"I am sorry" are the most difficult words to articulate in any language. Desmond Tutu believes, too, that our relationship with others is central to our existence as human beings. Being well acquainted with God and having no illusions about human nature, he agrees with Alexander Pope that to forgive is divine.

Oscar Wilde put it sublimely: "Always forgive your enemies; nothing annoys them so much."

In the early days of the struggle against apartheid, Tutu urged its victims: "Be nice to whites; they need you to rediscover their humanity." Like Nelson Mandela, he believed the oppressor must be liberated just as surely as the oppressed.

The first thing one notices about No Future Without Forgiveness* is its title - as magnificent as Mandela's Long Walk to Freedom; secondly, its dedication: "To the women and the `little people' of South Africa"; thirdly, its leitmotiv: George Santayana's adage, "Those who cannot remember the past are condemned to repeat it."

Tutu's Christian faith is also striking. On being appointed to chair the Truth and Reconciliation Commission in 1995, the commissioners agreed to his proposal at their first meeting that they should go on a retreat - "where we sought to enhance our spiritual resources and to sharpen our sensitivities". Despite their diversity, the commissioners accepted his call for "recollection and prayer".

Chairing the commission became as much a spiritual as a judicial undertaking. Although frequently appalled during the hearings at the depth of depravity to which human beings can sink, theology enabled him to distinguish between the deed and the perpetrator. Indeed, the commissioners witnessed remarkable scenes of repentance as well as forgiveness.

The commission represented a unique "third way" of dealing with South Africa's horrendous past. In rejecting the Nuremberg trial option, it was felt equally strongly that general amnesty would be amnesia. The negotiators of a miraculously peaceful transition from repression to democracy decided to go beyond retributive justice to restorative justice.

Those who had committed gross violations of human rights were offered amnesty in exchange for disclosure of the truth about their crimes; the victims were given an opportunity to be heard, as well as the prospect of reparation. Restorative justice seeks to rehabilitate both the victim and the perpetrator.

In the course of three years the commissioners heard 20,000 statements of atrocities. A piercing wail became the defining sound of the commission. "We were greatly privileged to be given that glimpse into the secret places of the souls of so many of our compatriots, where they held their most intimate anguish and pain," Tutu writes.

The commission confirmed the banality of evil. It established that the security police had used torture as a matter of course. Many came forward to apply for amnesty. The commission was sometimes able to reach the truth when the judicial system had failed. The perpetrator had to make a full disclosure to qualify for amnesty, whereas in court he tried to proclaim his innocence by lying.

"All this would have remained in the murky crevices where apartheid hid such secrets had it not been for the amnesty process." During the armed struggle many ANC activists were dehumanised too, most notably Winnie Mandela.

While telling their stories had a cathartic effect on the victims, listening day after day to accounts of atrocity was a traumatic experience for the commissioners. "We were upheld by the fervent intercessions of so many in South Africa and around the world," Tutu acknowledges. "Without this I know I would have collapsed and the powers of evil, ever on the lookout to sabotage efforts to attain good, would have undermined this extraordinary attempt to heal a wounded people."

As Tutu listened to harrowing tales of the viciousness we are capable of unleashing against fellow human beings, he thought there may have been moments when God regretted creating us. Observing the magnanimity of ordinary people, however, and the exploits of a Francis of Assisi, a Mother Teresa or a Nelson Mandela, he must have concluded: "No, it was worth taking the risk."

Reflecting on the mystery of evil, this eminent Anglican advances the doctrine of God suffering in humankind: the paradox that the Almighty needs our co-operation with his grace for justice to prevail. In describing the work of the commission, Tutu shows that reconciliation after conflict, although costly, is the only way forward - whether at the political or personal level.

He came away with a deep sense, "indeed an exhilarating realisation, that though there is undoubtedly much evil about, we human beings have a wonderful capacity for good". We are part of a cosmic movement towards reconciliation that has existed from the beginning of time. Echoing another great and good man, Teilhard de Chardin, Tutu asserts that what each of us does can hinder or advance the process at the heart of the universe.

He believes that ultimately laughter and peace and compassion will have the last word. Tutu notes President McAleese's beautiful tribute to Gordon Wilson, who forgave the killers of his daughter. His nobility reminds one of another Irishman, Roger Casement, whose last written words were: "My goodwill to all men; to those who have taken my life equally to those who have tried to save it - all are my brethren now."

We have much to learn from the South Africans, and there is no better teacher than the archbishop emeritus of Cape Town, who advises us not to let go of the dream of a new Ireland.

* No Future Without Forgiveness by Desmond Tutu (Rider, £14.99 in UK). Brendan O Cathaoir is an Irish Times journalist