AS the United Nations works for a durable peace for what was Yugoslavia it could do worse than take the status quo ante as at least a starting point for talks about the future.Some may say it is too late, that intransigent, hard-line nationalism has gone too far on all sides. Nonetheless, it is worth trying. Disenchantment, indeed disgust, with senseless civil war which is deciding nothing is appearing among all the belligerents. Awareness is growing too of the costs of this self-destruction and of the deep international disrepute the war has brought to their once widely respected country. A realistic look at the past - the status quo ante of the multinational, egalitarian state built by Yugoslavia's wartime leader, Josip Broz Tito - can provide a guide for the future. Tito himself was Croat. But the war and his understanding of Yugoslavia's complex ethnic mix of peoples and history made him first, foremost, and always a Yugoslav. He knew that with opportunity, the largest ethnic group, the Serbs, would always seek dominance, in the form of a "Greater Serbia," rooted in a medieval past. Tito's concern was always that no republic should be "more equal than the others." When his break with Stalin gave Yugoslavia its independence in 1948, he ensured the equality of the re publics, sometimes with harsh measures, but always with benefits for the whole. After the country became important for Western defense in the 1950s, massive economic aid from the West brought higher living standards and spurred social democratization. It encouraged the first moves by a communist state toward market-style reform. Step by step, Yugoslavs acquired the human rights the East Europeans were to wait decades to achieve. De-collectivization returned several million peasants to private farming. Freedom to travel, to work in the West, and to hold hard-currency accounts in Yugoslav banks became common. The Communists still ruled but were increasingly irrelevant. The republics became virtually states within the state, each with elections, a parliament, and government, with economic affairs subject only to predictable federal requirements. Each also had its own ambitions, but for 30 years Tito's authority kept them in check. But when he died in 1980, rival ambitions quickly supplanted common goals - and a decade of inexorable slide began, leading to today's breakdown. Serbia undoubtedly is the prime culprit. It first eliminated Albanian and Hungarian minority autonomy in its own territory. It then laid claim to Croatian territory, purportedly for protection of Serbs who lived there. This was a spurious claim. For years after the World War II, Serbs lived amicably among the Croats in those regions. In Kosovo, few Albanians considered union with Albania until Serbia annulled their local autonomy ostensibly to protect the relatively few Serbs living there. These moves set Croatia and Slovenia on a secessionist course, which they initially contemplated only as a last resort. Without escalating Serb bullying, each would have accepted a new, negotiated confederation, especially one which gave republics complete control of their own economies. They probably still would. Though the most economically successful of Yugoslavia's republics, they still are not up to Western standards nor ready to compete with the European Community. Like the others, they still need the unified Yugoslav market, and union of some sort remains a common interest. Without it, Yugoslavia will degenerate into six quarreling, and economically inadequate states, divided by frontiers, passports, customs, tariffs, and currencies. And they will remain a menace to themselves, to the whole Balkan region, and indeed, to Europe.