I decided to look at my own prudery and its role in my erotic life. Firstly, I realised I couldn't honestly locate prudery only outside myself, in society. I began to suspect that it is my private sense of what is naughty or forbidden that fuels my desires. It is as though I have two parts - a prudish one and a rebellious one. The rebellious part causes my excitement by antagonising or rousing the prudish part. Without the prudery there would be nothing to bounce off from, no resistance to overcome. No sparks would fly.

So what is my prudish part like? It finds nakedness offensive. It believes that if sex is to take place at all then it should be in marriage or a relationship of long standing. It forbids oral sex, pornography and even glamour photos, as well as any kind of eroticism. My prudish part is an internal image of the repressive attitudes to sexuality that still underlie our society. Yet, though I disdain it, I simultaneously cherish my prudish part for making eroticism possible. It comes down to pairs of opposites - black has no meaning without white; to realise freedom we need to know bondage (pun unintended).

I can see women showing most of their bodies on Bondi Beach, where topless bathing is now fairly common. This does not arouse me. Yet if I saw a woman showing as much - or far less - of herself in Martin Place, it would. Context is what makes the difference. The human body can be eroticised or de-eroticised, depending on how and where it is shown. A fleeting and unintended - by the woman, I hasten to add - glimpse of a bra or nipple in a train usually excites me. In a nudist environment, complete nakedness does not. What turns me on is the perception that the glimpse is inappropriate, stolen, surreptitious, immodest, slightly shameful even. It is not the thing in itself, whether breast or crotch, that is erotic. Only my attitude to it makes it erotic for me or not.

In fact, habitual nudity is positively anti-erotic, since it divorces nakedness from desire. Nakedness is arousing only so long as it remains an extraordinary state. A state of being half undressed is the divine medium between the opposites of starchy propriety and unabashed nakedness. Erotic effects rely on simultaneously revealing and concealing. The tension is in the contrast between the two. A semi-transparent brassiere is tantalising in a way that toplessness is not. Uncertainty is the essence of excitement. Stockings and lingerie accentuate, or create a woman's mystery. If it were not for prudery, there would be no mystery.

In Victorian times, people covered table legs and would not refer to chicken breasts or legs. By taking prudery to such extremes they eroticised objects and activities that we do not see as being connected with sex. Hence they found the glimpse of a female ankle arousing. I am also reminded of the rich Arab who had naked female statues placed in his garden. Only their faces were covered.

In modern times there is less scope for eroticism. The commonness of short minis and revealing tops has desensitised us males. What comes too easily is not valued. The complex and subtle world of 19th century eroticism is lost to us. When there are fewer rules to break we are denied the pleasure of breaking them.

It is the prudish part of me that frames certain actions or views as 'inappropriate' in the sense of being immodest, and consequently erotic. Without my prudish part, I suspect that a lot, if not all, of what is erotic for me would vanish. Thus if nudity were the norm rather than the exception, then the sight of a bare woman would cease to be erotic altogether.

Though it is hard for me to speak for other men, I conjecture that, in essence, the connection between prudery and eroticism is a general one. Of course, I am not talking about love, nor am I referring to sexual pleasure as such. My topic is the component of mental excitement, as distinct from physical stimulation.

I have only discussed visual erotic stimulation, but I think the same holds true for actions and physical sensations. Even orgasm itself could be de-eroticised, if - to give a somewhat far-fetched scenario - it were a daily, public and unimportant activity, comparable to eating lunch. Human beings could be sexual in the same way that animals are. Some moralists claim that this is already the case, but of course, they are projecting their own prudery in the form of imagining its opposite.

In essence, I believe that eroticism is inextricable from prudery. Forbidden fruit tastes best: it is the social repression of sex that causes eroticism. The overall social attitude to sexuality tinges private acts between consenting adults with the thrill of the illicit.

"Obscenity," Jonathon Green suggested, "is anything that gives an elderly judge an erection." Judges are not the only people who seem to equate eroticism with obscenity. Furtiveness, seediness and especially dirtiness can be potent turn-ons. Lindsay Honey puts it in his earthy way, "'Cor blimey she looks right dirty, a right horny little bitch... Do you think sex is dirty? No? Then you're obviously not doing it right."

