The generation gap has closed, and it now seems that, from Bill Clinton to Baby Spice, big kids rule. E Jane Dickson longs for a return to the days when grown-ups were grown-ups, and `middle youth' was middle age
Not so long ago, it was a comfortable fact of life that, as you approached your 49th birthday, a day would come when you would lift your nose and scent change in the air. Your old, fashionable clothes would slough off in a tussle of too-tight Lycra and you would emerge, sleek and contented, in easi-care slacks with elastic waistbands. When you opened your mouth to speak, you would find yourself starting sentences with "I think you'll find ... " and "Be that as it may ... " Your thoughts would turn, quite naturally, to loft insulation. You would, in short, be a grown- up.

Not any more. Now we are told, by the same pundits who announced that grey is the new black and peas are the new beans, that - ta-raa! - 40 is the new 30! We are to put an end to middle-aged misery and embrace "middle youth" instead. A whole new, exciting life-phase has been invented just for us; it is called - God help us - "adultesence".

Having just turned 38, I'm not entirely heartened by this. I was looking forward to the slacks. Now it seems I must brush up my skateboarding skills and take a string of lovers. All around me, peers are shedding decades like dandruff. Thirty is the new 20! Twenty is the new 10! The Paris catwalks are groaning with jailbait skirts and gymslips. Grown men are racing home from work to play Nintendo. In a recent magazine article, the comedian Sean Hughes described himself, with no particular shame, as "33 going on 12", and related how he enjoys playing pranks on shopkeepers and likes to drive round town waving an amusing big foam hand out of his car window.

Such larks, observes Hughes, are a sign of the times. "People are refusing to grow up; this generation is very weird. There's been this kind of cop- out. Even friends who are married are still kids in many ways."

There is much to support his thesis. Role models like Gazza, Liam Gallagher and the grimly girlish Baby Spice (who, come on, is 30 if she's a day) are all icons of arrested development. Captains of industry are having cook-outs in the woods and zapping each other with paint balls. Look around, and it's as if some inverted Pied Piper had lured all the adults into the hole in the hill and left the children clamouring, hopelessly, for attention. Where have all the grown-ups gone?

We are not the first generation to make a cult out of childishness. The Romantic poets of the 18th century idealised childhood as a state of innocence, prelapsarian and pre-intellectual. "Ah! happy years! Once more who would not be a boy?" sighed Byron, with more sentiment than syntax, in Childe Harold's Pilgrimage. By the 19th century, Wordsworth was skipping round the mountains with his shepherd lads and lasses, working up his theory of the child as "father to the man". But it was Dickens, with his creepy wise-children and even creepier child-women, who really popularised the (imagined) state of childhood, with the exquisite refinement that while boys are allowed to grow up into fine, stout-hearted fellows, little girls are marked down for death or perdition the minute they hit puberty. Nor was this nice sentiment contained within literature. John Ruskin's famous disgust at his child-bride's pubic hair and Charles Dodgson's prying photographs of his young companions are functions of the same fantasy. The scene was set for the figure who would definitively fix our notions of childhood in the 20th century: Sigmund Freud.

After Freud, you might say, no one ever grew up again. Freudian insistence on the primacy of infant experience in sexual and emotional attachment made us look at our childhoods in ways which became more and more extreme as the century advanced, taking in analysis, regression, re-birthing, primal screaming and culminating in the supremely irritating fad for the "inner child". By the late Eighties, every metropolitan dinner party seemed to include at least one guest who would babble artlessly about the joys of fingerpainting and mud pies. I recall with undimmed horror an evening when a mother of three explained how she had written a letter to her inner-toddler, forgiving herself for ruining her sister's birthday party and, better still, had received a letter back from her toddler-self (not, you note, from the aggrieved sister) telling her to consider the matter closed. And I wish I had been present on the occasion when another guest, his patience exhausted by such outpourings, begged for the inner child to be sent to bed.

