AFTER NEARLY 100 days in charge of American foreign policy, the Reagan administration has begun to produce some powerful evidence to support Goldman's Law: "The primary purpose of any new administration is to make the last one look good."

Guido Goldman, director Harvard's Center for European Studies, enunciated the law. It seems an apt description of the new administration's first three months, which have not been easy. Though they promised competence, firmness and steadiness, the new administrators of American diplomacy have often seemed indecisive and confused. They are clearly ready to confront Soviet power, but not at all ready to explain a coherent approach to world problems. It's clear what the new administration is against , but the world is still wondering what it will be for .

At his Senate confirmation hearings Alexander M. Haig Jr., the self-anointed vicar of Reagan foreign policy, promised a diplomacy of "consistency, reliability and balance," but the first 100 days have not produced it. Instead, Haig has become the most controversial member of an openly contentious administration, has angered the president's most intimate advisers and has raised doubts in Washington and in major world capitals about his staying power -- not least because of his repeated threats to resign. Haig's own efforts to establish a single line of adminstration policy have failed.

This month the U.S. secretary of defense was telling Europeans that talks on nuclear arms control in Europe should be put off because of Soviet "threats of violence or intimidation" against Poland. Days later, the White House justified its decision to lift the grain embargo against the Russia in part by pointing to Soviet "restraint" in Poland.

That secretary of defense, Casper W. Weinberger, has won a reputation in these 100 days as something of a loose cannon on the deck of Ronald Reagan's ship of state. In his first days in office Weinberger came out for American bases in the Middle East -- before establishing that any Mideast country wanted them -- and for revival of the neutron weapon in Europe, before learning that Europe wasn't interested, or that the United States might not be able to produce the fissionable material needed to deploy the weapon. More recently he has alarmed Western Europe with his rhetorical repudiation of any kind of detente with the Soviet Union. Later, when asked what he meant by "detente," Weinberger suggested he was referring to "unilateral disarmament."

Haig has gone to some lengths to repudiate or soften the impact of Weinberger's remarks, but because of his own difficulties, foreigners can't be sure whether Haig or the secretary of denfense (who is much closer personally to President Reagan) is actually speaking for the administration. And because Weinberger has sometimes contradicted himself (on the possibility of selling arms of China, for example), his remarks too carry uncertain authority.

All in all, it has been a rocky beginning -- at least as rocky as the Carter administratin's beginning four years ago. It is difficult to point to any substantial achievement of these 100 days of Reagan diplomacy, and the groundwork may have been laid for some very substantial disasters later on.

On the other hand, nothing irrevocable has occurred during these first 100 days, when the new administration has been preoccupied with its domestic economic policies. In the field of foreign policy, only one definitive comment seems fair now: The administration has squandered its chance to "hit the ground running," as presidential counselor Edwin Meese III and others promised it would during the transition.

Goldman's Law is based on the notion that "we have a lousy political system here," as its author put it in a recent conversation. No other western democracy provides for the complete turnover of virtually every policy-maker's job when a new government takes power. Indeed, only in America does the national security apparatus get more than a new top layer of leadership. The West European powers settle for a few ministers at the top of each department; but in America we can -- and do -- upend the entire government apparatus.

The Reagan administration not only cleaned out the policy-making positions in Washington; it also fired the ambassadors in most major world capitals.Though there were early promises to fill the jobs quickly, three months later many of them remain empty, or are occupied by designees who have not been formally nominated or confirmed by the Senate. The American embassies in nearly all the the major capitals still have no ambassadors. Much os this can be attributed to bureaucratic delay and confusion, but some of it represents the fruits of unresolved political struggles within the Republican Party. Sen. Jesse Helms (R-N.C.) has become The Great Intimidator of the new administration, personally holding up half a dozen or more key nominations in the Senate. At the White House this is dismissed as intraparty gamesmanship, but in the world it appears to be another sign of weakness and uncertainty.

