There's really only one compensation for the waning of summer: clothes. What a relief to be enfolded and disguised, swathed and buttoned, after months of exposure in revealing frocks and sticky tee–shirts. This season serious women have even more reason to rejoice as we witness the rebirthing of the classic trouser suit, beautifully rendered by Paul Smith in pinstripes, Dolce and Gabbana in grey, Nicole Farhi in boxy chocolate brown and Ralph Lauren with his tribute to the three–piece.

For women, these may be flattering, practical or playful variations on the standard male uniform. For men, the suit has been the most important and central item of clothing for over a century — smart, serviceable and anonymous. It's a wonderful device for looking appropriate without having to think too much about it — or at least for giving the air of not having thought about it Of course, the suit is a humanist issue, as challenging for those who eschew fashion and care little for their appearance as for those who deliberately manufacture their outward image. It is probably more revealing than any other sartorial choice, its effect a semiotic shower. The gap between turn–up and sock, the inside pocket overladen with biros, the shine, the sheen, the creases, the collars — there are so many ways in which even the most modest or sober of suits can betray you.

And those messages constantly shift and adapt according to the times — and the wearer. Wide checks for wide boys, collarless Cardin for the classless Beatles, zoots for the sharp, velvet for the hip, tweeds for the country gentleman and Brooks Brothers for the modestly ambitious. Although in these postmodern times the suit may seem to have lost some of its stranglehold it is still, as Michael Korda once put it, "the matrix of the modern man's wardrobe".

The historian Anne Hollander, in Sex and Suits, argues that the suit will always be with us because of its deep associations with two driving principles: sex and power. All Western male costume, she says, is designed to enhance and articulate the nude body, its rippling muscles and firm physique all the more present when so artfully covered. The covering itself represents the ability to conquer and contain libido. It conveys confidence, authority, utter control.

When John Birt joined the BBC his notorious Armani suit made his statements for him, branding him powerful and creative, rich, stylish and with an enviable physique. Fashion historian Colin McDowell describes Georgio Armani as "the undisputed genius of male fashion" because those delicious flowing lines and undulating fabrics do not disguise so much as emphasise and flirt with the powerful shoulders and toned muscles beneath.

It was not until the turn of the last century that the suit established itself as standard daywear for the professional man, gradually supplanting the waisted frock coat and then the lounge coat. By the mid–1860s an ensemble with matched coat, waistcoat and trousers was beginning to be adopted — the three–piece suit was born, its aggressive uniformity representing the culmination of centuries of refinement in male appearance.

In earlier times, men had rejoiced in flamboyant outfits. Now, though, male dress finally shed all decoration. What was gradually taking shape was a sharpening distinction between the sexes. Ostentatious fashions became the domain of women, increasingly associated with the trivial or the coquettish. Men needed to demonstrate their distance from petty concerns. They had empires to run and societies to order.

The pivot of this change was the Enlightenment, a time when the rational took ascendance over the mystical. Science and thought, logic and reason were the new masters. Modest, sober clothing was a manifestation of reason's domination over instinct. Just as the Reformation had cast out elaborate papal trappings, the French Revolution now wrought a similarly radical transformation. Restraint in dress represented a reaction to the excesses of a corrupt monarchy and decadent regime.

This deep–rooted mistrust of adornment in dress shows a curious correspondence between the devout believer and the passionate sceptic. It unites clerics and revolutionaries, monks and social reformers. It is a telling example of how, if you don't make conscious statements in your choice of clothing, you could be putting out quite contradictory signals. So beware — that shapeless jumper and faded corduroy ensemble favoured by so many intellectuals could, by accident, be conveying a love of Jesus or an allegiance to the Pope.

No such doubts plagued the Victorians, though. The men were far too busy zipping their libidos into quiet formality, while high fashion for women was becoming ever more elaborate and restrictive, epitomised by that most extreme of garments, the crinoline. Ever since the French Revolution female political idealists had been calling for dress emancipation. Their ideas were espoused by the American feminist Amelia Bloomer who recommended that women replace their heavy skirts with light, baggy trousers reminiscent of Turkish harem pants. Her ideas were echoed at the end of the century in London with the formation of the Rational Dress Society.

