The late Sen. Paul Douglas used to tell of the "civilizing" efforts of 19th-century American missionaries in Hawaii. "In due course," he said, "a curious exchange took place. The Hawaiians got the religion and the missionaries got the land."

Much of the history of mankind can be written in those terms. Nicaragua is such a case. Spaniards arrived in the 16th century, made Catholics of the Indian population, claimed their lands for the Spanish crown and exploited the country over the next 300 years. In the process, they "civilized" their wards by destroying their culture and their racial identity, imposed a new language on them and built cities and cathedrals to the glory of God. British, Dutch and French freebooters brought pieces of their own civilizations to the land and left behind a city -- Bluefields -- named after a 17th-century pirate. They were followed in the 19th and 20th centuries by North Americans from the United States and Canada.

Today the mutant society of Nicaragua is searching for some new identity. In that quest, the helping hands of outside powers are much involved. Thousands of new missionaries have arrived from the Soviet Union and Eastern Europe, Cuba, East Germany, Western Europe and the United States. Even Islam has sent a few prophets.

What this polyglot multitude seeks through its interventions in such a small land has become one of the great conundrums of our time. Economic exploitation is an unlikely motive; most of the gold is gone and the people are impoverished. Spotless humanitarianism is a possibility but that theory has few believers. The more commonplace explanation is that Nicaragua as a society and as a geographical entity is irrelevant to these outside actors except as a pawn in a geopolitical game .

The United States government has been candid about its own interests. Its aim is to prevent the creation of "another Cuba" in the hemisphere and is accordingly supporting rebels in their civil war against Nicaragua's government which is heavily populated with Marxists. This intervention was justified in evangelical terms by President Reagan last week: "Freedom is not the sole prerogative of a chosen few; it is the universal right of all God's children . . . . Our mission is to nourish and defend freedom and democracy, and to communicate these ideals everywhere we can." His liberal critics, while disagreeing with Reagan's tactics, essentially subscribe to that missionary concept, couching it in terms of "human rights."

The geopolitical interests of the Soviet Union and its allies are far less clear. They have made no policy declarations beyond altruistic statements of "solidarity" with the Sandinistas. But sinister motives and hidden agendas are perceived in Washington and in some Central American capitals, too.

Inside Nicaragua today, it is difficult to sort out the purposes of the new missionary forces at work here or what the revolutionary regime, the Sandinista National Liberation Front, seeks of them.

At one level, social-welfare services are being supplied on a large scale -- international brigades of coffee pickers, volunteer doctors, teachers and technicians with various skills. They render certain political services as propagandists and organizers of political constituencies in the United States and Western Europe.

At another level, Cuba and the Eastern bloc are contributing architects of the government and the Sandinista party organization. Tomas Borge and other Sandinista leaders speak passionately of their determination to create structures that are uniquely Nicaraguan. But thus far, there is a distinct foreign imprint on what has been done.

It is apparent in minor innovations such as the airport security and customs facilities installed by the East Germans: the passport inspection booths are equipped with overhead mirrors which allow functionaries to see who they are dealing with without being seen.

On a more significant level, it is seen in the neighborhood Committees of Sandinista Defense which perform certain police duties but also function, as a sympathetic observer has written, as ideological vigilantes. They discipline dissidents in various ways, such as withholding food ration cards or spray painting their houses with such slogans as, "CIA Lackey" or "Counterrevolutionary." The neighborhood committee concept was imported directly from Cuba, along with large numbers of military trainers and advisers.

At the top of the regime is a National Directorate composed of Borge, President Daniel Ortega and seven other "commandantes." It exercises the ultimate powers of the state and functions in ways similar to the Central Committee of the Communist Party in the Soviet Union.

Borge commands the Interior Ministry which performs police and internal intelligence functions. The president's brother, Commandante Humberto Ortega, commands the armed forces which are not answerable to the government but are rather under the control of the Sandinista political party. The party itself -- the FSLN -- bears a strong resemblance to the Soviet Communist Party.

