In a triumph of practical politics in defense of the status quo, Israel's parliament today voted 64 to 56 to turn back three motions of no confidence in the government and endorse its handling of the Beirut massacre inquiry.

The motions were offered by the main opposition Labor Party, another small opposition party and Israel's Communist Party, but the three only were going through the motions and had not expected to succeed. The outcome of the votes had been presaged Monday when the parliament, or Knesset, agreed to the retention of former defense minister Ariel Sharon in the Cabinet despite his condemnation by the commission that investigated last September's massacre.

Critics charged that the inquiry commission report demanded not only Sharon's complete ouster from political office but the resignation of the Begin government. In the end, however, too many factions in Israeli politics had too much at stake in maintaining the existing political lineup to bring about more than Sharon's downfall from the powerful Defense Ministry post, which was probably the bare minimum the government could get away with in light of the commission's suggestion that he be fired.

A week before the release of the massacre commission's report, Shlomo Avineri, a liberal professor of political science at Hebrew University, gave his explanation of why the extensive publicity over the inquiry would not have dramatic political effects.

Avineri said that while the world may have been impressed by the mass antigovernment demonstration in Tel Aviv following the massacre, the crowd, which according to some estimates numbered 400,000, represented Israel's hard-core, anti-Begin constituency from long before the Beirut slaughter.

"The question is who kept quiet," Avineri said. The vote today reflected the feelings of what Avineri called "the silent plurality" in Israel.

There was a flurry of speculation today about the possibility of attempts to form a "government of national unity" that would bring members of the opposition into the Begin government. Intense negotiations were said to be under way, spurred in part by fear of further divisiveness in Israeli society as exemplified by the death from a hand grenade explosion last week of a peace activist who was part of an anti-Sharon demonstration.

However, it seemed unlikely that the Labor Party would agree to join forces with Begin and his colleagues, particularly just a few days after the release of the commission report that declared the Israeli government bore "indirect responsibility" for the Beirut massacre.

Begin made it clear soon after release of the commission report that he had no intention of firing Sharon. Personal loyalty undoubtedly was a factor in this decision. But it also represented the politically safest course for the prime minister, at least for the moment.

The firing of Sharon would have risked defections from the government coalition by a handful of ideologically driven militant nationalists and the possible collapse of the government. While Begin has no fear of new elections--he is one of the few political figures who would welcome them--he could not be sure that others in his coalition, principally the National Religious Party, would not have jumped to the Labor Party and attempted to form a new government without resort to elections.

That is precisely what Labor Party leader Shimon Peres hoped would result from the massacre investigation, since public opinion polls suggest that Labor would lose ground to Begin's Likud Bloc if elections were held now.

Begin ran no similar risk of defections by keeping Sharon in the Cabinet. The cynical view in Israel is that most of the men around Begin, even Sharon's bitterest personal enemies--of whom there are many--value their positions in the government too much to bolt.

In the five months since the massacre, only two members of the coalition have even wavered slightly. In September, when Begin was strongly resisting establishment of the inquiry commission, Yitzhak Berman, a member of the Liberal Party, resigned as energy minister. Berman, however, has remained a faithful coalition vote in the Knesset.

In this week's two key votes, only Dror Zeigerman, a Liberal Party maverick, broke ranks by abstaining on keeping Sharon in the Cabinet.

Begin's Herut Party and the Liberals form the so-called Likud Bloc. But Begin dominates Herut, and as for the Liberals, they are dismissed by a pro-Begin observer of long experience here as "a joke, a complete appendage of Herut."

The Likud Bloc controls 48 seats in the 120-member Knesset, 13 short of a majority. Four other parties in the coalition make up the crucial difference and each was either strongly pro-Sharon or had a strong interest in not rocking the boat.

The National Religious Party, with six Knesset seats, and Tami, an ethnic party of North African Jews with three seats, are in a weakened political position and were anxious to avoid elections now to provide time to build their political bases.

The ultraorthodox Agudat Israel party, with four seats, opposed creation of the commission and denounced its findings. The fourth party, Tehiya, threatened to leave the coalition if its hero, Sharon, was forced from the government

By satisfying the far right wing of the coalition--those most likely to bolt because of Sharon--Begin kept the coalition together for the moment, which in itself was enough to satisfy the others.