Language is a good indicator of the persistence of what we now smugly label as Victorian ideas. Nearly all words describing sexual actions and feelings are either vulgar or clinical. Some of us persist in using phrases such as 'dirty weekend', 'playing up', 'having a naughty', 'smutty book'. This may often be done for comic effect, but there is something behind the humour. It is frequently a false bravado that seeks to cover up unease or discomfort about sexual matters. The human genitals are still universally used as swear words and insults. Is it not bizarre that comparing a person with the female genitals is the worst insult in English? It is as though there is fear and hatred as well as attraction and loving in human sexuality. Fear and hatred causes prudery, which makes sex seem dirty - and hence exciting. In truth this dirt is in the mind, though paradoxically, so is sexual arousal.

As one woman commented, "The element of seediness and naughtiness is an essential requirement. If it's allowable, perfectly all right, with clean sheets - then there are more erotic activities." The thrill of discovering sex in adolescence is in large part due to its being a hidden world that adults try to withhold from the young.

Suzanne Moore observed, "Sex does require a bit of 'dirtiness'. There's this feminist erotica, supposed to be anti-pornography, which is all sort of nice and cosy and warm and it just takes the sexiness out of sex... People like to think what they're doing's illicit even if it isn't."

Many men still have the old conditioning about the two kinds of women - the nice girl whom a man marries, and the not-nice girl who is sexually active and hence exciting. This double standard generates excitement, as well as much misery.

Pornography is only possible because of the tension of opposing stereo-types, viz. the madonna and the whore. Thus a refined and beautiful woman is thought too pure to be photographed having sex, taking part in orgies etc.

The US singer who markets herself as 'Madonna' has become the richest entertainer in the world by deliberately mixing those two stereotypes in a proportion that titillates millions of Americans. That's amazing when you consider she can't sing, act or dance, and is not even particularly good-looking. (Yes, I am envious.)

The prime attraction of pornography is that it is culturally forbidden. Due to the influence of the Church, sex was considered dirty and sinful until recent times. Had it been possible, St Paul and later Christian moralists would have forbidden us sex altogether. Whatever the arguments about permissiveness and so-called declining morals, we still live in a largely puritanical society. If not, then why isn't erotic literature as respectable a field as are cookery, cricket or horror?

We are conditioned to be insecure about our sexuality and hence seek to hide it. Pornography thrusts it into the open. By rejecting all social conventions of sex, it creates a feeling of liberation and release. The more energy a society expends on suppressing something, such as pornography, the more that same energy rebounds into a fascination with the subject. Prudery and porn go together. Prostitution and pornography both flourished in the Victorian era.

To the pure all is pure; dirt is in the mind of the observer. Those who are zealously prudish, like traditional moralists and the US evangelists, see filth everywhere. Nor can they resist the urge to look. In sexually repressed India, a lady called Shobha De has become the country's top-selling writer since Independence by writing pulp erotica. She has also caused unprecedented outrage. One of her readers commented, "This lady is a very dirty lady. Her books are full of wicked and filthy thoughts." Another admitted, "I am reading everything she is writing. In one book I am counting 73 copulations. I am shocked only. Really, her head is full of perversions."

A woman recalled an orgy she had participated in: "The actual thrill is not so much in the sweaty bodies, it's the idea you're playing out a game and you're doing something outrageous. The outrageousness is the thrill."

Fear and anxiety are not very distant from the feeling of excitement. Various fears in the sexual area, such as of pregnancy, of AIDS, performance anxiety, shame about one's body or sexual parts, the fear of being caught, the fear of intimacy (both physical and emotional), or of being thought 'cheap', can all add to the excitement of sexual activity. Ellen Severin spoke about her first and highly unsatisfactory affair, "It wasn't physically pleasurable in the least - it was frightening, but things that are frightening are frequently exciting."

In a sense sex is always unsafe. It makes us vulnerable and exposed, literally stripping us naked. Sex is that most private area where two individuals are intimately confronted with each other. It can be felt as a test of one's personality. Prudery intensifies the tension and excitement of this encounter.

Of course there are other factors besides prudery that give rise to eroticism, such as mystery and childhood conditioning. Yet I think that no single factor does as much to foster eroticism as prudery does. So give me prudery - only not too much!

In Praise of Prudery