When the shah was giving way to the ayatollah a year ago, President Carter declared the United States had "no desire to be the world's policeman." Set against that background, the position enunciated by the president in his State of the Union message last week represents a breathtaking progression from the dream world to the world of reality.

For the first time Carter explicitly recognizes that the United States has "vital interests" around the Persian Gulf. He commits this country to resist Soviet moves in the area by "force if necessary," and he backs the threat with a military buildup and a step toward the draft.

Still, the president has yet to diagnose in public how the area around the Persian Gulf suddenly became the cockpit of world politics. He treats the seizure of the embassy in Iran and the Soviet assault on Afghanistan as two wholly disparate events. He declares readiness to "cooperate with all Moslem countries" as though the United States could mobilize militant Islam against communist atheism.

In fact, what has happened to the old empire of the shah is a vast, historic unraveling, an event not unlike the coming apart of the Turkish empire at the end of the last century. The taking of hostages in Iran by a regime incapable of governing is part of the drama. So is the Soviet invasion of an Afghanistan that was falling to pieces. Similar forces of disintegration are at work throughout the neighborhood -- especially in Pakistan and the mini-monarchies of the Persian Gulf.

The United States cannot steady these countries simply by unfurling a banner or surging the fleet in the Indian Ocean or starting to register potential draftees. This country has to find means for first checking the Russians, and then infusing strength into regimes that are weak, anachronistic, corrupt and lacking in assurance.

The obvious step in that direction is a real, live American presence on the ground. A squadron of Navy fliers in Pakistan, for example, would draw a red line against the Russians and also transmit a feeling of confidence to local regimes. But the president has stayed away from such explicit commitments. He speaks only vaguely of temporary basing facilities for a stronger American fleet.

Even less defined are the future relations between the United States and individual countries in the area. The 1959 treaty with Pakistan that Carter reaffrimed is itself a subject of the most widely divergent interpretations. For example, it did not exactly prevent Pakistan from losing Bangladesh.

About relations with Saudi Arabia and the how of protecting oil fields, the president said nothing. Nor about connections with the sultans of Oman, and the Straits of Hormuz at the choke point of the Persian Gulf.

A continuing measure of self-deception makes the unfilled blanks look that much worse. The president asserts the need to strengthen the Central Intelligence Agency as an instrument of American political influence. But he calls on Congress to enact a new CIA charter -- a sure way to drown efficient operation in an orgy of congressional debate on such big-think subjects as accountability.

The Russians, according to Carter, will be made -- by such measures as boycotting the Olympics and embargoing grain sales -- to "pay a concrete price for their aggression in Afghanistan." But the president seems not to notice that the price will be paid most by Andrei Sakharov and the other dissidents whom this country once hoped would introduce a measure of restraint into Soviet behavior.

In the same vein, the president limits oil imports for 1980 to 8.2 million barrels daily. But that is above expectations -- and surely does not impose the kind of sacrifice allies in Europe and Japan would require as the price for a concerted energy policy.

"Skyrocketing world oil prices" are fingered by the president as the "biggest single factor in the inflation rate." But Carter takes heart from the recent drop in gasoline consumption -- which was largely caused by the higher oil prices. Though he announced a rise in defense spending, there are no cuts in social spending to hold down inflation. Instead, Carter points with pride to the "historic national accord with organized labor" -- which in fact will erode still further existing restraints on price and wage hikes.

So what Carter has done is to build up crisis without declaring the cost. He has presented a menu but not the bill. That may be the ideal tactic for a president seeking reelection. But as a strategy for traversing a truly dangerous period, it is only a first installment.