The words "Nelson Mandela is dead" feel strange in the mouth today, almost impossible to say, given the unique way he was both martyred and canonised during his lifetime. He embodies a paradox: on the one hand we love him for his humanity; on the other, he already passed long ago from the world of the flesh. He is a peak of moral authority, rising above the soulless wasteland of the 20th century; he is a universal symbol for goodness and wisdom, for the ability to change, and the power of reconciliation. In person, he was not notably affectionate, but his image beams a very particular sensation: you just look at him and you feel held, hugged.

Mandela epitomised those instincts we most associate with childhood: trust, goodness, optimism; an ability to vanquish the night's demons with the knowledge that the sun will rise in the morning. But he also made us feel good, and warm, and safe, because he found a way to play an ideal father, beyond the confines of his biological family or even his national one. He was the father we would all have wanted if we could have designed one. He was wise with age, benignly powerful, comfortingly irascible, stern when we needed containing, breathtakingly courageous, affirming when we needed praise – and, of course, possessed of the two childlike qualities that make for the best of fathers: an exhilarating playfulness and a bottomless capacity to forgive.

Mandela is often paired with MK Gandhi. Unlike the godly Indian liberator, however, he was an unapologetic (even if delightfully self-deprecating) patriarch. A leader's claim that his subjects are his children can be the very definition of tyranny, but what made Mandela so singular a leader of modern times is the way he re-appropriated such clichés. He inhabited his paternity in such a way that it seemed fresh and emancipatory even as it comforted in the way it recalled more traditional understandings of what a leader should be.

• Mandela: The early years & political life

In his own life, he was a failure as a father – in part, but not entirely, because of his three decades of incarceration. His daughter Maki once said to him, describing a rebuffed hug: "You are a father to all our people, but you have never been a father to me." Like so many great leaders, he found refuge from the difficulties of familial intimacy in politics and struggle – in the family of humanity. This led to a personality that combined "extreme heartiness with impenetrable reserve", as Arthur Schlesinger famously described Franklin Roosevelt, cited by Anthony Sampson in his biography of Mandela.

For most of humanity, only the heartiness was visible. "Ah, Elizabeth!" he once greeted the British queen with a rural bellow as she approached him at Buckingham Palace, folding her in embrace. "You are as beautiful as ever! How do you manage to keep so young?" While courtiers and diplomats expired with embarrassment at his multiple faux pas, the queen simply blushed – and giggled: "Nelson!"

Perhaps America's former president Bill Clinton put his finger on the power of the Mandela icon when he welcomed his fellow-president to Washington in 1998. Speaking of the universal experience of suffering and hatred as an "apartheid of the heart", Clinton said that the world adulated Mandela because it sought "wisdom from the power of his example to do whatever we can, however we can, wherever we can, to take the apartheid out of our own and others' hearts".

Second chances
Just as apartheid became a global semaphore for evil, so too did Mandela come to symbolise the power of good. More than that: the impulse, in an increasingly malevolent world, to look evil in the eye and do good. Listen, for example, to Clinton's description – 10 years after the above comment – of the roots of Mandela's sanctity: "Mandela is a very godly man because he's the living embodiment of the importance of second chances in life: giving them and getting them, and becoming bigger through adversity."

Mandela got his second chance – at liberty, at leadership, at love. Forgiveness allows both victim and perpetrator to start again, and the way that Mandela bettered himself through adversity serves as an object lesson to us all: if he can walk out of 27 years in jail without anger or the desire for retribution, we too can rise above our petty problems and disputes. Brilliantly, Mandela set himself up to embody the nation – and then, as he saw his effect, to allow himself to be turned into a symbol for that best of human impulses: the desire to make things better. He made a fetish of his biography. As he was in chains, so were we; as he managed to negotiate himself into freedom, so could we; as he forgave his oppressors and his adversaries, so must we. Now, though, this makes his death more complicated: witness ANC chief whip Mathole Motshekga's inane comments, made when Mandela was admitted to hospital in June 2013, that the ill man's "well-being is a barometer for the well-being of the nation".

