Faith and Reason: Fornication can never be trivial: Our series on sex is continued this week by Peter Mullen, who argues that, though the Pope may be wrong about these matters, he has the merit of being wrong in the right style.

A. N. WHITEHEAD said that all philosophy is footnotes to Plato. It might be said that all the Church's teachings about sexuality are footnotes to St Paul and St Augustine and that those men did not hold cheerful doctrines on the subject.

Post-Freudians would even look for the origin of Paul's and Augustine's gloomy view of human coupling in their own unhappy experiences. Paul, as is well known, confessed to his 'thorn in the flesh' which some scholars have believed to be a reference to a personal sexual obsession such as masturbation. And he once famously wrote, 'It is better to marry than to burn.'

Augustine was the classic case of poacher turned gamekeeper: a man with a voracious sexual appetite who, as he writes in The Confessions, 'came to Carthage burning, burning: and a cauldron of unholy loves fell about my ears.' After his conversion to Christianity he took a savagely negative view of sex in all its forms. One would not have to be a fully paid-up Freudian to see in this profound attitudes of selfpunishment and consequent selfjustification. In City of God, Augustine decreed that the sexual act must always and only be undertaken with the intention to procreate children and even that the attendant pleasure of it is a sign of Original Sin. In other words, sex is all right so long as you don't enjoy it - a doctrine not without its biological and anatomical difficulties, besides its ethical problems.

The teachings of these two authorities have been so influential in that the notion of the Church as irredeemably 'down on sex' is universal. This suspicion is not restricted to the Catholic Church. I was brought up in the Methodist Church and I turned Anglican in my teens, and there was never any doubt in my mind that Christianity and sex do not mix.

The Solemnisation of Matrimony in the Book of Common Prayer of 1662 makes the Church of England's doctrine plain: there must be no sex outside marriage which was ordained 'for a remedy against sin and to avoid fornication' being committed by men with their 'carnal lusts and appetites'. In other words, it is better (just about) to marry than to burn.

The 1928 Prayer Book was more squeamish and omitted the 1662 reference to men as 'brute beasts that have no understanding' and it speaks of 'natural instincts and affections implanted by God' which should be 'hallowed and directed aright'.

This is much more positive and affirming of sexuality than the Augustinian pessimism of 1662. The current Anglican usage in the Alternative Service Book of 1980 is almost gushing in its enthusiasm, praying that 'with delight and tenderness they may know each other in love'.

So the Pauline-Augustinian influence has waned somewhat, but its shadow is still cast so that when there is any talk of sin even the unchurched ordinary member of the public thinks only of sex. And indeed the Church's practice encourages this thought when it bars divorcees from Holy Communion and disciplines its members for sexual wrongdoing. Even St Paul made a whole list of equally vile sins: pride, vainglory, hypocrisy, envy, bitterness, party strife and so on. But we never hear of anyone barred from the choir trip for envy or thrown out of the Mothers Union for party strife.

The long shadow of sexual guilt and its extraordinary persistence even in secular times indicates something of the depth and seriousness of sex in human psychology and the consequent rules and laws with which it is hedged about. Sexual mores are deeply serious and that is why they generate so much feverish dispute and controversy.

Sex is not - as some taught in the 1960s - merely something pleasurable that you do with another, like having a drink or a dance; it has consequences which are definitively human, of which the most significant may be the procreation of children but which also extend into the heart of human relationships. Fornication may be casual but by definition it can never be trivial.

Roman Catholics have very specific instructions about the practise of sex and contraception outlined in Humanae Vitae of 25 years ago and reaffirmed in the context of general morality in the draft of the new encyclical. Catholics who disagree with this theology of contraception supposedly based on natural law, and which basically prohibits the pill and 'devices', are in an invidious position intellectually as well as morally.

For the Church is set up as an authoritative institution proclaiming truth to its members. A Catholic may not pick and choose among the bits of truth until he finds what he can accept. What would it be for a religion to be only partially true or only a little bit binding? Sexual morality is one of those flashpoints between revealed religious doctrine and the secular liberalism which leaves room for personal opinion, for people to take what goods they wish from the shelf in the supermarket of moral suggestions.

The Anglican or other Protestant is permitted a degree of utilitarian flexibility in his contraceptive arrangements, but when a Catholic disagrees with his church it is as if a person should disagree with the very language he speaks every day.

There can be no arriving at the absolute moral truth about which forms of contraception, if any, should be permitted and in what circumstances. Or rather there is a variety of moral absolutes depending upon the status of the moral agent. The Catholic must regard the teaching of his church on this as on every other matter as absolute. Otherwise he calls into question the authority of the Church and, as it were, unchurches himself. The Church, after all, defines what is true, what is permitted and what is disallowed. In this respect it resembles the God whom it claims to serve and who issued Ten Commandments, not Ten Suggestions.

Is the Anglican or the Methodist more fortunate in that he belongs to a more 'liberal' church in which there is more space for individual conscience? And what heed, if any, should the secular person pay to what can only be to him as various alternative pieces of advice?

The fact is, we don't know. There is no absolute moral truth discernible apart from that mediated by the culture to which you belong and the institutions to which you adhere. As Wittgenstein said, 'The meaning of a word is its use in the Lebensform' - the form of life.

Perhaps the strict rules of the Roman Catholic form of life come closest to due acknowledgement of the profound seriousness of human sexuality?