In her book Le Deuxième Sexe, published in 1949, novelist and philosopher Simone de Beauvoir examined how patriarchy and social constructions systematically oppressed women. Legendary designer Yves Saint Laurent deeply understood that appearances intricately supported these power games; clearly, men in their business suits had monopolized social and economic power. Mr. Saint Laurent’s revolutionary fashion design sought to undermine these norms, in turn helping to create a modern woman of power and grace, forever shifting the imbalances de Beauvoir illumined.

A stark white projection of the YSL logo poured across the dark cement floor of the gigantic hall of the Grand Palais in Paris last March. Designer Stefano Pilati was presenting his new fall collection for the house. At the smaller Petit Palais–across the wide Avenue Winston Churchill–final preparations were under way for another show opening in a few days, the Yves Saint Laurent Rétrospective, the largest exhibition ever mounted for a single fashion designer, just two years shy of his death.

Despite four decades of design, Mr. Saint Laurent’s contemporary relevance was striking. Mannequins modeled exactly 300 haute couture outfits and seven ready-to-wear looks, all fully accessorized and each numbered according to a specific theme, separated into 15 sections. Photographs, including the nude portrait by Jeanloup Sieff for a men’s fragrance campaign, design sketches, video reportage, film shorts, and runway footage, flanked the work, contextualizing the designer’s timelessness.

Mr. Saint Laurent’s annulment of female constraints began with “Trapèze,” the first collection for Christian Dior in 1958. The collections featured a charcoal wool grey narrow shoulder flare dress with a spread collar and tied with a bow, titled “Bonne Conduite,” as well as a flowing strapless organza gown named “Bonne Nuit.” The looks abolished Mr. Dior’s infamous New Look legacy of its rigid hourglass silhouettes, its soft shoulder jackets with tight waistlines, reminiscent of the corseted Belle Époque-era at the turn of the 20th century.

The Rétrospective further featured looks that shattered female fashion conventions–inventive, feminized alterations of the male suit or peacoat. Examples include the 1962 navy wool caban and white shantung pants; ‘66’s smoking tuxedo and sheer blouse; ‘67’s double breasted pinstripe wool gabardine with white shirt and black tie; ‘68’s cotton “saharienne” with Bermuda shorts; and ‘69’s violet jersey jumpsuit.

These “male” garments imparted power and authority, and a woman choosing to wear a business suit, albeit one with a seductive sheet blouse, in 1967 French society, would radically alter her position in the prevalent social norms. There was seduction, but also freedom.

Mr. Saint Laurent additionally found other ways to break societal boundaries. Decades before fashion’s total obsession with Hollywood and the art world, he married his fashion to cinema and celebrity with breakthrough designs for the young Catherine Deneuve in 1967’s Belle de Jour, a film by Luis Buñuel. His nods to art included the 1965 color block sheath, dubbed the Mondrian dress. This statement was later followed by the Russian Ballet Opera show in 1976, the Picasso blue period dresses in 1979, and the Matisse dress in 2002.

And Mr. Saint Laurent did so with deft imagination. Never leaving his studio, he created the gold lamé Russian Cossacks coats in 1976, the Spanish bullfighter look in 1979, and the feathers and tiger print dress of Africa in 1990–all the result of imaginary trips to these exotic and faraway places.

Still, high culture was not Mr. Saint Laurent’s singular inspiration. His 1971 flea market collection, homage to 1940s Paris during the German occupation, despite the scorn of critics, created a street credibility that younger women could relate to. The collection included outfits like the print short skirts made of curtain materials with broad shoulders, a green chubby fur coat, or a navy double-breasted coat with shorts and head turbans.

I had the opportunity to attend many of Mr. Saint Laurent’s shows–couture and ready-to-wear–in the decade prior to his retirement in 2002. Perhaps those weren’t his best years, but I could surely sense the work of a master couturier, often far removed from the trendy and fast fashion au courant of the time. The show I saw on July 12th, 1998 on the field of the brand new Stade de France in Saint Denis, a suburb on the outskirts of Paris, was the most memorable of all. Moments before the World Cup final between France and Brazil, in which the French won 3-0, Mr. Saint Laurent unleashed 300 looks on 300 models onto the field in the first live worldwide television broadcast of a fashion show, a feat still unmatched today despite the ease of live online streaming.

If Mr. Saint Laurent’s clothes reflected the times, they also reflect our current cultural landscape. The past several years have felt like a replay of the dioramas inside the Petit Palais: Dries van Noten’s usage of ornate fabrics from India echo the ornamentation; last fall, Phoebe Philo championed chic minimalism in her first Céline show; Phillip Lim and Stella McCartney lead this fall’s omnipresent utilitarian chic; and nearly everyone has military elements and trench coats.

What clearly stands out from Mr. Saint Laurent’s 40-year oeuvre is the pace by which he produced the collections. Innovative clothes are not possible if dictated by the strenuous seasonal output of six collections per year. How can current designers keep up and still leave a meaningful mark? Surely, if fashion of the past is more interesting than it is today, it is simply because designers then had the necessary time to truly design, often impacting much broader social and economic infrastructures.

Through August 29, 2010 at Petit Palais, Paris. YSLRetrospective.com.