Loyalty to ideas that no longer serve us is inevitably destructive. Laws kept on the statute book beyond the period of their purpose leave the law mocked and society prey to those who would undermine it. Religions contain many precepts that are redundant and thus pernicious. People are loyal to these precepts, feeling a duty to uphold what has made them and their forebears distinct from others. They ascribe to them a divine origin and defend their immutability. A time-bound teaching becomes an unchanging, unchangeable fiat of God and many people suffer.

Some religious laws had a benign purpose once, some were always wicked.

Both sorts must be done away with. It was always wicked to execute someone for arguing over the nature of Jesus of Nazareth. There might have been times when polygamy was a benign response to extreme circumstances.

Divinely sanctioned dietary laws might once have served a purpose: indeed, vegetarianism might be today’s munificent divine dietary option.

What are teachers of religious studies to do? Should we simply describe suttee, the St Bartholomew’s Day massacre and the Battle of the Ditch without comment? Should our lessons be simply amoral tableaux?

How should we tackle contraception? How should we tackle marriage? Should we suggest that people of a given tradition or place have no choice in this matter? Also on marriage, should we allow the young to grow up thinking that procreation and sexual partners are just matters of personal whim and transient passion?

Of course, there are some precepts that are simply neutral. Not eating chocolate during Lent and then eating a little bit too much on Easter Sunday is fairly innocuous, though the materialistic consumer fest that is now Christmas can disturb. But these are minor points compared to inquisitions, witch-hunts and dhimmitude.

The fundamental divide running through western religions now is between traditionalists and those who favour radical change. Conservative Protestants and Catholics have more in common than with the radical wings of their own churches. Where I live in the Hebrides, Presbyterian churches fracture and argue. Within Catholicism, priests like the Sri Lankan Father Tissa Balasuriya have been excommunicated for attempts at interfaith understandings.

In the interfaith sphere, we can see radical Christianity and reform Judaism agreeing on much with each other, sometimes more than they do with their apparent co-religionists in the more orthodox branches of their traditions.

A few years ago, Sir Jonathan Sacks, the chief rabbi, eloquently approached the interfaith issue in his marvellous book The Dignity of Difference.

Despite Dr Sacks’s Orthodox understanding, traditionalist rabbis took him to task for it. Within Islam, there is Irshad Manji, who tackles her own faith and its representatives with forthright bravery and intellectual rigour. Jonathan Sacks holds to traditional ground within Judaism: Irshad Manji goes into territory many Muslims seem to see as wild and threatening.

How should teachers of religious studies approach this divide? Should we look for the best in the traditions we hold dear and leave the rest in slighting silence? Should we pretend that all religious manifestations mean well, suggesting that all are attempts to honour an ineffable absolute? Or should we take the bull by the horns and point out that we humans are capable of goodness, heroism and great wickedness, and that our religions all share in this violence, kindness, delusion and truth?

Teachers of religious studies have a responsibility to be honest and knowledgeable about all manifestations of religion so that we can praise when goodness is apparent and condemn when a tradition’s evil is in plain view. And we must be a voice of reason when feelings flare. God can never be allowed to stand as an excuse for human depravity.

Individual teachers of religious studies will have distinct views. In any one department, teachers will disagree and have to debate issues among themselves. I am of the Old Catholic tradition in the Open Episcopal Church and would have to debate seriously with people whose religion condemns homosexuals, does not give women equal opportunity, regards books and institutions as inerrant or infallible, is not universalistically inclined - and considerably more. But religious studies in schools must contain this honest tension.

When necessary we must be ready to change our minds publicly. This is an example our young need. It is an example schools should provide. Teachers of religious studies must take the concept of faith seriously and, within that context, be examples of thoughtfulness, doubt and the courage to change one’s mind.

Michael Bartlett is a religious studies teacher in Lewis.