Muhammad Ali
Credit: Neil Leifer / Sports Illustrated / Getty Images
Since then, it's been aftermath – some of it legendary, some heartbreaking. Ali fought 10 more fights after Manila. In February 1978 he lost his title to Leon Spinks, a novice professional. Ali was in torment – the night after the fight, he was running down the street at 2 am, yelling, "Gotta get my title back! Gotta get my title back!" He regained it from Spinks seven months later – the only man to win the world heavyweight championship three times. But by then he was already showing troubling signs: His speech, for one, was turning thick. "They say I slur, but I'm just talking black," he said. He retired in mid-1979, but within months was training for a title match with the new champion, Larry Holmes. He never had a dominant moment in the fight, but he wouldn't drop. Holmes just kept hitting at a man who had the will to die on his feet. Ali fought one more match, with Trevor Berbick, on December 11, 1981. He lost by decision. After 21 years as a professional boxer, he never again entered the ring. He would not have been allowed to; his impairment was now too evident.

"You can overstay your welcome in boxing," George Foreman said in Facing Ali. "You can get physically hurt, wiped out, devastated mentally. Your brain can only take so many shots to the head." Ali was eventually diagnosed at UCLA as having fallen prey to "Parkinson's syndrome secondary to pugilistic brain syndrome" – an outcome that could not be repaired. His mental faculties stayed agile as ever, but his pace became a painful-looking amble, and in time he stopped speaking publicly. A terrible irony had invaded Muhammad Ali's being: He had prided himself, throughout all his years of boxing, on avoiding head blows and facial scars. He instead had allowed fighters to pummel his midsection, his sides and arms, in defiance of the boxing dictum that if you "kill the body, the head will follow." Yet it was likely those body blows, Ferdie Pacheco observed, that helped ruin his nervous system. Ali had absorbed his fears into a physical place where he could withstand them and make them work for him. All along, they were also working against him. Some – Frazier and others – believe that Ali's impediments might be self-willed, if unconsciously: a penance for his elated mistreatment of so many other fighters, or maybe an atonement for his greatest public sin, his renunciation of Malcolm X after Malcolm had helped fortify his nerve to become champion. But this appraisal also implies that Muhammad Ali deserved some sort of comeuppance for his conceit and impertinence, though it was those same qualities that had made him such an electrifying iconoclast.

In William Klein's 1974 film, Muhammad Ali: The Greatest, there's a sequence from just prior to the 1964 fight with Sonny Liston in Miami, in which a camera moves down a line of men who cite Liston as the odds-on winner, in a few rounds at best. The scene moves to black girls on a Miami street, clapping their hands to the beat of grinding rock 'n' roll, chanting "Liston! Liston!" Minutes later, after Clay has won, both young and adult black people surround his car, celebrating him. "Cassius Clay, the greatest man of all time," says one man. In between those two segments, which represent the span of perhaps a day, history changed. Ali demanded respect and warranted it; he wouldn't be refused, no matter the antagonism he met with. In the process he transformed the possibilities of pride, courage, and recognition for many other black people – in athletics, certainly, but also beyond. "One of the reasons that civil rights went forward," television journalist Bryant Gumbel said, "was that black people were able to overcome their fear. And I honestly believe that for many black Americans, that came from watching Muhammad Ali. He simply refused to be afraid. And being that way, he gave other people courage."

In January 2012, Muhammad Ali turns 70. He has had a long time – nearly half his life – to weigh his past boasts against unknown eternity. "I conquered the world," he has said, "and it didn't bring me true happiness.... Every day is a judgment for me." Still, he knows he has justified his time here. Biographer Hauser told of a moment from 1990 when Ali watched a commentator on TV say of him, "If he had it to do all over, he'd live his life the same way; he'd still choose to be a fighter." Hauser wrote, "Muhammad sat straight up in his chair and said, 'You bet I would.'"

For years Muhammad Ali was history in motion, headed in the right direction, turning the improbable into victories we hadn't thought possible. It couldn't last forever, but to see that it could be done, that was something else. That was hope made flesh, and for longer than anybody expected, it could not be stopped.