REPORTS of sexual misconduct by aid workers has, not surprisingly, caused outrage. It is appalling to think of donors’ and taxpayers’ money being spent on exploiting people who are already vulnerable through poverty and natural disaster. We expect those who do good to be good.

But human beings are, alas, not only complicated, but also capable of extraordinary degrees of self-deception. The late Canon Eric James, of Christian Action, used to say that he had never met a gifted priest who was not also deeply flawed, and I think that that is true for most who are called to a life of service. Somewhere, the notion of entitlement comes in, and the belief that virtue exercised at our own cost deserves a reward. I would call it the “Gehazi syndrome”, after the story in 2 Kings 5 about Elisha’s servant, who extorts money and goods in his master’s name after the healing of Naaman. There is a secret trade-off between the good that is done and the doer’s needy ego.

This is one reason that I continue to be disturbed by the responses to the allegations against Bishop George Bell (News, leader comment, 26 January). Those who have urged the Archbishop of Canterbury to clear his name are on viable ground when they ask for more convincing evidence of his guilt — evidence that may or may not be forthcoming. But some of the arguments for his name to be cleared are naïve, resting simply on readings of his public character. Such a palpably good man, it is said, could not possibly have been guilty of sexual misconduct; you are either a hero or a villain. But the truth is, some people can be both. Even saints cast shadows.

One of our authorised forms of confession suggests that we sin against God and our neighbour “through ignorance, through weakness, through our own deliberate fault”. Too often, we think of sin only in terms of the last of these categories: in other words, as deliberate, knowing, calculated wickedness. This is convenient for our consciences, because it puts sin at a distance, as something that only really evil people do, not people like us.

But sin is subtler than that. Our wrongdoing often stems from weakness and ignorance. We simply do not see our own areas of blindness. It is one of the paradoxes of our age that our increased awareness of human vulnerability not only helps the wounded to tell what has been done to them, but helps those who have done wrong to justify their actions to themselves. They did what they did because they were vulnerable and needy.

Those who seek consolation by exploiting the vulnerabilities of others often dismiss their actions as an excusable weakness. We cannot agree, but perhaps we should beware of casting the first stone.

The Revd Angela Tilby is a Canon Emeritus of Christ Church, Oxford