TO READ BACK over the clips of Laurence Stern, who died on Saturday at the age of 50, is not just to be reminded of the acute perceptions of this skilled newsman who, at the time of his death, was The Post's assistant managing editor for national news. It is also to take a kind of instant survey course in contemporary journalism - the issues, the perspective, the changing problems and obligations of those who try to perform an ancient trade under blindingly new - modern and different - conditions. Mr. Stern had covered it all: the region, the national scene, life (and death) overseas. He was there whacking away at the Maryland Savings and Loan scams, viewing firsthand Vietnam, explicating the inexplicable Robert Vesco. Trace the hot or moving or vital or outrageous stories of the past 25 years, and likely as not you will find that Larry Stern was there.

Mr. Stern, who once wrote of a prominent witness in the Bobby Baker case that she had a "beehive hairdo and a bouffant memory to match," was, in some impossible combination, a skeptic and a romantic, a joker and a bleeder. As a journalist he had that first essential ingredient: speed. He was a quick study and a quick man with a wisecrack and he could get it all down on paper faster and more comprehensively than anyone else. Editors who wanted something inconceivable accomplished would call on Mr. Stern. Four gillion words by quarter to six - that sort of thing.

This kind of old pro stuff was a mark of Mr. Stern's journalistic upbringing, a prized vestige of bygone days when staff was scant and news abundant and people were accustomed to the discipline of getting it fast and getting it right. But many newsmen who came out of that tradition were unable to accommodate to a changing journalistic scene in which it sometimes seemed that every old certainty and truth and piety was about to go down the tube. There was a time (young readers will, of course, not believe it) when vast areas of U.S. government activity were thought to be certain lapses and improprieties on the part of elected officials were not thought possible, when all personal conduct not identical to that of the Osmond family was thought to be aberrational and mad.

Well, times do change, but not everyone can face up to the destruction of comfortable assumptions this entails. Mr. Stern could. And that is why he was so successful as a journalist. In an article about the decade - the sixties - in which so many illusions came crashing down, he wrote of his own experience:

"America's Sixties conformed almost exactly to my thirties. I too confess to having watched the parade begin at the Inaugural mount in Washington with that January's sense of crisp thrill. The ensuing memories come in sharp images...reading the first bulletins from Dallas...being roused by a telephone call in a Mississippi hotel room earlier that year to learn that...Medgar Evers had just been shot...hearing a White House press spokesman announce in the spring of 1965 that the arrival of American Marines in Danang signified "no change of policy" toward the Vietnam War."

Mr. Stern went on to wonder whether the "myths, rages, shocks and disenchantments" of the decade would immobilize people or produce no change or possibly provide some kind of "lesson" to others seeking to wield power in the country and, in the country's name, abroad. It was most characteristic of him to answer his own questions with a question - he didn't know, but watching and inquiring and pursuing the answer was the name of the game. The game was journalism, and Larry Stern was inordinately good at it.