Jean-Antoine Houdon took the measure of man in an age when man truly became the measure of all things. Arguably the premier sculptor of 18th-century Europe, he adapted the new empiricism of his day to the creation of startlingly lifelike portrait busts. Working from life-masks and death-masks and putting caliper to skull, he combined direct observation of a sitter with the precise quantification of his physiognomy. The oft-told story is that when John Paul Jones was disinterred (the American naval hero, not the Led Zeppelin bassist), the dimensions of his head were found to exactly match those of Houdon's portrait of him.

Houdon's portrait of Jones joins roughly 60 other busts, statues, and reliefs in plaster, terracotta, marble and bronze for "Jean-Antoine Houdon (1741-1828): Sculptor of the Enlightenment." The show opened last month at the National Gallery of Art in Washington, D.C., which bills it as the first international exhibition devoted to the sculptor.

The show features more than just portraits, however, including examples of the full range of the artist's career, from L'Ecorché (Flayed Man), executed while Houdon was studying in Rome (a work that was destined to become the standard classroom anatomical model), to Summer and Winter, the seasons allegorized as young girls, one hale and hard-working and appointed with a modish watering can, the other shivering and draped only in a shawl.

Houdon weathered the political upheavals of the French Revolution and the decades following, remaining in favor and sculpting both Louis XVI and Napoleon Bonaparte, as well as Jacques Necker, the finance minister whose dismissal sparked the storming of the Bastille; Antoine Louis, the physician who invented the guillotine; and astronomer and politician Jean-Sylvain Bailly, who lost his head to it.

The late 1700s saw the rise of the independent thinker and man of letters as culture hero, and it was in portrayals of this type that Houdon triumphed. Representations of Molire and d'Alembert, not to mention a pantheon of American founding fathers and Revolutionary War leaders -- Washington, Franklin, Jefferson, Lafayette -- herald an age shaped by new ideas.

Houdon's Diderot, which the young sculptor displayed at the Salon of 1771, a couple of years after returning from Rome, marked the first appearance of a unique method of rendering the sitter's eyes. "Carving the iris into the shape of a bowl," catalogue essayist Guilhem Scherf writes, Houdon "evoked the pupil by hollowing out a small depression in the bottom, and he left a section of material in relief along the edge of the iris to allow for the play of light and shadow and to simulate the liveliness of the gaze."

When viewing conditions are just so, an Houdon bust possesses an uncanny sense of vitality. But even more than paintings, which can carry their own sources of light, sculptures are extremely sensitive to their environment. If the lighting isn't quite right or if the viewer is too far away to be able to pick out subtle detail or so close that it registers as artifice rather than illusion, Houdon's signature technique can dissolve into intrusive gimmickry.

Where it works best is in a remarkable trio of portraits of Voltaire -- not the monumental full-length rendering created for Napoleon's expanded "Temple of Great Men" in the Panthon, but the more modest works of 1778 and 1780, which the writer had sat for shortly before his death, after returning to Paris from a nearly 30-year exile.

In their wry consideration of the era their subject helped prod into shape, these Houdons capture the Enlightenment's defining intellectual attitude: skeptical, rueful, witty and wise, filled not with the promise of a bright and glorious tomorrow but with the humbler and more sensible notion that the future might, if we put our minds to it, turn out somewhat better than the past.