With “Canova: Sketching in Clay,” the National Gallery of Art takes up similar themes with a close look at the Italian sculptor’s terracotta and plaster models for work that he (or his assistants) would later make in marble. In the late 18th and early 19th centuries, Antonio Canova probably made hundreds of these hand-modeled “sketches” and preparatory works, and the museum has assembled about half of the 60 or so that have survived.

It is hard to imagine a starker contrast between first and finished thoughts than that seen here. It is almost as if two entirely different artists were at work: one manic in his manipulation of soft clay into raw and writhing forms, the other equally obsessed with burnishing away any sign of tactile engagement or perfervid emotion. In clay, Canova is a fiery romantic. In marble, he is an icy classicist.

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In fact, that is not fair. Canova is Canova, no matter what he was working with. But he clearly used clay to different purposes than the visions he sought in marble. Clay was for exploring and inventing ideas, or for making small work that could be shown to patrons before it was enlarged, refined and finally chiseled into stone.

The most exciting of the works on view are the ones in which Canova seems to be improvising his first thoughts, rough forms that capture a sense of movement and visceral energy, often anguished, erotic or both. The spine of a tormented figure is little more than a gash, the gaping mouth and sunken eyes perhaps rendered with the stab of an oval-tipped blade, musculature defined by a few quick indentations in the wet material.

Canova was born in 1757 in a small town northwest of Venice. In 1779, he moved to Rome and around that time kept a journal that gives a brief, circumscribed sense of his work habits. Modeling in clay was a way to process the paintings and sculpture the young man was discovering in the art metropolis of the Western world. It was also an apparently nightly activity. After eating supper, Canova would retire to his room and think in clay, like a musician strumming his guitar both aimlessly and purposefully in the dark.

Portraits of the artist often show him surrounded by the tools for scraping and incising clay rather than the tools for carving marble. Exhibition curators C.D. Dickerson III and Emerson Bowyer suggest in a catalogue essay that the tactility of clay delighted and inspired the artist, even though most of these works were not meant to be exhibited. The bulk of the work his studio produced in marble was done by assistants and employees, before the artist added his final touches to the exquisite stone surfaces.

Writers on aesthetics in the age of Canova compared modeling in wax or clay to the sketches artists made before finishing a picture in paint. The critic and philosopher Johann Joachim Winckelmann wrote, “As the juice from the first pressing of grapes makes the best wine, so the genius of an artist is displayed in all its naturalness and truth in works in soft material or on paper.”

This privileging of first thoughts as the most authentic appeals to our contemporary psychological understanding of creativity: Inspiration is everything, while editing is drudgework. In both this exhibition, and the Met’s broader look at unfinished work, the challenge for viewers today is to step outside that limited understanding of the creative process. Finishing a work, refining it and editing it are equally important, and finished works express different but no less valid ideas than improvised ones.

That can be difficult with Canova, whose work in marble often feels as if it is clad in the armor of perfection. It is demure, polite and perfectly dressed. Faces wear masks, while bodies are supernaturally beautiful, draped in miraculous swaths of flowing fabric. You are simultaneously aware not just that the skin looks soft, but also that the skin is made of stone yet still looks soft. The virtuosity of the carving is inseparable from the enjoyment of the illusion.

This exhibition is focused mainly on the works in clay but does include a few finished works in marble, among them Canova’s seated portrait of Napoleon’s mother, Letizia Bonaparte, known as Madame Mere. Clay studies, and a larger half-size plaster model, show the evolution of the portrait. Her position in the chair becomes more relaxed yet confident, the ease a product of her elevated status and an embodied wisdom learned through the rigors of life. In marble, her face becomes individuated and engaging, and you can hear her sardonic response to her son’s success: “Let’s hope it lasts.”

In clay, you can see the marks of Canova’s hand, in some cases finger and thumbprints, plus a sense of the material caught in the moment of its manipulation. This reads to us as a sign of life, as if the energy of the artist’s hands has been transmitted and perpetuated in the clay itself.

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In one particularly evocative small clay sculpture, two figures that may represent a satyr and a nymph are embracing. Their bodies, and the earth beneath them, have been scored, likely by the metal tines of a fork-like tool. The hatching pattern suggests an energy arising from the earth and animating both bodies, rather like the patterned fields and skies of a Van Gogh painting suggest some latent, feverish power that makes air and matter quiver with equal intensity.

This sculpture may also represent Cupid and Psyche, the subject of one of Canova’s most revered finished works in marble. If so, it is a way station far from the final product, in which the arms of the prostrate Psyche frame an elegant circle around the head of the winged Cupid, who seems to have alighted only momentarily to kiss the dying princess. Any uncertainty about whom these clay forms represent is only part of the pleasure they give.

In clay, Canova creates figures who both precede and transcend subject matter, elemental forms that have both the specificity and anonymity of figures we encounter in dreams. Adam and Eve mourning the dead Cain could also be Oedipus and Antigone mourning the dead Eteocles and Polynices, two subjects also modeled by Canova. In clay, secular and sacred and myth are irrelevant distinctions, and even gender becomes a bit fuzzy.

To modern eyes, this reads as an appealing universality, achieved through abstracting the particulars into intimations that are left up to the viewer to resolve. Within a century, Rodin would be making large public work, carved in stone or cast in bronze, that followed many of these same aesthetic promptings. In the early 19th century, it would have been an affront to Canova’s public, his patrons and his sense of professionalism to pretend that his first ideas in clay were fully finished, independent works of art.

And there is the challenge of this show, a welcome challenge, not just to enjoy these studies in clay, but to enjoy them in a particular way. This exhibition does a good job of showing the evolution of Canova’s ideas as expressed in clay, but mostly leaves unaddressed the larger question of what it meant to finish the work, the process whereby private thoughts become public works, what “finishing” the work added to the original nexus of meaning expressed in the clay forms.

It is easy to think that the finished work was a kind of luxury good, or status symbol that diluted the original, more authentic, improvised artistic inspiration. It certainly cannot be the case, but why? Madame Mere, in marble, looks as if she could whisper the answer in your ear. It would be something like: One does not go out dressed in clay, my dear.

Canova: Sketching in Clay Through Oct. 9 at the National Gallery of Art. nga.gov.