They advocated more sensible clothing to liberate women from the impractical, often deforming and darkly erotic fashions which they felt restricted women's intellectual as well as physical movement. Like medieval monks in their flowing skirts, the dress reformers believed that freer clothes would free the mind. This was an idea enthusiastically taken up by the Fabians in the early part of the twentieth century.

Edith Nesbitt, best known for her children's stories, was a prominent Fabian who welcomed the personal as well as the political liberation that the movement promised. She and her circle of radical friends like Eleanor Marx, Olive Schreiner and Annie Besant would sport flowing Liberty gowns, cut their hair, smoke cigars, ride around the countryside in bloomers, while writing pamphlets and campaigning for social reform.

A fellow Fabian and close friend of Edith Nesbitt was George Bernard Shaw.

He was an admirer of the German scientist Dr Gustav Jaeger who advocated the wearing of wool next to the body and railed against tight clothing. An enterprising Englishmen bought the name Jaeger for his retail clothing outlets, and made a fortune selling fine fabrics to wealthy liberationists.

Despite his conviction that his Jaeger suits were responsible for his sudden success with women, Shaw actually wanted to go further in his pursuit of rational dress, believing that suits should be replaced by woollen breeches and tunics. Perhaps he was unaware that his sartorial notions were veering dangerously close to those of the clergy who also connected freedom of movement with freedom of thought.

The most radical advance in fashions for both men and women was the advent of ready–to–wear clothing during the nineteenth century. For men, it meant the suit was available to everyone — those aspiring to power as well as those with it. Ubiquitous and affordable, the suit became a symbol of respectability — rejected and mocked by proponents of the Aesthetic Movement like Oscar Wilde who rebelliously flaunted ever more fanciful costumes. Conversely, the Surrealists in the early part of the century and more recently the artists Gilbert and George adopted suits in order to confound expectation and subvert convention.

The democratisation of the suit was completed at the end of World War Two, when every soldier was issued with a 'demob' suit. Which may be why another humanist role model, George Orwell, continued to carve out an image at odds with the standard male uniform even when he could have afforded something more dapper. He chose cheap, slightly hairy square jackets with grey flannel trousers rather in the style of postwar British jazz bands. Evoking a somewhat Mods and Rockers–ish distinction between snappy–suited bebop musicians and the new dilettantes, George Melly recalls in Owning Up: "An extreme sloppiness was de rigeur."

Women, too, had benefited from the advances in mass produced clothing.

By the end of the nineteenth century it was acceptable for women to wear tailor made suits — sensible skirts with fitted jackets — suitable for working in the office or for campaigning for the vote. Ever since, women have been seeking ways to emulate and acquire the enviable powers of men. From Vesta Tilley to Marlene Dietrich, Katherine Hepburn to Annie Lennox, image–carvers have used men's clothing to underline their own formidable sexuality.

Boucled Chanel suits, though far from masculine, did much to free women into the working world, and made way for the arrival of the full–blown bid for male status in the 1960s: the trouser suit. By the greed–propelled 80s, power–dressing had reached satirical proportions. Joan Collins epitomised the rampantly ambitious boardroom queen in Dynasty, where she delighted in wearing ever more extreme suits with built–up shoulders and exaggeratedly armoured waists.

Women's attempts to ape men's clothing may sometimes shock, but they hardly surprise. What could be more natural, after all, than emulating the more successful sex? But the very idea of a man dressing like a woman can only be seen as laughable. Drag queens do not emulate us. They merely express their scorn through parody. Pantomime dames personify the absurdity. For the one profession where skirts for men are acceptable, the clergy, those flowing robes are more a renunciation of sexuality than a bid for equality.

Until this distinction between men and women's clothing disappears, fashion is telling us that the gap between the genders will remain. Even Jean Paul Gaultier, who confidently challenges the sexual orthodoxy by giving men corsets, skirts and feather boas, has not had much effect beyond the catwalk.

Let's hear it, then, for the one indisputably masculine man, worshipped by boys, a pin–up for girls, who dared to wear a dress in real life. When soccer supremo David Beckham donned a sarong on a recent trip to the far east, the media was baffled. How could their hero be seen in a skirt? But maybe this was a pivotal moment. The moment when a strong man showed the world he could take on his inner woman and survive.

Humanists have a similar duty to rescue the skirt from the Church and the temple and put it back where it belongs: in the menswear department, alongside the equally acceptable unisex suit.