Here in Personality City, where the name of the game is names--who's up, down, in or out--the fashionable wisdom now has it that Secretary of State Alexander Haig is up, Defense Secretary Caspar Weinberger is down and William Clark, the White House national security adviser, is in. This, it is said, accounts for a certain mellowing, a new moderation and a greater measure of coherence in the Reagan administration's approach to foreign policy: arms control, for one example, East-West relations in general, the Mideast, Central America, Taiwan.

And perhaps it does, up to a point. But it strikes me that something more fundamental is at work. True, there has been a significant shift in the policy-making center of gravity in the Reagan administration, and it doubtless owes something to the artfulness (or artlessness) of the infighters. It owes something, as well, to a vast improvement in the control mechanisms installed by Clark.

But it owes far more to a sort of collective acceptance of reality. One senses a heightened recognition of the need to adjust preconceptions and powerful past predelictions to fit the harsh exigencies of the real forces at work, at home and abroad: "peace" movements, economic constraints, the intractability of allies, the intransigence of adversaries.

And this says something important about the president himself--something that tends to get lost in the "names" game's preoccupation with the relative preeminence of his advisers. For better or worse, the Ronald Reagan who came across throughout his campaign and most of his first year in office as forever fixed in the concrete of archconservative ideology is capable of behaving like, well, other presidents --of being strong enough to bend.

A confident John F. Kennedy crashed quickly into the Bay of Pigs. Thereafter, his inaugural call to arms ("We shall pay any price, bear any burden") gave way in practice to policies better attuned to less well-remembered passages in the same speech--those summoning East and West, North and South, to a "long twilight struggle" against "the common enemies of mankind: tyranny, poverty, disease and war itself." In office, he conceded he couldn't find the "missile gap" that had yawned so alarmingly in his campaign.

Lyndon Johnson hit the ground running with an inherited national security team and a firm commitment to the struggle in Vietnam. He had to discover for himself that, hard as he hammered, he could not nail that Vietnam coonskin to the wall.

Jimmy Carter's good intentions paved the road to Camp David, but also in a certain sense to the shock of discovery of Soviet malevolence in Afghanistan and to the collapse of American policy in Iran. Having entered office pledged to reduce spending for defense, the Carter administration wound up doing just the opposite.

Circumstances alter cases, in short, along with untoward events, new perceptions, hard knocks and the quite unpredictable play of politics in this country and in those with which we deal. While this is not to say that every adaptation is the right one, it does put some sort of premium on at least a capacity to adapt. That is what we are increasingly witnessing in the Reagan administration's approach to foreign policy.

Without going into the nuts and bolts, the mere fact of the president's latest strategic arms control proposals, not to mention their timing, constitutes an accommodation to allied concerns and a response to the home-front anti-nuclear movement as well. Scorned for a year, the Camp David peace process is re-emerging as the centerpiece of American Mideast policy: progress on the Palestinian question is now recognized as essential to the development of the "strategic consensus" that preoccupied the administration in its early days of concentration on the Persian Gulf.

Congress has compelled a second look at Central American strategy. Even while support for the Salvadoran right-wing government is solid, diplomatic feelers go out to Nicaragua's Sandinista government for some sort of deal. Cooler heads have turned the heat off European allies to scrap their Siberian pipeline as a means of pressuring the Soviets on Poland.

Tradition and practical politics impel the administration to deny any change. But when Norman Podhoretz (in The New York Times) is crediting his fellow neo-conservatives for a large hand in Ronald Reagan's election while (on McNeil-Lehrer) expressing his "disappointment, bordering on despair," you have to believe that the Reagan administration is abandoning some of its original true beliefs.

If being in love with Reaganism in 1980 means having to say you're sorry in 1982, there must be some reason for those of us who entertained more than a few reservations about early Reaganism to feel better.