When Prime Minister Menachem Begin makes his final choice between a diplomatic or a military solution in Beirut, he will know he has the majority of his country behind him.
True, the Israeli public is anxious to avoid additional Israeli casualties. True, a strong and angry Israeli minority opposes full-scale Israeli entry into west Beirut and agonizes over civilian casualties there.
But the majority of Israelis accept their government's arguments for driving the Palestinians out of Beirut no matter what the cost. In a country peculiarly insulated from the realities of Beirut, world criticism does not dent their firm belief that they have every right to do it.
Israeli polls have shown the government's position has been strengthened by the war. During the first week in August, a poll commissioned by the newspaper Haaretz showed 56 percent of the public supporting government handling of the country's problems, compared with 44 percent who felt that way just before the war. Backers of the government Likud Party rose to 44 percent, compared with 33 percent in early June.
The government's strong showing reflects a widespread perception that this war is just. Almost all Israelis supported Israel's initial goal of pushing the Palestine Liberation Organization back 40 kilometers from Israel's border. As for the Beirut campaign, while few might echo Prime Minister Menachem Begin's suggestion that the war was ''divinely ordained,'' a majority of Israelis feel that Israel is doing the world a service by battering the PLO.
For government supporters, civilian casualties become a regrettable necessity of war. Says Knesset (parliament) Defense and Foreign Affairs Committee chairman Eliyahu Ben-Elissar, ''. . . so many losses in public opinion have been caused us in the wake of those certainly not pleasant pictures of war in Beirut, particularly on the television screen. But this will pass. And the truth is that when the Middle East will be free of the PLO terror, when Lebanon will again be independent . . . then, in fact, everyone will see just how right we were.''
Jeff Halper, an instructor of anthropology at Haifa University, who opposes the war, offers another explanation for the Israeli attitude toward civilian casualties in Lebanon:
''Most Israelis look at things in practical terms,'' he says. ''They can't afford to philosophize. They are convinced of their rectitude so they don't see why they should talk about it.''
This conviction is reinforced by the totally black image of the PLO here. Prior to the invasion of Lebanon, most Israelis' knowledge of the PLO was limited to its record of international terrorist attacks and attacks against Israeli civilians. Since the invasion, the Israeli media has been filled with articles detailing PLO mistreatment of Lebanese civilians over the past seven years (but lacking mention of violent deeds committed by other Lebanese factions , including Israel's Lebanese Christian allies).
Prime Minister Begin, in a letter to President Ronald Reagan, compared Israeli forces to a valiant army flushing ''Hitler and his henchmen'' out of Berlin. The reference captured not only the prime minister's intense hatred for the PLO but the constant linkage in his and the public mind of PLO intentions with the Nazi Holocaust against the Jews.
Opponents of the government, such as Labor Party shadow foreign minister Abba Eban, have commented on the language being used by government officials to describe the PLO (always prefixed by ''terrorist'').
''There is a whole new vocabulary with special verbs,'' Mr. Eban said, listing '' 'to pound,' 'to crush,' 'to liquidate,' 'to eradicate,' 'all to the last man,' 'to cleanse,' 'to fumigate,' 'to wipe out.' ''
One advertising agency in Rehovot printed a postcard on behalf of a client to donate for soldiers to write home, ''Firm X exterminates insects,'' it read ''Tsahal (the Israeli Defense Forces) destroys terrorists.'' The agency was denied permission to distribute the cards to the Army.
It is in Jerusalem districts like Nahlaot, a shabby but vibrant collection of two- and three-story apartment buildings and rebuilt shacks housing ''oriental'' Jews of Kurdish, Turkish, and Syrian descent, that the intense support for Mr. Begin can be heard clearly. Nahlaot voted overwhelmingly for the Likud. So did Nissim Levy, a worker in a pharmaceutical company who lives with his wife, Rahel , and four children in a modest flat. A religious man whose father emigrated from Aleppo, Syria, he notes proudly that his firm donated pharmaceutical supplies to help the Lebanese.
''Of course we had to go to Beirut,'' says Mr. Levy firmly. ''The PLO would just have continued attacking us from behind the 45 kilometer line.''
''The world knows Israel is right,'' adds Rahel Levy angrily, cradling a baby against her gray print dress. ''But the world is hypocritical,'' the slim, dark woman adds. ''It's all because of oil.''
Asked about Lebanese civilian casualties, Mr. Levy's nephew Shlomo, a soldier on the West Bank, snapped, ''The world is critical of us for civilian deaths. But the US should remember Hiroshima.'' Injected Rahel, ''The same civilians hiding in a house would come tomorrow to bomb us.''
In fact, there is a sense of distance here from the reality of Beirut's civilian casualties, despite the ire roused by the issue and the protests from a minority of Israelis.
''Beirut is so far away from their experience,'' says Jeff Halper. ''They are so insulated here. People don't know exactly who lives in Beirut. They think everybody is either PLO or hostile Muslims. They think if Lebanese let PLO into a building, they must be fellow travelers.''
Few Israelis understand the reasons why Lebanese civilians remain in Beirut -- a combination of fear, concern for their possessions, lack of money, and no place to go.
''The civilian population of Beirut has been given the opportunity to evacuate and whosoever decides to stay takes full responsibility on himself,'' one Israeli Army officer told Israel radio last week.
Israeli television -- liberal in its interviews with some Israeli soldiers who questioned government moves and with Lebanese and Palestinian civilians in south Lebanon -- has been much more sparing in showing foreign news clips of civilian carnage in west Beirut. Jordan television, received by many Israelis, shows a full panoply of horrors, but is watched mainly by those already opposed to the war.