Memorandum to Sen. Sam Nunn (D-Ga.).

Subject: your recent applause for President Reagan's promise of "swift and effective retribution" against terrorism directed at American citizens and for Secretary Haigh's new emphasis on international terrorism as our highest human rights priority.

As a starting point, you would "revitalize" the Revolutionary War slogan "Don't Tread on Me," which is fair enough.

But before this sort of talk becomes a substitute for policy, I offer a modest recommendation: take a former hostage to lunch.

You discover first off that ringing phrases like "Don't Tread on Me" have a rather different resonance to those who were behind bars in the hands of often cruel and always unpredictible captors than they have from the safety of a Senate chamber or a home-front podium. For the most part, when they consider the alternatives, the hostages seem to come down firmly on the side of patient diplomacy, despite all the rigors and terrors of their long ordeal.

Now you can put that down to no more than sheer relief for having emerged more or less unscathed. But what comes across most forcibly from the statements of some of the former hostages, and from talking at length to one of them, Moorehead Kennedy, is their reluctance to leap to conclusions -- either about their own case or about new policies for dealing with future terrorist acts againt American embassies.

The hostages may know something we don't know: the Iranian hostage crisis, with all its complexities and with all that we still don't know about its origins, is a bad case on which to base new policy on terrorism and hostage-taking.

The normal American impulse after steback is to look for lessons. Secretary Haig had good reason for launching a full-scale, government-wide policy review. Perhaps we may yet ge to the heart of the Iranian experience.

But if it is going to take a year and a half, or more, to discover its true nature, that in itself says something of consequence about the limits on this country's capacity to deal "swiftly and effectively" with any new terrorist act involving the taking of American hostages. Almost inescapably, there will be more of them -- the record of recent years makes that practically certain. But what the State Department's catalog of past incidents also reveals on close inspection is that the circumstances are almost never exactly the same.

The identity, missions, goals, affiliations and degree of outside support or sympathy of the hostage-takers very as widely as the ability or willingness of host governments to lend a hand. Worse, uncertainty is often most acute in the crucial early hours or days -- the prime time for "swift and effective retribution."

Thus, it is significant that Moorhead Kennedy unfailingly speaks of those who took him prisoner as "students." His wife, Louisa, a leader among the hostage families, carefully uses the word "captors." Both reject the term of choice of the Carter administration -- "militants" -- for its imprecision as well as for its implication (as yet undocumented) of either Iranian government complicity.

The hostages may be wrong -- though they were closer to the scene than the rest of us. They concede that the original hijackers of the American Embassy were joined later by some who looked a little over-age. The know that along the way assorted elements in the ragged Iranian power structure endorsed and/or exploited the hostages. Says Moorhead Kennedy: "We eventually became a pawn in their political game."

But there were also times when the socalled Iranian government seemed to be struggling to take the hostages out of the bands of their keepers.

Would any of the bold moves recommended (mining of porst, declaratins of war, blockades and all the rest) have brought effective pressure to bear on anybody in a strong position to respond?

This brings us back to Sen. Nunn, who, in fairness, had more than revolutionary slogans to offer. He also had specific proposals; better intelligence; more sophisticated military means, under clear command and control; a strengthening of domestic law enforcement agencies.

He also recognized that "there will be instances that demand prudence and restraint. If an embassy in a friendly nation is sacked by a mob, the United States cannot bomb a friendly nation nor invade with Marines. . . ." Or, terrorists may seek deliberately to provoke American intervention when military action might be "inappropriate."

The distinction Nunn makes is between patience in negotiation or other non-military measures and paralysis by excessive preoccupation. "We must not develop a seige mentality," he argues. Obsessive concern, he warns, overalues the hostages in the minds of their holders, while giving the impression of a nation incapable of dealing with whatever else may be going of around the world.

Now that's a crucial distinction and a useful lesson from Iran. But it may get lost when, at the same time, Americans are being rallied to combat something as complex as international terrorism with anything as simple as "Don't Tread on Me."