During my more than 50 years in the public eye, I have met hundreds of renowned celebrities, artists, athletes, and world leaders. But only a handful embodied the self-sacrificing and heroic qualities that defined my friend and mentor Muhammad Ali.

A master of self-promotion, Ali declared early in his boxing career, “I am the greatest!” This kind of boasting enraged many people, just as he’d hoped, ensuring there was a large audience that just wanted to see this upstart boy taught a lesson. But it was Ali who taught the lesson, because, as he once said, “It’s not bragging if you can back it up.” And back it up he did. Again and again. And not just in the ring.

Part of Ali’s greatness was his ability to be different things to different people. To sports fans he was an unparalleled champion of the world, faster and smarter than any heavyweight before. To athletes, he was a model of physical perfection and shrewd business acumen. To the antiestablishment youth of the 1960s, he was a defiant voice against the Vietnam War and the draft. To the Muslim community, he was a pious pioneer testing America’s purported religious tolerance. To the African-American community, he was a black man who faced overwhelming bigotry the way he faced every opponent in the ring: fearlessly. At a time when blacks who spoke up about injustice were labeled uppity and often arrested under one pretext or another, Ali willingly sacrificed the best years of his career to stand tall and fight for what he believed was right. In doing so, he made all Americans, black and white, stand taller. I may be 7’2”, but I never felt taller than when standing in his shadow.

The secret to Ali’s power and impact as a performer is the sly sophistication of his approach. He adopted the persona of the Shakespearean court jester, whose role in the bard’s plays wasn’t just to entertain the court with his foolishness but to infuse his antics with insights of truth about them. The jester’s witty repartee made those bitter truths easier to swallow—and kept the royals from cutting off his head for his impudence.

In the end, Ali was not able to hide his outrage at injustice behind his entertaining disguise, and they did indeed come for his head. His conversion to the Nation of Islam in 1964 resulted in him being stripped of his heavyweight champion title. His refusal to submit to the draft during the Vietnam War on the grounds that “my conscience won’t let me go shoot my brother, or some darker people” caused him to be sentenced to five years in prison, fined $10,000, and banned from boxing for three years, his license to box being revoked in all states. He didn’t fight for three years during his physical prime, when he could have earned millions of dollars, because he stood up for a principle. While I admired the athlete of action, it was the man of principle who was truly my role model. (In 1971, Ali’s conviction was overturned by the U.S. Supreme Court in an 8–0 decision; Justice Marshall disqualified himself because he was solicitor general when the government brought its case against Ali.)

The golden rule of business is to figure out what the public wants and give it to them. With the rise of the civil rights movement causing so much social turmoil and unrest, Ali figured out that what white America wanted was things to go back to the way they were: voices crying out for equality silenced; blacks quietly waiting for whites to decide if and when to give them the gift of equality. Ali represented that upstart voice, and defeating him would send a message to other blacks speaking out.

Well, Ali outfoxed them all. They didn’t defeat him, and their efforts only inspired others—black and white—to fight for equality. Not just racial equality but gender, sexual, and religious equality. He never stopped being the entertainer, quick to launch a witty barb or make your keys disappear. But the message beneath it all was said with a grin on the lips, and with steel in the eyes: “I am America. I am the part you won’t recognize. But get used to me. Black, confident, cocky, my name not yours. My religion not yours. My goals my own; get used to me.”

Most young people today know Ali only as the hunched old man whose body shook ceaselessly from Parkinson’s Disease. But I, and millions of other Americans black and white, remember him as the man whose mind and body once shook the world. And the world has been better off because of it.

Kareem Abdul-Jabbar is a bestselling author and columnist, and the NBA all-time leading scorer. His latest book, Writings on the Wall: Searching for a New Equality Beyond Black and White, will be published by Time Inc. Books in August.