Think of this book as a map. The land is vast and tumultuous -- a big, complicated country with jostling values, and always captivated by the glint of the new. The stakeholders here, as it happens, are American artists, and the language of contemporary art, like the country itself, is polyglot, alive to the influence of its immigrant voices.

For all of those voices there is an idea residing at the heart of the country: the idea of the representative, the one who reflects the many, or the many who reflect the many more. The word shares its root with a crucial art term, representation, which, in a general way, means a picture that captures, if only for a moment, the essence of a thing. That is what this map of American art means to be: a representative survey that somehow summarizes this teeming, ceaselessly shifting landscape of artists. "Among democratic nations new families are constantly springing up, others are constantly falling away, and all that remain change their condition," Alexis de Tocqueville wrote 170 years ago in Democracy in America. He could just as well have been talking about art in America today.

Of course, it is a generalization to say that this constant need to reinvent ourselves is as much in the marrow of our art as it is in marrow of American life -- and generalizations bite back. Yet this same likeness is reflected in another pairing: the ideal of equality and the astonishing variety of art-making now. That ideal replaces fixity and hierarchy with fluidity and diversity, and no words better suit contemporary art.

Some recent history: In postwar America, the critic Clement Greenberg was the titan who ruled the art world. He had an explanation, a theory by which he could champion the abstract painting he admired. As he put it in his landmark essay "Modernist Painting" from 1960, "visual art should confine itself exclusively to what is given in visual experience, and make no reference to anything given in any other order of experience." In fact, it was more than an explanation; it was a command.

The only art that could be of real value and matter (at least to him) would exclude everything but its own devices, its own materials. No references to the world, no figures in a landscape. Nothing but paint and canvas whose subject was paint and canvas, so that the art object would be acknowledged as the purest of things. For a time, Greenberg's proscriptions held sway. Abstract Expressionism and its direct descendants were the triumph of this view. And while succeeding generations thumbed their noses at his decree to exclude the world from their work, the idea that art was pulled away from the world, floating in its unique individuality, was irrefutably seductive. Like Tocqueville's prophetic sense of Americans' restless drive, Greenberg's art objects, freed from any restraints but their self-imposed rules, were a declaration of independence, a license to roam.

The art that you see in these pages, in its eclectic range, is the flowering from these seeds. Consider the array: from Gregory Crewdson's fantastical photographs of Hopperesque women and Spielberg-inspired scenes to the raucous scrawl of Trenton Doyle Hancock's stories and cartoonish imagery of a protean, prehistoric ape-man whose obsession is nature's beauty; from the coolly calibrated geometries of Benjamin Edwards' schematic paintings of layered cityscapes to the richly drawn though entirely austere nature studies in pencil and graphite by Valerie Demianchuk; from the domestic voyeurism of Nicole Cohen's ghostly videos, which inhabit suburban interiors with a dream world of speculations about daily life, to the sandblasted stone and glass of Stacy Levy's memorial art, whose task is to celebrate and mourn the ecology of the industrial landscape, still gleaming here and there with magic pockets of the unspoiled. And so on.

Paintings, photographs, installations, sculptures, videos, textiles, assembled or sumptuous blown glass, the individuality and pluralism on view here is a representation of the great sprawl of sensibilities that coexist within the boundaries of American art and beyond them. This is the great flattening, the creation of a maximal equality among mediums, approaches, styles, traditions, technologies, means of construction, and methods of display. At least across the art world, this is the practice of tolerance with or without consensus. The vista of art in our times is, if anything, like cyberspace: a massively distributed network that exalts in its mutability and carries no single identity. And at its heart, if you can say that something so sprawling has a heart, is a loneliness, an immigrant's loneliness, exuberant in the freedom of the new, and yet always, somehow, looking for home.

Consider the photographs by Crewdson. In some images, there is a sense of anomie, of longing or alienation -- what are these blank-faced women staring at from their suburban windows as night comes down? In other pictures (and they are gorgeous, big photographs, the size of heroic paintings), you sense a yearning for childhood's iridescent openness of imagination; the chance that anything can be, that the laws that come with adulthood don't yet apply as we ponder a brilliant blue cloud of butterflies or the feverish creation of a mysterious flower totem, the way that the actor Richard Dreyfuss in Stephen Spielberg's film Close Encounters of the Third Kind built a mountain shape from dirt in his backyard, not knowing why.

