Ronald Reagan has no doubts about America's role in world affairs. In a March 17 Chicago speech -- one that Reagan's advisers call "the bible" of his foreign policy views -- he set out his credo in two unequivocal sentences:

"We did not seek the leadership of the free world, but there is no one else who can provide it. And without our leadership there will be no peace in the world."

They are words that are getting a lot of scrutiny as Reagan prepares to go to Detroit to receive the Republican presidential nomination that could lead him into the White House next November. For, as he begins his time of testing against President Carter, both Americans and foreign diplomats will be engaging in increasingly feverish speculation about how a Reagan victory would affect the course of U.S. foreign and defense policies.

In Reagan's case, the speculation is bound to be especially intense because of his bedrock conservatism. Among American liberals, that means the verdict on Reagan already is in: They listen to his speeches, ringing with the ruffles and flourishes of Cold War rhetoric, and condemn his ideas out of hand as a scenario for igniting a new world war.

Elsewhere, among those foreign leaders seeking to read the tea leaves bubbling to the surface of the American political process, the questions about Reagan are more subtle and complex.

They, too, have heard his tough talk, and it has many of them frankly worried that a Reagan presidency would have major disruptive effects on the broad-gauged continuity in U.S. policy that they have come to expect from Democratic and Republican administrations.

That is why there is considerable concern in Western Eruope and elsewhere over the exclusion from the Reagan inner circle of Henry A. Kissinger, who is widely regarded abroad as the godfather og the policies central to the conduct of foreign affairs in the Nixon, Ford and Carter administrations.

The arm's-length treatment being accorded Kissinger and other old hands from the Republican side of the U.S. foreign policy establishment has caused foreign governments a great deal of frustration in trying to piece together a picture of what living with a Reagan presidency would be like.

They know that Reagan's election would mean a move to the right by the United States, but they don't know where the turns would come or how sharp and abrupt they might be. In addition, they don't know who, among the largely unfamiliar faces around Reagan, would wind up calling the turns on policy and whether they would treat the candidate's campaign pronouncements as holy writ or adjust them in the process of running a government. In short, they don't know what a Reagan presidency would be all about.

Much of their nervousness might be dispelled if there were a really clear idea of who would wield power in a Reagan administration. Some of the names mentioned -- most notably former NATO commander Alexander M. Haig, former treasury secretary George Shultz and former defense secretary Donald Rumsfeld -- sound relatively reassuring to America's allies.

But, as Reagan's intimates keep pointing out, no decisions have been made about who would be likely to get what job. In the meantime, those seeking clues to Reagan's ultimate direction have been reduced to trying to sort out the pecking order of his defense and foreign policy advisory groups in an effort to deduce who is likely to be most influential.

These advisory groups, collectively numbering about 100 people, were put together by Richard V. Allen, overseer of diplomatic and security issues on Reagan's staff, after combing the right side of the political spectrum.

Under the direction of Allen and his cohort, Fred C. Ikle, a former director of the Arms Control and Disarmament Agency, the advisers are engaged in producing a blitz of papers intended, in effect, as a sort of correspondence cram course to familiarize Reagan with every conceivable global issue.

The roster shows some interesting omissions -- the most notable being Kissinger and his most readily identifiable former key lieutenants such as Helmut Sonnenfeldt and William Hyland. In addition to being anathema to Reagan's hard-core supporters on the Republican right, Kissinger is regarded by the other advisers as having a reputation and ego that wouldn't permit him to play on the team without insisting on being its captain.

Allen, who worked briefly and unhappily for Kissinger in the Nixon White House, insists that they're still friends who keep in close touch.But, there's little question that the Reagan people are determined to keep Kissinger shunted off in the ceremonial role of being a party elder statesman.

For the rest, Allen's teams are almost a Who's Who of leading rightist theoreticians and activists, leavened with a few centrists. Most are former officials from the Nixon-Ford era or academicians recruited from a variety of campuses and conservative-oriented think tanks. In the opinion of outside observers, they vary widely in the quality of their ability and intellectual prowess.

Some are old cronies of Reagan, and some have never met him. Some are well-scarred veterans of diplomatic wars, and some are youngsters hoping that their work for Reagan will win them entry into the corridors of power.

