A Brazilian archbishop has provoked a storm of protest through an act of excommunication. He expelled a woman from the faith – and condemned her to eternal torture – for failing to prevent her nine year-old daughter from having an abortion.

This heartless behaviour by Archbishop José Cardoso Sobrinho has itself been roundly condemned by politicians and even some theologians.

The girl was repeatedly raped by her stepfather over a period of at least three years. The stepfather has not been excommunicated. That retribution was saved for those who displayed compassion and understanding towards the girl – her mother and the doctor who performed the procedure.

What is surprising, though, is that people are surprised.

Sobrinho acted correctly – at least within the strictly limited boundaries of his world.

A religion is defined (and differentiated from others) by its belief system – its rules, its doctrine. The particulars of any one religion lie at the root of its claim to be the only true religion. They are what falsify all other faiths.

These rules and boundaries exist because they are the means by which the specific faith declares “this is who we are and what we stand for”. They are claimed as truths before which we must all yield. They are also the framework for the faith’s claim to morality.

This raises a problem. Although religious believers often lay claim to a moral superiority, the fact is that this doctrine represents a straitjacket. It denies the believer many avenues of moral, ethical, empathetic and humanitarian action.

Adherents must act according to these rules, otherwise they are not true believers. In that context, Sobrinho not doubt understood that excommunication, however immoral and uncaring it may seem to the rest of us, was unequivocally demanded. The basic tenets of the faith trump all humanity.

Now, it’s entirely possible that some bigwig in the Roman Catholic church – the Pope himself, perhaps – might override this decision. It’s happened before when such an act of faith has resulted in a PR nightmare for the church. What what would that mean for the religion?

If matters of doctrine become flexible, they also become meaningless. These matters are not defined and guided by reason. They are deemed to be eternal ‘truths’. As soon as they are seen to be alterable, in the interests of good publicity or other less spiritual motives, then they reveal the entire faith as hollow.

This might go some way to explain the diminishing of religions like Roman Catholocism. Either they remain rigid, true to their core beliefs – and thus reveal themselves as uncaring, inhuman and irrelevant to modern life. Or they adapt, and thus admit that the ‘eternal truths’ at the heart of the faith are nothing of the sort.

It’s a stark choice – to be irrelevant or meaningless.