Who is your favorite painter? Jed Perl, the art critic for the New Republic, responds: “Whenever I’m asked to name my favorite painter I reply, without a moment’s hesitation: ‘Watteau.'”

Come again? Watteau? A confection of the ancien regime, Jean-Antoine Watteau was born in 1684 and lived a mere 36 years, dying in 1721, the master of the fête gallant and the portraitist of the commedia dell’arte. It’s not the answer you might expect to come out of a tough-minded critic on the contemporary scene.

But “Antoine’s Alphabet” (Alfred A. Knopf, 224 pages, $25.95), a brief, deeply felt follow-up to “New Art City,” Mr. Perl’s muscular account of the New York art world at mid-century, defies expectations. “I may be perceived as being somewhat sardonic,” Mr. Perl writes in his introduction, “or ironic, or even impish when I say that Watteau is my favorite painter, as if I were trying to mock the question, or were hiding my true feelings behind a dandyish façade.”

Far from retreating from reality, however, Mr. Perl finds engagement with the present moment through Watteau. “This artist who said hardly anything about his paintings and struck most of his friends as something of a mystery man took as his essential subject the invention of self-consciousness, the struggle to feel fully alive.” While this critic who rails against the commercialism of the contemporary art world makes no mention of today’s art politics, one cannot help but see a counter-example in the fancy-free Watteau to the predetermined art that now fuels record sales at Sotheby’s and is bought up by the oligarchs of Beijing, Moscow, and New York as cynical investments.

In its best sense, Mr. Perl sees the birth of the modern in Watteau’s figures awakening to their own imperfections. “Watteau’s young people seem to want, above all else, to feel at ease, somewhat at ease, in an uneasy world,” he writes. In work such as Watteau’s famous painting of “Gilles,” the contemplative clown, Mr. Perl finds “doubts,” though they are “clothed in the commedia dell’arte lightness of an improvisation or a folly.” He calls Watteau “The man who practically invented the bohemian imagination.” In his aesthetic wanderlust, his reveries of vagabond performers, Watteau did not follow the dictates of the church or a rich clientele, but pursued art for art’s sake, the prototypical modernist.

“Antoine’s Alphabet” is not a generic appreciation, or a typical brief history. Mr. Perl presents his volume as a primer, arranged as an alphabet: A is for actors, Anthony, and Art-for-Art’s-Sake; B is for Backs, Beardsley, and Beginnings, and so on. “The power of certain great paintings,” Mr. Perl writes, “no matter how much self-conscious craft the artist brings to the work, is the quality of a daydream, an orchestration of elements whose meaning remains ambiguous or contradictory.” Mr. Perl follows the same daydreaming impulse in the footloose presentation of his book. Each definition examines an aspect of Watteau while also offering a meditation on the Watteau-esque — a glint of history, an inspiring theme, a personal rumination. For example, we get:

Beginnings: So much begins with intense yet fragmentary experiences. At the start of a friendship or a love affair there may be some acute recognition, some striking sliver of experience, although initially it’s impossible to know where this will go, if indeed it will go anywhere. …

Cappricio: Watteau is recklessly capricious, a weaver of arabesques who embraces the grotesque, not in the sense of gothic horrors but in the sense of curious divagations and transmutations.

My favorite is “Enough: One day in his studio, D said to me: ‘I’ve always had enough. I’m tall enough, I’m good-looking enough. I have enough money.'” Enough said.

The literary games on display might, in the hands of another writer, come off as an indulgence, but here they serve a clear purpose: They not only describe the mood of an artist, but they let us inhabit his sensibility. The book speaks in the serendipitous language of Watteau’s canvases — serendipitous, additionally, because we know very little about Watteau outside of his work. “At the time of his death,” Mr. Perl writes, “Watteau was a famous figure in Paris, with his share of devoted friends. The nuggets of reliable information about his life, however, are few and far between, so that every attempt to construct a biography from what scattered facts there are appears bound to fail.”

Mr. Perl is not the first to take an unorthodox approach to his history of this artist. Watteau’s most successful biography, Mr. Perl recounts, came out of a fictionalized memoir by Walter Pater called “A Prince of Court Painters,” which was published in 1885, and which, “in assembling and readjusting some of the facts of the artist’s life … constructs a fable about Watteau that is truer to what we feel when we’re looking at his paintings and drawings than a more straightforward account could possibly be.” In his story, Pater “imagines himself as a part of the eighteenth-century Pater family that actually knew Watteau.”

Mr. Perl here does something of the same, going one step further. Rather than merely imaging himself an associate of Watteau, he becomes a Watteau in print. So am I crazy to see a resemblance between the portrait of Watteau drawn by François Boucher, reproduced in the book, and the photo of Mr. Perl on the dust jacket? Mr. Perl constructs his book around the arabesque, the daydream, and the fragment. “Much of the fragment’s fascination has to do with its delicious air of possibility,” he writes, “for a fragment provokes a partial experience that can leave us with a heightened awareness of what we are missing.”

Many of those “experiences” are personal for Mr. Perl. But that does not mean they are artful dodges. Rather, Watteau allows this trenchant thinker — arguably our best art critic writing today — to show, for once, his own hand. We see the painted ceiling of his boyhood home in Brooklyn, and are given a manifesto of his desires in paint: “What I really want from art is a variety of qualities, a multiplicity of qualities, a kaleidoscope of qualities, the unpredictability of qualities, qualities that are as varied as the artists who create the works of art.”

In its oddity, the book gambles and wins. I hope that “Antoine’s Alphabet” will become a cult classic among artists, a call to caprice, in the way that Dave Hickey’s “Air Guitar,” a critic’s libertarian riff, gave license to a generation of artists to forego politics for the rapture of the marketplace. In this capricious cross-pollination of history and memoir, Jed Perl does not merely show us how to live. Like Watteau, he illuminates the struggle to feel fully alive.

Mr. Panero is the managing editor of the New Criterion.