They include a gaggle of supperhawk military men like retired Adm. Thomas H. Moorer and Gen. Daniel O. Graham. There are throwbacks to the 1950s' era of pleading the cause of Eastern Europe's "captive nations" (Lev Dobriansky of Georgetown University) and there are disaffected former supporters of Carter and the Democrats (Robert Osgood of Johns Hopkins, Jeane Kirkpatrick of Georgetown, Nathan yglazer of Harvard).

Some, like Robert Ellsworth (a recent dropout because of conflicts with his Reagan fund-raising activities), Robert G. Neumann and James Theberge, earned generally high marks for their performances in various ambassadorial posts under Nixon and Ford. By contrast, John Davis Lodge, a former ambassador to Spain and Argentina, is vividly remembered in both countries for reaching heights of almost inspired bumbling.

Despite Allen's efforts to screen out what he calls "irresponsible elements," there are people on the team with a penchant for behaving like "loose cannons." That was demonstrated by one defense adviser, Joseph Churba, who turned up in South Africa last month to assert that the United States should treat that country's white-supremacist regime as a "fighting ally on an equal footing."

If Reagan were to become president, Allen, despite his disclaiming of personal ambitions, would be expected to get the nod as national security adviser, and Ikle would almost certainly be slated for some unspecified but influential post.

Others whose names increasingly figure in speculation about key diplomatic assignments include Ray S. Cline, a former intelligence official (possible director of the CIA); Laurence H. Silberman, a former ambassador to Yugoslavia with provocative ideas about restructuring the foreign service (deputy secretary of state); Kirkpatrick (ambassador to the United Nations); Richard E. Pipes, a Kremlinologist (resident strategist on dealing with the Soviet Union), and Neumann (head of Mideast policy).

Then there are a number of gadfly types who don't fit into convenient pigeonholes, but who are known to have considerable influence among the advisers. These include Richard J. Whalen, a best selling author and Washington wheeler-dealer; Edward N. Luttwak, a Georgetown University expert on just about everything in the defense and dipolmatic arena, and Frank Shakespeare, a broadcasting executive who mixes an aura of show-business pizazz with hard-line anti-communism.

The guessing about who's up and who's down among these assorted personalities is what caused one high ranking West European official to confide to friends during a recent visit here, "To us in Europe, Reagan is almost a total enigma. We really know nothing at all about where he gets his ideas or even what those ideas are."

A visitig Israeli political leader was even more outspoken. After a meeting with Reagan, he told almost everyone he encountered in Washington: "Reagan knows as much about the Middle East as I do about making films in Hollywood."

Reagan's lack of experience and expertise in foreign affairs is readily conceded by his advisers. But, they point out, the same was true of Jimmy Carter four years ago.

In the meantime, aides like Allen say, the key to understanding Reagan rests not in his mastery of facts and figures but in his deeply held convictions about America's proper place in the international scheme of things.

Certainly, it's true that when Reagan speaks, as he did in Chicago, about the United States as leader of the free world, he's not just expressing campaign rhetoric. Instead, his words reiterate a theme that has served American conservatives as an article of faith since the beginning of the long push across the frontier that transformed the United States into a world power.

At different times, to suit different circumstances, it has borne a variety of labels: from "manifest destiny" in the 19th century to "Pax Americana" in the 20th.

But, whatever the situation of the moment -- from turn-of-the-century imperialist adventures in the Pacific and Caribbean through the carnage of two world wars to the nuclear cat-and-mouse games of the Cold War -- it has been a major motivating force and philosophical justification for America's actions in the international arena.

Stated in its simplest terms, it is the idea that the United States, has an inescapable duty to act as the tutor and protector of the free world in confronting the alien ideologies that threaten western values.

During recent years, the efficacy of that idea has been called into question for many Americans by the disillusionment of Vietnam and its aftermath. But, amid all the doubting, there have been those seeking to keep the flame of the old faith alive, and it was for them that Reagan spoke when he said in his Chicago speech: "We must rid ourselves of the 'Vietnam syndrome.' It has dominated our thinking for too long."

At a surface glance, Reagan's blueprint for reasserting this leadership seems easy to read. It is laid out in his March speech to the Chicago Council on Foreign Relations -- the only occassion so far in the campaign on which he has addressed foreign policy matters at length -- and in the Republican Party platform hammered out this past week by his operatives in Detroit.

