When asked why President Reagan felt compelled to send Congress a special message on "Freedom, Regional Security and Global Peace," White House Chief of Staff Donald Regan explained that many people were wondering whether the administration has an "overall policy." The answer, Regan said, "is yes, we do, and here it is."

I can almost hear Dean Acheson responding as he did in a comparable situation some years ago: "Policy, shmolicy."

As a key contributor to the famous (or infamous) Truman Doctrine, Acheson developed a keen sense of the political utility of generalized foreign-policy declarations ("I believe that it must be the policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures"). But he also acquired a keen concern for the pitfalls. He had good reason to, when you think of the way the Truman Doctrine emerged and then was used and abused as successive administrations bent its generalizations to fit particular circumstances or honored it in the breach.

There are equally good reasons now to handle with care what some (but not the White House, to its credit) would call the "Reagan Doctrine." It has the same majestic sweep: "The American people believe in human rights and oppose tyranny in whatever form, whether of the left or the right." It seemed to suggest a departure from the "Kirkpatrick Doctrine" as set forth by Jeane Kirkpatrick in a 1979 article in Commentary magazine. Her argument was that a measure of repression by authoritarian, right-wing, anticommunist regimes was tolerable because such regimes were subject to democratic reform in a way that totalitarian, communist regimes are not. Reagan liked this line of thinking so much he made her U.N. ambassador.

Now, it's true if you take a few sentences or phrases from Kirkpatrick's dissertation and set them against that one seemingly pregnant sentence in the president's message that you can make the case for a new line of thinking. That's what you're supposed to do. The argument against Ronald Reagan's approach to Nicaragua has centered on his apparent preoccupation with the communist menace to U.S. security and consequent blind eye to human-rights violations by anticommunist despots.

But you have only to read the sentence immediately following the supposed pronouncement of "new policy" to discover that the White House national security adviser, Vice Admiral John Poindexter, is quite right: There is "nothing new" here.

"We use our influence," Reagan went on to say, "to encourage democratic change, in careful ways that respect other countries' traditions and political realities as well as the security threats that many of them face from external or internal forces of totalitarianism."

In other words, we play it by ear. Poindexter said as much: "The whole point of the president's message . . . is that different policies have to be used in different cases. We need different policies toward communist dictatorships that repress their own people and subvert their neighbors, different policies for nondemocratic regimes that are slowly evolving toward democracy and different policies for nondemocratic regimes in which there is no viable democratic center and the only alternative is chaos or a new dictatorship." That last category leaves a large loophole for tolerance of "nondemocratic" repression when the only alternative looks like a communist takeover.

And it is here that the history of the Truman Doctrine is illuminating, for Truman was trying almost 40 years ago to solve a comparable problem in exactly the same way. Indeed, the Truman administration's scare talk could serve as a model for what we are hearing today about Central America.

In a meeting with congressional leaders, Secretary of State George Marshall warned that, if Greece went communist, Turkey would be surrounded. "Soviet domination might thus extend over the entire Middle East to the borders of India," he said. "The effect of this on Hungary, Austria, Italy and France cannot be overestimated. It is not alarmist to say that we are faced with the first crisis of a series which might extend Soviet domination to Europe, the Middle East and Asia."

But not even Truman's most ardent advocates of aid for Greece and Turkey were comfortable with the fateful sentence in the president's address to a joint session of Congress. It is not too much to say that it was never intended to be taken literally.

The same may be said of the president's special message. True, it presents the administration's human-rights approach in a new way. But whether the administration intends to put its human-rights approach into practice in a new way will only become apparent case-by-case.