It is unfair to lay the whole blame at Freud's door, but there is no doubt that the psychology culture of the late 20th century has helped extend childhood beyond its natural limits. It is as if, having recognised the value of looking at our childhood, we refuse to look beyond it. There is a memorable scene in the 1978 movie Escape from Alcatraz when a prison inmate asks Clint Eastwood how his childhood was. "Short," says Clint, the very model of unreconstructed machismo. It's not an answer you would hear much today. And while it is hardly desirable to take Hollywood's number one hard man as our role model, this is certainly preferable to the more recent slew of overgrown-kiddy movies. No actor can now consider himself major league unless he has plumbed the emotional depths of the playpen. John Travolta nearly bust a gut being adorable in Look Who's Talking. Robin Williams was frankly ridiculous as Peter Pan. Tom Hanks showed how cute it could be to be a child trapped in a man's body in Big, and then got to do his wide-eyed wonder bit all over again as Forrest Gump, a retarded child-man who wins through as the very spirit of the American Dream. What, you have to ask, does it say about the Zeitgeist when innocence is so overwhelmingly prized above experience? Psychoanalyst and author Adam Phillips acknowledges that we are in danger of becoming over-infantilised. "There is a kind of idealisation of childishness because there is a kind of despair about thinking of an alternative to it," he suggests. "The modern preoccupation with childhood means that people have lost a sense of there being a difference between adults and children, and, of course, psychoanalysis, along with other kinds of psychology, has been complicit in this by suggesting that adults are fundamentally children. Ironically, you create a world in which there are only children, and then the question becomes: who is going to look after the children?"

This is, of course, the point. If 40-year-old women choose to wear baby- doll jim-jams and pile their beds with teddy bears, that is their grisly prerogative. If High Court judges wish to wear nappies and be spanked in their lunch hour, more power to their mammies' elbows. But while these "big kids" are taking their puddle-stomping pleasures, there are real children out there, proper little tiny ones, who are getting awfully confused. For the inevitable obverse of the "big kid" syndrome is the "little adult": as our imaginary childhoods are lengthened, real childhood is necessarily cut short. Consider the wrenching pathos of those Tudor and Jacobean portraits where seven-year-olds gaze out, stiff and itchy, in miniature replicas of court dress. Then look at contemporary advertisements for Baby Gap. The materials may be more forgiving, but the message is the same: children are just adults scaled down. It is possible today for a 60-year-old, a 20-year-old and a two-year-old to step out in exactly the same T-shirt, chinos and trainers. Girls of three are tripping around, just like mummy - or, for that matter, granny - in miniskirts and crop-tops. If we can't look like children (and few over-30s can get away with smocked frocks and Start-rites) then we are determined the children will damned well look like us. The effect of this stylised sexualisation of infants in terms of paedophile abuse has yet to be quantified, but it would be disingenuous to ignore the possibility. It's Dickens and the child-woman all over again. From Little Nell to Baby Spice in the span of a century.

"The edges between the generations have been blurred," according to Adam Phillips. "It is more difficult now for people to work out what are the differences between children and adults, and why those differences matter."

They matter crucially. The winsome, "children are just small people" school of parenting places an intolerable burden of autonomy on a child. "Children need adults to look after them, to contain them," confirms Phillips. "It makes the children very frightened of themselves if the adults abrogate this responsibility."

Yet at every supermarket check-out parents are down on their knees to toddlers crazed for E numbers, explaining man to man, as it were, why they're not to have the sweets. Or, even worse, they stand by smugly while the weary child explains to them. My own frazzled response, "Because I say so and I'm the mummy," could not provoke a more scandalised reaction in Waitrose if I was caught giving my three-year-old Chinese burns. But is it really possible, or even desirable to deal with a toddler "on equal terms"? You may see an equal but the child sees a competitor and the fight is fixed from the beginning. Similarly suspect are mothers who pride themselves on being "more like sisters" to their sons and daughters. This is almost never calculated to reflect well on the maturity of the child, but rather to deny any suspicion of matronliness in the mother. Like ogres in a fairy tale, we steal our children's youth.

There is no universal benchmark for maturity. According to Catholic dogma, a child must look to its own salvation from the age of eight. Chinese tradition decreed a child "responsible" once it could carry a brimming rice-bowl of water over a set distance without spilling it. In our own country, the age of responsibility appears to be index-linked to our social history. In 1914, boys left school at 14, were ceremonially presented with their first pair of trousers and could be dead in a trench before they needed a new pair. Adolescence was a luxury imported from America after the Second World War. From the Sixties on, childhood has been steadily extended. Now pupils can be attending school until they're 18 or 19. They can legally vote, smoke, drink and marry, but by some kink of sentiment they are always called schoolchildren, never "school adults". This sliding scale of adulthood is particularly contentious when it comes to sex. Only in a country deeply confused by the whole issue of responsibility could we end up with separate ages of consent for straight and gay sex.

