To Graça Machel and the Mandela family; to President Zuma and members of the government; to heads of state and government, past and present; distinguished guests - it is a singular honour to be with you today, to celebrate a life unlike any other. To the people of South Africa – people of every race and walk of life – the world thanks you for sharing Nelson Mandela with us. His struggle was your struggle. His triumph was your triumph. Your dignity and hope found expression in his life, and your freedom, your democracy is his cherished legacy.

It is hard to eulogise any man – to capture in words not just the facts and the dates that make a life, but the essential truth of a person – their private joys and sorrows; the quiet moments and unique qualities that illuminate someone's soul. How much harder to do so for a giant of history, who moved a nation toward justice, and in the process moved billions around the world.

Born during world war one, far from the corridors of power, a boy raised herding cattle and tutored by elders of his Thembu tribe – Madiba would emerge as the last great liberator of the 20th century. Like Gandhi, he would lead a resistance movement – a movement that at its start held little prospect of success. Like King, he would give potent voice to the claims of the oppressed, and the moral necessity of racial justice. He would endure a brutal imprisonment that began in the time of Kennedy and Khrushchev, and reached the final days of the Cold War. Emerging from prison, without force of arms, he would – like Lincoln – hold his country together when it threatened to break apart. Like America's founding fathers, he would erect a constitutional order to preserve freedom for future generations – a commitment to democracy and rule of law ratified not only by his election, but by his willingness to step down from power.

Given the sweep of his life, and the adoration that he so rightly earned, it is tempting then to remember Nelson Mandela as an icon, smiling and serene, detached from the tawdry affairs of lesser men. But Madiba himself strongly resisted such a lifeless portrait. Instead, he insisted on sharing with us his doubts and fears; his miscalculations along with his victories. "I'm not a saint," he said, "unless you think of a saint as a sinner who keeps on trying."

It was precisely because he could admit to imperfection – because he could be so full of good humour, even mischief, despite the heavy burdens he carried – that we loved him so. He was not a bust made of marble; he was a man of flesh and blood – a son and husband, a father and a friend. That is why we learned so much from him; that is why we can learn from him still. For nothing he achieved was inevitable. In the arc of his life, we see a man who earned his place in history through struggle and shrewdness; persistence and faith. He tells us what's possible not just in the pages of dusty history books, but in our own lives as well.

Mandela showed us the power of action; of taking risks on behalf of our ideals. Perhaps Madiba was right that he inherited, "a proud rebelliousness, a stubborn sense of fairness" from his father. Certainly he shared with millions of black and coloured South Africans the anger born of, "a thousand slights, a thousand indignities, a thousand unremembered moments … a desire to fight the system that imprisoned my people".

But like other early giants of the ANC – the Sisulus and Tambos – Madiba disciplined his anger; and channelled his desire to fight into organisation, and platforms, and strategies for action, so men and women could stand-up for their dignity. Moreover, he accepted the consequences of his actions, knowing that standing up to powerful interests and injustice carries a price. "I have fought against white domination and I have fought against black domination," he said at his 1964 trial. "I've cherished the ideal of a democratic and free society in which all persons live together in harmony and with equal opportunities. It is an ideal which I hope to live for and to achieve. But if needs be, it is an ideal for which I am prepared to die."

Mandela taught us the power of action, but also ideas; the importance of reason and arguments; the need to study not only those you agree with, but those who you don't. He understood that ideas cannot be contained by prison walls, or extinguished by a sniper's bullet. He turned his trial into an indictment of apartheid because of his eloquence and passion, but also his training as an advocate. He used decades in prison to sharpen his arguments, but also to spread his thirst for knowledge to others in the movement. And he learned the language and customs of his oppressor so that one day he might better convey to them how their own freedom depended upon his.

Mandela demonstrated that action and ideas are not enough; no matter how right, they must be chiselled into laws and institutions. He was practical, testing his beliefs against the hard surface of circumstance and history. On core principles he was unyielding, which is why he could rebuff offers of conditional release, reminding the Apartheid regime that, "prisoners cannot enter into contracts". But as he showed in painstaking negotiations to transfer power and draft new laws, he was not afraid to compromise for the sake of a larger goal. And because he was not only a leader of a movement, but a skilful politician, the Constitution that emerged was worthy of this multiracial democracy; true to his vision of laws that protect minority as well as majority rights, and the precious freedoms of every South African.

