Some sportsmen simply do not have anything to say or anything to stand for. They are not interested in moving beyond the confines of their sport. They are not interested in ideas or in the lives of others. They dream only of the next goal, the next match point, the next chequered flag, the next fence. Their sport limits them. It does not set them free.
Some have things to say but are too afraid to say them. They are cowed by society and the Establishment. That seems to apply more and more in an era where they are controlled by public relations executives who hover in the background looking scared that their client might say something original or, God forbid, interesting.
Some sportsmen worry they will say something that will damage their brand and cost them money. The great basketball player, Michael Jordan, did that once when he refused to endorse a Democrat who was trying to unseat North Carolina's notorious Republican senator Jesse Helms. 'Republicans buy sneakers, too,' Jordan is said to have remarked to a friend.
Jordan's greatness died as soon as he left the basketball court. Tiger Woods's greatness died as soon as he walked off the golf course. They were kings of their sport and yet they became pygmies, puppets controlled by faceless money men when they left the arena. And that damages them. It limits them. It hurts their legacy. Muhammad Ali was totally different. He was nobody's puppet.
That was why there was such an outpouring of grief and emotion on Saturday. The greatest sportsmen are about something greater than sport. The greatest sportsmen do not allow the spirit that they show in the ring or on the pitch or on the court to be quashed in the arena of real life. Their spirit travels with them out of the ring and lights up the world around them.
The world came to love and revere Ali for the very thing that America hated him for when he shook up the world by beating Sonny Liston in Miami Beach in 1964 and won the heavyweight crown for the first time. Liston was a brute of a man, surly and forbidding, but America wanted him to teach the man then known as Cassius Clay a lesson.
'Liston used to be a hoodlum; now he was our cop,' the influential social commentator, Murray Kempton, wrote in The New Republic magazine later that year. 'He was the big Negro we pay to keep sassy Negroes in line and he was just waiting until his boss told him it was time to throw this kid out.'
Except Liston didn't throw the kid out. He tried but he couldn't. That was the thing about Ali, the greatest athlete of the 20th century and the greatest sportsman we have ever known. No one could throw him out. Until Parkinson's disease came and took him, nothing could imprison him, either.
Ali came to be adored, not just because he was a beautiful, intelligent, brave, brilliant boxer but because he was a symbol of freedom and independence and a refusal to bow to the dictats of the Establishment.
Part of his allure, part of the reason that he was regarded with so much affection, was that he was impossibly charismatic. He amused the public and the media with his doggerel verse and his taunting of opponents. He floated like a butterfly and stung like a bee, he said, and how apt that description was. He was so fast, he said, that when he got up to turn the lights off in his room, he was in bed before it was dark.
But that was surface stuff. It wasn't the reason why his legend has endured. In the 1960s, he represented freedom and protest when they were dangerous, threatening concepts for an American public that saw enemies everywhere. His rise came at a tumultuous time. It was set against the backdrop of the Civil Rights movement and growing opposition to the Vietnam War.
Sure, Ali's momentous fights against Liston, Joe Frazier and George Foreman, his barely believable courage, his mesmerising grace, his unrivalled dynamism and athleticism are part of the reason why he has been acclaimed for some time as the greatest sportsman. Even the names of some of those meetings - the Rumble in the Jungle and the Thrilla in Manila - are enough to send tingles of nostalgia and wonder down the spine.
But being The Greatest, is about more than just sport. If it were just about sport, if it were just elegance and dominance that were used as a measure, then Roger Federer, Wayne Gretzky, Lionel Messi or Jordan would be The Greatest.
But there was more to Ali than there was, or is, to any other leading sportsman. Boxing was not a marginal part of life back then in the way that it is now. To be the heavyweight champion of the world was to be the king of the world and Ali was an icon of protest and a rebel. He scared people in the way that Marlon Brando, James Dean and Elvis Presley scared people, too.
But he went further than them. Presley joined the army when he was told to, after all. Ali refused. He did not let the Establishment grind him down. Back then, when the heavyweight champion of the world was the greatest title in the whole of sport, Ali turned his back on it for the sake of his beliefs.
