There is a saying about building castles in the air: Once they are there, you have to build the foundations under them.

Therein lies the paradigm of the designer business, hardly a model Philip Johnson might recommend. And it is the simple reason why so many fashion castles fall. Tommy Hilfiger is the only designer to have succeeded by taking the exact opposite approach. There are no fantastical castles to dream on yet, just a firm foundation, as fit for a castle as for a suburban tract house.

Mr. Hilfiger is building with a new blueprint. His latest move backward to the top is creating an upper-end women's line, to be introduced on the runway in October, along with a women's fragrance, Tommy Girl. This week, he showed his lower-priced women's Tommy line to the retailers who had bought $45 million of it, sight unseen. It will be in stores on Aug. 1.

The stereotypical designer house (and its Gatsby-like inhabitant) invents needs concocted from extreme aspects of street life, or history. It whips them into a runway spectacle, as if to prove there is a vision, and then looks for a way to make the vision commercial.

Mr. Hilfiger said that his models would not look like heroin addicts, that he would not try to create artificial needs and that he did not care whether he saw his clothes at Le Cirque. That thinking, for designer fashion today, is subversive.

"Let's face reality," he said. "Everyone wants to be rich. So, why do something that creates such a risk that you may just lose in the next season? I want to win in the next season. I want to sell a lot of clothes to a lot of people. And the way to do that is to give the customer what she wants. You don't have to create something she's going to be afraid of, or won't look good on her, or something she can't afford."

The strength of that statement is based on a bankruptcy in 1977, when he owned a small retail business called People's Place.

"I don't want to design clothes for the museum and worry about paying the rent," he said. "I like the idea of having the wherewithal of doing whatever I want to do."

He has that. But pop icons (Mr. Hilfiger's status as that has been carefully engineered) always want to be taken seriously, a la Sharon Stone in "Last Dance."

Mr. Hilfiger took in $5 million as the Tommy Hilfiger Corporation's chief executive last year. And the public company saw a 46.7 percent increase in fourth-quarter earnings, to $17.9 million, compared with the same quarter a year ago. Despite all that, Mr. Hilfiger still feels compelled to face the not-always-friendly fire of the onerous women's runway. Until now, he's done it all on the strength of his men's-wear empire -- preppy clothes that rappers love, too -- and the men's fragrance, Tommy, distributed by Estee Lauder.

What "Rent" did at the Tonys, what "Braveheart" did at the Oscars, Mr. Hilfiger did last week at the Fifis, the fragrance industry's awards, sweeping five categories.

So, the prospect of his October show is enticing, because with the backward Hilfiger paradigm, it's castle-building time if he is ever to rise from being considered a brand.

By setting his sights on fashion -- as opposed to clothing, which has earned him his good name and his fortunes -- he runs the risk of revealing, in larger-than-life runway proportions, the undeniable banality that informs his esthetic. And it is a risk that could hurt even a house with a strong foundation: the wizard could be just a small man with a megaphone. The same model that gave us the Gatsby designer, after all, has also taught us to expect designers' runways to make us dream, not just to give us things to wear.

"I want people to walk out saying, 'Wow, I didn't know he could do that,' or 'Wow, I didn't know I'd see that,' " he said. "I think giving them the expected can be kind of boring because it is a show. Yes, I want to sell the clothes on the runway, but it is most exciting and challenging to give them a little bit of a surprise."

Still, he added, he has literally earned that right. "If you go out on the runway and create a collection that doesn't sell, and the risk of going out of business is high, you should have your head examined," he said. "But on the flip side of it, speaking from an artist's viewpoint, I can understand what drives a designer who just wants to create great pieces of art and then show them. Those designers should have a great business partner -- to convince them it's not a good idea."

He carefully describes himself as a "designer/businessman."

Meanwhile, one by one, other designers are slowly bringing out lower-priced, less-serious lines, as if it were a revolutionary concept that a designer suit might be purchased for less than four figures or that clothing might be machine washable. You can intuit what might be the expression on Mr. Hilfiger's face, compared in print with those of Scott Hamilton (in a Beatles wig), Billy Mumy (grown-up) and Alfred E. Neuman.

It is competing designers who should worry about his first Tommy women's collection.