ALMOST without thinking, we divide up our recent history into neat compartments called decades - the 1930s, the '60s, the '80s. So it's not a bad idea now and then to take a decade and subject it to a more thoughtful scrutiny. That, in fact, is what they're doing here at the Centre Georges Pompidou: looking at ``Les Ann'ees 50.'' This massive exhibition covers all the media of the '50s - from product design and architecture (story, next page) to film and comic books.
Up on the fifth floor is a large show of painting and sculpture of the '50s. This is no haphazard potpourri, designed to give off a period whiff just by stirring around in the variety of whatever happened to be going on in the art world from 1950 to '59. It's highly selective - so selective that it's easy to name artists who were working with considerable effect in the decade but who are missing here; I think of American sculptor painter Edward Hopper or British sculptor Henry Moore.
At the same time, artists at the end of their careers were not excluded if it was felt that they were still changing and growing: Matisse, for instance, is represented by a couple of a resonant black-and-white paintings and some of his famous ``decoupages,'' with their pasted cut-out colored paper.
What the organizers have looked for on the whole might be called ``connections.'' They have asked what some of the issues of the period were, and have then chosen works of art to illustrate these issues.
Perhaps one of the most obvious and yet revealing comparisons of the decade was between ``the school of Paris'' and ``the school of New York.'' Neither, strictly speaking, was a school at all. But to see the Atlantic divide shrunk in this show is to see how superficial the similarities are - and how subtly crucial the differences.
Such contrasts keep recurring: Here are the bold, heroic, apparently improvised paintings of American Franz Kline facing those of French artist Pierre Soulages, whose canvases are so calculated and Oriental. Over there are the accumulative calligra-phics of Mark Tobey facing the slick blotches and swaggering brush-style of Georges Mathieu. And then there's the brutal 1950 ``Woman I'' of American Willem De Kooning: Her deadly teeth and staring eyes meet up with the mad naivet'e of Jean Dubuffet's two amorphous, grinning, staring female figures in his ``Gymnosophic'' of the same year.
The up-and-coming New Yorkers do not seem to have been in deliberate conflict with the experiments and adventures of the French. If the critic Clement Greenberg is right, these American Abstract Expressionists thought only of trying to rival or even equal French art; they did not perceive themselves to be in opposition to it. And a European like Dubuffet has such kick and spit about him - such brute vitality - that one cannot too easily conclude that the rising star of the new world simply coincided with the demise of the old.
Even so, it was then, in the '50s, that perceptions changed about where the center of the art world might be. It was then that New York started to become what Paris had so long been. The paintings by the Americans that are shown here bear this out: They have a guileless directness, an unself-conscious originality that makes many of the Europeans look stylized and showy and thin.
On both sides of the Atlantic, the '50s also saw the difference between abstraction and figuration battled out on a fresh plane. The exhibition shows several works by Jackson Pollock in which figures have begun to suggest themselves in the heaving movement of the black and white surfaces. It's an advance or retreat (depending how you look at it) from complete abstraction. The shift suggests that Pollock never saw his earlier move into the abstract as total and final. The show effectively juxtaposes these Pollocks with excited, painterly, figurative/abstract paintings by the ``Cobra'' group of painters - Asger Jorn, Pierre Alechinsky, and Karel Appel - and the common ground is startling.
The Cobra painters - from Copenhagen, Brussels, and Amsterdam - are among the few to be admitted by this exhibition as something of value actually happening outside Paris or New York. The show can too easily be criticized for the geographical narrowness of its viewpoint. The 1950s, after all, took place all over the world.
But such narrowness allows a different sort of concentration - on themes rather than on national characteristics. This has its own value. There are glances at ``political art'' of the time (Picasso's ``Massacre en Cor'ee'' sticks in the mind). And there are looks at kinetic art by artists like Vasarely and Soto on the one hand, and Calder - who is represented by a beautiful array of mobiles - on the other. Such ``Art Cin'etique'' is especially valuable because it turns the show into a look forward as well as a look back: It reminds one that the ``Op Art'' of the 1960s had earlier, less trumpeted roots. The same is true of '60s ``Pop Art'': Its beginnings belong in the '50s, and this show rightly gives fair space to assemblage artists like Rauschenberg and Tapi`es who were both making something not far from Pop in '55 and '56.