Banners in both English and Afrikaans urged supporters of Prime Minister Pieter W. Botha at a recent party congress to "conquer doubt through faith and courage." The bilingual message was a telling sign of the times.

Despite unprecedented economic prosperity, unequalled military might in the subcontinent and a more-than-adequate capacity to quash internal dissent against its racial policies, the ruling Afrikaner establishment, after two years of Botha's premiership, is marked by spreading doubts about apartheid's viability and morality, by an increasingly open admittance that, economically at least, it has failed and by a debate on how it should be changed.

The main catalyst for this crisis of faith is one Afrikaners would rarely admit in public: the black student insurrection of 1976 that cost more than 700 lives. That experience shocked the rulers of this racially divided country and focused the attention of politicians on facts they previously had chosen to ignore.

Simple demography was at least one of those. By the year 2000, South Africa will have at least 35 million blacks and 6.6 million whites. The flow of blacks to the white-controlled cities that was supposed to reverse itself under the racial system set up in the 1950s was exposed in 1978 as a myth as blacks continue to flock to the urban areas to find jobs.

In addition, in the past five years three white minority governments have been toppled in neighboring states. That has caused the growing realization here that the hostility of black Africa and the rest of the world will not cease until there is some kind of black rule in this country.

All these factors have impacted on the Afrikaner's mentality.

"When you must make a choice between obvious eclipse and possible eclipse, you most probably choose the possible," said Stellenbosch University philosophy professor, Willie Esterhuyse. "This perception is growing among Afrikaners."

Significantly, the Afrikaner's unease and doubts have surfaced during a year of economic prosperity caused by the higher prices of gold. At the same time, Western governments have reduced much of their anti-South African rhetoric and applied little or no real pressures on Pretoria while internally, there has been chronic but limited black opposition.

The crisis of faith is most evident in Botha's ruling National Party where speeches by Cabinet ministers admitted to uncertainty about the future and offered little but cold comfort. Internal Affairs Minister Chris Heunis appealed to the gathering to "trust us."

The editor of the main opposition party newspaper, The Rand Daily Mail, said, "The National Party has become a party with almost as many policy variations as it has members. Talk to three different Cabinet ministers about what government policy is today and, as likely as not, you will get three different answers."

The malaise of the party was diagnosed by Erich Leistner, head of the government-subsidized research body, the Africa Institute, when he said, "The traditional ideology of Afrikaner nationalism that has served well in the past to mobilize a divided and often backward people and enabled it to adapt to the challenges of urbanization and industrialization is now clearly incapable of unifying the Afrikaner behind political and intellectual leaders whose analysis . . . has led them to conclude that far-reaching changes are called for if the people is to survive."

The disquiet is emerging in other places besides the National Party. The chief executive officer of the largest Dutch Reformed Church, whose support for the government's apartheid policy has made it into the "religious wing" of the national party, resigned last month because of disagreement with more conservative officials about their attitudes on segregation.

In a farewell sermon, Frans O'Brien Geldenhuys warned that unless solutions were soon found, the South African people will be "plunged down [the] precipice." Following his example at least 15 other whites publicly resigned from the church in protest against its support for "unjust laws."

In August, a group of Afrikaner university students publicly broke away from the conservative national student organization, the Afrikaanse Studentebond, because of its support for the government's racial policies. They formed a new group called Polstu, which stands for equal citizenship and political decision-making for all races, its officials said.

This disintegration of consensus adong Afrikaners has roused emotions, and those who question the old views are subject to verbal and physical abuse from their conservative brethren.

Polstu officials were bombarded with eggs and tomatoes at meetings. A right-wing group calling itself the White Commando set off an explosive device outside the Pretoria University office of one of Botha's key advisers after he offered a plan to give blacks a say in government at the local level. And an Afrikaner historian was tarred and feathered when he suggested that an Afrikaner religious commemoration be downgraded from an official government holiday.

This ferment in their society has led Afrikaners, isolated from other racial groups here by more than 30 years of segregationist laws, to believe there is tremendous change going on in their country. They are genuinely baffled when outsiders do not see this.

But most outsiders are watching for what will emerge from the Afrikaners' agitation that has brought South Africa to a "pivotal period, a decisive phase," according to Afrikaner political scientist Andre du Pisani. They are waiting to see if the result will be a new model of minority domination and control as most critics put it, or a gradual liberalization and move toward real political power-sharing.

So far, under Botha's leadership the government has at least recognized that it has a constitutional crisis and has set in motion a search for a new political establishment, leading some to predict that the 1980s will be a decade of "constitutional experimentation" for South Africa.

"South Africa's political stability, as a prerequisite for the sound, voluntary economic growth of domestic society was normally assumed rather than debated among businessmen," wrote Jan Lombard, a Pretoria University professor of political economy and a top aide to Botha.

"During the past year or so, this attitude has largely changed toward one of greater concern. It has clearly become necessary to accept and even to encourage a serious movement toward a rather different political dispensation," he added.

As a result, the South African public has been inundated with a plethora of constitutional models and newspaper columns are continuously filled with long, dull essays on "constitutional concepts.

"It's like cars, there's a new model for each year," said Du Pisani, who regards the phenomenom as "an indication of an underlying crisis in the country. As it deepens, there will be a proliferation of models."

One hoary proposal receiving new interest is one for an all-white homeland in which even domestic servants and manual laborers would be white. The idea is being actively pushed by an ultraconservative, government think-tank, the South African Bureau for Racial Affairs. But generally it has elicited more amusement than serious consideration with some suggesting that its national motto could be "my country white or wrong."

The model that has aroused most interest so far is one proposed by Lombard who, in his 1978 book "Freedom, Welfare and Order" argues that "the greatest hope for political stability in South Africa remains . . . maximum, decentralization of welfare responsibilities and opportunities." In this way, the "problems of political participation which at present are unsuccessfully treated at national level might be more easily solved on a regional level, "Lombard wrote in a tract for businessmen.

Lombard proposed for formation of eight regions in South Africa, each composed of a black homeland, a "rural authority" and a metropolitan area. Each regional government, which would have far greater powers and areas of responsibility than local government does now, would decide on its own political setups, multiracial if desired, and after that, a central government would be created.

Botha publicly kept a long arm's length from Lombard's plan, which the professor urged the public to debate, but his theories are clearly the basis on which Botha has put forth his idea for a confederation of states within South Africa. Botha will take the first concrete step toward that when a special parliamentary session will establish a President's Council to work out a new constitutional model for the country.

But the council does not include blacks and this flaw of Botha's initiative is the key indicator that the Afrikaners' turmoil of self-doubt and their recognition of the necessity for change has not brought them to the point where they are on track toward a solution to South Africa's basic political conflict.