If the thread of abstract art in the early 20th century could be unraveled, it would reveal two very different strands. One would be spun from those artists intent on capturing the objects of the physical world and rendering them, more or less recognizably, on canvas. One thinks of Paul Klee.
The other would be spun from those who looked toward an immaterial universe of the spirit and tried to express, through painting, its inherent aesthetic laws. One thinks of Piet Mondrian.
Between them - or rather above and interwoven with both - would stand Wassily Kandinsky.
The strength of the current Kandinsky exhibition here at the Pompidou Centre (through Jan. 28) lies in its effort to map, for the viewer, the chronological route that brought Kandinsky to that overarching position. Following Kandinsky's development from early drawings through late canvases, it sets out, in the honorable tradition of French didacticism, to teach the viewer how Kandinsky progressed from canvases filled edge to edge with thick, primary-colored countryside scenes to the airy, buoyant compositions of his later work.
For the viewer who already knows where Kandinsky is headed, the first part of the exhibition, while instructive, is a bit of heavy going. It is made even more so by some poor lighting. But the shape of the painter's oeuvre comes into focus as the exhibition follows him through the four major divisions of his career: Munich (1908-14), where his painting ''Der Blaue Reiter'' (not included in this exhibition) lent its name to one of the century's major movements; Moscow (1915- 21), where he came in contact with the Constructivists; the Bauhaus (1922-33), where his work was sharpened by the influence of architecture; and finally Paris (1934-44), where the more fluid shapes of Joan Miro and Jean Arp made themselves felt. It is a chronology that explains perhaps two-thirds of Kandinsky's astonishing progress from representational painting into compass-and-ruler-drawn shapes - and then out the other end into the soft, bright, and almost clownlike exhilarations of his late works.
The other third? That's where Kandinsky the thinker and theoretician must be sought out. It was Kandinsky, after all, who strove so consistently to find the principles underlying and uniting painting, music, and the other arts - and who wrote (in his now-famous manifesto of antimate-rialism, ''Concerning the Spiritual in Art'') that ''Generally speaking, color directly influences the soul.'' Color, he continued, ''is the keyboard, the eyes are the hammers, the soul is the piano with many strings. The artist is the hand that plays, touching one key or another purposively, to cause vibrations in the soul.'' Example? ''The sound of colors is so definite,'' he explained, ''that it would be hard to find anyone who would express bright yellow with base notes, or dark lake with the treble.''
And it was Kandinsky who summarized the history of modern art with his own twin threads. On one hand, he saw ''the breaking up of the soulless-material life of the 19th century; that is, the falling down of the material supports which were thought to be the only firm ones, the decay and dissolution of the individual parts.'' On the other he saw ''the building up of the psychic-spiritual life of the 20th century which . . . manifests and embodies itself even now (1912) in strong, expressive, and definite forms.''
That those two sides emerge as clearly as they do in this exhibition is a tribute to its organizers. There is plenty of evidence here of the struggle to overcome ''soulless-material life,'' to retreat from objects into essences, to paint pure constructions of line and mass and color in which feeling arises not by association with a physical world but by appeal to aesthetic principles. Just as clearly, too, there is evidence of the ''expressive and definite forms'' of an art set free to redesign a universe of strange birds, tightrope walkers, and odd forms of marine life.
Seen all at once and in retrospect, it was a full and rounded career that reached, in those last works, the pinnacle it sought. He reached it, in part, by weaving together the tremendous discipline of Mondrian and the utter whimsy of Klee. But he added, throughout, a full measure of the joy of discovery that was all his own, and that shines through so nicely in this exhibition.