... the best children's classics have always evoked the dark side of life. Alice's Wonderland reveals the arbitrary demands and heartless craziness of the adult world from a child's perspective. The sinister menace of the Wild Wood is a constant threat in The Wind in the Willows. In the novels of Frances Hodgson Burnett, children are regularly abandoned, bereaved, neglected and ill-treated. Some parents would prefer their children to read books that are more upbeat, but Wilson's success and the endurance of these classics remind us that children know instinctively what is best for them, and find that their worst fears become more manageable when they are made explicit. It seems that many children have not yet succumbed quite as fully as adults to the "positive thinking" that is fast becoming a social orthodoxy.

Increasingly it is becoming unacceptable to voice legitimate distress. If you lose your job, become chronically ill, or fall prey to loneliness or depression, you are likely to be told - often abrasively - to look on the bright side. With unseemly haste, people rush to put an optimistic gloss on a disaster or to suggest a patently unworkable solution. We seem to be cultivating an intolerance of pain - even our own. An acquaintance once told me that quite the most difficult aspect of her cancer was her friends' strident insistence that she develop a positive attitude, and her guilt at being unable to do so.

Every evening the television news beams images of anguish from all over the world right into our homes - we live on constant terror alert. We naturally want to keep what distress we can at bay. But while it is important not to succumb to despair, it is also dangerous to deny the suffering to which flesh is heir.

As TS Eliot said, humankind cannot bear very much reality.

Some forms of religion encourage us to bury our heads in the sand to block out the suffering that surrounds us on all sides. The rich man in his palace can reconcile himself to the plight of the poor man at his gate by reminding himself that this is part of God's bright and beautiful plan; those who suffer poverty and oppression in this life will be recompensed in the hereafter. When thousands die in an earthquake, we can tell ourselves that God knew what he was doing.

If we deny the reality of suffering, we will ignore the distress of others. At its best, religion requires the faithful to see things as they really are. In Buddhism, the First Noble Truth that is essential for enlightenment is that life is dukkha: "unsatisfactory, awry". The Buddha's father tried to shield him from sorrow by imprisoning him in a pleasure-palace, walled off from disturbing reality. Guards were posted to drive away any distressing spectacle. For 29 years, the Buddha lived in this fool's paradise, locked into a delusion and unable to make spiritual progress. Finally the gods intervened and forced the young man to confront mortality, sickness and decay. Only then could he begin his quest for Nirvana.

The Buddha's palace is a striking image of the mind in denial. As long as we immure ourselves from the pain that surrounds us on all sides, we remain trapped in an undeveloped version of ourselves

The failure to confront unpleasant reality can also be politically dangerous. In the Bible, those preachers who told people to look on the bright side, that God would protect Jerusalem and that everything would work out for the best are condemned as "false prophets". The prophet Jeremiah has become a byword for excessive gloom, but if people had listened to his dire predictions, the Babylonian army might not have destroyed Jerusalem. He was not being "negative"; he was right.

... In the past, we have sometimes pursued policies that have resulted in great suffering, telling ourselves that all would ultimately be well. We have let conflicts fester until they have become intractable. We have supported such allies as Saddam Hussein, ignoring the atrocities they inflict upon their people. We are now rightly outraged by his massacre of his Kurdish subjects, but at the time we ineffectually turned a blind eye. Today we are reaping the reward of our heedless karma. The pain that we ignored in some parts of the world has hardened into murderous rage.

... The First Noble Truth requires us to acknowledge the ubiquity of pain, even when we are happy and successful. If we get a coveted job, other candidates are disappointed; if our country prospers, it may well be at the expense of other nations that are languishing in poverty and despair. In our privileged first world, we have been living in a bubble of false security that is not unlike the Buddha's pleasure palace. On September 11, reality broke in. If we turn our backs on the suffering in our troubled world, it will come back to us, in a terrible form.