Fashion designers always are in the difficult position of having to prove their worth. An auto executive can commence production of a flashy off-road vehicle whose sole job is to impress the neighbors and no one bats an eye. The owner of a sports team can happily pour money into a losing franchise for years and folks just write it off as the cost of doing business. And film studios regularly spend millions on embarrassingly bad movies and rarely does anyone question the viability of Hollywood.

There is, perhaps, no other group of professionals who must reconfirm their reason for being on a seasonal basis. Fashion houses regularly must fend off complaints that they are out of step with consumers. They must struggle to remind cultural critics that their work fills a niche just as surely as do films and plays. They must conjure evidence that their clothes, at their best, can reflect both conscious and subconscious shifts in society.

But each season designers rally to the cause, reflecting, exaggerating, distorting and even glamorizing our foibles and issues--ostentation, self-indulgence, female empowerment, drug addiction, the inevitability of multiculturalism.

Of course, there is not always greater meaning in a tight skirt and a pair of stilettos. But hindsight reveals that fluctuations in fashion invariably come to fit comfortably into some grand cultural statement like a piece in an elaborate jigsaw puzzle.

Marc Jacobs is one of the few American designers who regularly has an opinion strong enough to add another detail to the picture. Jacobs, who presented his spring 2000 womenswear collection Monday night in New York, offered hints of Western style, '70s mod, a girlish femininity, a London hipster rhythm and the almost hick sex appeal that still can be found in tight-fitting designer jeans.

The eye takes time to adjust to Jacobs's vision, but that is what the best designers require. Their work shouldn't be too familiar. It shouldn't wash over folks without causing a stir. His silhouettes are tricky. The tight jean-style trousers, for instance, have sunbursts of pleats on the back pockets. The "flood" cuffed pants rise high on the calf, falling lower than capris but too high to be considered cropped.

There are sweet sundresses in floral prints dusted with sequins or inlaid with quarter-size circles of doily lace. And there are sailor blues adorned with matte paillettes that march in uniform precision around a jacket hem or up the side of a pant leg.

Already Jacobs and other designers such as Michael Kors, John Bartlett and Tom Ford have helped focus attention on such simple shapes as dungarees, T-shirts and A-line skirts. They have reinterpreted American iconography. Recalling the sort of simple sex appeal inherent in well-fitting jeans, they have redrawn the line separating femininity and masculinity after all these years of androgyny, as defined by the oversize camouflage clothing embraced by a generation of young men and women.

Jacobs's collection had a clear-cut point of view. To be sure, the often repetitive collection had its flaws, with some pieces so studiously crafted that they looked forced, costumelike. But as a whole, Jacobs offered proof of why he continues to be one of the most-watched American designers. The evidence, unfortunately, is not in his sales receipts or the number of free-standing stores. Instead, Jacobs's worth, as underscored this season, is in his ideas and in the fact that after his earlier experimentation with slim jeans, schoolgirl details and mid-calf chunky boots, all of these ideas can be found in places such as the Gap and Nine West.

Often designers prove that fashion is no more exempt from thoughtless slights and inconsistencies than are other forms of expression. At the BCBG presentation Monday night, designer Max Azria used his program notes to reflect on diversity. Indeed, on each seat was a small book of photography by Steve McCurry depicting ethnicities from around the world, suggesting that the collection would be a celebration of cultures.

Unfortunately, however, Azria's runway was mostly devoid of the diversity that inspired his collection. He slipped into the inescapable fashion cliche of using the usual crop of blond and brunet models who dominate the covers of the glossies.

The clothes were a lyrical medley of embroidered organza dresses, crushed satin jackets and short shoulder bags stitched out of embellished burlap. At times the collection continued this fall's overwhelming interest in hippie style and haute bohemia; at other times the line was slick and propelled by young socialite glitz.

But it was not so much the inconsistencies in styles but rather the conflicting messages that were problematic. Azria's self-described celebration of cultural awareness looked more like tourists browsing a souk, determined to find a bargain or the "it" piece of the season rather than any sense of authenticity. Of course, such casual cultural slights are common everywhere from TV to film. Fashion is only as enlightened as the culture out of which it is created.

The spring collections' heavy emphasis on party dresses and evening attire reflects optimism about the economy. Indeed, the veteran Oscar de la Renta showed a collection--bold floral prints and embellished silk and cashmere sweaters--that was imminently wearable but spoke proudly of wealth and a lifestyle of leisure.

It is wise of de la Renta to experiment with denim, pairing it with embroidered leather or a white pique evening gown. There is a whole new crop of young millionaires who can afford to indulge in pricey designer clothes. His collection, in fact, seemed to be divided into two: There were the sheath dresses and matching coats for his die-hard clientele, the older ladies who would prefer not to reveal their arms and like their hemlines to fall to a reserved length. But there was also the denim, the thigh-high silk shorts and the low-cut halters for the younger woman who is happy to be a bit of an exhibitionist.

The fashion industry long ago moved on from the minimalist style of evening wear; a simple sheath no longer is quite jolly enough. There is a '50s feel to much of the new evening wear, a sort of swinging, cocktail-party style in which comfort gives way to a look that bridges the gap between the ladies who remember wearing white gloves to lunch and the young women who could be their daughters.

At Badgley Mischka's show Monday evening, the skirts were often A-line, with just enough fullness to conjure visions of couples twirling about on a shimmering marble floor as a big band blares out upbeat jazz. There was plenty of glitter, but instead of reserved shades of platinum and urbane geometric patterns, the emphasis was on dresses crowded with candy-colored blossoms sprinkled with sequins and bubblegum-pink cocktail ensembles sparkling with silver paillettes. Quite often the Badgley Mischka trademark youthfulness was defined by garish pastels so sweet as to cause the incisors to ache.

Designer Linda Allard for Ellen Tracy once again showed her skill at taking a sensibility of a season--in this case, cropped trousers, cheerful colors, bared midriffs and glitz--and translating it into clothes that are welcoming and unapologetically commercial. She was at her best this morning with her ankle-cropped trousers in styles ranging from the casual comfort of chinos to those brushed in a delicate watercolor print of lilac. She tops her slim-fitting trousers with short jackets, wrap blouses and crisp tunics in colors such as tomato red, periwinkle blue and tangerine.

Allard has said one of her challenges is convincing retailers to stock more than just her suits, so appreciated by working women. And indeed, in this collection, she made a strong argument for her more adventurous separates, particularly the cropped tops and low-slung trousers that, paired together, revealed a wide expanse of abdomen. The style looked terrific on her young models with their concave tummies, but these demi-shirts are an all-or-nothing proposition: One either has the abs to carry them off or not.

As quintessentially American designers such as Allard present their collections this year, the European sensibility seems increasingly obsolete. The designers who have shown so far are presenting clothes that are logical. One never has to struggle to envision where the clothes could be worn. Perhaps designers such as Donatella Versace lead far more intriguing lives. Perhaps they have the ability to create occasions for their metallic gold micro-minis.

But if there is any overwhelming sense so far in these collections, it is that spring 2000 is not a season for either the sublime or the ridiculous. These are times shaped by technology and the aspiration for logic, efficiency and ease. There is still room for the eccentrically beautiful, for the indulgent moment. But even then, such ostentation must be able to survive--without mockery--on a city street, not merely on a stage.

CAPTION: Above, Badgley Mischka's sequined top and swirly skirt; left, BCBG's embroidered dress by Max Azria.

CAPTION: A separate piece: Pantsuit from Linda Allard for Ellen Tracy.