Taken at face value, it would all but abandon present U.S. foreign and defense policies. The linchpin of those policies -- the detente strategy mapped by Kissinger under Presidents Nixon and Ford -- would be cut back sharply in favor of a more openly confrontational approach to dealing with the Soviet Union.

To hem in the Soviets and make them behave in a manner that the United States considers responsible, tens of billions of dollars would be diverted to building up American military strength. Along with the big bucks, the armed forces would have a big new influence in plotting U.S. strategies. So too would a reinvigorated "intelligence community" freed from the restraints imposed on it is recent years.

In the sensitive area of Third World relations, the Reagan approach would, in effect, discard such distinguishing hallmarks of the Carter administration as its emphasis on human rights. Instead, his Chicago speech talks of the need to "regain a reputation of reliability toward our allies" by judging governments in Latin America, Africa and the Far East on a scale that gives greater weight to their pro-America reliability than their commitment to home-grown democracy.

But, while the Chicago speech seems like a large canvas rendering of Reagan's ideas in bold brush strokes, a closer examination makes clear that it really is only a rough, preliminary sketch. Nowhere does it contain any of the fine detail necessary to answer such questions as where Reagan would get the tax dollars to pay for his proposed massive military outlays or how his theoretical ideas could be translated into specific policies to deal with specific countries and situations.

According to Allen, these details will be provided by the position papers being prepared for Reagan by his advisory teams. But the sheer undisciplined diversity of those groups means that any attempt to trace the outlines of a Reagan foreign policy by probing the views of its individual members is bound to bog down in confusion.

For example, some of the advisors like Luttwak, Amos Perimutter of American University and Uri Ra'anan of the Fletcher School of Law and Diplomacy, are former residents or citizens of Israel who advocate strong and unswerving support for that country's position in the Middle East. But there also are others on the team described by one member as having "an unbounded admiration" for the Mideast policies favored by the big oil companies which want to court the goodwill of the Arab world.

Then there is the question of Taiwan. Reagan, who bitterly opposed Carter's breaking of relations with the island republic, has talked of defying China's potential anger and raising the level of U.S. diplomatic ties with Taiwan. In that position, he has the ardent support of some advisers, who, as one says, "are still burning incense at the shrine of Chiang Kai-shek."

However, an apparently even larger number of his advisers believe that the smartest move of the Carter administration was its opening to Peking because of the opportunities that offers in playing off China against Russia. As a result, this group feels it would be a major mistake for Reagan to risk straining the U.S. relationship with China by making conciliatory gestures toward Taiwan.

Nor does the potential for collision end there. Perlmutter, for example, has drawn an elaborate and controversial scenario for a U.S. seizure of the Persian Gulf oil fields in a crisis. But that runs against the grain of the belief expressed by other advisers that the United States currently is at such a strategic disadvantage in the gulf region that it would be folly to attempt any type of military operation there.

Sometimes, it's not just a case of opposing theories, but of a position that contains its own built-in contradictions. Robert Osgood, a specalist in Western alliance affairs, notes that the Reagan people talk simultaneously of downgrading detente and forging a special new relationship with West Germany, without offering any explanation about how such a move could be reconciled with the important role that detente has come to play in West German political and economic life.

These conflicts have led at least one team member, a prominent academician who asked not to be identified, to conclude that the exercise was a bad mistake that will hit Reagan with such a barrage of contradictory paper that he won't even have time to read in the pressures of the campaign.

"In restrospect," the adviser says, "it would have been much wiser for Reagan to assemble a group of the Republican policy pros that he knows and respects -- people like Al Haig and Don Rumsfeld and a few others -- and sit down with them for a few hours od intensive boning up that would enable him to get through the campaign by answering questions on the issues with some semblance of intelligence."

That view is disputed strongly by Allen, who says: "We went into this fully expecting that we would have a collision of ideas and egos. We told everyone that these would be papers without status -- that we were offering nothing more than a chance for the participants to present their views to Reagan for his consideration."

"In the end," Allen insists, "we want to be able to give the candidate a lot of facts and a range of ideas that he can use or discard as he sees fit, but that will be the foundation of some very specific policy proposals that the voters will be hearing about as the campaign progresses."

Reagan may have his own proud vision of where he would like the United States to stand in the arena of world affairs. But, by the admission of his own aides, he has yet to make the choices of ideas that will enable him to stand before the voters and try to convince them that he has a policy capable of transforming the vision into a reality.