ART REVIEW : An Elusive Master of Shadow and Light : The magnificant drawings of Joseph Beuys make for a demanding show, but one that ultimately leaves the viewer asking for more.

In the United States, and especially outside New York, Joseph Beuys remains very much a mystery man. Aside from a problematic 1979 retrospective at the Guggenheim Museum, only a smattering of substantive shows of his work was mounted here during his lifetime. Beuys may be the most important and influential artist to have emerged in Europe since World War II, but for Americans he remains more shadowy legend than three-dimensional figure, barely integrated into our understanding of recent art.

For this reason, the magnificent show of Beuys’ drawings that opened Sunday at the Museum of Contemporary Art is a signal event. “Thinking Is Form: The Drawings of Joseph Beuys” spans five decades--the artist died in 1986 at age 64--and its 172 drawings together provide an absorbing chronicle.

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A difficult and demanding show, it’s slow to pull a viewer in and finally exhausting in its breadth and scale. Once hooked, however, you discover a fullness and depth that articulate the largest concerns of Beuys’ pivotal sculpture. You’re likely to want even more.

More could certainly be had. Beuys was nothing if not a prolific draftsman. More than 10,000 drawings are known. You can’t help but wonder how this curatorial selection was made, and whether an exhibition with a very different feel or set of insights might be constructed from an alternate group.

Still, the present show, which was jointly organized by Bernice Rose of the Museum of Modern Art in New York, where it had its debut in February, and Ann Temkin of the Philadelphia Museum of Art, where it travels next, is profoundly compelling. Together with its excellent catalogue, “Thinking Is Form” outlines Beuys’ gradual but momentous evolution: From an artist buried beneath the ashes of the National Socialist horror in Germany, he grew into a radical social and political reformer, for whom art was an essential means by which to rebuild a shattered soul.

Many of Beuys’ early drawings are fragile and spare, employing light pencil marks and pale washes of watercolor. You strain to visualize images within them, like finding evocative pictures in random tea stains.

The relationship between Beuys’ drawings and his sculptures is sometimes direct, as with any artist who works out ideas for translation into three dimensions. But Beuys also invented unusual mediums for works on paper. Beize , a German word meaning stain or corrosive, is composed of an iron compound suspended in solution; Braunkreuz --literally, “brown cross”--suspends the rusty brown pigment in heavy oil, making the delicate sense of inevitable decay more dense.

When brushed on paper, Braunkreuz has an especially material feel. Its weight and presence transforms the sheet of paper from a pictorial field into a tangible arena. Drawing is stripped to its core, which is to function as a concrete form of thought. The conceptual link between drawing and sculpture is underscored.

American Abstract Expressionism is important to this development in Beuys’ work, as is American postwar art’s concern for the mythic and the prehistoric. Many of Beuys’ drawings focus on animals--the earliest, 1948’s “Sheep Skeleton,” has a positively paleolithic feel, as if scratched on the wall of a cave--while the rabbits, stags, elk and bees that come later evoke specifically Germanic legends.

For the lovely “Untitled (Harewoman)” from 1952, Beuys used beize , pencil and a transparent paper to draw an eccentric, erotic figure of a long-legged woman. Her voluptuous buttocks are the pictorial focus, while her head has been transformed into that of a flop-eared rabbit.

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Compositionally bunched at the upper left of the sheet, the hare-woman seems to be scampering across the page, about to disappear from view. The materials, the subject matter and the composition all heighten a sense of flux, transformation and fecund possibility--not to mention urgency.

Throughout Beuys’ work from the late 1940s to the early 1960s, a sense of starting over, of going back to a tabula rasa, is pervasive. It’s easy to see why--and to see how dreadful was the task.

Beuys worked in the awful wake of the Nazi nightmare, which had aestheticized a totalitarian state. He also faced a repressive reconstruction of Germany, which had focused on hollow, materialist successes. His art meant to resuscitate the dangerous necessity of a spiritual consciousness--without any perverse, ideological notion of “the Aryan soul.”

By the 1960s and 1970s, that inescapably sociopolitical program was accelerated through Beuys’ teaching at the Dusseldorf Academy, where he himself had studied art. It was also manifest in a form of “happening,” or performance art, to which he gave the politically aggressive name Aktionen , or “actions.”

In the same way his drawings had given tangible form to thought, he regarded these public actions as “social sculptures.” Engaging the citizenry in the planting of 7,000 trees, for example, created a life-giving counterpoint to the industrial brutalization of the landscape, while resonantly echoing the image of the forest in Germanic myth.

Appropriately, drawing now became a public activity for Beuys, rather than a private one, as it’s more commonly perceived to be. When he spoke to an assembled throng about the social, spiritual and political nexus of art, he drew with chalk on slate blackboards--literal tabulae rasae--diagramming the complex relationships.

Several of these blackboard drawings are on view. The show’s one disappointment is the absence of “Directional Forces” (1974-77), which consists of easels on a large platform strewn with piles of blackboards. This climactic piece was at the heart of the exhibition in New York, but it has not traveled with the show.

The absence is marked, but the survey is otherwise terrific. “Thinking Is Form” goes a long way toward illuminating the lasting significance of a most extraordinary artist.

*Museum of Contemporary Art, 250 S. Grand Ave., (213) 626-6222, through Sept. 12. Closed Mondays.