What was going on when I was born?

The United States said today that the Marines would not land in Beirut on Sunday, as planned, because no accord had been reached on the Israelis' pullback from Beirut International Airport. In a separate incident, officials said, four United Nations military observers, including two American officers, were killed outside Beirut today when their vehicle ran over a land mine. (Page 22.) Also in Beirut, Israeli officials said they expected their troops to be out of West Beirut by Sunday night, paving the way for deployment of the multinational peacekeeping force. (Page 23.)

JERUSALEM AFTER the events of last week, Israel may never again be able to feel the same way about itself. Something snapped. The belief, the conviction that Israel was somehow different, somehow special amid the brutality and hypocrisy of the world's nations, was profoundly shaken if not swept away. Only at the pinnacle of governmental power did a tight circle of moral certainty seem to remain. Prime Minister Menachem Begin, wrapped in the mantle of virtue he has always worn, dismissed as ''a blood libel'' the assessment that Israel bore some responsibility for the massacre by its Lebanese Christian allies of hundreds of Palestinian men, women and children in two refugee camps in Beirut. ''No one will preach to us ethics and respect for human life,'' Mr. Begin thundered. And then he had the full Cabinet endorse his declaration, despite the quiet misgivings of several ministers. The Prime Minister's sense of righteousness found some echoes among those who wear their bigotry proudly. ''Who cares?'' people were heard to say. ''Let the Arabs kill each other. They deserve it.'' Rabbi Meir Kahane, who heads the Kach movement, the Jewish Defense League of Israel, issued a written statement saying, ''The massacre in Beirut merely shows, in all its clarity, the nature of the Arab.''

The Milwaukee Brewers, who have averaged six runs a game this season as the strongest hitting team in baseball, found a master tonight: 36-year-old Jim Palmer of the Baltimore Orioles. One night after the Brewers had cuffed Baltimore pitching for 18 hits and 15 runs, Palmer stifled the Milwaukee bats in a classic performance before a standing-room crowd of 53,568 at County Stadium. He allowed only four hits, pitched a 7-2 victory and cut the Brewers' lead over the Orioles in the American League's East to three games with eight to play. Five of those games will match the Brewers and Orioles again, so Milwaukee may have one more confrontation with Palmer before the race is decided. But even for a man with 263 career victories, Palmer rose to lofty heights of professional skill tonight as he won for the 13th time in his last 14 decisions.

Mayor Koch, his gubernatorial ambitions shattered, is returning full time to the problems of New York City, some of which grew more acute during his unsuccessful five-month campaign for the Democratic nomination. Of particular concern to many officials is a deteriorating economic picture, which has magnified the city's budget woes. Absent from City Hall often during his race against Lieut. Gov. Mario M. Cuomo, Mr. Koch returns at a time when there are likely to be some changes in his administration. A handful of commissioners are reported to be preparing to leave, some at the Mayor's urging as he reassesses his policies and the performance of city agencies. Other top officials, including all three of his Deputy Mayors - Nathan Leventhal, Robert F. Wagner Jr. and Karen N. Gerard - said they were not sure how long they would stay in government.

BETTE LOU FLETCHER said ''ten-four,'' put her radio microphone back on its rack, reached for her Hagstrom's atlas to check a location and then headed for some trouble in her squad car as she began another tour of duty as a Suffolk County police officer in the Sixth Precinct. During the next eight hours, Officer Fletcher would intercede in a domestic dispute concerning the trespassing of a drunken nephew, tell a teen-ager to get his unlicensed dirt bike off the road, and aid a young man who passed out in a vacant lot in a suburban neighborhood after consuming an undetermined quantity of beer and Quaaludes. Officer Fletcher, who stands a little over 5 feet tall and weighs 120 pounds with her bulletproof vest on, would also scour a subdivision in search of a missing car and respond to calls placed at headquarters when night-time cleaning personnel unfamiliar with the security systems at a local bank inadvertently set off the burglar alarm. The calm, soft-spoken, 30-year-old officer would also politely and professionally intrude on a couple of young lovers who parked in a corner of a deserted high school parking lot. ''Vandalism at these lots is a real problem,'' said Officer Fletcher, who had sidled up to the parked car in her squad car before flashing her sidelights onto the parked vehicle.