For this, however much you dress it up in fancy demographics, is what the whole New Infantilism thing boils down to: a pettish ducking of responsibility: children don't have to make life-changing decisions and live with the consequences so why should we? Children demand instant gratification so why should we control our adult appetites? The President of the United States can't even control his own trousers. And when he is caught with them round his ankles (again) he hides behind the vaporous skirts of spin doctors who explain that the President, poor lamb, is suffering from "sex addiction".

If Bill Clinton didn't exist, Freudians would have to invent him. He is the Ur -adultescent, the naughty boy repressed and excited by controlling women. One of the most extraordinary things about the whole inglorious spectacle of Monicagate was the way female commentators came fluttering from every corner, begging indulgence for the President because he was "just a Big Kid". Now, I can see, at a stretch, why women might want to mother a Big Kid, I might even vote for one if I liked his policies, but I'm damned if I would want to sleep with one. (Surely the maddest thing in the Michael Hutchence affair was Paula Yates cooing, with motherly pride, that her self-strangled lover was "a dangerous boy".) But when it looked like Bill's boyish charms were not enough to save him, it was time to change tack. In a last-ditch attempt at image-rehabilitation, and after God knows what inducements, Hillary Clinton was wheeled on, like Patient Grizelda in a power suit, to tell us in her world-syndicated Talk magazine interview why we should stand by her man. "He's a grown- up," she said, pointedly, but not before she had milked her husband's miserable childhood. "There was terrible conflict between his mother and grandmother," she confided. "A psychologist once told me," she added darkly, "that for a boy, being in the middle of a conflict between two women is the worst possible situation."

There are, arguably, boys in Kosovo or East Timor right now whose trauma is greater than the infant Clinton's, but that is another debate. It is entirely reasonable to suggest that a bad childhood informs bad adult behaviour - it may even explain it - but can it endlessly excuse it? Surely, if there is to be any kind of resolution, there comes a point when the inner adult has to take charge.

Sex addiction - has there ever been a more transparent willy-measuring construct? - is just the tip of the dependency iceberg. Last month, a British woman, dismissed from her job for spending working hours surfing the Net, sued for unfair dismissal on the grounds that she is an Internet addict, and therefore not responsible for what she does with her computer terminal. In the US, billions of dollars are paid out every year in legal damages to the responsibly challenged: $1.8m to the woman who tipped a take-away coffee over herself in a moving car (it was the fault of McDonalds for making the coffee hot); $50,000 for the New Hampshire teenager who caught his teeth on a basketball net while attempting a slam-dunk (it was the net's fault for being net-shaped). And now, following the success of the mass litigation against tobacco companies, a class-action suit has been launched against toothbrush manufacturers and the American Dental Association on behalf of all the people who brushed their teeth too hard and made their gums sore. Is it any wonder that companies are responding with Orwellian nannying tactics? Can we blame the New Jersey company which has developed a surveillance technique for ensuring catering workers wash their hands after using the lavatory? I am only surprised there is not a hygiene facilitator crouched in each stall to make sure they wipe their bottoms first.

Even if we do not expect financial rewards for our inadequacies, there is a growing feeling that we must somehow be protected from the real, grown-up world. One might have hoped, for example, that the break-up of Take That, terrible as the event must have seemed to teenage fans, would be regarded as a kind of rite of passage, on a par with the sad truth about Santa Claus. But no. Incredibly, youngsters were urged to visit dedicated counselling centres where paid professionals talked them through their trauma. Are we really surprised when these youngsters grow up to be the kind of adults who hang, weeping, on the railings of Kensington Palace, devastated by the death of a woman they never knew?

