The ordeal of the Achille Lauro was mercifully brief and the message is loud and clear: chest-thumping, let-me-tell-you-how-to-do-it generalizations about "international terrorism" are worse than useless. To the degree they suggest some sure way of ridding the world of the terrorist scourge, they not only deceive. They also make it harder to deal with individual terrorist acts in the only way you can: case by case.

And circumstances alter cases, sometimes drastically. Last time around, for one example, it was an airplane. Some people said TWA 847 should never have been allowed to land at Beirut, which is a lot to ask of an air-traffic controller when a pilot says he will run out of fuel in five minutes. Other tough guys said once the TWA crisis was over, the United States should proclaim a policy of strict sanctions against any country harboring hijackers or hostage-takers.

Now the next hijacking has come and gone. But it was a boat, which is to say that it was at sea. So much for rules about safe havens for hostage-takers.

The last time, Henry Kissinger, former undersecretary of state Lawrence Eagleburger and The Wall Street Journal led a chorus proclaiming the need for an unambiguous policy of retaliation -- the only language terrorists understand. "What the U.S. policy ought to be when this incident is over (is) to announce that the U.S. government from now on will retaliate -- time, place and target of our choosing," said Eagleburger.

Not the least of what was wrong with this prescription was that it already was U.S. policy. Within a week of taking office, Ronald Reagan said, "Let terrorists be aware that when the rules of international behavior are violated, our policy will be one of swift and effective retribution."

As recently as last February, in a major policy statement on terrorism, Secretary of State George Shultz argued that "experience has taught us over the years that one of the best deterrents to terrorism is the certainty that swift and sure measures will be taken against those who engage in it."

Experience has taught us nothing of the sort. The United States has no firsthand experience. In every instance when the United States has been the target of terrorism (bombings of embassies as well as the Marine compound, hostages held in Beirut and Tehran), the question of where and when to retaliate has turned out to be too hard. And the experience of the one country in the world that has had no problem with the question, Israel, has amply demonstrated that retaliation does not, in fact, deter. From the Israeli record, a case can be made that, if anything, retaliation incites.

That's the loudest message from the Achille Lauro. Consider that only a week or so before it was seized, the Israelis had practiced what the Reagan administration preaches by sending bombers to pulverize the headquarters of the Palestine Liberation Organization in Tunisia. The Reagan White House obviously approved (though it had second thoughts about how effusive its public approval ought to be). And the Israelis had a right to expect approval. Only a year ago, Shultz had pointed to Israel's policy of retaliation as a model.

"No nation has had more experience with terrorism than Israel, and no nation has made a greater contribution to our understanding of the problem and the best way to confront it," Shultz told a gathering at a synagogue in New York. "Israel's contribution goes beyond the theoretical," he added. "Israel has won major battles in the war against terrorism in actions across its borders, in other continents, and in the land of Israel itself."

If that's not a ticket to Tunisia ("across its borders, in other continents"), it is surely a recommendation that retaliation is the way to go. And yet within a week Israel was once again the target of a hostage- taking; the hijackers were demanding the release of 50 or more Palestinians from Israeli jails.

You don't have to connect the Tunisian air strike to the ship seizure (which would have taken more than a week to organize) to make the point. There are only two possibilities. One is that PLO chief Yasser Arafat could have called off the operation and didn't, which would suggest that he was not much cowed by the Tunisian strike. The other is that, as he insists, he was not the original villain in the case.

Either way, what the experience of the Achille Lauro teaches us one more time about terrorism is 1) that diplomacy sometimes works but (2) deterrence, Israeli style, does not deter.