Pablo Picasso was a restless young artist of 25 when he first saw examples of African and Pacific Island sculptures in a Paris museum. The "shock" and "revelation" radically altered his approach to art and in 1907 gave rise to the fusion of his precubist work with tribal art. "What really interested him about all primitive art was the notion of art-making as a magical process," explains William Rubin, director of painting and sculpture at New York's Museum of Modern Art. "Picasso felt that art had to get back to being the kind of thing that did not mirror the world but changed the world, changing the man who made the art as well as the people who looked at it."

Rubin's thesis is no mere speculation. His second home is located near Plan-de-la-Tour in the south of France, a 50-minute drive from the town of Mougins, where Picasso lived. "I got to know him quite well," Rubin says of Picasso (who died in 1973). "He didn't like to talk about his art so you would have to slip in questions slyly."

How well Rubin succeeds in finding answers is reflected in a stunning MOMA exhibit titled "Primitivism" in 20th Century Art: Affinity of the Tribal and the Modern. To make his point, Rubin's show dramatically juxtaposes 147 works by such modern masters as Picasso, Matisse, Gauguin and Brancusi against 218 examples of African, Eskimo, Oceanic and American Indian art (see following pages). Assembled on a budget exceeding $1 million, the exhibit will be at MOMA until Jan. 15, moving then to the Detroit Institute of Arts (Feb. 27-May 19) and the Dallas Museum of Art (June 23-Sept. 1).

Accompanying the show is a two-volume, 700-page MOMA publication of the same title (cloth, $80; paperback, $30 until Jan. 30, $40 thereafter), edited by Rubin, 57, a onetime clarinetist who describes himself as a "disappointed orchestral conductor turned art historian." After earning a Ph.D. from Columbia, he taught at Sarah Lawrence College for 16 years ("Jill Clayburgh was a student of mine") before joining MOMA in 1967. Among his major exhibits was the acclaimed Picasso retrospective four years ago.

For the current Primitivism exhibition Rubin assembled pieces lent by museums and private collectors from around the world. "This is probably the first time a large number of tribal objects has been collected by someone whose interest is purely aesthetic rather than anthropological," Rubin says.

A dozen of the tribal works are from Picasso's own collection, much of which was of marginal quality in Rubin's view. "Picasso was not a big spender even when he became incredibly wealthy," Rubin says. "He rather liked the idea of getting something on the cheap. Of course, an object could be important to Picasso and not be a particularly good example of its type. As he said to me, 'You don't have to have a masterpiece to get the idea.' "