The small genre masterpieces of the French painters of the 18th century are so frothy, so delightful, so charming and sometimes so naughty that it is hard to associate them with such weighty themes as philosophy and revolution.

But an extraordinary exhibition of these paintings, currently at the National Gallery of Art in Washington, makes the persuasive case that these great artists, no matter how frivolous their subjects often seemed, reflected the philosophical ideas of the Enlightenment that coursed through France during these decades and laid the groundwork for the French Revolution. A visitor does not need to know all this to savor these wonderful works, but the historical dimension adds a special flavor that helps bind the artists together.

The show, which began at the National Gallery of Canada in Ottawa and goes on to the Gemaldegalerie of the Berlin city museums after closing in Washington on Jan. 11, is titled “The Age of Watteau, Chardin, and Fragonard: Masterpieces of French Genre Painting.” The curators have headlined the names of the three best-known French painters during these years, but the exhibition, in fact, consists of 108 paintings by 27 artists. It is trying to show the works of an era, not a trio.

These paintings are not meant to be subversive. They do not expose the evils of the Old Regime. But when Jean-Antoine Watteau painted young couples in outlandish costumes flirting in gardens, and Jean-Baptiste-Simeon Chardin painted an eavesdropping maid just back from the market, and Jean-Baptiste Greuze painted the warmth of a family hailing a marriage contract, and Jean-Honore Fragonard painted a half-naked young girl frolicking with her dog, they were breaking with tradition.

During the 70-year reign of Louis XIV, the “Sun King” who died in 1715, artists were expected to paint huge canvases replete with serious scenes from history, literature or the Bible. These tended to glorify the church and the monarchy. Even after Louis XIV died, the French Academy of Painting and Sculpture extolled these historical paintings and looked down on everything else.

Genre paintings -- scenes of everyday life -- were regarded by the academy as the lowest of the low. Yet as Philip Conisbee, the senior curator of European paintings at the National Gallery and the former curator of European painting and sculpture at the Los Angeles County Museum of Art, explains, “There was a good market for them.” Genre paintings sold for some practical reasons in 18th century France.

After the reign of Louis XIV, the royal court moved from Versailles to Paris, forcing the nobility and rich bourgeoisie to build townhouses for themselves with walls that required smaller paintings than the usual historical extravaganzas. The royal treasury dwindled, allowing fewer commissions for the large works admired by royalty. On top of this, Conisbee says, “an elite, sophisticated, urbane society” developed in Paris that favored intimate paintings rather than massive murals of historical propaganda.

Two innovations helped to expand the popularity of genre painting. In 1737, the academy staged its first salon, showing the works of artists to the general public. Since there were no museums in those days, the salons represented the only chance for most French citizens to see a distinguished painting. Although the Academy still favored historical painting, many artists showed their lowly genre paintings as well, and these caught the fancy of the salon visitors. In another innovation, art criticism emerged: Intellectuals began writing about the paintings of the salons in newspapers and pamphlets and praising the genre artists.

But there was a deeper reason for genre painting’s popularity as well. The writers of the Enlightenment -- led by Voltaire, Denis Diderot and Jean-Jacques Rousseau -- insisted that knowledge would liberate the minds of individuals and enable them to enjoy happiness on their own. Happiness did not depend on blindly following the strictures of the church and an absolute monarchy. This generated a new mood of concern for humanity and individuality -- a mood that fostered genre painting.

The exhibition opens with nine works by Watteau, the painter “who set the tone for much of the 18th century,” according to Conisbee. Watteau came from a town in northern France bordering Flanders, where genre painting had been popular for many years, and he turned his back on historical painting early in his career. He kept so far from glorifying the monarchy that one of his early paintings, “The Portal of Valenciennes,” shows dispirited and weary French soldiers resting after a defeat.

Watteau, who died of tuberculosis in 1721 at age 37, was best known for what the French called fetes galantes, festive and fanciful scenes of the rich at play, sometimes wearing exotic costumes as if they were actors onstage. In a typical Watteau painting, “Venetian Pleasures,” one couple dances to bagpipe music while other couples flirt in a lavish garden watched over by a lifelike, seductive statue of Venus.

The Enlightenment philosophers preached the importance of nature, family life and homespun, simple virtues, and the works of younger genre painters began to reflect these currents. The most important was surely Chardin, who is represented by a dozen paintings in the exhibition. Chardin, a Parisian who said, “One uses color, but one paints with feeling,” is the first significant genre painter to explore the world of the French servant class.

This world of the servant, as Chardin painted it, was orderly, far from repressed and replete with enigmatic narrative. In his “The Return From the Market,” a remarkable painting much like a Vermeer, a servant has returned from the market with loaves of bread and a butchered lamb. Her head turns as she eavesdrops on a younger servant talking with a partially obscured man at the door. There is a story here, but we, of course, do not know what it is.

Chardin was very popular. The demand for “The Return From the Market” was so great that Chardin painted four versions of it. Whenever his painting attracted crowds at the annual salon, engravers made prints that would circulate throughout Europe. He was prized by royalty throughout the continent. Catherine the Great of Russia owned five of his paintings, and the version of “The Return From the Market” in the Washington exhibition was purchased originally by the Prince of Liechtenstein.

Greuze, a generation younger than Chardin, was born in the Burgundy region but studied in Paris. He started as a history painter but soon found that genre painting offered greater rewards. He was much more moralistic than Chardin and soon became a hero to the writers of the Enlightenment. Diderot, the novelist, Encyclopedia editor and father of art criticism, once wrote: “I really like this Greuze fellow.... To begin with, genre appeals to me; it is moral painting.... Take heart, Greuze, my friend, and practice morality in painting.”

There is no doubt that he did. The exhibition has 11 works by Greuze (more than those by Watteau and almost as many as those by Chardin), and the moralistic tone is obvious. Unlike the healthy, ordered and satisfied servants of Chardin, Greuze’s servants can be slovenly, brought down by their sins, as in the painting “Indolence.” His scenes demonstrate the strength and warmth of family life, whether the family is portrayed in celebration (“The Marriage Contract”) or caught in adversity (“Filial Piety”).

Fragonard, who came from Grasse in southern France, is the most represented artist in the exhibition, with 15 paintings, including a pair worked with his sister-in-law, Marguerite Gerard. Fragonard did not continue the moralizing of Greuze but returned to the fashionable and amorous world of Watteau, a painter who died before Fragonard was born. Fragonard, according to Conisbee, created “the most celebrated erotic images of the century,” and these scenes were sought by wealthy collectors. Madame Louise d’Epinay, the hostess of a well-known Paris salon, dismissed him as a painter who “wastes his time and talent earning money,” but his paintings have remained popular for more than two centuries.

When a visitor to the exhibition takes in “Young Girl Playing With Her Dog,” which portrays a nearly naked girl lifting her legs and a dog at the same time, it may be difficult to discern the painting’s relation to the Enlightenment. But Conisbee says Fragonard reflected Enlightenment thinking by depicting “the sexual drive as a continuous force in nature.” The fashionable upper-class world portrayed by Fragonard was shattered by the French Revolution in 1789, and the painter died impoverished in 1806.

In their catalog introduction, the curators of the exhibition -- Conisbee; Colin B. Bailey, chief curator of the Frick Collection in New York; and Thomas W. Gaehtgens, chairman of the art history department at the Free University in Berlin -- point out that the artists in the show are usually studied and exhibited separately. By putting them together, the curators say, the exhibition is able to chart the development of an art form -- genre painting -- that served in part “as a constantly changing mirror of Parisian life and culture” in the 18th century.