Of South Africa it can be said that there are no surprises, only inevitabilities.

For decades, nothing new has emerged about the deadly issue dividing that beautiful but troubled land into armed racial camps inexorably bent on each other's destruction. It springs from the ancient notion of master-slave relationships that has always produced violent conflict and revolution.

There is nothing new either about the way the world increasingly has reacted to the looming tragedy at the tip of the African continent. For decades, the South African government's unyielding policy of apartheid, or separation of the races, has been bitterly denounced worldwide. And for just as long, the government's pig-headed reaction has always been the same: to become more stubbornly repressive in rejecting anything that might ease the conflict. No matter how many tentative moves it has made toward reform, its basic policy has always been to maintain at all costs absolute control by the minority white population.

But it is news when the president of the United States, even if motivated by the best of intentions, seems to misunderstand that nation's history or misreads it in deciding how the United States should respond to this latest and gravest crisis.

Ronald Reagan has opposed economic sanctions against South Africa, saying these would hurt the besieged black majority that the United States seeks to support. By this reasoning, such sanctions could harden the government's attitude and lead to harsher measures against blacks. This analysis completely ignores the way that the South African government has behaved repeatedly in each of its racial crises since World War II -- violently, viciously, repressively.

This pattern was established long before the uprising of blacks in Soweto 10 years ago this week.

In the early 1950s, for example, a series of fatal riots led native blacks to organize a campaign of passive resistance. The reaction of the regime headed by Prime Minister Daniel F. Malan was a massive and oppressive clampdown. Stern new laws and regulations expanded color bars on the statute books. "Pass laws" were enacted to control blacks' movements even more rigidly. Complete freedom of movement was denied them; the government dictated where blacks must live, where they might go, how and why they might travel and how long they might be out at night without special permission.

The government defended these totalitarian steps. In the words of Malan's secretary of native affairs, they were deemed necessary to eliminate "stresses and strains which would inevitably lead to conflict unless very careful control were exercised."

That control meant abrogation of basic democratic rights for everyone. White opponents of the regime were suppressed as well as blacks and "coloreds," those of mixed blood. The government took upon itself the power of entry into private residences at any time of the day or night without a warrant. Parents were denied the right to decide the type of school their children would attend. A series of new laws delegated judicial powers to ministers and bureaucrats to ensure even tighter control.

Now, more than 30 years later, the reaction of President P.W. Botha's government to blacks' newest drive for equality has been depressingly and predictably the same.

The world watches another massive government clampdown. Once again, a virtual state of martial law exists. Once again, citizens' rights have been suspended. Once again, the knock sounds on the door in the middle of the night, and dissenters and suspected "subversives" are led away by authorities. Censorship of the media is virtually total. And, once again, these police-state trappings are justified by the reasoning of decades past.

When the Malan government imposed its policies of the iron fist, it pronounced them necessary in the name of security and control. When the Botha regime imposed similiar acts, it employed the same sort of rhetoric to justify them: The stability of the state must be preserved. Stripped of niceties, that means, of course, that control by whites must be maintained.

Given such a history, the question about U.S.-imposed economic sanctions is not that they might hurt blacks. The question is how a great power claiming world moral leadership can continue to do business with a government that deserves condemnation and should be made to pay a price for actions outside the pale of acceptable human behavior.