Besides cleaning out the government, this new administration has decided to radically overhaul the bureaucratic arrangements for the making of national security policy. The Reagan group set out to significantly diminish the role of the National Security Council staff, one objective it has accomplished. Instead of the tightly knit group that dominated the foreign policy process in the first Nixon, Ford and Carter administrations, the Reagan NSC operation is apparently passive and loose-knit. Coordination has not been its strong suit. a

Last week Meese told newspaper editors in Washington that the Reagan administration had solved the problem of the State Department fighting with the NSC. But in some cases at least, this has been accomplished only by both units agreeing to do nothing. For example, as of early last week the administration was still struggling to agree on a reply to a month-old letter from Leonid Brezhnev to President Reagan, according to an NSC source. This government can't decide how to deal with Brezhnez's proposals for new negotiations, the source said.

One objective of the new approach to the NSC has been to keep it out of the news, and this has been accomplished -- with two notable exceptions. One was a speech by Richard V. Allen warning Western Europe not to succumb to neutralist pressures, a speech reinforcing the confrontational image of the new administration that most alarms European governments. The second was an interview given by Richard Pipes, a Harvard histroian and well-known hardliner now working for Allen. According to Reuters news agency, Pipes said the Soviet Union would eventually have to chose between modifying the communist system and going to war. He also said the West German Foreign mimister was susceptible to Soviet pressure. Haig quickly and brutally repudiated these undiplomatic remarks (which, according to Pipes, were misquotations in the first place).

But the real problem about the Reagan administration's system for formulating and executing foreign policy is that it hasn't yet got one. Senior members of the administration acknowledge the disarray in private conversations. Foreign service officers in the State Department say they are working in a state of constant confusion. Officials involved in debates over arms control policy describle the administration's new officials as stubbornly indescisive. Foreign ambassadors report that their efforts to find out what the new administration is planning are extremely frustrating. It seems safe to predict that whatever becomes recognized as the Reagan approach to diplomacy hasn't been seen yet, but is still to come.

If the administration is without a system for policy management, it is also largely without a policy, except in a negative sense. Reagan, Haig, Weinberger and the others have made clear that this administration opposes Soviet expansionism. They have made a staunch anti-Soviet position the centerpiece of their rhetorical policy. But this has not been translated yet into concrete terms, except for a request for an enormous increase in defense spending.

Even that step left some confusion about administration intentions. During 1980 Reagan compaigned ardently against the SALT II treaty signed by Jimmy Carter, but the huge military buildup Weinberger has proposed contains no new program that would violate the terms of SALT II. This could be changed later, but so far at least the new administration has confirmed the view expressed by SALT supporters that the treaty would not impinge on any needed American program. "You'd have to go out of your way to find a program that would violate the SALT II treaty," said a new, senior official at the Pentagon who himself used to help the opposition to the treaty in the Senate.

Meese declared last week that the administration was off to a good start in foreign policy: that the allies were united and appreciated the new attention they were receiving. The administration's "so-called hard line," Meese said, had improved the United States' ability to communicate with the Soviets, and gives Americans "a better sense of ourselves."

The combination of more arms and stern anti-Soviet rhetoric has established a new posture for the United States, but it has not produced specific answers to pending policy delemmas. In word and deed the new administration has indicated that it is more drawn to military solutions than its immediate predecessors, but it has not yet attempted a military solution to any specific problem.

On a number of points the Reagan regime has had to move away from positions enunciated by Reagan the candidate. Whatever the candidate meant about raising the level of relations with Taiwan, the president has done nothing but reassure Peking. Reagan as candidate was much more sympathetic to white rule in South Africa than he has thus far been as president -- an ambiguity that has clearly annoyed the South African government. Haig's early effort to transform El Salvador into an East-West battleground has been quietly abondoned, at least for now. Strong skepticism about arms control negotiations has had to yield to intense European desires to see them continued.

These are all examples of how international realities now restrict any American president's freedom of action. Reagan and his associates seem to yearn to return to an era when America's word was decisive in international affairs, but there are numerous other governments that refuse to let that era be revived.

Nigeria and the other black African states can and will influence American policy toward Southern Africa. Both Arab and Israeli interests will continue to alter American policy toward the Middle East. The government in Peking can now make its weight felt in Washington's policy deliverations. Most important of all, the United States' NATO allies can be crucially important to most significant American undertakings in international affairs, particularly in the Soviet-American relationship.

