Why sexual taboos are everywhere the same

What is sin, anyway? The exhortation by a Church of England working party that we should all stop using the phrase "living in sin" was greeted yesterday with the amused insistence that no one except vicars said it any more nowadays.

But not just that. The truth is that sin itself has largely fallen from the contemporary vocabulary. And quite right, many will say, in this secular age. But is sin just a churchy word for doing wrong? And where are the boundaries between taboo, immorality and plain bad manners?

For a long time everything was clear enough. Sin was factum, dictum, vel concupitum contra legem aeternam, said St Augustine - anything done, said or desired against the eternal law. This natural law was not revealed to a chosen few from a mountain top but is written into the hearts of all people. "Everyone, somehow, knows this truth," said Aquinas.

Social psychologists may argue that all behavioural norms are taught. And yet there are hardly any tribes or civilisations in which certain taboos - against incest and murder, for example - are not shared. Other lesser taboos - against theft, sex during menstruation, or the consumption of forbidden foods - are extraordinarily widespread.

Among different peoples these instincts or innate senses were articulated in different ways, most commonly by attributing them to a deity and then creating a priestly caste which took upon itself the right to interpret and codify the divine intention.

Trying to separate the original impulse from the codification and accretions of the years is what those intent on the process of renewal - such as the Church of England working party - must embark upon. It is never easy.

Take "keeping holy the Sabbath day". It is not many years since I saw, in Belfast, the swings in a children's playground chained up one Sunday. How to separate the form from the essence in that? It would be easy to reject the whole sabbatarian notion. Yet even many non-religious folk would acknowledge that this commandment encodes the valuable impulse that everyone is entitled to a break from the quotidian grind (and, by implication, that in the rest of the week, men and women have the duty and the right to work).

Codification was the strong suit of canon lawyers for centuries with their labyrinthine distinctions between mortal sins (which brought eternal damnation) and venial ones (which did not). It is only recently that theologians have come to think of sin not in terms of individual actions but of the way it affects an individual's psychological well-being.

Thus the nature of sinful actions changed according to their social context and shifts in social consciousness. It has always been so. Christianity attracted women in the first place because it was a religion whose teaching on adultery and divorce enhanced the status of women at the time. Jesus Christ was something of a revolutionary here. His teaching that adultery by a man was as much of a sin as adultery by a woman and his prohibition on divorce were, in first-century Palestine, moves that significantly increased the power of women in marriage, divorce being at that time almost always initiated by the man.

With the change in the dynamic of marriage in our own times, following the insights of feminism, it is unsurprising that those bent on renewal feel that new rules may be needed to achieve the original intention of fostering respect within relationships. In a society in which rule-based modes of living have been abandoned in many spheres it is unsurprising that a reassessment should be thought appropriate here too.

There may be arguments about whether they have reached the right conclusion. But the attempt to do it is not a sign of the weakness of the modern church but rather of its vitality.