WILLIAMSTOWN - Are you turned on by what you know best? Do you relish the rich and roiling atmosphere of home? Or is what's right in front of you never quite enough? Are you stimulated more by the visions in your head than those at your feet, beguiled by the beyond, the romance of elsewhere?

In other words, are you Constable or are you Turner?

John Constable (1776-1837) and J.M.W. Turner (1775-1851), the two most celebrated artists in the English canon, and great rivals to boot, are the focus of "Turner and Constable: The Inhabited Landscape," an exhibition at the Clark Art Institute, as well as a new book by the poet Stanley Plumly, "Elegy Landscapes: Constable and Turner and the Intimate Sublime."

The Clark show - 50 or so paintings, oil sketches, watercolors, drawings and prints - celebrates a 2007 gift of British art from the Manton Foundation and gives a good idea of both artists. There are gorgeous things in abundance, but the only real showstopper was in the Clark collection all along: Turner's late masterpiece, "Rockets and Blue Lights (Close at Hand) to Warn Steamboats of Shoal Water," 1840. (Turner's titles reliably reek of sea spray and peril.)

Plumly's book is perhaps the more significant event. Filled with useful facts, it's also the freshest and most personable piece of art writing I've read in a long time. Plumly leads off by laying out the things that distinguished these two almost exact contemporaries.

Constable was a late starter whose early attempts suggest an artist whose ambitions surpassed his gifts (very much like Van Gogh). Turner, on the other hand, got off to a flying start: At 26, he became the youngest painter to achieve full status as a member of the Royal Academy. (Constable wasn't confirmed until he was in his 50s.)

Constable was a homebody. He loved stability, structure and the perfume of a landscape that changed, but never really changed, like the drift of a happy childhood. Turner couldn't stop moving. He painted in so many places that there is nowhere on a map of England more than 40 miles from a Turner scene, and he roamed widely across Europe. He loved energy, flux, drama. Turner was obsessed, as Plumly writes, "with ships and storms, architecture and ruins, fire and water, burning and brilliant sunlight."

Constable was a realist: English artists before him could not paint a landscape without making it look like Italy, littering it with Virgilian shepherds, cavorting satyrs and comely river gods. Constable dispatched with all that. He painted what he saw with his own eyes in all its particulars. People go weak at the knees over his cloud studies (one of which is in the Clark show), but he loved clouds less, I'd wager, than he loved weeds, undergrowth and rough bark.

Turner, as his career progressed, seemed to grow impatient with ordinary reality as he intensified his search for the sublime. (The word describes a kind of greatness or grandeur that causes the brain's capacity for comprehension to crack apart, like a clay pot left too long in the kiln.) His interest in particulars all but evanesced in spiraling mists of radiant, moisture-laden air.

I could keep going. But I wonder: Why is it we so love these oppositions? The critic and linguist Roland Barthes thought there was something in our moral vision of the world - good on this side, bad on that - that makes us transform every word in our shared cultural lexicon into a watchword against its opposite. Truth vs. appearances, conservative vs. progressive, romantic vs. classical and so on. The impulse echoes down into all the most famous rivalries: Matisse/Picasso, Beatles/Stones, Pepsi/Coke, Ronaldo/Messi, Kanye West/Taylor Swift, Nike/Reebok.

I'm not here to dismiss such fighting talk. The distinctions we make are real - or real enough - and a certain antagonism between opposites is exactly what makes life lively. Without oil and vinegar, salads are just green stuff. But do we sometimes traduce the truth for the sake of a bit of tartness and tang?

Of course we do. In the case of Turner and Constable, the differences in style and sensibility are real. But they have fanned out, predictably, into more dubious assertions. Turner's Romanticist love of storms and flux, for instance, caused him to be cast as a political progressive. He wasn't. (Nor, by the way, was Delacroix, the leading Romanticist painter in France, and an admirer of Constable: "A revolutionary in his studio, [Delacroix] was a conservative in the drawing room," wrote Victor Hugo).

Constable's politics were more in line with expectations. The son of a well-off pastoralist, he loved the landscapes of his childhood with the privilege of assumed possession. He was a Tory. His paintings will always appeal to nostalgic types in England, hence the cliché of "Constable Country," the kitschy beer coasters and tea towels, and the critic Robert Hughes' description of Constable's art as "conservatism writ in leaves and wheat."

But is it fair to reduce 200-year-old art in this way? Must we start with the cartoon, the cliché, and rewind from there? Why not start with the pictures themselves?

Plumly does. He describes paintings with real prowess (his previous books include a biographical study of John Keats), but he's not fussy about it. He's always lifting his pen, straightening up and surveying the view. He provides useful historical and biographical context, makes insightful comparisons and speculates keenly on feelings and psychology.

He writes, for instance, about the density in Constable's brushstrokes. At the Clark you feel this particularly in Constable's studies of Willy Lott's house and the sketch of Salisbury Cathedral from the River Nadder. Opaque, ruggedly broken paint helped Constable convey the weight of things in the world, but also a psychic groundedness - the feeling of home. He reinforced both kinds of weight with favored motifs - heavy-hooved work horses, thick timber barges - and a developing understanding of how the same gravity that affects the earth and trees also affects the forms of clouds in the sky. (His early efforts can feel like two pictures grafted: one above the horizon, the other below.)

Constable never leaves anything out for the sake of pictorial decorum. If it interests his eye, he puts it in: a forking path, a cathedral spire, a rainbow, a boy drinking from a stream or "a far toss of birds," in Plumly's phrase. That's what makes his pictures so astonishingly adhesive. Once you really look at a Constable, you can't leave off. It's like the face of someone you love. There's always more to see.

Turner, early in his career, was driven by a similar impulse. He rivaled the Dutch maritime painters of the 17th century in his knowledge of ships, rigging, sails, firepower, sea, waves, sky and clouds. He loved, too, pictorial storytelling. But as he grew older, his vision became more distant and philosophical. He shrouded the weight and specificity of the physical world in fleeting tumults of mist, fog, cloud and spray. Everything became light, and about light.

And unlike Constable, whose sensibility turned on the landscape of his childhood, Turner's imagination was ignited by travel. His frenzied peregrinations produced a stream of wonders - including upward of 20,000 sketches, watercolors and drawings.

Both the Clark exhibition and Plumly's book remind us that if an opposition is truly active, its terms tend to twist toward one another, like braided hair, or like the double helix on which human life itself is built. It's instructive, for instance, that both artists, for all their differences, inspired the Impressionists: Constable with his truth-telling and fluent, responsive brushwork; Turner with his light and acute awareness of contingency. (Monet's Rouen cathedrals without Turner? Unimaginable.)

Rivalry comes from "rivalis," Latin for river - a reminder that rivals wouldn't be rivals if they didn't draw from the same Stygian source. So it's apt that Plumly, as his book progresses, comes to see that Turner and Constable shared "an equal motive: the deaths of the two people whose loss changes them." In Constable's case, it was his adored wife, Maria. In Turner's, his loving father.

The dynamic of rivalry, for us in the stands, asks us to choose: thumbs up or thumbs down? But all these years later, the great thing about playing the game of "Who do we like better?" is precisely that it's a game. You can parse the distinctions between rival artists all you like. But it's not like marriage: You don't have to choose only one person.