The Lebanese civil war started two years ago with the machine-gun ambush of a bus by Christian militiamen that killed 27 Palestinians returning from a memorial service for slain comrades.

Now, some 60,000 lives later, Lebanon lies in ruins. A fragile peace has been maintained since November in most of the coutry by a Syrian dominated 30,000 man Arab peace force. But the underlying political, economic and social tensions that caused the war remain unresloved and are exacerbated by the ferociousness of the battles and the economic chaos resulting from 19 months of fighting.

The people of Lebanon - which once considered itself the Switzerland of the Middle East because of the way its 17 different Christian and Moslem sects appeared to live in harmony - are now more bitterly divided than they were before the war started on April 13, 1975.

The Christians and Palestinians are still fighting - but now the battle-ground has shifted to southern Lebanon instead of the streets of Beirut or the mountain villages in the center of the country.

The only major change has been in the attitudes of the most influential Arab nations, which have made peace with each other so that Lebanese factions are no longer being used as proxies for feuding Arab powers.

As a result of the continuing instability - vividly illustrated by the revenge killings of Christians by Druze following the assassination last month of leftist leader Kamal Jumblatt - neither Westerners nor Arabs nor Lebanese are bringing money in for reconstruction.

The government estimated direct economic losses from the war at $2.5 billion and indirect losses at between $10 billion and $15 billion. The center of Beirut, once the financial hub of the Middle East, was so battered by [WORD ILLEGIBLE] that veterans of other wars cannot how the destruction [WORD ILLEGIBLE] accomplished without air power.

More important, one of the few western bankers who has returned [WORD ILLEGIBLE] said, "there's nothing going on in this place, businesswise. No one is [WORD ILLEGIBLE] in." He is spending more time in Syria to get up enough business to meet his bank's overhead.

The port of Beirut - once the busiest in the Middle East, handling 4 million tons of freight a year - is now a mess of flattened warehouses and twisted cranes. Its major export is the ravages of war, scrap metal from its docks that is sold for $165 a ton.

Estimates put the rate of inflation at 85 per cent above a year ago, many middle class Lebanese are spending so much on necessities that they have no money to rebuild their shops or apartments.

Lebanon's 60,000 death toll mens that proportionately this country lost 75 times as many people during 19 months of civil war as the United States lost during the eight years of fighting in Vietnam.

There is hardly a family in Lebanon - save those of some wariord chiefs on both sides - who escaped unscathed. Many of those killed were civilians who died in the almost constant shelling of residential areas that marked the most cowardly aspect of the war. Indeed, an urbane, well-educated army officer spoke at lunch the other day of how much "fun" it was to lob shells into residential neighborhoods.

Yet, many Lebanese appear to have an infinite capacity to forget what went on during the past two years. They never refer to it as fighting or war. It is always "the troubles" or "the events," and they are always behond Lebanon's control.

What remains is a social, economic and political system that leaves control in the hands of the Maronite Christian minority. Under the unwriten law, a Moslem can never aspire to be president or head of the army. The Christians still have most of the economic power, and remain the social leaders they were in pre-war Lebanon.

The Marionite Christians - an archaic branch of the eastern Catholic church consider themselves the one defender of Christianity amid the sea of Islam in the Arab world.

This view of themselves as an embattled minority has enabled them to forge an alliance with Israel in southern Lebanon against the Palestinians, who they hate as strangers trying to take over their Country. For Israel, the alliance has provided an almost completed security belt of tiny villages keeping the Palestinians pushed back in Leganon.

The Christians, to preserve their way of life, are ready to partition Lebanon - something Moslems here and in the rest of the Arab world strongly oppose. The Christians are busily constructing their own international airport and have set up the skeleton of a telephone and telex system that could link their quarter with the outside world - something missing during the war, when the communications system was in Moslem hands.

But there is just one power in Lebanon today - the might of Syria and its army, syria entered in June to fight on the side of the Christians against the traditional allies of Damascus, the Palestinians and Moslems. In October, the Syrian army changed hats and moved into Beirut under the aegis of an Arab summit conference as the mainstay on a peace force.

Now it is trying to pull the strings of the Lebanese government from Damascus. It contolled the fighting in southern Lebanon last week - supporting it when it wanted and showing it when its aim of breaking the Israeli security belt was accomplished. Editorials from Al Baath, the newspaper of Syria's ruling Baath Party, are read as gospel on Beirut's nightly television news. Generally, what Syria wants in Lebanon, Syria gets.

Syria wanted Gen. Hanau. Said replaced as head of the Lebanese army. Despite the opposition of Christian warlord Camille Chamoun, a former president and perhaps the strongest Lebanese political power, Said was replaced.

Syria would like to pull its army from Lebanon, according to diplomatic sources here and in Damascus. But when it goes, it wants to leave behind a pro-Srian Lebanese army, internal security force and government.

President Elias Sarkis is considered pro-Syrian. A former civil servant, lawyer and banker, he is slow to take action - sometimes too slow for Syria's taste, some diplomats here say. With Syria's backing, though, he is firmly in control of and appears to be forging an alliance with the rightist Phalange Party against Chamoun and to be appointing his own people to key government positions.

He may succeed in bringing Lebanon back. Even so, it appears it will be a long time before the scars of the war are healed - physically with the removal of the ruins from the city, economically with the revival of business, and psychologically with the end of factional and sectarian bitterness.