Dec. 13, 2001 -- For eight years, Will Smith refused to take on the role of Muhammad Ali, saying he didn't believe he was up to the job of playing the man he calls "the greatest figure over the last 100 years."

"Intellectually, I didn't feel that I possessed what it took to become Muhammad Ali," Smith told Primetime's special correspondent Tavis Smiley. "I absolutely, positively did not want to be the dude that messed up the Muhammad Ali story."

Ali and his family even personally asked Smith to take the part. But it was the film's director, Michael Mann, who finally convinced Smith that he'd be able to capture every aspect of Ali in the bio-pic.

"He said, 'We're going to find the greatest trainers in the world to teach you how to fight,'" Smith recalled. "'We're going to understand every second of Muhammad Ali's life. We're going to understand what he ate … how he viewed the world … how his mother felt about him, how his father felt about him."

With Mann's plan laid out, Smith said he "could really see the road … It was a rough, jagged, uphill road in the rain, but he brought it to light so that I could at least see what the road was."

It was at that point, Smith said, that a "weird confidence" came over him. "I felt confident that this was the role that I was born to play."

Getting It Right

For almost two years, Smith trained his body, rehearsed his voice, and tried to encapsulate the soul of Ali, who changed his name from Cassius Clay when he converted to Islam.

"I picked up the spiritual aspects fairly easily," said Smith. "I understand the basic tenets of Islam, and I had an Islamic instructor."

The most difficult parts, he said, were the physical training and learning Ali's dialect.

Throughout the making of the film, Smith felt Ali's imposing presence and the pressure to get it right. He asked Ali to give him three months before watching him rehearse.

He didn't let Ali down. "He is a perfect actor," the 59-year-old said. "I even thought he was me."

Ali said he still hasn't seen the movie in its entirety, because he wanted to see it with a crowd. "I am waiting to be surprised," he said. "Waiting to feel the effect of it, to see how people feel."

A New Cause

Like Ali, who has been a champion of civil rights and who served time in prison for refusing to be drafted during Vietnam, Smith said he has a moral code he lives by and political views he feels strongly about.

"I try to speak my points of view about black America, and how I feel about black men and the role that black men should play in their lives with their children and in their lives with their women," he said.

"Tons of women would love to have sex with me," he said as an example. "I hate the image of black men as promiscuous and unable to control themselves sexually. I don't like that image. So that's why I specifically make it a point and struggle and fight to not put myself in those types of situations."

Smith found a new issue to act on while filming Ali in Africa, where he discovered that almost everything he had been taught about the continent was wrong.

"The best and the worst of everything in the world exists in Africa. And people think that it's just animals walking down the street," Smith said. "I was shocked to see a 40-story building in Africa. I was shocked to see girls rolling in BMW's and I was shocked to hear rap music. I just didn't know."

Smith, who bought a house in Johannesburg, is now talking about spending the year in Africa with his wife, actress Jada Pinkett, and their children. He said he doesn't want his kids to be "completely miseducated" about their heritage, like he was.

'I'm Profoundly Changed'

When Ali opens on Christmas Day, Smith will reach the end of the journey he began two years ago. But he says the trip he made through the life and times of "The Greatest" will last him forever.

"I'm profoundly changed," he said. "There's a bittersweet emotion that I feel from playing this role … I want the world to be different because I was here. However lofty or crazy or delusional that may sound, I want people's lives to be better because I was here."

Smith, who first made a name for himself as a rapper, has worked his way up the Hollywood pay scale with films like Independence Day and Men in Black, and now earns $20-million a movie. Now that he's finished Ali, he's not sure what's next.

"It's quite highly possible that I have peaked," he said. "I mean, I just can't imagine what else I could do beyond this. It's really a bittersweet kind of feeling."