The answer, for men, would seem to be castration. Better than drink: it takes away both performance and desire. Plato, in The Republic, has Sophocles say that the end of sexual yearning is like escaping from a vicious tyrant, usually quoted as "being unchained from a lunatic". Visions of the madman vary; I always picture him naked, wild-haired and bearded, a bit like Terry Jones in Monty Python, capering and scampering into the distance across a rain-swept Clapham Common. The writer Guy Kennaway, in his memoir Sunbathing Naked, writes: "The chain broke, and I was the madman."

Better have them off. A couple of half-bricks, a moment's exquisite agony and then peace descends.

Because when it comes to desire, we only have two choices now, here in the West at the beginning of the third millennium AD: we're madmen, or we're history.

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And if we're madmen, we're one of two sorts: buffoons or psychotics. Men's desire, emotional or sexual, must either mimic women's or be classed as deviant, probably deliberately so. No self-control. Evil instincts. Clumsy. Emotionally inarticulate. Weak. Predatory. A perve.

Let's take my own case. I truly believe that the peak of nubility for a woman is around the age of 12 or 13. I believe that a pubescent boy can only be honoured, and learn from, the erotic attentions of an older man. I believe that it is the natural duty of a woman to serve the sexual needs of her man, and that she must never refuse; if she does, out she goes. As for her own feelings... I believe that a normal woman is little troubled by sexual feelings of any kind; her desires focus upon looking after her man and caring for his children and otherwise just keeping quiet. I can't see what the fuss over prostitutes is all about. I believe that a man is quite entitled to keep a mistress providing that he chooses a social inferior within his financial means and, when he tires of her, helps her find a husband of her own class. I believe that black women are libidinous and immoral. I believe that one of the duties of my female staff is to accommodate my sexual urges whenever required. And I believe that a grown man who allows himself to be buggered is as much of a criminal pervert as one who performs cunnilingus.

And I know nobody who disagrees.

Or, at least, I would have believed all these things had I been born into different societies at different times in history. The existence of sexual and erotic desire is a given; but what it points itself towards seems almost entirely cultural.

It's a mystery, to be honest. Our Renaissance forebears thought nothing of taking a 12-year-old wife, and it didn't occur to their neighbours to dob them in, beat them, bang them up, chip the sods, deport them, make them sign the sex offenders' register and plaster their faces all over the tabloids ("Leering Gary", though the "leer" was the rictus common to all terrified anthropoids). The gentlemen of classical Athens valourised pederasty. Rich men had ceramic jugs, cups and punchbowls decorated, at vast expense, with picture of middle-aged men and beardless (the beardlessness was crucial) "beautiful boys"; Plato (again) named homosexuality as the highest desire in one episode of the Symposium, yet would have been repelled by the civil partnerships (with adopted children) that we now applaud (despite the fact that just over 40 years ago, the same men would have been put in prison).

And those same classical Athenians, as their symposium drew to a close, would have called for the euphemistically named "flute-girls", or tottered off to an expensive hetaira, or perhaps humped the slavey in the peristyle. Romans in their bath-houses bathed promiscuously, and more, and our very word "fornication" comes from the fornices – the arches – of the amphitheatre where low-rent prostitutes plied their trades; the Victorian gentleman-artists who painted them so lovingly also had an eye for a tart, a shop-girl or a pubescent, not to mention the cult of "passionate friendship" with the inevitable mental images of entangled bushy beards and twanging sock-suspenders. Slave-owning Americans extolled the compliancy and enthusiasm of their female property (and, in a curious reversal, contemporary American pornography has a minor obsession with depicting white men watching their wives being transported to bliss by the superior powers and sensual vigour of black men: Google "cuckold" and see for yourself).

On it goes... and the curious thing is that, to our imagination now, so much of it seems horrid. Yet it can't have seemed horrid to them (though there must have been the odd Athenian gentleman who had to grit his teeth to get through the awful pederasty business, and the odd one whose heart sank as the bloody flute-girls appeared just when he wanted to go home to bed) or they wouldn't have done it, let alone made it into the normal, the done thing.

You have to conclude that while our sexual and erotic (they're different, of course) urges are instinctive, their manifestations are as much a matter of time, place and custom as what we eat or how we dress. If everyone else is doing it, one would be a fool to do otherwise. And any sexual behaviour, for men at least, with our relatively easy route to orgasm, is going to be reinforced by pretty powerful rewards.

Yet now we are not guilty until proven innocent, but guilty. Academic tutors are given little lectures on how they mustn't ever let their eyes drop below their students' collarbones, while the 20-year-old woman who faces her, let's say, 30-year-old tutor in a short skirt, plunging neckline, and no underwear (it has happened, and not infrequently) is an innocent victim who will yell the place down if his glance flickers. A friend of mine, at the top of his profession, had to resign because after a couple of drinks over the eight, he flattered a junior colleague on her appearance ("leching").

