They took a low land to new highs. An exhibition of Dutch landscape paintings at Amsterdam's Rijksmuseum reveals one of art history's most intriguing ironies.

A VISIT to the Netherlands only drives home the point. How extraordinary it is that the Dutch, of all people, were so inspired by sky and sand dune, woodland and canal that they ``for all intents and purposes invented the naturalistic landscape.''

This assessment is made by Peter Sutton in his revealing introduction to the ambitious exhibition at Amsterdam's Rijksmuseum of ``Masters of 17th-Century Dutch Landscape Painting.''

Holland's countryside is so flat and unpretentious that it would seem the most unlikely food for artistic exhilaration. Yet this exhibition shows that it deeply moved Jacob van Ruisdael and Meindert Hobbema, Jan van Goyen, Jan Both, Aelbert Cuyp, Philips Koninck (not to mention Rembrandt).

These painters were not - as is sometimes thought - merely obliging servants of their affluent and patriotic bourgeois patrons: They did not paint without inspiration for commerce alone, unless their patrons were exceptionally discerning and inventive. No degree of sensitive patronage could explain the newness, originality, and confidence of Ruisdael's cloud-shadowed panoramas, trees, and waterfalls; or Cuyp's pervasive gold sunlight; or Hobbema's dramatic tracks through the fringes of woods. Their paintings have, at their best, the hallmark of discovery; they reveal a surge of positive realization.

Certainly most of these artists were more naturalistic than their predecessors in the art of painting landscape. Those among them who looked more toward Italianate landscape - or who hadn't grown fully away from the Mannerist bird's-eye views favored by earlier Flemish painters - only show by contrast how down-to-earth what we now perceive as typical Dutch landscape was.

The new viewpoint was at eye level. The subject matter was no longer a comprehensive ``world view,'' but a specific locale with recognizable trees, with recent cart ruts and ordinary-looking people.

Yet straightforward, immediate observation (like that of the much later Impressionists) was never their aim, any more than mere topographical accuracy was. Keen travellers some of them were, certainly, observing their own and others' lands with relish, but they thought nothing of changing the course of a river or relocating a church spire for the sake of the final picture. They may not all have fantasized landscapes as completely as the visionary artist Hercules Segers. (One of the prizes of the show is the large, rugged Segers landscape that belongs to the Uffizi in Florence). But it is still rather surprising to 20th-century sensibilities that while many of them did sketch and draw in the open air, none of them ever actually painted their landscapes outside their studios.

At this exhibition, the only possible exception to this rule is a brilliant little oil on panel by Rembrandt called ``Ice Scene near Farm Cottages'' from Kassel. Thick brush strokes, painted wet on wet, give this small image its vigorous impact and freshness. But the experts don't agree with each other about this: The catalog note says one thing, the label in the exhibition another. ``It is very unlikely,'' the label says, to have been painted on the spot. Rembrandt landscape paintings survive in very small numbers anyway and most of these are total fantasies, partly influenced by the admired Segers. So this little scene is even an exception in his own work. He did unquestionably make swift, accurate observations of Dutch scenery, but these are to be found in his drawings. They are so accurate, in fact, that a scholar has even made a study tracing the routes he followed on his sketching trips.

One fruit of the competition that existed between the large number of landscape painters in 17th-century Holland was specialization. Landscape was clearly divided into different types. An 18th-century writer on the subject, Gerard de Lairesse, noted that ``it is not unusual that each landscape painter has a special inclination'' - ``the one to wild and desolate views, the other to still and calm; still a third to nordic and cold, sun or moonshine, waterfalls and dunes, water and woody views.'' Some of the most undyingly popular Dutch 17th-century landscapists were such specialists.

Hendrick Avercamp, for instance, with his wide winter scenes full of skaters, or Paulus Potter with his standing and sitting cows. Others represented in the show made remarkable paintings of snowfall, of storms brewing, of sunset, of moonlight. Claes Berchem's ``Landscape with Crab Catchers by Moonlight'' is a notable example, a painting that also emphasizes the importance in many or most Dutch landscapes of the presence of people. They may be peasants or Biblical characters or hunters or even crab-catchers, but the telling fact is that the majority of them are simply travelers. And they are often casual enough to suggest that they are simply out for a stroll. They wander or pause in the dunes or meadows, or stand at the waterside, for the pure enjoyment and escape of it all.

A high percentage of people in the Netherlands during this period lived in cities. That is where the art buyers and the painters were. Those opulent city people saw the countryside - and the pastoral paintings of it - chiefly as a happy relief from the pressures of urban life. Looking at a van Goyen or a Ruisdael on one's wall, though it might have hinted some unemphatic moral precept, was chiefly a way of unwinding pleasurably after work. There are worse reasons for art. To Jan. 3.