Condemning apartheid is easy. Some people could do it in their sleep. An ambitious and exhaustive five-part documentary on PBS this week asks more: that one consider the historic, economic and combative background of South Africa and its shame.

After all five hours, one well may arrive back at Point A, that South Africa's system of racial separation and oppression is an abomination on the earth, but now one has considerably more understanding. The first two hours of "Apartheid" air at 9 tonight on Channel 26 and other public TV stations; the second two hours air tomorrow night at 9, and the conclusion airs Wednesday at 10.

Parts 1 through 4 were produced last year by England's Granada Television; executive producer Brian Lapping also did the extraordinary Granada docudrama "Breakthrough at Reykjavik," seen on PBS stations last week.

Part 5 of "Apartheid," produced by "Frontline" (the umbrella under which the whole series is presented), looks at possible signs of hope in South Africa as exemplified in an unprecedented conference held earlier this year in Senegal. Exiled black leaders of the outlawed African National Congress (ANC) met with white Afrikaner intellectuals who hope reconciliation can avert the bloodbath that to some seems inevitable.

A reading of the history of South Africa reveals that not all heroes are black, and not all villains white, one member of the ANC observes. An Afrikaner dismisses widely held suspicions that the ANC, which is admittedly allied with the South African Communist Party, is some sort of puppet of Soviet imperialism. "That's outrageous; they're not into that," the Afrikaner says assuredly.

When the Afrikaners returned home after their series of conferences, they were greeted with signs accusing them of "treason." An Afrikaner grimly notes that "it might take a form of holocaust" to settle the race issue in South Africa, and fiery radicals both left and right, black and white, are doing their part to precipitate that.

Tonight's first chapter goes back to the twisted roots of apartheid, which did not become official policy until 1948. Roles played in the development of the country by Zulus, Boers, Voortrekkers and British colonials are recalled. Ancient artifacts offer archeological proof that blacks were in South Africa long before whites, but the Afrikaners insist on thinking of the land as their own.

Part 2, which follows at 10 tonight, documents early stirrings of revolt against apartheid, after blacks and so-called "coloreds" had been systematically uprooted from their lands and homes and consigned to reserves and townships. There is early film of Nelson Mandela, the ANC leader who was later jailed and has remained imprisoned by the white government for nearly three decades.

Acts of sabotage committed against the white government by black radicals were perpetrated, the narration acknowledges, "with help from the Communist Party." But the white government's policy of labeling all dissidence as communist-inspired seems laughable given the cumulative evidence in the report.

A pretense of lawfulness was fitfully maintained by the government. ANC leaders were brought to trial, but after five years of these trials, no convictions had been secured against any of the 156 defendants. Later, of course, the laws were changed so that now anyone can be detained indefinitely for any reason, or no reason.

Well-known figures in the ongoing struggle pop up throughout the series: Winnie Mandela, with a frightening call to violence against suspected informers; Archbishop Desmond Tutu; Steve Biko; the Rev. Allan Boesak; and the current president, P.W. Botha, who seems hopelessly trapped between clashing forces. Too much reform and the right-wing whites go on rampages; too little, and the black population riots.

Although the documentary is persistently (and sometimes deadeningly) talky, there are pungent images of South Africa and its tragedy. Parents wash police tear gas off the faces of their children; a black mob perpetrates a shocking, ritualistic act of "necklacing," with a tire and burning gasoline, on a suspected government sympathizer; a banner raised in protest of the country's passbook laws reads simply, and optimistically, "Freedom in our lifetime."

World reactions to apartheid, and attempts at economic sanctions by companies in the United States and elsewhere, are scarcely mentioned in the report; nor do leaders and spokesmen address the possible consequences, for good or ill, of such gestures. But "Apartheid" is for the most part thorough and dispassionate, and according to PBS, Granada's crews filmed it at some risk, considering the censorship restrictions imposed by the Botha regime.

The South African regime has attacked CBS News and Walter Cronkite for the network's recent documentary "Children of Apartheid." It is to be expected that the PBS effort will be denounced as well. That kind of condemnation has become a badge of honor; when the government decided to allow the film "Cry Freedom" to be shown there, it practically certified the movie a gutless wonder.

Among the last words in Part 5 are those spoken by an Afrikaner over the grave of a black youth killed by the police. "Struggle was his life, and the struggle was his death," the mourner says. Earlier it is noted that as the conflicts escalate, many black students have the attitude that "if we die, so what?"

In calm, deliberate, authoritative tones, "Apartheid" sounds its cry of alarm. It is just as clearly a cry of despair.