My own exposure to counselling culture was brief but educative. After a miscarriage I woke up in hospital to find a white-coated woman telling me I must be feeling angry and should perhaps seek counselling. I said, truthfully, that no, I did not feel angry, just desolate at the loss of a longed-for child, and that I considered this normal. An appointment, however, was duly made, and anxious not to appear stroppy and jeopardise my relationship with the hospital where I hoped to have further fertility treatment, I went along. A completely well-meaning counsellor explained that I would probably feel resentment towards mothers with babies, that I might even, subconsciously, wish them harm, and that I must "permit myself" to feel these things. I replied that on the contrary, if I found myself cursing babies in their prams I'd be giving myself a bloody stiff talking-to, and we concluded, with mutual relief, that counselling was not for me. More receptive souls, I know, have been helped by this process and I'm glad of it, but it is a horribly inexact science. Counselling borrows much of the language of psychology, but, unlike psychology, it is not a closed shop. It takes a skilled therapist to route volatile feelings, like some nuclear cargo that travels by night, to a safe dumping ground. Too often counsellors, who are not stringently regulated, encourage clients to spill their guts, only to find that they have no idea how to fit them back in again. Yet counsellors are the figures we now look to for advice and absolution, for the Disney-style assurance that, just by dint of being helpless, we are lovable. The whole "I feel therefore I am" culture is a kind of celebration of immaturity, as if we were infants at the mercy of our emotions, forever incapable of moral or rational action.

What then, has caused this mass retreat to the kindergarten? Certainly, as life expectancy grows, the old milestones are shifted. Women today are having children in their 30s and 40s, or increasingly are deciding not to have them at all. Their mothers had their babies in their 20s. Their grandmothers may have started families in their teens. Clearly this is going to alter the life structure of these women and their mates, but I am uncomfortable with the idea, now gathering momentum, that social responsibility only kicks in with parenthood. Again and again, faced with an atrocity like Dunblane or Springfield, we are told that "every parent must share in the horror". Well, what about every human? Is social conscience really such a poor, etiolated thing that we can only sympathise with people exactly like ourselves? This is equally insulting to those with children and those without.

There is no doubt, however, that putting off childbearing creates a whole new consumer group, active and aspirational, with a disposable income and leisure to spend it. It is therefore entirely in the interests of the market economy to promote the idea of "middle youth" or "adultesence", though "retail retards" would be nearer the mark.

Or is it, as Sean Hughes suggests, a considered cop-out by an entire generation, a last fling before the baby-boomers' bust? The very term "baby boom" carries a kind of blithe assurance, a post-war confidence that warm days will never cease. They came into a world high on euphoria and their lungs are unadapted to anything else. The old-timers' complaint, that what young people nowadays need is a bloody good war to buck up their ideas, is clearly grotesque, but could it be that today's thirty- and forty-somethings, secure from birth in the knowledge that the cataclysm of the Second World War, or for that matter Vietnam/Korea/The Cold War, was not their fault, have decided that nothing will ever be their fault, or even their responsibility, again? The first duty of the baby-boomer was to enjoy the freedom he or she was born to and the second, less piously observed, was to be a thorn in the side of the establishment.

"I think there is a problem for our generation in identifying with the one who is in authority," says Adam Phillips. "We dread being the police, whom we see as purely punitive, not protective, but we don't know what else to be. One of the things that belief in God sustained was the idea that there was someone who understood us, who carried possibility of authority, and in secular cultures there is an anxiety about where you look for authority. It is almost as if people are searching for someone to look after them, someone who will tell them what it means to be an adult today. And of course this makes the whole thing politically rather frightening, because you can't have a democracy unless you have adults."

It's a pertinent thought when you consider the lamentable turn-out at the polls for the last general election. But, cometh the hour, cometh the man. One of the things that appeals, or appals, about Tony Blair is the fact that he looks so unalterably like a dad. He flaunts his nasal hair. He irons his jeans. Any minute now he will take to tattersall checks. (In strict contrast, William Hague, who looked and sounded 40 aged 15, is doing his damnedest to reverse the effect.) And now that he has perfected the look, Blair is moving smoothly to phase two: the rant about "young people today". While his current moral crusade may be more helpful to the Labour Party than to gymslip mothers, he has at least dragged the notion of adult responsibility out of mothballs. It is not a requirement of adulthood to accept a prescribed moral code, but there must at least be a moral sense. It is hard, given the Thatcherite pall which still trails over our thinking, to distinguish between selfishness and self-determination, but it should not be impossible.

But hell, we are the rock'n'roll generation. We hoped we'd die before we got old, and now we're just redefining our terms a little. We meant really, really old, not just a bit wrinkly, a bit flabby round the middle. The refusal of the newly middle-aged to put away childish things is just fear of the dark, an exhausted call for one more story, one more kiss before lights out. Growing up is hard to do, but to borrow from the French philosopher Maurice Chevalier, it's better than the alternative.