For the second time in less than a year South Africa has thrown down the gauntlet to the rest of the world.

Characteristics of the country's leadership that surfaced in the first challenge - the crackdown on black dissidents last October - were apparent once again in this week's Cabinet decision to back out of the U.N. - supervised elections in Namibia (Southwest Africa).

First, is the readiness of the 26 million Afrikaners who run this country to fight, to defy the world rather than be forced into an action they believe threatens their political survival. In this case, a Marxist-oriented government taking over in Namibia.

The decision to hold elections in Namibia exclusively under South African supervision means that South Africa has committed itself to a long-term military presence there. This could lead a Vietnam-style war against the Soviet-armed and Cuban aided black nationalist movement, the Southwest Africa Peoples Organization (SWAPO).

The Cabinet decisions also places South Africa in direct confrontation not only with the black-ruled countries to its north, but also with the Western countries that stand between South Africa and the isolation that would come with economic sanctions.

The "go-it-alone" decision demonstrates that a certain fatalism about sanctions. The belief that they are inevitable has been growing ever since Vice President Walter Mondale told Prime Minister John Vorster in Vienna last year that the United States was expecting the one-man-one-vote principle to come to South Africa.

Afrikaners believe that after the Rhodesian and Namibian conflicts are settled, the pressure on South Africa will grow intense. They argue that nothing they do short of one-man-one-vote will satisfy the world; that sanctions will be imposed eventually, and that it is better to face them now, while South Africa still has Namibia.

This fatalism pervaded remarks by Foreign Minister Pik Botha regarding the South Africa for doing this very thing, this most democratic principle on which the American democracy is based, then look, we would have got it [sanctions] in any case."

Rejection of the Western-sponsored plan made it clear that, faced with a hostile world, South Africa's authoritarian state is basing political decisions on an emotional perspective of its chance of survival. Logic demanded that South Africa go along with the U.N. plan to minimize its military committment and win a needed relaxation of tension. It could then use its economic leverage to influence the newly independent government in Namibia, just as it does with the Marxist state in neighboring Mozambique.

But logic did not prevail over emotional antagonism to SWAPO, against which South Africa has been fighting a low-level bush war for 12 years. Western appeals to Pretoria to compromise fell on only half-bearing ears. The besieged South African government is more concerned with conbattling immediate threats than with ensuring long-term security.

Finally, in its action this week, the government showed its inclination to do what black leaders complain about constantly: instead of negotiating, to listen, grant few concessions and then do what it wanted to in the first place.

It appears that South Africa took part in negotiations on the U.N. plan on the chance that it would not succeed because SWAPO would not go along.