Forgiveness is the greatest human capacity. Animals cannot forgive and do not live in a world where such a thing is even relevant; only free men and women can forgive, and hence loose themselves from what might otherwise be a never-ending chain of retribution and counter-retribution in their lives. And forgiveness is one of the greatest political virtues, the one that finally can bring an end to war and hatred. The Arab-Israeli conflict and others like it will never be solved until the two sides forgive one another for the sake of a peaceful future.

Hannah Arendt and Heinrich Blucher — two German political thinkers who emigrated to America to escape the Nazi death machine — knew a thing or two about forgiveness. They pointed out that the idea of forgiveness as an indispensible element of life initiated with Jesus of Nazareth; and indeed, Christianity gives us the most potent philosophy of forgiveness that there is. Forgiveness does not play a big role in Old Testament religion, where one is more likely to find God smiting the unworthy. And the Mosaic code — the law set down by Moses that include the Ten Commandments — is a law of retribution against those who go astray.

Retribution is a much more natural response to a transgression than forgiveness. It acts, we think, as a deterrent to future wrongdoing, and it is emotionally satisfying in the crudest way. These are the reasons one hears most often as an argument for the death penalty. But retribution is a poor guide to life — following it involves a simple slavery to one's passions, and it can lead to horrific consequences. We all do and say things without possibly being able to realize all the possible harm we might do others in the process; and unless people exercise their capacity for forgiveness, and often, the world would be stuck in a constant cycle of wrongdoing and retribution.

This is where Jesus comes in, the man who had perhaps the "greatest influence that any single man ever has had" over world history. Blucher said of him:

If we consider him not as the the Son of God (as he is taken by believers) but merely as a man (as he has been taken by many thinkers since the end of the eighteenth century) then we find that as far as personality goes he is the most amazing man that one could ever hope to encounter.

Blucher took the radical step of considering Jesus as a "philosopher", shorn of religious content, who had "something absolutely new and amazing to say". This will sound strange to many ears, but why might it not be so? Centuries of distortion and usurpation of the message of Jesus and the development of Christian religion - of which there was no such thing when Jesus walked the sand of Palestine — might have clouded it and made many react instinctively against the idea of religion and the ideas underpinning it as anything but pernicious. But the message of Jesus has clearly had widespread appeal and has been instrumental in the development of the western world. His message about the importance of forgiveness in human life was as revolutionary as it was long-lasting.

The Catholic tradition of confession does not, if I may be so bold, find any support in the New Testament. The epistle James says: "Confess your faults one to another, and pray one for another, that ye may be healed." The crucial part here is "to one another"; and it was the particular power of forgiveness in human relations that Jesus discovered. Jesus does not say that only God can forgive sins — which is what the pharisees say - but rather stresses the necessity of forgiveness between people. For instance, he says at Luke 5:24 that "the Son of man hath the power upon earth to forgive sins", where "son of man" has the meaning of people in general (in Hebrew this phrase is "son of Adam"). And Christians pray to God to "forgive us our trespasses, as we forgive those who trespass against us".

This is one of the ways that the teachings of Jesus can be seen as promoting the protection of human dignity and freedom; it is what makes him the great philosopher of forgiveness. When Jesus is being crucified, he says "forgive them Lord, for they know not what they do". We usually do not know what we do in life in general; we can never predict the consequences of our actions and how they might affect others. And without forgiveness this unpredictability which is inherent in life would quickly get out of control.

What makes human dignity and freedom so central to this message is the way it stresses forgiving an individual for the sake of that individual, even if one cannot forgive the deed. We are all familiar with this experience, where we forgive a family member or friend because we realize they are much more complex and mean much more to us than the single deed we found so insulting. It means realizing the enormous potential for creativity and flux in every human being, and that no one can ever be perfect; "they know not what they do". We forgive a person for the sake not even necessarily of what they are — certainly not for the aspect of them encapsulated in the deed they committed — but because of what they may be in the future.

This is the way in which forgiveness is so central to politics. And I do not mean politics in the banal, everyday sense, but in extremis. The South Africans have something to teach us about this. The Truth and Reconciliation Commission was as much about forgiveness as punishment; it meant eliminating the enormous burden of guilt and the desire for retribution that hung over the country. It meant whites and blacks forgiving each other for the sake of the possibility of their future together and the future of their children — it meant the recognition of the possibility of human change for the better. It inevitably meant that deeds went unpunished, but it was not about retribution: it was fundamentally about forgiveness and human dignity; about freedom, the freedom to forgive and move on rather than unthinkingly retaliate.

Yet there are always things that cannot be forgiven; Arendt writes that these are, in fact, the things we cannot imagine how to punish. Recently in Britain, a man was found guilty of systematically and purposefully murdering five prostitutes: and the relatives of the dead said that they were in favour of the death penalty for him, as no punishment could be too great for such a man. The death penalty was simply the harshest, most fashionable alternative they could imagine — they could have suggested a life of torture, but for obvious reasons did not; in reality they mean he cannot be punished.

Willed evil of the sort this man displayed is a very rare thing, and in a category different to trespass. Arendt says: "Here, where the deed itself dispossesses us of all power, we can only say with Jesus: 'It were better for him that a millstone were hanged about his neck, and he cast into the sea'." We will always feel that when it comes to men such as Hitler, Stalin, or other perpetrators of genocide, that forgiveness indeed can only lie in the realm of the divine; the forgiving capacity of men is repelled at the thought. And for as long as men commit deeds that others feel are unforgivable, that rob them of the very basic humanity that forgiveness aims to save, there shall be an unending cycle of violence in this world.