THE late premier of France, Georges Clemenceau, supposedly said, ''America is the only nation in history which ... has gone from barbarism to degeneration without the usual interval of civilization.''
The remark is also attributed to Anthony Trollope's mother and to Oscar Wilde. Obviously somebody said it. Maybe they all did.
Washington in this wintery season is a good place to test such a proposition. The National Gallery of Art has mounted exhibitions of two painters - one 17th-century Dutch, the other 19th-century American. Thousands of people line up for hours each day in the capital city's cold blustery weather to spend a few minutes with Johannes Vermeer and Winslow Homer.
Vermeer was born in 1632 and lived all of his 43 years in Delft, a large Dutch town between The Hague and Rotterdam. Not much is known about his life. Only 35 of his paintings exist. Twenty-one of them presently fill eight rooms of the National Gallery. They are scenes of ordinary life exalted by what the show's co-curator, Arthur K. Wheelock Jr., calls ''a radiance of inner peace.''
The much larger and more diverse exhibit of Winslow Homer's works is in 12 gallery rooms. To many critics and laymen, Homer is the great American painter. Born in 1836, he covered the Civil War as a magazine illustrator. When he turned to painting his range was varied and colorful - from scenes of rural childhood and Adirondack lakes and forests, to his celebrated pictures of the sea in all its moods.
Americans have come from all over this vast country to see the two shows - each day 3,000 to 4,000 pass through the Vermeer galleries, and 6,000 to 7,000 visit the Homer exhibition. Judging from conversations with some of them, what inspires these thousands to come to the National Gallery is a particular sort of curiosity.
They know there is such a thing as great painting. They want to see what it is. Crowded almost shoulder to shoulder in the Vermeer rooms, they succumb to that ''inner peace.'' The hushed atmosphere resembles that of a cathedral.
Outside the larger, brighter Homer show, a man who hadn't been able to get a ticket to see it greeted his wife as she emerged. ''What'd he paint?'' he asked.
''America,'' she answered.
That curiosity, which brings so many thousands here, gives great art questions to answer. Without those profound questions that cannot be precisely stated in words, the art ceases to be great.
The curiosity of so many thousands, thus, is one of the deeper roots of American civilization.