The FSLN has developed means for dealing with opposition. A number of former Sandinista revolutionaries -- out of favor with the regime -- have gone into exile either voluntarily or under pressure. The central trade union federation, a long-time ally of the AFL-CIO, has been curbed by government decrees and undermined by the creation of parallel unions created by the FSLN. The Sunday homilies of Catholic bishops were made subject to censorship. The news media for the most part have been taken over by the party apparatus and the only opposition newspaper, La Prensa, is censored daily. According to Princeton scholar Richard Ullman, the State of Emergency decrees of 1982 also have suspended "right to liberty and habeas corpus, the right to freedom of travel, and the rights of association and peaceful assembly."

The similarities to the Soviet system are obvious. But there are sufficient differences to dispute the notion that Nicaragua is a wholly owned subsidiary of Moscow or Havana. A degree of political pluralism remains. Furthermore, Tomas Borge, a Marxist-Leninist disciple, insists "I have not said anything about a socialist system . . . . We have a mixed economy, a social regime that includes free enterprise to a large degree . . . . That is the system we choose and that is not a publicity stunt but a strategic concept."

He rejects, too, the allegations made in the United States that Nicaragua will ever become a Soviet military outpost. The regime, he said, is prepared to give guarantees that there will "never be any foreign military bases here . . . . The only way we can be a menace to United States security is to put nuclear weapons here. They say in the United States 'Never say never.' But I say it will never happen."

Reassurances of this sort are, of course, meant to placate the United States. But the larger view of Borge, President Ortega and other government figures is that whatever path Nicaragua chooses is not the business of the United States or of any foreign power. They are very passionate on the subject and raise a profound philosophical question that could have been put to the Spaniards four centuries ago:

By what right or principle does one nation intervene in the affairs of another?

The principle of self-defense has been invoked through the ages. Colonial powers claimed divine rights to civilize savages for the glory of God and king. The United States developed in the 19th century a messianic doctrine of "manifest destiny" and more lately in this century has justified interventions in the name of democracy and the "rights of man."

The Soviet Union has developed a "preservation of empire" rationalization for interventions in Eastern Europe and elsewhere. It has also accepted the classic Marxist doctrine that the international struggle of the "proletariat" against the "bourgeoisie" is both necessary and inevitable and has nothing to do with national boundaries or ethnic identifications.

Interventionism has been the underlying principle of American dealings in the southern hemisphere since the Monroe Doctrine was enunciated more than l60 years ago. And it is precisely that doctrine which is being repudiated today by the Nicaraguans. There is little doubt that the society, under its present leadership, is evolving into a Marxist-Leninist state. But to that, Borge and Ortega reply: so what?

You have no right, they insist, to manage our lives or our affairs; if we want a communist society or a fascist society or a Fabian society that is our business and not yours.

That philosophical assertion is not consistent with the universal imperatives of Marxist dogma. But it is consistent with liberal democratic thought: Nowhere is it written that a democratic political system is the 11th commandment of God. The right to impose such a system on another nation does not exist. Only might sustains the proposition.

That is at the core of the present debate in the United States over Reagan administration policies in Nicaragua. It is a debate between those who would, in effect, eradicate the Marxist-Leninist regime and those who would live with it and would attempt through other forms of intervention -- economic assistance or human-rights appeals, for example -- to moderate its tendencies.

The eradication policy has had some short-term successes: Nicaragua has apparently all but ceased aid to the rebels in El Salvador; it did hold a presidential election; it continues to tolerate some opposition and a mixed economy. But American policy is not likely to really erradicate the Saninistas without intervention by American armed forces, which even the Reagan administration has described as unthinkable.

The better alternative is a policy that is very difficult for both liberal and conservative missionaries and problem-solvers in the United States to accept. It is called benign neglect -- not an end to military pressure to be replaced with economic and political pressure, but real neglect.

Such a policy deprives the United States of no future military options, as Tomas Borge is quite aware. If, he says, Nicaragua were to take military action against any of its neighbors "anyone with common sense can see that the United States would intervene." He also concedes that the United States has legitimate national security interests in the region which preclude the creation of hostile military bases.

Castro shakes his fist and defies the Yankee colossus from his isolated island kingdom, living on alms from a Soviet society that is itself an economic failure. He is, in the final analysis, a beggar. If the Sandinistas choose that course, wish them God speed.