• Mandela: Retirement years

The Jesus imagery has always been present. Listen to Archbishop Emeritus Desmond Tutu: "Suffering can of course embitter the one who suffers. But in many other circumstances it can ennoble the sufferer. We are richly blessed that the latter happened with Mandela."

But to view Mandela's prison experience solely through the prism of revelation is to misunderstand his life. Certainly, he went into jail a militant hot-head (in the 1940s, if you needed a meeting broken up you called Mandela) and came out a profound statesman. Even if prison damaged him irrevocably in some senses – how could it not? – he did succeed in using it as both a political laboratory and a place of profound introspection. Sampson describes how he was "cut off from mass audiences, public images and television cameras, stripped down to man-to-man leadership and to the essentials of human relationships". He thus "learned about human sensitivities and how to handle the fears and insecurities of others, including his Afrikaner warders. He was sensitised by his own sense of guilt about [the] family and friends he had used during his political career." Mandela, writes Sampson, was "racked by remorse" about his absence as a husband and a father. By coming to see himself as an actor – a perpetrator, if you like – as well as a victim, he developed his most admirable quality: a capacity for empathy.

He used this to formidable effect, and while he may indeed have lived the racial reconciliation he preached, this is critical to any understanding of the man and his political gifts: he deployed empathy as a strategy to get what he wanted – for himself while in prison, for his people, and for his country. He learned Afrikaans in prison not because it was a beautiful language or even because he wished to use the master's tools to destroy the master's house, but so that he could sweet-talk his warders into granting him and his fellow-prisoners the concessions that would make their lives more bearable.

He came upon his almost inhuman lack of bitterness and desire for reconciliation in the prison laboratory because he saw that this approach lifted the scrim of prejudice from his savage captors' eyes and transformed them into human beings. Once they were human, they could reason, and once they could reason, they would – as he had – understand that South Africans' futures were interlocked, and that they were dependent on each other.

Politics of gesture
He might have had an extraordinary instinct, but he was profoundly instrumentalist: he often told intimates that his legendary humour was part of his "sense of duty", used either to help his interlocutors relax, or to disarm them, or both, depending on the circumstance. He did not take a step – do a jig – without calculating its odds.

From the way he cultivated a romantic "Black Pimpernel" image while in hiding during the 1960 state of emergency, through to the way used the 1995 Rugby World Cup to deepen his project of racial reconciliation, he was a master at the politics of gesture. Even his legendary public outburst at FW de Klerk during the 1992 multiparty negotiations cannot be simply described as a pot boiling over: it was carefully calibrated to humiliate the South African president at a key moment, thereby demonstrating both to recalcitrant whites and to impatient blacks that the balance of power had shifted. As Jacob Zuma once told me – speaking, no doubt, from personal experience – if you wanted to win a battle, you needed to get Mandela on to your side.

The conventional wisdom is that Mandela's extraordinary sense of self, unassailable by even the grossest depredations of apartheid, has its roots in his heritage as a Thembu noble. While there is truth to this, he bore another – potentially damaging – legacy from childhood: he was also a fatherless son, taken on by the Thembu king out of obligation to a trusted adviser. From a distant branch of the royal house, he was raised to be a courtier himself, without the expectation of ever attaining power. This trained him to be frank and strategic. He was an outsider – both in the Thembu royal house and in the ranks of the ANC elite he would find in Johannesburg – and he would need wit and courage and charisma to match his ambition.

He was always a maverick within the ANC. In two critical instances, he took on the conventional wisdom in his movement and won. In the 1940s and 1950s, when the ANC was the preserve of conservative "Black Englishmen", he advocated taking up arms and fomenting insurrection; three decades later, when the ANC was too often blindly following revolutionary theory, he insisted on laying down these arms, even if it meant being branded a sellout. He was deeply and intractably loyal to the ANC – and often, to a fault, to many of his comrades in it its leadership. But, unlike his successors Thabo Mbeki and Jacob Zuma, he transcended membership of the "ANC family" into the "South African family" once he came out of jail, and self-consciously sought to embody the nation rather than just the movement.