Finally, Mandela understood the ties that bind the human spirit. There is a word in South Africa – Ubuntu – that describes his greatest gift: his recognition that we are all bound together in ways that can be invisible to the eye; that there is a oneness to humanity; that we achieve ourselves by sharing ourselves with others, and caring for those around us. We can never know how much of this was innate in him, or how much of was shaped and burnished in a dark, solitary cell. But we remember the gestures, large and small - introducing his jailors as honoured guests at his inauguration; taking the pitch in a Springbok uniform; turning his family's heartbreak into a call to confront HIV/AIDS – that revealed the depth of his empathy and understanding. He not only embodied Ubuntu; he taught millions to find that truth within themselves. It took a man like Madiba to free not just the prisoner, but the jailor as well; to show that you must trust others so that they may trust you; to teach that reconciliation is not a matter of ignoring a cruel past, but a means of confronting it with inclusion, generosity and truth. He changed laws, but also hearts.

For the people of South Africa, for those he inspired around the globe – Madiba's passing is rightly a time of mourning, and a time to celebrate his heroic life. But I believe it should also prompt in each of us a time for self-reflection. With honesty, regardless of our station or circumstance, we must ask: how well have I applied his lessons in my own life?

It is a question I ask myself – as a man and as a president. We know that like South Africa, the United States had to overcome centuries of racial subjugation. As was true here, it took the sacrifice of countless people - known and unknown - to see the dawn of a new day. Michelle and I are the beneficiaries of that struggle. But in America and South Africa, and countries around the globe, we cannot allow our progress to cloud the fact that our work is not done. The struggles that follow the victory of formal equality and universal franchise may not be as filled with drama and moral clarity as those that came before, but they are no less important. For around the world today, we still see children suffering from hunger, and disease; run-down schools, and few prospects for the future. Around the world today, men and women are still imprisoned for their political beliefs; and are still persecuted for what they look like, or how they worship, or who they love.

We, too, must act on behalf of justice. We, too, must act on behalf of peace. There are too many of us who happily embrace Madiba's legacy of racial reconciliation, but passionately resist even modest reforms that would challenge chronic poverty and growing inequality. There are too many leaders who claim solidarity with Madiba's struggle for freedom, but do not tolerate dissent from their own people. And there are too many of us who stand on the sidelines, comfortable in complacency or cynicism when our voices must be heard.

The questions we face today – how to promote equality and justice; to uphold freedom and human rights; to end conflict and sectarian war – do not have easy answers. But there were no easy answers in front of that child in Qunu. Nelson Mandela reminds us that it always seems impossible until it is done. South Africa shows us that is true. South Africa shows us we can change. We can choose to live in a world defined not by our differences, but by our common hopes. We can choose a world defined not by conflict, but by peace and justice and opportunity.

We will never see the likes of Nelson Mandela again. But let me say to the young people of Africa, and young people around the world - you can make his life's work your own. Over thirty years ago, while still a student, I learned of Mandela and the struggles in this land. It stirred something in me. It woke me up to my responsibilities - to others, and to myself - and set me on an improbable journey that finds me here today. And while I will always fall short of Madiba's example, he makes me want to be better. He speaks to what is best inside us. After this great liberator is laid to rest; when we have returned to our cities and villages, and rejoined our daily routines, let us search then for his strength - for his largeness of spirit - somewhere inside ourselves. And when the night grows dark, when injustice weighs heavy on our hearts, or our best laid plans seem beyond our reach - think of Madiba, and the words that brought him comfort within the four walls of a cell:

It matters not how strait the gate,

How charged with punishments the scroll,

I am the master of my fate:

I am the captain of my soul.

What a great soul it was. We will miss him deeply. May God bless the memory of Nelson Mandela. May God bless the people of South Africa.

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