YOU PERHAPS have been wondering how "quiet diplomacy," the Reagan administration's chosen method for furthering human rights, works.

The visit of President Ferdinand E. Marcos, the Filipino dictator, does not make it immediately apparent.

The tough little president, with his glittering wife Imelda by his side, arrived at the White House in a black limousine, as the herald trumpeters ranged along the steps struck up a fanfare.

If you're Marcos, you obviously don't start worrying that anybody is going to berate you for abusing your own citizens.

Marcos got a cordial handshake from Reagan. Wife Imelda, refulgent in a pumpkin- yellow Filipino dress, got a kiss from first Lady Nancy Reagan. Certainly no cause for alarm there.

Nothing was "quiet" about what followed: a 2l-gun salute, the bewigged, slow-marching Old Guard Fife and Drum Corps playing "Yankee Doodle."

President Reagan's welcoming remarks made Marcos sound like a paragon, a champion of liberty and freedom. Reagan referred to "shared history and common ideals." The way the common ideals work out in Marcos' country is something called "constitutional authoritarianism" -- which involves jailing or exiling political opponents, stamping out unionism, arresting labor leaders and having soldiers beat up peasants who dare to strike.

Amnesty International issued a report last week which described unusual brutality including "disappearance" and extrajudicial execution , all carried out with tacit government approval.

But Marcos had nothing to worry about. Ronald Reagan assured him of his warm friendship, both for himself and his country.

Pope John Paul II is not an adherent of the "quiet diplomacy" school. In a 1981 visit to the Philippines, he lectured Marcos to his face about his lamentable record and said there was no excuse for it.

Just in advance of his visit, the mere occurrence of which is a triumph for Marcos in his efforts to expunge his reputation for thuggery, Cardinal Sin, the archbishop of Manila, called on Marcos to resign for the good of the country.

But Ronald Reagan cannot concern himself with what popes and cardinals say about dictators. They, after all, do not have to guarantee bases in the Philippines.

His tough-looking little guest, he hailed as "a voice for reason and moderation."

It was a description that would not have been recognized by Father Edgar Sanguinin, a 47-year old Filipino diocesan priest who spent the spring in Washington trying to rouse American public opinion against Marcos.

Father Sanguinin founded the National Federation of Sugar Workers, which now has 30,000 members. They get from 50 cents to $2 a day and, because of wretched working conditions and inadequate diet, are much subject to tuberculosis.

Sanguinin believed himself to be a target of what is euphemistically called "salvaging," which means being saved from life by a paramilitary hit squad. He did not dare to go home again.

President Marcos laid the anticommunist rhetoric on thick in his reply to Reagan's effusive welcome.

Reagan, he said in a voice deeper than expected from so slight a man, is nothing less than the savior of the world. Marcos begged God to strengthen Reagan's hand "so that hand may be strong on the lever of power and save our humanity."

Reagan, it seems, is God's annointed to "save modern civilization against the threat of a possible Second Dark Ages."

Across the street in Lafayette Park, a small crowd, mostly young and exceptionally cheerful, was chanting a different view of the meeting.

"Marcos, Marcos, smile while you can," they shouted, "remember what happened to the shah of Iran." There was a puppet show, with a man wearing a Reagan mask pulling strings over a Filipino bound to a cross.

The spokesperson for the dissenting Filipinos explained the meager turnout: "People are now afraid to have their pictures appear in the paper."

The recent murder in Seattle of two young Filipino union reformers in a cannery workers union has sent a chill through their countrymen. The fear is that Philippine intelligence agents are harassing and infiltrating anti- Marcos groups in the United States in the style of agents of the shah of Iran, another dictator who was lavishly praised by another American president, Jimmy Carter, who ironically invented the human rights policy.

Exactly how "quiet diplomacy" will be brought into play against Marcos is not clear. Perhaps there will be a quiet moment during the festivities when Reagan could say, "Look, I hate to bring this up, but. . . ."

On the other hand, he might not. After all, when somebody has called you a savior to your face, it would be tacky to tell him you think his people need to be saved from him.