The merely astonishing proceeds apace, the unimaginable is freely predicted, and the utterly impossible seems inevitable. South Africa is lurching toward racial justice.

It's still a long way off, mind you, but both the pace and the specifics of change make it hard to imagine South Africa ever being the same again.

Nelson Mandela and other political prisoners have been released, political exiles returned, the dreaded state of emergency lifted. Mandela and Gatsha Buthelezi have met and worked out an accord between their long-warring organizations, the African National Congress and Inkatha. The state president's son is said to be engaged to a colored woman.

The hated pass laws and the Mixed Marriages Act are history. And President Frederik W. de Klerk announced last Friday his intention to scrap what remains of the country's apartheid laws: the 78-year-old Land Act, which bars blacks from owning land outside the 13 percent of the country reserved as "homelands"; the Group Areas Act, which mandates strict racial segregation in the towns and cities; and the Population Registration Act, which classifies all South Africans by race and color.

Even the ANC, the principal battler against apartheid, has praised de Klerk's announcement and the simultaneous release of his "Manifesto for the New South Africa," calling it "a fundamental departure from the apartheid framework which deserves recognition."

But the end of official apartheid is not the same as racial justice. Blacks are still voteless, overwhelmingly poor and poorly educated. There's no place for them in a parliament that does make space for other nonwhites -- Asians and mixed-race "coloreds." Negotiations for a new political arrangement have yet to be started, or their participants agreed upon.

Tremendous practical problems remain, not the least of which is the trial of Winnie Mandela, wife of the man who could become South Africa's first black president, on murder charges. Her conviction could be a major embarrassment to the ANC; her acquittal (assuming the evidence against her is credible) could panic whites.

The dismantling of apartheid's legal restrictions is one thing, black ownership of land quite another. Until now, the emphasis has been on the restrictions; soon it will be on the mechanics of transfer. Merely granting blacks the right to purchase land won't result in much substantive change, given the poverty of the country's black majority and the likely refusal of whites to sell to blacks. Listen to Allister Sparks, the South African correspondent of The Post:

"If the scrapping of the Land Act will be huge in symbolism, it also will be fraught with more difficulties than any reform that de Klerk has attempted so far. . . . To blacks, it is axiomatic that a scrapping of the act must be followed by a redistribution of the land. To them, the Land Act entrenched in law the dispossession of their land by the white pioneer settlers nearly two centuries ago, and scrapping the law will enable them to reestablish themselves as farmers. As they see it, their stolen birthright must be given back. Little attention is paid to how this redistribution is to be brought about."

Comparable difficulties remain for the political structure of the country. Who will be in charge while the new arrangements are being worked out? An interracial group, as the black majority insists? Or the existing government, as de Klerk has in mind? Will South Africa undertake some sort of quota system to ensure whites a share of political power, or will blacks succeed in achieving the one-man, one-vote dispensation they insist upon?

Where, given the sanctions-wracked South African economy, will the money come from to open the present all-white schools to the far-more-numerous black students or to lift the quality of medical care for blacks to the level now enjoyed by the white minority?

In short, tremendously difficult questions remain -- many of them scarcely thought about while the emphasis was on repealing the legal underpinnings of apartheid.

As Christopher Wren of The New York Times put it: "In effect, like an ingenious building contractor, Mr. de Klerk has proposed to jack up the edifice of white-minority rule while demolishing its basement. He has yet to spell out how he can fill the considerable void with the 'temporary transition measures' he proposes."

Still, de Klerk has been both bold and imaginative, and with nonwhites unified behind the charismatic and statesmanlike Mandela, South Africa may have a better than even chance of pulling it off. Given this extraordinary pair, the impossible just may be inevitable.