COUNCIL MEMBER John Ray's letter today on investment in South Africa gives short shrift to the essentials of the issue. As in almost every matter involving the system of legalized repression known as apartheid, the temptation is to rush to a position "against" it. That way lies a certain emotional satisfaction and a certain public applause. Urging that the District pull its pension funds from companies and banks trading in South Africa, Mr. Ray takes that position with a vengeance.

The hard and necessary question, though, and the one Mr. Ray passes by, goes to the effects of disinvestment on the people in whose name the proposal is made, South Africa's black majority. The weight of knowledgeable opinion, including black opinion, is plainly on the side of going slow on disinvestment. We cited the other day a Rockefeller Foundation study chaired by the black who runs the Ford Foundation; it was very tough on apartheid, but still favored continued investment to bring jobs and a better life. Within South Africa, the government stifles free discussion, but respected black voices can still be heard.

Bishop Desmond Tutu has leaned toward disinvestment, but even he has expressed approval for what happens to be the Rockefeller stand: American corporations in South Africa should stay and use their money and influence to provide education, training and housing as well as jobs for blacks. Zulu chief Gatsha Buthelezi has said that people propagating foreign economic withdrawal are destroying the basis for progress in South Africa. Trade union leader Lucy Mvubela says: "What I have tried to advise the American companies . . . is to set up technical training centers for our people and to disregard whatever the government apartheid policies are. And if . . . this is accepted and if technical training centers are set up and our children gain higher education and are able to be absorbed in industry and commerce, I would be the happiest. . . . We have never had this opportunity in previous years."

The American companies, well watched, can claim to be among the leaders in promoting equal employment. They sponsor a school in Soweto that offers blacks the crucial step up to higher business education. These gains are pitifully inadequate when measured against the scale of the injustice, but they make real contributions to black needs.

Among South Africans, frustrated black opponents of apartheid cry for disinvestment, and smug white defenders of the system argue that disinvestment is unwise. The fact is, however, that although the economy undergirds the apparatus of white control, it is the engine of black progress at the same time. To disinvest is to slow that engine down.