ali was considered such a threat that Floyd patterson became the equivalent of the Great White Hope.

There is something else to mention, too. There is the day in the lobby of a Washington hotel when Ali was in town to speak and he was holding court with some young people. It must have been one of those conventions for high school students because the group around him was that age. They were mostly black and Ali joked with them and chided them but then he turned deathly serious and he gave them a little talk about education. It is hard now to recall his words, but he said something about how school was important and education was critical and if the words don't come after all these years, what does stick is the faces of the students. He was a hero to them and there wre very few real heroes around.

So these are the things to mention and they are mostly about youth. Ali was young and for that reason he could do what he wanted and say what he wanted because he was big and quick and strong and mostly because he was young. But he was not young in the ring the other night and the first thing you saw was a body that no longer was taut and tight, but one that sagged here and there and looked more human. It was a body that was showing its age.

The fight was on the television set and there were some people over and they paid lieele attention to what was happening on the tube. But as the rounds went by you could see that something terrible was happening. The time came for Ali to do his thing, to come in so full of confidence and take his man apart and he simply could not do it. He kept stepping back and then trying again as if this was a question of technique or tactics, rather than simply one of age. You could not sec his eyes on the set, not look into heart, but if you could I could tell you what you would have seen. You would have seen the fear that comes to a man when your body has quit taking orders.

Anyway, the fight was on television and Brent Musburger, a Wurlitzer of a type artist, was going the blow-by-blow and he was talking all the time about Ali's age. He was saying the man is 36 years old, which is old for a fighter - which is older than the fighter should be. It is the age of someone who's been champ on and off since 1964. Since Sonny Liston, since the Vietnam war and all that. Ali has been around for a long time, longer than any of them.

There is a thing about athletes. You can mark your life by them. At first, they are always older than you and you think that age is the difference. Later you learn that there is more to it than years but whatever that difference is, age will take it from them sooner or later. So one by one the heroes of your youth come to join you on the bench - Mantle and Mays, Koufax and Chamberlain and just recently Joe Namath. Ali was the last. He was overdue.

So there he was in the rign with Leon Spinks and he was getting hit. He was throwing punches that were not telling and he was moving too slowly and he was, in short, just showing his age. He was in there and he didn't have it and he should not have been where he was. He should have been on the sidelines with the rest of them, but what he was doing was making up for those years that they took from him - those years when the title was stripped from him and he couldn't fight because he thought differently from most people. They took something from Muhammad Ali that they could never give back. They couldn't take his pride nor his convictions nor, for that matter, his talent. So they took something else instead.

They took his youth.