The late president-elect Bashir Gemayel had just been interred in his native village of Bikfaya today when a tall, silver-haired mourner in dark glasses was asked who might have killed this man who was to have been inaugurated as Lebanon's youngest leader next week.

"In Lebanon, one's adversaries are known," said the 82-year-old Camille Chamoun solemnly. "Here one does not have to be a prophet to discover one's enemies."

As a former president himself and the patriarch of one of the dominant Christian Maronite clans, Chamoun knows of what he speaks. But pressed to identify who might have set the bomb that blew up the 34-year-old Gemayel and dozens of his Phalange Party supporters Tuesday in largely Christian East Beirut, Chamoun pushed on to his car in silence.

For Gemayel, until his election last month the commander of the Christians' powerful Lebanese Forces militia, the problem was never one of knowing who his enemies were but figuring out which might present a clear danger to him.

Having dealt as harshly with fellow Christian rivals as with his traditional Moslem opponents, and treated foreign allies as warily as sworn neighboring enemies, Gemayel had no lack of antagonists. A measure of the enemies made in his brief, but bloody, rise to political power came today in the plethora of alleged culprits cited -- though without credible evidence.

The list of potential assassins offered ranges from agents of Israel's Mossad secret service to Syrian intelligence agents, Moslem fanatics, Palestinian terrorists, feudal Christian revenge seekers or turncoats within Gemayel's ultranationalist Christian Phalange Party.

The apparent precision of the attack had local cognoscenti of violence accusing the Israelis who -- hated as they are by many in Lebanon -- are respected for their martial efficiency. Gemayel only days before had been portrayed by Moslem, and some Christian, opponents as a malleable tool of the Israelis because of their support for his militia and his presidential candidacy.

Holders of the Israeli theory, by far the most prevalent in Moslem West Beirut, noted that Gemayel had recently sought to distance himself from the Israelis to win the support of his Lebanese Moslem opponents. Israel, many here say, had wanted to move into West Beirut and was looking for an excuse.

This was the theory expounded today in Rome by Yasser Arafat. But at the same time, Israeli officials darkly hinted that it was members of Arafat's own PLO who killed the man who had held Lebanon's Palestinian refugees -- and their armed representatives -- responsible for Lebanon's ills.

Those denying this theory argue that the now dispersed PLO does not have the expertise, or manpower in place, or access to East Beirut, that would have been necessary to assassinate Gemayel, even if some of its more extreme members had wanted to.

A more likely candidate than the PLO or Mossad, many here maintain, is the Syrian government, which Gemayel blamed for its heavy-handed usurpation of Lebanese sovereignty and dignity during the six-year occupation of its "peace-keeping" Army here. The force was sent to Lebanon under the the Arab League in 1976 to put an end to bloodletting between Christians and Moslems.

But Lebanese Moslems and Palestinians who know their Syrian neighbors best say the Syrians are as unlikely as the PLO to have managed to get at Gemayel at his party headquarters in the Christian bastion of Ashrafiyeh.

"The problem is nobody really knows who did it -- the investigation has just begun," said Dori Chamoun, the former president's eldest son. "Those who don't like the Syrians blame the Syrians. Those who don't like the Palestinians blame the Palestinians. And those who don't like the Israelis blame the Israelis." Others blame Christian opponents. They might have had the greatest potential for infiltrating Gemayel's militia.

Former president and rival Christian leader Suleiman Franjieh lost his son and heir, a granddaughter and 30 clan bodyguards in 1977 to gunmen from Gemayel's militia. The attack set off a blood feud that resulted in the car-bomb death of Gemayel's 18-month-old daughter in 1980. There also are many who have raised their eyebrows about Chamoun, the octogenarian former president and power broker. In 1980, between 100 and 400 Chamoun militiamen, and many of their relatives, were killed in a surprise attack by Gemayel's Lebanese Forces.