But we know why. Because these pictures, like the Dreyfuss character, are after something only glimpsed in the back of the mind: a hankering for community, a need to belong. True, as in so many fairy tales, there is a hint of darkness that all isn't right. Yet the pictures tender no endings. They are like the story that your father has left off reading at bedtime. Now you must close your eyes and imagine the rest.

The images in this book reveal something else. The special effects and easy glide between the fantastic and mundane, the large scale that seeks to turn every picture into a spectacle, the interest in pop culture, and the fluent use of technology are essential to so much of this art. The mass media -- television, movies, pop music and videos, the Internet, video games, and commercial graphics -- are the air in which contemporary art breathes, the mirror in which artists see themselves, the filter through which their objects pass. For the artists on these pages, it is unlikely that the lessons of art history or of their own craft have had any greater influence on them than the last 30 years of film and TV.

In essence, what this comes down to is their relationship to the slipperiness of fact. Of course, artists have always moved between the real and the imaginary. But the speed, the fluidity, the sense of weightlessness with which one image is morphed into another, and the saturation of these mass-media effects has rendered the whole atmosphere of the visual as unstable as quicksilver. In this these artists are also the heirs of Greenberg, creating new rules that lift their works free from the laws of the daily world. And while they do not ignore the world, they engage it by making images that always seem to have some aspect of watching, of reflecting on the act of looking, of being the spectator. What could be more natural for the generations grown up as consumers of the mass media?

Whether it is Matt Saunders' superimposition of empathy and private feeling on scenes and faces grabbed from the cinema or Santiago Cucullu's collapse of private narratives and historical ones in a jigsaw-puzzle art of compressed spaces or Amy Wheeler's psychologically freighted compositions of shimmering urban lights seen from a hovering viewpoint, and always from the outside looking in, there is a simultaneous feeling of nearness and remoteness, of that slipperiness once again in which everything -- the private and the public, the personal and the historical, the internal and the external -- is mutable, locked down for no more than an instant.

These are some of the contemporary markers on Tocqueville's map of the American character, so quick to form new families, with others constantly falling away and changing. For all of the media-savvy self-consciousness on view here, there is the counterpoint of work that attunes itself to more purely optical and tactile pleasures. Dante Marioni's blown-glass vessels, for example, or Hillary Steel's weavings. But whatever side of the Continental Divide of conceptually-based art you're on is blurred again and again in the ceaseless rush forward. On the flood plain of art today, diversity is an expression of an infinitely horizontal momentum-an equality in all things, a mobility that holds invention dearer than history. This is the impetuous drive that Tocqueville noted, when he wrote about the new Americans, "Those who went before are soon forgotten; of those who will come after, no one has any idea."

That is the inherent sadness of our Yankee practicality, always bent on rushing ahead, and it is also our inherent optimism. It is our sense of what Tocqueville called "the indefinite perfectibility of man." Americans are perpetually after the next thing, the better thing, the renovation and reinvention of ourselves despite, even in light of, our moral dilemmas. Nostalgia for the past is like Will Cotton's candy landscapes, bright and sweet and yet everywhere tinged with a cloying sense of the molten danger of looking backward. We have replaced innocence with innovation, which can leave us a little naïve in our hopefulness, though alive with energy.

For all its polish and sophistication, there are still those qualities of the raw and wide open in our art, not wanting to be too constant, too fixed. And so I amend what I said at the beginning of this essay. This book is an animated map, charting a place continually in flux. The lonesomeness and kick of always looking forward are there, of wanting to find something but not getting stuck. It is what Huck Finn, says, with his wandering spelling and punctuation that only affirm his ways, outward and onward at the end of Mark Twain's novel Adventures of Huckleberry Finn: "But I reckon I got to light out for the Territory ahead of the rest, because Aunt Sally she's going to adopt me and sivilize me, and I can't stand it. I been there before."