The wheel of civil unrest has turned full circle in South Africa, and once again mobs of stone- throwing and petrol-bombing black youths are pitted against police in almost a dozen townships. The violence could yet be in its early stages, and a death toll so far of nearly 40 people may not be the end of the tragedy. As usual, most of the public commentary on the events is superficial, reflecting partisan viewpoints on both sides. The situation defies easy diagnosis.

The present unrest has had a fairly long buildup. In 1983, after two quiet years, school boycotts involving 10,000 black pupils occurred throughout the country. Up to early September of this year, well over 100,000 school pupils have been involved in a spreading pattern of boycotts and demonstrations. Six school pupils have been killed in these demonstrations, one 6 years old and one aged 14.

In the past few weeks parallel violence has broken out in black townships. Although most of those involved are also youths, the immediate issues have been rent increases and cost-of-living increases. A sharp political focus is evident in the brutal murders of four black town councilors seen to be agents of the authority. Evidence of other motives is also seen in the destruction and looting of scores of shops, 45 of them belonging to Indian traders.

Accompanying these events were other boycotts protesting the election of Indian and colored representatives for the new three-chamber parliament, which excludes Africans, during which over 600,000 colored schoolchildren and students and eight universities and colleges went out on strike. At some institutions the protests continued to coincide with the inauguration of P. W. Botha as the new executive state president.

Also coinciding with the general pattern of unrest is a running conflict between black supporters of the United Democratic Front, a nonracial federation of community organizations operating in the tradition of the banned ANC, and Inkatha under the leadership of Chief Buthelezi, head of the nonindependent homeland of Kwazulu. Individual attacks and petrol bombings of supporters' homes are currently in the news.

Add to all this the violent demonstrations by black schoolchildren in a Natal township against an official visit by Cabinet Minister Piet Koornhof to inaugurate a new municipal authority. Over 40 incidents of violence occurred during the elections for the Indian chamber of parliament in late August. There has also been a noticeable increase in sabotage over the past four weeks.

The immediate reasons for all these events as given by spokesmen are always very specific. In the school boycotts, it is capital punishment, lack of recognition of pupil representatives, the supply of school books, the poor quality of teachers, alleged sexual misdemeanors among teachers and the exclusion of overaged pupils. In the township disturbances, the reasons given are rent increases; in the Eastern Cape, transportation problems; and in Natal, a government decision to incorporate certain townships into the Kwazulu homeland. At the universities, the protests are directed against the new constitution.

It is quite clear, however, that underlying factors and organization are more important in understanding these events than the superficial triggers. Dr. Motlana, the well-known opposition community leader in Soweto, has blamed the disenfranchisement of Africans, saying that voteless people are compelled to vote with petrol bombs. The black student organization, the Congress of South African Students (COSAS), which is most closely associated by the authorities with the school unrest, has written in a student journal that "the education struggle goes hand in hand with other struggles in society . . . we must mobilize women, students, workers and so on." On Aug. 19, at one of the nationwide first anniversary meetings of the United Democratic Front, introductory speaker Cassim Salojee observed that "a spirit of defiance against race rule is alive in the land."

Some suspicion might exist among the authorities that the United Democratic Front is directly involved in the disturbances, but this issue is complex. There was a degree of violence that could have been contagious in the days of the colored and Indian elections, and the UDF was prominent in calling for opposition to the elections. The UDF also held a prominent meeting in the township in which the recent major wave of school boycotts first started shortly afterwards. The UDF, through an affiliate, the Joint Rent Action Committee in Natal, is involved in the dispute with Inkatha. The enthusiastic response to the UDF and the rising tensions among black youth, however, may both simply be symptoms of the same underlying factors.

In attempting to assess the causes the following are relevant: The government's recent constitutional reforms, whereby white members of parliament are joined by Indians and coloreds, have raised expectation and fomented a mood of political restiveness. Controversy over the exclusion of Africans from the new constitution and last year a furious debate over African urban rights, after which the government temporarily withdrew new legislation to control the movements and residence of Africans, has created a political climate in which simmering frustrations have come to the surface.

These developments have occurred at a time of deepening recession with rising African unemployment and sustained double-digit inflation. At a time like this, rent increases are a particularly sensitive issue. It is the African youth for whom anxiety is greatest. The pass rates in an increasingly overstressed black educational system have been falling dramatically in recent years, and unemployment among black school leavers is rising equally dramatically.

The mobilization of black youth is extensive. There are scores of committees and organizations in the black pupil community. COSAS, the major student organization, has 44 well organized branches linked with local committees. When COSAS joined the UDF, hundreds of thousands of black pupils became, fairly self-consciously, members of a national political movement with romantic similarities to those of the banned ANC.

The authorities are probably correct in claiming that political organization is behind the disturbances. No political movement anywhere in the world is entirely spontaneous in the sense that it develops without leadership and mobilization. But whether the unrest is said to be due to "agitation" or to "mobilization" is largely a choice of words. It could not have occurred without a welling of poliical sentiment and grievances that have made black youth amenable to calls for demonstrations and boycotts.

The state has taken action to damp down the political mood. Several leading members of the UDF have been detained, and a ban has been placed on all indoor meetings in major centers unless official permission is obtained. As before in our history, if the unrest continues, the government will use its large and effective security machinery to scoop off the leadership and induce caution among the rank and file. This was the pattern in 1976 and in the early '60s.

Governments that are in full control of modern security resources are not easily dislodged by violence. This is an issue which the black movement of South Africa will have to ponder increasingly in the months and years to come. For the first time in decades the South African state and the influential business community are conceding the need for reform in South Africa. The restlessness and the frustrations of the black communities fully deserve sympathetic understanding, but the realities may require that alternatives to violent confrontation must be sought.