If you are looking for something you can depend on in the way of promises or prescience, political party platforms are about as likely a place to look as the Dead Sea Scrolls, which is not at all to say that they are without value.

On the contrary, they are, in a sense, the archaeological digs of American politics. Taken out of context they tell you very little. But when you read them sequentially in the context of past pronouncements, they tell you quite a lot about how the thinking of the party's best (Available) ideologues has been formed -- and transformed -- by unforeseen events.

They tell you, in fact, a lot more than a prudent party leader would willingly concede.

When future political archaeologists dig into this year's Democratic Party platform, for example, and compare it with the 1976 manifesto, they will be struck more forcibly, I suspect, by the way Jimmy Carter's Democratic Party has revised its approach to the making of foreign policy. What they will discover, in short, is a longish list of Democratic Party discoveries about the real world -- as distinct from Jimmy Carter's dream world of four years ago.

This year's Democratic Party platform writers, for instance, have discovered the pitfalls of accommodation; there is no mention this time around of the 1976 hopes for "normalization" of relations with Vietnam. They've also discovered the perils of disengagement; there's no talk this year of removing American troops and nuclear weapons from South Korea.

The Palestinians as a people with a cause and a positive purpose are another discovery; four years ago they were dealt with in only a glancing reference to "Arab refugees." The Persian Gulf, undiscovered in 1976, is now the strategic center of American concern in the Mideast; in 1976, the Mediterranean was where this country should make its naval presence felt.

But the big discoveries have to do with power-balancing and this country's world role, and with U.S.-Soviet relations, in particular.

Four years ago, "human rights" and "our nation's commitment to the ideal of individual freedom and justice were the central themes. "The security of our nation depends first and foremost on the internal strength of American society," the Democrats declared.

True, it was acknowledged that "Soviet actions continue to pose severe threats to peace and stability in many parts of the world." But detente was still in style: "A principal goal must be the continued reduction of tension with the U.S.S.R."

Human rights remain a large preocupation in this year's platform. But the Soviet threat looms larger on the list of Democratic anxieties. "At the heart of our polict toward the Soviet Union must be a clear recognition of the reality of Soviet power," 1980's platform sternly warns. Along the way it explicitly reaffirms the Carter Doctrine and cities the Afghanistan invasion as one more reason why "we must reject the easy mythology that the Soviets see the world as we do."

As for detente, the Afghanistan crisis "has sidetracked our pursuit of a productive relationship with the Soviet Union," this year's platform reports. p

Defense needs are, accordingly another rich field of discovery. Four years ago, the Republicans were chided for "having undermined the security of our nation by neglecting human needs at home while, for the first time in history, increasing military spending after a war."

This year, presumably profiting from sharper hindsight, the Democrats have discovered that the Nixon-Ford administrations "actually presided over a steady decline of 33 percent in U.S. military spending between 1968 and 1976." So much for that historical postwar precedent.

Since 1976, the new platform claims, the Democrats have reversed that dismal Republican trend. In the process, they have also reversed a "threatened decline in America's world position" -- a decline that wasn't visible, or at least went unmentioned, four years earlier.

Rather, four years ago, the Democrats were promising to knock $5 billion to $7 billion from annual defense cost without, naturally, upsetting the balance of power or weakening "America's world position."

The 1980 platform's promise, by contrast, is of an annual real growth in defense spending on the order of 3 percent. Proudly, the Democrats point to a "real increase in our defense spending in every year since 1976." So much for those $5 billion to $7 billion annual cuts.

This turnabout, to be sure, is not going to be enough to remove foreign policy and national security as a big item in the fall campaign. Ronald Reagan guarantees that. But the Democrats have come a distance in the past four years. That gentle tinkling you hear is the sound of scales falling from the eyes of Jimmy Carter's foreign policy ideologues.