LET'S HEAR IT for haute couture, the defuser of revolutions.

High fashion has worked three times in the last 20 years to help abort rebellions in progress, and it is time to assess this achievement as either a CIA plot or the secret genius of the American system.

Taking on the hippie movement, women's liberation and punks, fashion managed to copy, co-opt and eventually dismiss the visible aspects, thereby dismissing much of the content as well.

Herein lies a great, if appalling, lesson. It appears to be a fundamental truth that when the appearance of an idea becomes pass,e, those who cling to the notion can also be regarded as merely quaint, and whatever threat they used to pose can be ignored.

In other words, whom the fashionable would destroy they first make gorgeous.

The hippie movement of the late 1960s was a genuine threat to the American way of life at the time. It offered truly subversive notions of sexual freedom, drugs and pacifism, and the even more subversive idea of non-consuming.

The great "they" of fashion, whoever they are, waded right in. They took the most visible aspects of hippiedom and made them chic.

Suddenly Lord & Taylor was selling $300 beaded necklaces, designer pot pipes and custom-made rags, and every model had waist-length tresses. Secretaries started turning up in headbands and even stockbrokers' hair crept below the collar line. It was all very exhilarating.

For awhile. Although an individual's clothing may be a political statement and always is a personal message to the world, haute couture by definition is ephemeral and content- free, adopted for decorative purposes only.

It is whimsy, entertainment, art, craft and shock value, but its politics are purely conciliatory: the customer is always right.

Fashion, also by definition, changes with the season. As fast as long hair and beads became passe, so for the most part did the ideas that originally went with them.

The rebels, sincere as they were, had made a fatal error: they mistook new establishment hair length for new social policy. They were actually pleased as they disappeared into the mainstream.

Now any male still in a ponytail is making a political statement, sure enough, but nobody's sure about the message. Like some construction workers I have met, we are all free to smoke dope and wear long hair as we vote for Ronald Reagan.

Women's liberation was and is truly revolutionary. It has jarred the American power structure, traditional property-ownership patterns and the family system. But fashion, after an uncertain period that reflected society's indecision, has channeled the visible aspect of assertive women into the much narrower notion of women trying to be men.

Voila, the menswear look: pinstripes, flat shoes, neckties. The dress-for-success suit, when it first came out, caused gagging in most of the women for whom it is now a uniform.

This has paved the way (mark my words) for the return to the office of ruffles and frills, the rebirth of coyness and the re-legitimization of feminine dependency.

What have we got, in fact, in the tight, filmy new spring fashions? "Draped to be raped," said designer Karl Lagerfeld, in a remark that ought to be branded on his thigh.

The punk movement is another example. Born in working-class Britain of desperately unemployed and uneducated working-class kids, punk was and is truly nihilistic. Its raging songs advocate little but destruction, criminal and/or orgiastic behavior and sabotage, and its outward show is truly shocking.

You think orange Mohawks and safety pins as nose rings will never be fashionable? You haven't been to Great Britain lately. There are secretaries with green hair; the latest runway fashion shows featured off- centered makeup in great colorful slashes.

On this side of the Atlantic we are ahead of the curve: posh department stores are offering "face paint kits" for Christmas giving; upper-class high-schoolers bound for college already affect the punk look, almost before our disaffected youth can get hold of it.

The process is not yet complete, however, and punkishness is still haute couture as well as real rebellion. But we can be sure that nihilism is soon to be pass,e, just like hippiedom before it.

The implications of all this are fascinating. Democrats could infiltrate haute couture salons and bring back the preppie, young-Republican look in order to destroy it down the road. In a parallel development, trend spotters have noted the beginnings of a backlash against haute cuisine, with "real food" dinners of meatloaf and mashed potatoes even being served in Georgetown!

About two years ago, fashion took on war itself. Rushing in where George Shultz feared to tread, the needle brigade launched guerrilla chic: khaki evening gowns, camouflage cloth knickers and jeweled bandoliers.

The look was really big for children and especially big in Washington, where fans of Washington Redskins fullback John Riggins decked themselves out as "Riggo's Rangers." But it never really took off nationwide.

People who are pro-war are not yet numerous or vocal enough to be a real movement with their own "look" for fashion to react upon.

Instead, combat fatigues are mostly sported by Vietnam vets, and one can only blanch at the thought of their reaction on finding the badges of their suffering selling like hotcakes at Bloomingdale's.

But perhaps the vets can be brought around. After all, if the people who can afford to wear designer clothing start thinking war togs are chic, they may tire of the real thing as fast as they tire of the clothes.

That would bring peace into fashion again, and we could all go dig those old lovebeads out of the trunk.