It is naive to believe, as many in both the ANC and his own family have, that he was duped by his advisers into setting up his Nelson Mandela Foundation, outside of both family and party, as custodian to his legacy: he did this very deliberately, precisely so that he could put himself beyond the reach of more atavistic familial or political ties – and remain there, even when he no longer had agency, or life.

• Relive Mandela's release

But it is equally naive to believe that Mandela was duped into his last – and very grand – public act: appearing before the rapturous masses at the party's final 2008 election rally, as if to grant a benediction to Zuma, the ANC's presidential candidate. Certainly by this point Mandela was, if not in his dotage, then stuck on certain subjects, in the way that very old people often are. One of these subjects was Mbeki: how poorly he had treated Zuma, and how he had wrecked the ANC. Certainly, too, many of Mandela's closest friends and advisers were now firmly in the Zuma camp, including Mac Maharaj, and his own grandson Mandla Mandela.

Still, to the last, the elder Mandela was calculating. He saw how Zuma's global reputation was deeply sullied by both the corruption and the rape charges, and he understood how this might negatively affect South Africa's own global reputation. Zuma would be president with or without Mandela's imprimatur: the elder statesman thus calculated that it would be in the national interest to lend his moral authority to the new leader.

Perhaps, too, Mandela succumbed to Zuma's flattery: the new leader's promises that he would return the ANC to a Mandela style of leadership from which the party had strayed under Mbeki. But even if Mandela's support for Zuma was driven in part by his often-remarked-upon vanity, it had a salutary effect on South African statecraft: it re-established "the Madiba way" as the ANC way, the South African way.

Zuma set out to emulate Mandela, and claimed to subscribe to his values of reconciliation and non-racialism, of accountability and responsiveness. But in Zuma's singular failure as South African president – and the ANC's unwillingness to let go of him – there is an important lesson: an empty template, like an empty icon, can be filled to suit one's own needs. And in the way that Julius Malema distorted Mandela's history in the ANC Youth League to buttress his own ambitions, we saw the Mandela legacy further sullied; a short-cut to demagoguery and tyranny rather than the model for a way out of it. Even when it is practised with the finesse and integrity of a Nelson Mandela, paternalism is ultimately antithetical to democracy.

'This brick once imprisoned me. Now I will hold it captive'
My relationship with Mandela was professional, not personal. I met him frequently as a journalist and interviewed him several times. It is no measure of my prowess that he always recognised me, and sometimes remarked on something I had written: he practised this art indiscriminately, on my colleagues great and small. I learned one great lesson from him, in 2003, when, in my capacity as heritage curator at Constitution Hill, I showed him round the site.

Constitution Hill is the home of South Africa's Constitutional Court, built on the site of Johannesburg's notorious Old Fort prison; constructed, brilliantly, out of the very bricks of the prison, and surrounded by the abandoned old buildings, as if to demonstrate architecturally how the possibilities of South Africa's future are built on the difficulties of its past. Every significant political prisoner passed through the Old Fort's gates, from Gandhi to Mandela, who was held there twice.

On his visit, Mandela was presented by the then-chief justice Arthur Chaskalson (his legal counsel at the Rivonia trial) with one of the bricks of the old jail, encased in glass. As always, after painstakingly greeting every construction worker and cleaner, Mandela said the right thing, upon receiving the brick: "Ah! This brick once imprisoned me. Now I will hold it captive!"

More edifying, for me, was his attitude during the tour of the old prisons. As we pored over a model of the site and explained it to him, and took him to see the cell he was held in when he was arrested in 1962, he seemed listless and even a bit bored. He only lit up when we mentioned to him that there was a new centre for research into and treatment of Aids across the road, animatedly asking questions to which we were not qualified to respond.

His lesson was an invaluable one, and one I am sure he would want us to apply to his own life: do not dwell in the past. Use it, rather, to attack the problems of the present.

Mark Gevisser's next book, Dispatcher: Lost and Found in Johannesburg will be published by Farrar, Straus & Giroux, Granta and Jonathan Ball in early 2014.