Every Sunday in a modest social hall in a suburb of Johannesburg, a 67-year-old white man who once was a pillar of the Afrikaner establishment that enforces the strict system of racial segregation here, joins a handful of black domestic servants in a worship service and a little African dancing.

The process that brought C. F. Beyers Naude from a position of prominence in the powerful Dutch Reformed Church and the Afrikaner secret society Broederbond to virtual house arrest and social ostracism illustrates the contradictions and doubts felt by many whites about their privileged role here.

Naude's punishment for becoming what is regarded as an ethnic traitor was extended last week when the government served its second banning order on the Afrikaner community's most implacable dissenter.

Banning is a severe form of restriction that prohibits people from speaking publicly, limits their movements and prevents them from having social contact with more than one other person at a time. The original, five-year banning order was due to run out Sunday, and Naude's many admirers here and abroad hoped he would become free at that time.

Although he has not softened his condemnation of apartheid as immoral, they hoped the government would relent because of his age and because his wife Ilse, 69, is in poor health which doctors say is due to the strain of living under the banning order.

But there has been no relenting. The new banning order, imposed for another three years, repeats the restrictions of the old one, save for a minor concession that Naude no longer has to report weekly to a police station.

The government's action has met with strong condemnation from religious leaders and members of the political opposition here.

There has been no comment from any government spokesman, including the minister of law and order, Louis Le Grange, who issued the banning order.

Naude's credentials as a member of the Afrikaner volk, the Dutch-descended settlers who after 300 years regard themselves as indigenous to South Africa and have ruled it with a zealous group nationalism for 35 years, are impeccable.

His father, Jozua Naude, was chaplain to a famous general on the side of the Boers (as Afrikaners were then called) in their war of independence against imperial Britain at the turn of the century. He named his son after the general, Christiaan Frederick Beyers.

At the war's end Jozua Naude, a fanatical Afrikaner nationalist, was one of a handful of bittereinders (bitter enders) who refused to lay down their arms at the signing of the peace treaty with Britain.

He was also one of six men who founded the Broederbond, the secret society widely considered to be a controlling influence in Afrikaner political and religious affairs.

Beyers Naude was a member of the Broederbond for 23 years. Like his father, he was a minister of the Dutch Reformed Church, South Africa's biggest faith to which 64 percent of all Afrikaners belong and which wields enormous influence over the community.

Naude rose to be the moderator, or leader, of the church's biggest division, the Southern Transvaal Synod. He was one of the rising stars of the volk -- bright, articulate, charismatic. Some people spoke of him as a possible future prime minister.

Then Naude's whole philosophy began to change. It was a slow process, but gradually his Biblical studies convinced him that the Afrikaner government's policy of apartheid was in conflict with the Scriptures.

It is said of Afrikaners that they are konsekwent in their thinking, meaning they follow a Teutonic pattern of logical consistency that requires that one face up to all the consequences of one's convictions.

This is one reason the South African government has been so slow to start with small reforms, like integrating sports or park benches, because logical consistency requires that the implications of such steps be followed all the way to permitting people of all races to vote.

Naude is an archetypal Afrikaner in this respect. A one-time associate has said of him: "The trouble with Beyers is that his ideas continually have little ones." Thus his initial doubts procreated others and sent the minister back to his Bible for more searching. "It was a frightening experience," he recalls, "like a pincer movement closing in on the foundations of your life."

What made it particularly frightening is that he realized the shattering implications if he ever began voicing his doubts. It was like staring over a precipice. One step and he would be gone.

That step came when Naude formed an ecumenical group called the Christian Institute in the early 1960s to establish contact with black Christians. The Dutch Reformed Church disapproved, ordering Naude to quit the institute or forfeit his ministry. He chose the institute.

With Naude as director, the institute became a multiracial body that sought to exert pressure on the Afrikaner oligarchy to change their ways. But during the 1970s, Naude reached the conclusion that trying to achieve change in South Africa through appeals to the ruling whites was a forlorn hope.

The institute began supporting black initiatives and in time to endorse a black vision of the country's future. Naude started coming into confrontation with the government.

Government spokesmen, and even a commission of inquiry, hinted that Naude and the institute were supporting the black underground. In 1977 the institute was outlawed and Naude was banned.

In the lonely life he has led since then Naude has undertaken what he calls "pastoral counseling," which is giving personal advice to individuals who call on him -- one at a time.

Many are young whites anguished about being conscripted into the Army for what they see as an unjust war against African nationalist guerrilla movements. Others are young blacks anguished about whether they should leave the country to join these guerrilla movements.

Early last year Naude gave up his membership in the whites-only Dutch Reformed Church which had played such a big part in his earlier life. He joined the black branch.

Now the one-time church leader and Broederbonder worships with the few blacks who live in his Johannesburg suburb. He is the only white member of the congregation and often the only male, but he mixes easily and without artificiality.

Sometimes the service ends with community singing and a little dancing, and he joins in that, his only taste of social activity.