FOR the last few months, some residents of the Thimble Islands have been enjoying 20th-century conveniences along with the 19thcentury serenity provided by their isolation. Electricity was brought to three of the 24 inhabited islands - Davis, East Crib and Dogfish - in the summer, and while residents of two other islands in the chain have expressed an interest in seeking electricity, others are grumbling. On the newly powered islands, bottled-gas generators, lanterns and old-fashioned iceboxes have been discarded and washing machines, clothes dryers and electric refrigerators installed. ''Electricity means not having to hunt for flashlights in the middle of the night,'' said Nancy McAllister of Dogfish Island. ''All through July, I made do with one tiny icebox,'' she recalled, ''and that's when I had my family visiting me.''

THE LOSER By George Konrad. Translated by Ivan Sanders.315 pp. New York and San Diego: A Helen and Kurt Wolff Book/Harcourt Brace Jovanovich. $14.95. To a recent conference on writing and political censorship, the exiled Russian poet Joseph Brodsky remarked that writers in repressive societies are forced to take words more seriously than writers who have the luxury of saying anything. A diet of torture and prison may not be the healthiest way to feed a writer, but Mr. Brodsky's observation contains a certain truth. In the last 20 years terrifying political power has produced a body of superb writing in Eastern Europe. Some writers, like Aleksandr Solzhenitsyn, directly address politics; others, like the Czechoslovak novelist Jiri Grusa, engage passionately in formal experiments condemned as ''decadent'' by state censors. The effort to give a complete picture of enslaved life has prompted writers like the Yugoslav novelist Danilo Kis to cross and recross the frontier between fiction and reportage, while the cunning tactic of getting around censorship by writing allegory, as Aleksandr Zinoviev does, has given new vigor to that literary genre.

DICK MOSS recalled the time a friend persuaded him to attend a c oncert given by Liberace. The piano player was dressed in customary a ttire - a shimmering sequin suit and enough glittering jewelry to f ill a display window at Tiffany's. But this wasn't the only manner i n which Liberace flaunted his wealth. Moss said the entertainer s pent more than half the performance talking about it, too. What i ntrigued Moss even more was how the audience apparently enjoyed l istening to this discourse on opulence. ''Here he is, telling a Midwestern, blue-collar audience how much money he makes and they're applauding,'' Moss said. ''I couldn't believe it.'' Such public applause for entertainers does not appear to extend to athletes, who are entertainers, too, and who the public knows are making big money, too.

IT lies within sight of Manhattan, a mostly vacant or abandoned 1 8-mile sliver of land hugging the base of the Palisades on the west b ank of the Hudson River. Although development has proceeded apace inr ecent years on top of the Palisades, where a long column of luxury h igh rises stand guard, the narrow strip of land below has lain f allow. Developers have eyed the property for years, and there has been no shortage of proposals to resurrect the wasted land that once hummed with busy railroads, ferries, piers and factories. At least 16 major plans have been produced in as many years, but most of the land remains undeveloped. Now, however, without the aid of any master plan, land up and down the Hudson waterfront from the George Washington Bridge to Jersey City is finally being bought, cleared and readied for development. Just last Wednesday, Governor Kean announced plans for a $500 million, privately financed waterside housing and hotel development on the abandoned Port Authoriy piers in Hoboken. Other developerfunded projects range from a regional shopping mall alongside the entrance to the Holland Tunnel in Jersey City to a new city in West New York and Weehawken, where 30,000 people will live and work.

HAUPPAUGE IT was laundry week at the State Department of Environmental Conservation, and experts here carefully weighed two bundles of testimony relating to the chemical NTA. One load of evidence indicated that the addition of NTA to detergents would produce whiter whites and brighter brights, but the other load suggested that longterm exposure to the chemical could pose a health hazard. The Procter & Gamble Company, the nation's largest manufacturer of detergents, is currently test marketing a formula of the detergent Tide that contains sodium nitrilotriacetate - NTA - in most of New York State except Long Island and New York City. Attempts to introduce the product on Long Island have been thwarted by local officials, who are unimpressed with the company's assertion that, when it comes to cleaning power, NTA is the next best thing to the banned phosphates.

The 12th Quarter As the nation enters the year's final quarter, Administration officials have seized on recent data revisions and estimates of economic growth for the second and third quarters to proclaim the onset of recovery. But given the margins for error in measuring such things, the gains are more likely to be statistical than real. As most analysts see it, the economy remains mired in a recession that began three years ago and hasn't ended. Output has stayed remarkably flat over the period despite nine quarters of growth. By year-end, economists at Data Resources estimate, output will have risen a mere 0.1 percent since 1979's fourth quarter.

The most energy-efficient buildings, architects say, are those built into mountains. Officials of East Windsor Township, N.J., wanted an energy-efficient building, but didn't have a suitable mountain.