CALLING THE long-awaited meeting between African National Congress leader Nelson Mandela and Inkatha Freedom Party leader Mangosuthu Buthelezi a major breakthrough may be going too far. Measured against the goal of ending white-minority rule and establishing the black majority's rights, the Mandela-Buthelezi summit was less than a defining moment in South Africa's history. But the accord they reached, and President F. W. de Klerk's subsequent announcement of his intention to seek parliamentary repeal of the segregationist Group Areas and Land acts, together represent the achievement of necessary milestones in the long struggle toward building a democratic order in South Africa.

As a reference point, this week's ANC-Inkatha meeting is an important event against which to measure progress toward social peace among blacks, a prerequisite to achieving a united black front for the coming negotiations with President de Klerk's government. But an end to the rivalry will not come quickly or without overcoming some obstacles, as Mr. Mandela and Chief Buthelezi warned after their meeting, and as yesterday's bloody factional clashes in Natal Province confirmed.

The peace summit was worth seeking, though, even if agreement was not reached on all issues. To say that Mr. Buthelezi needed the summit to legitimize his own standing as a major player deserving of a seat at the negotiating table with the government -- as Mr. Mandela's supporters suggest -- understates the value of the accord to both the ANC and Mr de Klerk. While the meeting apparently served as a catharsis for Chief Buthelezi to air his personal grievances against the ANC -- they agreed to refrain from future personal vilification -- a deescalation of the violence will give all parties a chance to turn to immediate problems that have continued to grow worse, even since Mr. Mandela's release from prison. Not only the continued high rate of violence but the crisis in education as indicated by the failure of examinations by two-thirds of black high school students, and the collapse of authority in the townships as a result of mistrust -- all these are problems that grow more acute with each passing day of black factional warring.

Ending black violence also eliminates a convenient excuse for right-wing whites to resist the dismantling of all aspects of legal apartheid and talks on power-sharing. It should embolden President de Klerk to move more forcefully toward formal multiracial constitutional talks. But differences among blacks -- no matter how acute they may be -- cannot obscure the fact that institutionalized white domination continues to reign in South Africa and constitutes the principal obstacle to racial decency and a new democratic system.