Cultural concepts are always fuzzy, but that doesn’t make them useless. We may never know the exact beginning or end of Romanticism or the Gilded Age, or where lies the line between art and entertainment, or what distinguishes great talent from genius. But that doesn’t make those concepts hollow, just fluid and approximate.

A new entertaining and insightful exhibition at the Smithsonian’s National Portrait Gallery confronts one of the most dynamic and hard to define concepts in American cultural life — the cool. “American Cool” broaches its subject through photographs of people who helped define and embody the cool since before the idea had even taken definite form, to the current day when it is highly questionable if the “cool” is still meaningful. If you want to know how porous the category is, consider all of the following, officially inducted into the realms of the cool by this exhibition: Walt Whitman, Frederick Douglass, H.L. Mencken, Buster Keaton, Jackson Pollock and Susan Sontag. They join artists, entertainers and celebrities who are more traditionally and obviously defined as cool: Lester Young (who plays the central historical role in defining and promoting the idea of cool), Humphrey Bogart (the first and greatest mass-market embodiment of the cool) and Jack Kerouac (who helped export the cool from jazz to broader countercultural application).

To govern what seems at first like a highly subjective free-for-all, curators Joel Dinerstein and Frank H. Goodyear III laid down a four-part test for each of the 100 people included. First, they must have made an original artistic contribution, with a signature style; second, they must have in some way been rebellious or transgressive; third, they must have iconic status; and fourth, they must have left a significant cultural legacy. But even those parameters can’t contain the many things we think are definitional about the cool, the aura of mystery, the stoical indifference to criticism, the attitude of self- possession, and seemingly superficial yet important questions of dress and personal style. In a catalog essay accompanying the exhibition, Dinerstein piles on with yet more things that are the opposite of cool: “To be cool is not to be nice or good or heroic; cool is the opposite of innocence or virtue. Cool has an edge and a dark side: to be cool is not to strive to be fabulous . . . or saintly.”

Dinerstein is, among other things, a scholar of jazz, and Goodyear has a degree in American studies, and so they present the cool as essentially a pop culture phenomenon, and distinctly American. Other cultures have similar ideas — nonchalance, sangfroid, sprezzatura — but they are not “cool.” Sprezzatura dates back to Castiglione’s “Book of the Courtier,” which prized a seemingly effortless virtuosity in all things, from art to social behavior. Sangfroid is distinctly French, a sense of composure and equilibrium, especially under fire.

These are, according to the curators, concepts derived from aristocratic entitlement, whereas American cool is generally working class, an “earned individuality” rather than an inherited sense of self-worth. Perhaps, though the aristocratic definition of these ideas was breaking down around the same time that this exhibition posits the origins of the cool. Walt Whitman — the first personality featured in the exhibition, which calls him “the guiding light of American bohemia” — published “Leaves of Grass” in 1855; in 1844, Alexandre Dumas began serializing “The Count of Monte Cristo,” in which a self-made working-class young man assumes an aristocratic name and character to exact revenge on his enemies. Few characters in literature are more suave, self-possessed, disciplined, eccentric and alluring — in a word, cool. And none of that was technically inherited.

But the authors have a point. In America, at least, cool is distinctly lower or middle class, reflecting its origins in African American culture, where it was a compensation mechanism for living under the brutal regime of racism. When Lester Young said “I’m cool,” writes Dinerstein, “it meant ‘I’m keeping it together in here against invasive social forces.’” Frederick Douglass, whose oratory was fiery, not cool, merits inclusion in the exhibition because, according to Goodyear, he used a carefully constructed photographic identity to challenge preconceptions about race and African American men. “Though he lived prior to cool’s popularization, his cultivation of this mask of stylish stoicism presaged the rebellions of others who sought to live within yet also apart from the mainstream.”

Stylish stoicism is an excellent phrase. But as the exhibition charts the historical evolution of the cool, “stylish stoicism” fits less well with the later, countercultural appropriation of the cool. Transgression becomes more important than style and talent, even directionless, purposeless, self-destructive transgression. When Marlon Brando’s character in the 1953 film “The Wild One” is asked “Hey, Johnny, what are you rebelling against?” and he answers, “Whaddaya got?” — the cool has clearly gone through a critical permutation. Brando is, of course, featured in the exhibition, looking sad, innocent and distracted in a 1950 image by Philippe Halsman.

The exhibition situates this evolution of the cool in the period from 1960 t0 1979, but it was clearly nascent earlier than that. “Cool & Counterculture: 1960-1979” is one of the most fascinating and provocative stretches of the show, including diverse figures from Andy Warhol and Paul Newman to Jack Nicholson and Bill Murray. One particularly evocative juxtaposition places a reprint of a 1966 photograph of Muhammad Ali with his fist thrust directly into the camera lens next to a 1971 image of Clint Eastwood, holding an enormous handgun in a visually analogous confrontation with the viewer. Clearly the concept has become elastic if it can encompass a black boxer playfully enacting an aggressive identity and a white actor appealing to working class (and often racist) fantasies of public order and vigilantism.

The exhibition ends with what it calls “The Legacies of Cool: 1980-present.” Here we find David Byrne (definitely cool), Steve Jobs (geek cool), Willie Nelson (long-haired, hippie stoner cool) and Jon Stewart (really?). Perhaps the most telling image is a photograph of skateboarder Tony Hawk, doing a move in his kitchen. His young son sits at the kitchen counter while his wife cradles a baby. The dishwasher is open, there are decorative plates above the standard-issue wooden cupboards and the whole thing screams suburbia. The wall text notes his success as an entrepreneur, with a popular line of sports equipment and a video game series. In an interview Dinerstein acknowledged that old ideas about transgression may not be so important any more. What matters now is “new strategies for individuality.”

The exhibition is heavily focused on celebrity, though there are some surprises (the Hawaiian surfer Duke Paoa Kahanamoku appears in a circa 1915 photograph). But as the concept of the cool becomes more and more open-ended, it’s unfortunate that it isn’t extended further beyond popular music and film. Susan Sontag definitely seems a worthy inclusion, but are there no classical musicians, ballet dancers or post-structuralist philosophers who are cool? Was the great violinist Jascha Heifetz cool? Or just cold? Was the literary theorist Jacques Derrida cool? Or just inscrutable?

It’s also unfortunate that the cool isn’t treated more critically as a concept. There is a dark side of cool, dumb, impassive, disengaged, dismissive and even violent (see the oeuvre of Quentin Tarantino). Think of the phrase “too cool for school,” and all that implies. Although “geek” cool makes a brief appearance in the person of Jobs (on a motorcycle), the rise of geeks and nerds as positive cultural archetypes may be a sign of a healthy resistance against the stupid underbelly of cool. As much as this exhibition celebrates the American invention and export of cool, one might argue that the fetish for cool is really just a sign of our overwhelmingly narcissistic provincialism.

Dinerstein and Goodyear would, no doubt, argue strenuously with all that, as a misinterpretation of the concept. But again, that’s the beauty and appeal of cultural concepts: They are as useful as they are spongy, and all the more fascinating for their essential fluidity.

“American Cool” opens at the National Portrait Gallery on Friday. For more information visit