A member of the Nation of Islam, a disciple of its leader, Elijah Muhammad, and for some time a close friend of the Nation's firebrand preacher, Malcolm X, he was distrusted not just by white America but by elements of the African-American community, too.
Ali did not crave acceptance from white America, like some in the black community. He was a Muslim at a time when Islam was feared almost as much as it is now in some quarters.
It was easy to paint him as some sort of bogey man and America did not hold back. When Ali defended his title against Floyd Patterson in 1965, the fight was promoted as a Holy War, 'the good crusading Christian integrationist versus Ali, the evil Saracen separatist'.
Divorce from white politics was part of the creed of the Nation of Islam and part of the reason why Ali refused to take the required step forward before the Draft Board in Houston in 1967 when he was called up for the Vietnam War. 'I ain't got no quarrel with them Vietcong,' Ali said famously. 'No Vietnamese ever called me n****r.' He was arrested and stripped of his title the same day.
He was exiled from boxing for three and a half years, the years that would have been his prime. His exile, his act of civil disobedience and his anti-war stance, placed him at the heart of America's political ferment.
And even though he never became closely involved in the Civil Rights movement, his courage made an impact even on men like Martin Luther King Jnr. 'They don't like me because I'm free,' Ali said then. 'The Negro has always sold himself out for money or women but I give up everything for what I believe. I'm a free man. I don't belong to nobody.'
Ali did not fight from March 1967 until October 1970 when it became apparent the US Supreme Court was ready to reverse his conviction for draft-dodging. By then, Joe Frazier was the heavyweight champion and in March 1971, after a couple of tune-up fights, Ali challenged him for the title at Madison Square Garden.
Their meeting is known now simply as The Fight. It was a magnificent exhibition of courage and fortitude by both men and although Ali lost on points, he won a lot of respect. It was a brutal fight that shook both men to the core. Ali proved once and for all that he could walk the walk as well as talk the talk.
It seemed for a while as though Ali might never recapture the title he had been forced to give up. It was a golden age for heavyweight boxing and soon Frazier had lost the title to a younger man, another giant of the ring called George Foreman.
Even though Ali avenged his defeat to Frazier early in 1974, few gave him a chance against Foreman in Kinshasa, Zaire at the end of the year in the Rumble in the Jungle, Don King's most exotic promotional triumph. Ali stunned the world again by using the rope-a-dope, probably boxing's most famous tactical triumph, to allow Foreman to pound him for seven rounds before exploding into action in the eighth and knocking out the exhausted champion.
A year later, he fought Frazier for the third time in the most famous meeting of their trilogy, the Thrilla in Manila. The two men pushed each other to the very limits of human endurance.
Its details, too, are part of boxing folklore. Ali said later that the fight 'was the closest thing to dyin' that I know of'. He was not sure whether he could emerge for the 15th and final round when he saw that Frazier's corner would not allow him to fight on. The face of Frazier, who died in 2011, was so swollen he could not see. 'It's over,' his trainer Eddie Futch told him as Frazier pleaded to fight on. 'No one will ever forget what you did here today.'
Neither man was quite the same after that. Ali still found it within himself to defeat fighters of the quality of Ken Norton and Earnie Shavers but there were already concerns about the damage boxing was causing him.
His last bout was against Trevor Berbick in December 1981 but his final fight was against the Parkinson's disease that manifested itself soon afterwards.
Many may recall him only as a man shaking violently as he struggled to light the flame at the 1996 Atlanta Olympics and his death carries all sorts of awkward questions for boxing. He was sport's greatest pride and its guilty conscience, a man who fought for freedom and was imprisoned by disease.
A man who was bigger than boxing and bigger than sport. A man who inspired hundreds of millions. A man who still symbolises youth and rebellion. A man who takes so many of us back to a time in our own lives where everything seemed possible and when we were kings. A man who stood up for himself and would not be cowed. A man who was free and who is now free once more.