Andrew Young is the exorcist of U.S. foreign policy - intent on driving out the evil spirits that have bedeviled U.S. relations with the Third World and leaving only what he believes is "the essential goodness of the American people."

That was the dominant impression to emerge from Young's whirlwind 12-day, 10-nation tour of the Caribbean, which ended today as Young returned to the United States.

Officially Young was here to discuss issues before the United Nations with his Caribbean counterparts. His real purpose, though, was to lend his high visibility and his stature within the Carter administration to Washington's effort to dramatize a policy of rekindled attention for the problems of the United States' Caribbean backyard.

In terms of salesmanship, it was a brilliant move. In Young, the administration had the ideal person to articulate a message that transfers the ideas forged in the U.S. civil rights struggle to international relations.

Young hammered tirelessly at the same themes: That the American people realize they cannot manipulate the lives of others in the interest of U.S. power and profit, that the United States has an obligation to defend the human rights and dignity of all people, regardless of their color or class, and that Washinton must respect the right of other countries to go their own way in choosing political and economic systems.

It was a message that caused quite a stir in this region, which has regarded itself alternately as exploited or ignored by the United States. It was given special point by the realization that the messenger was not just another second-string spokesman for the State Department but a man whose influence with President Carter on questions involving the Third World rivals of the secretary of state.

However, Young's bravura performance in setting the scene for Washington's new Caribbean policy raised some nagging questions about what happens in the next act.

Trailing in the ambassador's wake were several of the diplomatic and foreign aid professionals who will be responsible for giving the outlined form the substance. While they are unanimous in applauding the impetus of Young's trip, some are also worried about the risk of the venture producing some serious misunderstandings.

Among many people here, the Carter administration's interest in the region has reawakened memories of the early 1960s, when the late President Kennedy became a beloved figure throughout Latin American because of his effort to promote the Alliance for Progress. There is a tendency to assume that Young's visit symbolizes a return to the policies that were disrupted by Kennedy's death and the Vietnam war.

However, despite surface similarities, there is a great difference between 1961 and 1977. The Carter policy does not contain one of the central premises of the old alliance - the idea that Latin America's deep-rooted economic and social problems can be solved by throwing massive amounts of U.S. financial assistance at them.

Washington is prepared to make some substantial increases in its aid. In fact, almost every one of Young's stops has included an announcement of additional financial and technical help for his host country. But his main economic message has been that there are distinct limits to how much the United States can contribute and that the Caribbean countries should do more to help themselves by banding together in improved regional cooperation efforts.

Although Young was careful to stress that point, U.S. officials are fearful that, in many cases, it may have been lost in translation. They say many people may be harboring unrealistic expectations about U.S. aid that could lead, as has happened so often before, to disappointment.

There is another fundamental difference between the Kennedy and Carter approaches. The Allicance for Progress was an ideological response to the sudden emergence of Communist Cuba on the hemispheres scene - a situation that, in the atmosphere of early 1960s, raised fears about Soviet influence spreading through the "soft underbelly of the United States" and that temporarily made Latin America an area where Washington and Moscow competed for influence.

In marked contrast to that time, Young described that Carter administration's policy as "divorcing the North-South dialogue from the East West conflict." By that he means that the United States intends to move away from viewing relations with developing countries as an extension of Cold War rivalry and to judge their governments by how closely they conform to U.S. norms of reliability.

In a remarkable impromptu statement in Haiti, Young spelled out his view of what the old approach had accomplished:

"We found that the government of which we were so proud was responsible for propping up many military dictatorships and some of the most corrupt governments in the world. The American people found that their tax dollars, which they had worked very hard to earn, were goinh abroad only to make the rich richer and essentially not contributing anything to help the poorest of the poor."

With the election of Carter, he asserted, the American people had signaled their desire to excise such immoral, ideological considerations from their dealings with the Third World - to stop rewarding repressive regimes because they dutifully echoed an anti-Communist line and to stop penalizing other government whose efforts to help their people came into conflict with U.S. strategic or business interests.

In his swing around the region, Young stood quite a few of the positions taken by Washington during the past decade on their heads. It was no accident, for example, that he made his blunt statement about dictatorship and corruption in Haiti, where for years the United States found it convenient to overlook some of the most savage, brutal repression in the world.

Although Haiti's present rulers have eased up somewhat in their treatment of dissidence, the country remains very much a dictatorship. Young minced no words in publicly telling the Haitian regime that "treating people with brutality does not do anything to further the development of society" and in making it clear that future American support will be related to improvements in Haiti's respect for human rights.

Conversely, two regional leaders who have been treated like pariahs by Washington in recent years - Jamaica's Michael Manley and Guyana's Forbes Burnham - got warm embraces from Young.

Both had run afoul of the Nixon and Ford administrations because of their attempts to develop their countries through systems of radical socialism' their nationalistic hostility toward traditional foreign investment and their coziness with Cuba's Fidel Castro.

In both countries, Young went out of his way to make it clear that the Carter administration considers it their rights to hold these positions, and that Washington will not only accept the Manley and Burnham governments on their won terms but is willing to help them with some fairly substantial increases in foreign aid.

That, Young also made clear, does not mean that either the Carter administration or he personally is advocating radical socialism as a model for other developing countries.

Instead, he said, the basis of the Carter Administration's Third World policy is to recognize that any government, if it respects the rights of its citizen and its neighbors, should be free to follow Capitalism, Marxism or any other system that it feels will give its people "the most basic of human rights - the right to survive economically."

He perhaps put it best in a discussion with Costa Rican university students. After hearing one ideologically intense student attack the U.S. free enterprise system as unsuited to the needs of Latin America, Young replied that the world could still learn a few things from the American way of doing things and added:

"Remember, whether it's hamburgers or computers, we do it better than anyone else. But that's a choice for you to make. It's up to you to decide."