AS A RULE in art exhibits, the more artists and styles crammed into a show, the less possible it is to absorb the impact of the art. The fairest way to display any artist's work would be to collect every drawing, painting, and sculpture he had done since kindergarten and arrange them in chronological order. That way you could see every angle of the artist's creativity, really get to know the man and what he is trying to say.

For that reason, retrospectives have an automatic edge over group shows. Unity is built in, whereas multi-artist conglomerations often contain "representative" pieces by artists whose works have nothing more in common than the walls on which they hang.

The Modern Tradition: Twentieth Century Drawings and Watercolors, now at the MFA, is a dubious lumping together of the fragments and varied styles of 20th century art, of schools and schisms which recoil from the cohesion of a term like 'tradition.'

Curator Clifford S. Ackley has aggravated the problem by deliberately arranging the works so as to "creatively confuse people by breaking down categories" within the art. Confusion might be creative at a cocktail party, but it does little to increase the understanding of art.

The exhibition is a visual smorgasbord. It offers a taste of most major twentieth schools and artists, but still leaves you hungry. You're invited to sample, but not to savor.

The list of artists redeems the show. From Picasso to Giacommetti to Klee to Miro, the assortment is a Whitman's Sampler of the finest art of the century, worth seeing no matter how it is exhibited.

The common denominator of the collection is abstraction, a breaking away from the representational art of the previous century. The art reveals man's attempt to catch up with the dazzling and bewildering world of the Machine Age.

The most abstract works, those of the Russian Constructivists, are some of the best in the show. The hard-edged geometric shapes and angular explorations of space tread a thin line between cool control and explosive violence. The works, produced in Russia at the time of the Revolution, recapture the spirit of a nation seizing new politics and new technology.

In his tiny watercolor "Composition," with its chips of buildings, red sun-moons, checkerboards and triangles, Wassily Kandinsky rejects the traditional rules of artistic composition. El Lissitsky's paper collages employ similar elements but are more subdued and aesthetic.

The other works in the show are not clearly grouped in styles, but share common elements with pieces in all three rooms. In much of the work, abstraction combines with realism to produce ambiguous and often disturbing images. "The Fabulous Beast," a pencil sketch by Max Ernst, shows a half-organic, half-machine animal. A faint tracing of a sun in the background implies that this creepy creature inhabits Ernst's (and our) world.

Fernand Leger standardizes the human forms with assembly-line monotony. The people of his "Multicolored Acrobats" do not show the exposed cranks and gears of Ernst's animal. Rather, the smooth, curved limbs and torsos have all the sleek, internalized mechanization of an IBM Selectric.

THE HUMAN form--manipulated, distorted fractured, parodied--recurs throughout the show. In Picasso's "Woman in an Armchair" a schematic body is cut into two-dimensional sections as if from plywood. A later work with the same name shares the hideous distortions of the figures in his "Guernica" mural. Inhuman cones and spirals combine in odd juxtapositions of anatomy.

Jacques Villon's "Seated Woman" is an equally disturbing comment on the effects of modernity on human beings. A tiny figure huddles in the background while its huge rabbit-like feet lunge into the foreground. The image is not comical; the clenched fists, open mouth and oversized staring eyes cry out like Edvard Munch's tortured souls.

In Henri Lauren's small watercolor the figure masquerades in abstraction; the face builds up in blue, white, pink, and red planes. A black rectangle with minute white stars frames the face as a geometric hair/hat. A sparing use of decisive lines and simple curves reveals Lauren's mastery of a very distilled abstraction.

Emile Nolde's "Portrait of Mary Wigman," one of the few non-abstract works in the collection, stands out in bold simplicity to the rest of the works in the show. In an exhibit where you have to peer at Paul Klee's miniscule scribblings with your nose six inches from the paper, Nolde's portrait grabs you from the doorway.

Despite the Hall-of-Fame line up of artists in the show, the works of some of the big names are less than stellar. Alberto Giacommetti's sculpture "Walking Woman" has none of the impact of his more famous anorexic forms. The works of Miro, Gorky, Moore, and Brancusi are equally disappointing.

As a whole, the show leaves you slightly befuddled. It's like flipping through someone else's photograph album. You have a vague sense that it all fits together somehow, but you're not really sure who's who, who knows who, or when the photos were taken. You can enjoy looking at the pictures, but you don't really know what you're seeing.