A tiny, giant step in South Africa

In Alan Paton's new novel of South Africa, ''Ah, But Your Land Is Beautiful, '' an Indian girl becomes a heroine in the 1950s by quietly insisting on the right to study in a segregated library. She would be amazed to hear of what is being offered to Indian as well as Colored (mixed-race) South Africans under a new multiracial governmental plan. As one Indian of today remarked, it amounts to a very small step for South Africa but a giant step for its Afrikaner rulers.

This perspective is worth noting as Prime Minister Botha is criticized for the plan by those both to the left and the right of him.

Yes, the step is tiny, most conspicuously because the plan has no place for South Africa's black majority.

But the step is large for the governing National Party, whose recent unanimous approval of the plan opens the door to a dramatic departure from exclusive white rule.

The worry is that the adjustment is simply part of a larger plan to keep blacks forever unfranchised. The hope is that even a small start toward multiracialism could foster a change of attitudes away from the adamant assumptions of apartheid.

The plan includes provisions for an executive president with so much power that concerns about dictatorship have been expressed. Separateness of the races would still be emphasized by having three parliamentary chambers, one white, one Colored, one Indian. But there would be some legislative role for the multiracial President's Council, which is now merely advisory.

With the black majority relegated to ''homelands'' and omitted from the plan, the current discussion may all seem to be taking place in a vacuum. But here at least is a specific proposal of ''reform'' as promised by Prime Minister Botha when he came into office warning that South Africa must ''adapt or die.'' He says it is not practical politics to try to put Indians and Colored into ''homelands.'' Does anyone really doubt that someday it will not be practical politics to keep blacks there either?