In his opening address to the General Synod, the Archbishop of Canterbury said: "There is a revolution in the area of sexuality, and we have not fully heard it."

His reference was primarily to same-sex relations and the Marriage Bill, but my concern is that the Church of England has still not really caught up with the shift in public attitudes to sex in general.

In the wearying debate about sexuality in the Church, repeated reference has been made to the "teaching of the Church" that the only right context for a sexual relationship is within marriage. But this is a teaching ignored by the vast majority today, Christian or not, including, in my experience, almost all those who none the less do marry in church.

This was brought home to me a few years ago in a confirmation class of rowdy teenagers. I was attempting to explain that the rites and sacraments of the Church follow us through life, bringing Christian meaning to adulthood, marriage, children, sickness, and death. One boy queried "What about sex?", prompting much sniggering. I assumed, cynically, that that was his objective, but he was quite sincere. As far as I can recall, I did my best to explain that one can pray for God's help in whatever circumstances, even if, for some, the Church has not seen fit to provide specific words.

Readers might be disappointed that I did not explain that the liturgy he needed was the marriage service, and nothing else. But I really do not believe that would have helped. Like the vast majority of young people today, he hoped, with some likelihood, to lose his virginity towards the end of his teens, preferably within an established relationship.

He may, of course, have been disappointed. But all that made no difference to the fact that he would hope one day to marry, almost certainly in church, and mean, then, everything he said to his bride in the marriage service.

THIS perception is reinforced by those who come to marry in my parishes. It is now a novelty to meet a couple who are not already sharing a home. In nine years of ministry, I can think of only one couple whose marriage was probably unconsummated until after the service.

Discussions with local colleagues support this. One told me how, in a seminar on sexual health 25 years ago, the professor pointed out that for two people to marry, having not already had sex with one another or anyone else, was so rare as to be considered deviant.

These changed assumptions can be picked up in unlikely places. In the recently published memoirs of a gay ex-soldier, James Wharton, Prince Harry is praised for defending him from homophobic bullying. The context was that in competitive boasting about a weekend's sexual exploits, the former Lance Corporal had let slip that he himself had been "successful" with a fellow soldier.

Neither in the narrative nor related media reporting did I notice any criticism of the free-for-all sexual ethics of regimental life.

THE reason why this matters is that we still appear to be conducting our debates about marriage as if the constraints imposed by the law or the Church on who may marry whom will have some effect on the sexual lives of the population. They will not.

If, as it seems, we are only holding up an ideal to be aspired to, we are doing something different. Rather than inhibiting relationships, we are making a public disapproval of those that already exist, and telling those in them that the ideal is impossible for them.

But whereas marriage has become detached from sex, it has not become detached, at least for the middle class, from childbirth. For most of the couples I marry, the established track seems to be: relationship, cohabitation, marriage, parenthood.

In other words, it is quite normal to expect a baby to follow, if not in nine months, then quite soon after the marriage, just as in the pre-contraception days when that would also have been the norm.

My suggestion is that this has reinforced a tendency to focus the morality of marriage on the proper circumstances for bringing up children, to the impoverishment of the concept as a whole. This has been seen quite extensively in the same-sex-marriage debate, notwithstanding the fact that adoption by same-sex couples as two parents, irrespective of marriage, has been legal since 2005.

This situation poses a familiar choice to Christians striving to cope with a changed world. Some will, of course, maintain the traditional teaching, and I know of many Christians, mostly now married, who would be happy to be classed among the "deviants" referred to above.

Looking for a coherent reference to the subject among the Church of England's official publications, one only seems to find a sort of embarrassed silence. Some support for an alternative approach may be found in considering how heavily the traditional teaching depends upon interpreting "porneia" in the New Testament as covering all sex outside marriage, but there is no easy way forward.

But one must be found. I fear that the official line of "marriage or nothing" is coming close to being treated by a wide range of Anglicans in a similar way to that in which many Roman Catholics treat their Church's teaching on birth control. The result is similarly destructive for the authority the Church may be felt to have over this important area of life.

The reality is that sexual relationships, within and outside marriage, may be beautifully self-giving, but also exploitative or casual. To all situations it ought to be possible to apply Christ's fundamental ethical teachings to treat others as we would wish to be treated, and surrender our own wants, in love, to the greater needs of others. This need not detract from continuing to hold up Christian marriage for all who seek it as the highest and best ideal.

The Revd Neil Patterson is Rector of Ariconium, in the diocese of Hereford.