Western Europe, as the Reagan administration has already discovered, is not prepared for a policy of total West-East confrontation. On the contrary, a confrontational American line is likely to feed the very real pacifist and neutralist strains in European thinking that most alarm today's West European leaders -- and should alarm Americans, too.

The Europeans have brought this message to Washington and delivered it to traveling Reagan administration officials in Europe. They have conveyed it privately and publicly; to government officials, journalists and anyone who will listen. West Europeans are grownups now; they are worried about the developing world, about Southern Africa, about the Arab-Israeli conflict and about all the big issues of the day. In Europe very few of these look like simple East-West conflicts. And European governments will not blindly follow an American policy they disagree with; if they tried they could easily lose the support of their own people.

The principal European lever for influencing American policy in the near future may be the NATO plan to modernize nuclear weapons in Europe by deploying new American missiles that can reach Soviet territory with Germany, Italy, Britain and perhaps other countries. NATO has only agreed to this deployment in principle, and on condition that strategic arms control is pursued with Moscow at the same time.

The Reagan administration's desire to look tough to the Russians could be destroyed if the NATO agreement on new missiles were to fall apart. The Europeans can be expected to take advantage of the influence this situation affords them. (The administration may also throw away its tough image unilaterally with its decision to lift the Soviet grain embargo, a decision that must baffle the Soviets but delight them too.)

Even on matters in the American backyard, the Europeans will be heard from. During the Haig-sponsored furor over El Salvador, for example, West Germany's conservative and hard-line party, the Christian Democratic Union, forcefully disassociated itself from the Reagan administration. The president of El Salvador, Jose Napoleon Duarte, is himself a Christian Democrat to whom the Gesman Christian Democrats feel fraternal ties. It's a nice example of how complicated the modern world can be.

Last year Ronald Reagan told The Wall Street Journal: "Let us not delude ourselves. The Soviet Union underlies all the unrest that is going on. If they weren't engaged in this game of dominoes, there wouldn't be any hot spots in the world."

Ronald Reagan has not been a very visible figure in the first 100 days of his administration's foreign policy. His principal contribution has been rhetroical. The tough rhetoric he has used has suggested that he really believes the view he gave to The Wall Street Journal.

If he does, and if that sort of unqualified anti-Sovietism becomes the basis of Reagan's foreign policy, it is likely to prove spectacularly unsuccessful in the months and years ahead, even if the administration does eventually get it act together. A United States government that attributes (for example) the Palestinian problem, the Iran-Iraq war, the struggle for independence in Namibia and insurrection in the Philippines entirely to the Soviet Union's machinations is doomed to diplomatic failure.

Yet this is the line Secretary Haig seemed to adopt when he described a communist "hit list . . . for the ultimate takeover of Central America," of which "the seizure of Nicaragua" was the first state. Remarks like that one sound like determined simplification or sloppy thinking. So did Haig's comment on the day of the attempted military coup in Spain that this was "an interal matter" for the Spanish. Haig had to spend a day in Spain this month trying to patch up the damage that one caused by reassuring the Spaniards that this administration really does care about the fate of Spanish democracy.

Or listen to the words of the unbiquitous senior official who travels with secretaries of state on their world trips (if he has the same identity in this administration that he had in the last wo, his name is Alexander Haig). This was a comment the high official made as Haig's plane left the Middle East earlier this month:

"There wasn't a place we went that there wasn't a profound lack of confidence in the United States, long-standing doubts about America's staying power, its leadership . . . and above all its willingness to stand up to Soviet aggression. And the minute we addressed these issues in a manner in which it was clear that the United States . . . intends to reassert its global responsibilities and regional responsibilities, to maintain consistent and reliable policies . . . and to induldge in a dialogue in which their views are considered in the formulation of our own policy, this automatically turned each of our hosts into an entirely different mood and attitude."

If improving America's position in the world is as easy as that, the Reagan administration faces the rosiest of diplomatic futures. The suspicion persists, though, that the real prospects aren't that good.