Not only are our desires wrong, they are also risible. To start at the bottom of the moral chain, in a trade which knows precisely what people want, a porn film of a woman masturbating is considered both erotic and inherently beautiful; a man wanking is risible and vile, conjuring images of the unsprung sofa, the scattered pizza cartons, the solitary sock for afterwards. Almost every woman knows what it is to be desired, in a way that hardly any men ever do. I remember talking to the actress Kathleen Turner about this; on a good day, she said, she knew she could have nine out of 10 men in the room. I pointed out that there are only a few men who could say that, on a good day, they could have one out 10 women. And, of course, most of them are gay, and don't want to have any.

The rest of us are just... baggage. Young men now seem to have reached a sort of affable affectionate ease with women that escaped earlier generations. They share beds happily and chastely. They are best friends. They talk about their feelings. But lust and libido and passion seem strangely absent. They're dreadfully held-in-check, and prey to the body dysmorphias that for so long in the Age of the Image have victimised women. They go to the gym endlessly; they buy magazines devoted to the abdominal muscles; they gel and tan and sack-back-and-crack, vogue and pose, fret and pump iron, eat cabbage leaves and nibble on dry biscuits... but unlike women, who hope that this horror will end with them being desired, the young men just hope, I suspect, to be forgiven. If they can make themselves nice enough, in a parody of manual-labour masculinity plus beauty-salon pubescence (body hair a no-no), it might not be so terrible that, at the end of it all, they are still men.

But how do you get to be a man now? Not by submitting to the embraces of an old dude round the back of the Temple of Hephaistos, for sure, nor by going off and tupping the nubile ancilla. You get to be a man (if you get to be one at all) by acquiring the "virtues" of fidelity, emotional articulacy, sexual discrimination and social co-operating. In other words, you get to be a man by imitating a woman, except with a six-pack. But no body hair.

You do this because, first, the social roles for the "manly" man have faded with our manufacturing economy. It doesn't require courage or physical strength to poke at a computer screen, which is what most work (and much flirtation) now consists of. Aggression and decisiveness count for nothing in a call centre (or at least, not decisiveness).

And you do this, secondly, because masculinity is evil and the phallus – once a symbol of fertility, fun and good fortune – has become a lethal, corrupt and infecting agent of violence. The phallus ravages children. The phallus injects HIV. The phallus, if uncalled for, destroys lives, and never mind how. It injects children who must be borne and nurtured by lone, unsupported women. And – Sophocles's vicious tyrant – it drags its possessors (or its slaves) about the place, heartlessly. Gray Joliffe's Wicked Willy cartoons about sum it up; except, unlike Joliffe's affable, happy little chap, the real thing is vicious and unheeding. A madman.

Any man, then, is a sort of zombie with a loaded revolver. Lock up your wives, your daughters, your sons. Lock up the dog. There may be a man about.

Yet the idea of a man as an imitation woman ignores some fundamental truths. First, that, like any culture, we get the sexuality we deserve. Second, and more importantly, women and men are fulfilling, above all, their evolutionary destiny. Social Darwinism is a horror, but you can say, for sure, that if you're going to evolve an intelligent, sexually reproducing species, the first damn thing you have to evolve is sex. EQ, compassion, quadratic equations and sushi come later; or, if you fail to evolve sex, they don't come at all. The bit of us that has sex isn't the bit of us that thinks, and behind every bishop raving about homosexuality is not only a bishop who hasn't noticed that Jesus says damn-all about sex (and when he does mention it, it's to go against Mosaic law), nor only a bishop who has too much time on his hands, but a bishop who is both culturally and biologically ill-informed.

The odd thing is where this has all come from. I don't know a single woman (except, fleetingly, a couple who were seriously deranged) who hate men or want us to be like them. Most women seem to quite like men, and resent as much as we do the prevailing culture of contempt and suspicion. They don't want articles asking "Are Women Really Bored By Men (Yes Of Course!!!)". They don't like the portrayal of men in the media either as violent, raping, child-abusing, monosyllabic incompetents just waiting to whip out their wangers and wreck someone's lives.

Nor is it simply a matter of intolerance. I don't want you to tolerate me, or anything about me. That's not in your gift; to say you are prepared to tolerate me is simply arrogant. Intolerance? No; though W H Auden, in arguably the most beautiful love-poem of the last hundred years, "Lullaby" (ostensibly a hymn to gay promiscuous sex) speaks to all our erotic hearts when he writes of

...lovers as they lie upon

Her tolerant enchanted slopes

In their ordinary swoon

But that's a different tolerance: a tolerance closer to the original meaning of the word: a bearing of the burden of our common humanity.

Who's doing this? Who's responsible? I don't know, but I don't like it and neither do you and it's not true. We aren't hateful nor are we vile; I don't even think we're particularly ugly, though I wouldn't fancy one myself. Men and women are really quite like each other. The thing is, we're also utterly different. It's the culture's task to negotiate that paradox, and right now I don't think it's doing a very good job.