All those who yearn for peaceful change in South Africa cannot but be anguished by the recent outburst of violence in Pretoria. However sympathetic the outside world is to the plight of the nation's blacks, it can only view with abhorrence the bomb explosion that killed 17 people and wounded more than 200, many of them civilians. It will take no less than moral and spiritual fortitude on every side to cool passions and prevent the escalation of urban terrorism.
Violence as a tactic of political struggle simply breeds more violence and, with it, more hatred and fear. Yet in South Africa today the great need is to persuade the ruling white minority that it need not fear political change, that it has nothing to lose and everything to gain from gradual reform of a system which oppresses the black majority and in fact deprives whites from fulfilling the highest sense of Christian justice and therefore the highest sense of themselves.
On the face of it, the terrorist act in Pretoria - for which the African National Congress appears to take responsibility - can be seen as a response to violent acts by the South African government, including the raid into Lesotho last year which killed 42 Congress supporters. But in its deeper meaning it represents black frustration over the lack of hoped-for racial progress. In some ways there has been change. A qualified form of power sharing with Coloreds and Asians is developing. Some blacks are moving up into skilled jobs; legalized black unions are working to improve conditions. There are efforts to improve black education and housing.
But the basic system of apartheid remains in force. If there is some change, it is far from fundamental reform. Apartheid laws are being applied with renewed vigor. Removal of blacks to the homelands has been stepped up. Detention of black union leaders has increased. Prime Minister Botha's power-sharing ''reform,'' meantime, is being resisted by right-wing opponents. Blacks, too, have greeted it with skepticism, seeing it not as an opportunity for Coloreds and Asians to use their new political role to agitate on behalf of blacks, but as an excuse for the white government to claim it is making progress and to further isolate whites from blacks.
There is, in others words, a violence in the system itself, a violence that is meted out every day against racial equality and against the human spirit. That is what must be addressed, not only by the many blacks and whites of conscience in South Africa itself but by those abroad who share a vision of a South Africa in which all races can one day share power and live together in peace.
In this connection it must be asked whether the United States has contributed all that it might to the evolution of racial harmony in South Africa. The Reagan administration's policy of ''constructive engagement'' was designed to encourage white accommodation and conciliation. But it seems to have achieved very little. In fact: has it not simply made the South African government feel immune from criticism by the US and from any economic or political pressure that could help foster progress, both on the racial front and on the question of Namibia? Many thoughtful observers believe it is time for a reassessment of that policy and a concerted Western diplomatic effort to bring about the independence of Namibia. This in itself would help assure South Africa's blacks that they are not forgotten or unsupported in their aspirations.
The bomb explosion in Pretoria was lamentable. It must be met - not with more violence but with a renewed determination of blacks and whites to find a peaceful way out of their mutual dilemma.