This being roughly the tenth anniversary of the fall of Saigon, and the shameful spectacle of the last American officials' being lifted off the embassy rooftop by helicopter, the ''Vietnam Syndrome'' is much on the minds and tongues of scholars and commentators. How serious is it -- and are we recovering?

Harper's magazine put the question to a panel of historians, military analysts, an economist and a novelist, and published the answers in this month's issue. The collective effect, nonetheless, left me convinced that somehow we have got this thing all wrong.

A snydrome, says Webster's, is ''a number of symptoms occurring together and characterizing a specific disease or condition.'' Thus the catchwords ''Vietnam Syndrome'' convey some disability that is getting in the way of orderly, forceful, traditional conduct of national security policy and of a well-defined view of the U.S. role in the world.

Activist, interventionist geopoliticians deplore this condition. They hunger for a return to normality, most often defined as the glory days of the 1950s Pax Americana, when responsive allies joined in concerted containment of international communism.

What's wrong with this analysis is that it confuses what is aberrational with what is the natural American condition. The real syndrome (in the sense of something out of keeping with the national character) was the heady, bipartisan internationalist impluse of immediate postwar years. The operative word here is ''impluse.'' Then, as now, political leaders and policy makers talked like world policemen. But more often than we sometimes remember, they talked a better game than the public or Congress or the military were ready to play.

What's different now was well put in Harper's by Yale Prof. Paul M. Kennedy. The last quarter-century, he said, has seen an enormous change in Third World attitudes toward the United States'' -- a reaction against ''overwhelming American presence.'' Our European allies have become stronger, and less willing to follow America's lead; the Russians have caught up militarily and the United States is no longer ''the clearly predominant'' superpower. ''These gradual transformations,'' he added, ''would have occurred even if Vietnam had never happened.''

That the public is more squeamish -- and the military more cautious -- about active U.S. engagement around the world can certainly be credited in some part to the Vietnam experience. But when another panelist, Georgetown University's Edward Luttwak, goes on to argue that ''if our country was not traumatized by Vietnam, the whole affair in El Salvador would be concluded very quickly,'' he is making less sense than when he said, ''The problem is that the American people never really saw their country as an imperial power; the United States was not designed to manage an empire.''

The novelist Peter Marin made the key point: ''Americans love an image of strength.'' Reagan presents ''an image of power while avoiding those concentrations that might put it to a test, which, in my view, is precisely why Americans like him.''

That's also why Americans liked Harry Truman. Yet Truman prudently turned to the United Nations for international ratification of a Korean ''police action'' rather than put the proposition to a divided Congress as a ''war.'' As for the post-Vietnam caution of today's military, Truman's military was not exactly looking for trouble when it defined America's vital interests in the Pacific in a way that excluded Korea at least a year before the North Koreans attacked.

A five-star general, Dwight Eisenhower, was in the White House and John Foster Dulles, a moralizing anti-communist crusader practicing ''containment,'' was secretary of state when Fidel Castro launched his revolution and ultimately delivered Cuba to communist control. Yet we are doing far more to ''contain communism'' in El Salvador and Nicaragua -- after Vietnam -- than the Eisenhower administration did in Cuba, which was nothing.

John F. Kennedy's bracing inaugural rallying cry (to support any friend, oppose any foe, etc.) was not matched three months later by his fatal scaling down of open U.S. military support for the brigade of Cuban exiles at the Bay of Pigs. Lyndon Johnson campaigned for the presidency in 1964 promising that American boys would not have to fight wars that Asian boys ought to fight.

The point of all this is not that Vietnam has left no psychic scars and still less that it has not profoundly affected the attitudes of a whole generation. But the result has been not so much the transformation of the collective American view of the world and the proper U.S. role in it as it has been a reinforcement of doubts and reservations that, with rare exceptions, have historicaly inclined Americans against ''getting involved'' -- as witness the U.S. performance right up to the Japanese attack on Pearl Harbor.

In this sense, the attitudes that have accounted for congressional constraints on the Reagan administration's policies in Central America and Lebanon -- and are so frequently attributed to the ''Vietnam Syndrome'' -- are not so different from the attitudes that Lyndon Johnson shrewdly recognized in his stealthy escalation of the U.S. entanglement in Vietnam. What we are witnessing is not an aberration but a natural condition -- not a consequence of the Vietnam failure but the cause.