The young man stood immobile, his face betraying no emotion, as two students slowly unbuttoned his white priest's cassock and stripped it off.

Beneath the robe he wore a tattered black shirt and jeans. Another student silently stepped forward tied a long, sheathed bolo knife around his waist. Then the young man rolled up his trousers.

Nearly a thousand people jamming the pews of the circular, domed church burst into applause and shouts: "Fight. Fight. Do not be afraid."

A slender girl translating the Tagalog to a visiting foreigner explained: "He hasn't left the church. He's taking the church to the people."

This scene took place a few nights ago at the Church of the Holy Sacrifice on the campus of the University of the Philippines in suburban Quezon City. It was the climax of a two-hour play entitled "People's Mass."

The play, written by former political prisoner Bonifacio Ilagan, now a student at the university, is a blunt, bitter denunciation of five years of martial law under President Ferdinand E. Marcos. Its message: The students, the church, the peasants, and the poor urban workers must unite against the government.

What goes unspoken in "People's Mass," but is largely understood, is that the only organization with the potential to organize opposition against the government is the Philippines Communist Party and its armed wing, the New People's Army.

According to one of the most senior military officers in the country, the New People's Army has succeeded in recruiting large numbers of guerrillas in the last year, many of them from the campuses.

The officer, who refused to be identified, noted that a year ago Marcos claimed the New People's Army had been reduced to 900 fighters. "Today," the officer said, "They're up to 2,700 and a major reason is that young subversives, instead of limiting their activities to the universities and the streets, have gone into the hills with the Communists."

As the actors and audience sang, "Praise God/We will fight and we will win/Don't be sad, Mother Philippines," the young man playing the priest held up the gold-starred tricolor that is the national flag, its red stripe in his right hand as a symbol of war. Cries of "Down with martial law, down with martial law" drowned out the final words of the song.

This kind of defiance - along with recent clashes between rock-throwing students and armed police and several illegal strikes - has been on the increase as the Sept. 21 anniversary of the imposition of martial law five years ago approaches. The government has reacted with a mixture of tolerance and toughness.

"The president is willing to tolerate such things as the play if that's the way the students want to express their dissidence," said Maj. Gen. Fidel V. Ramos, head of the powerful Philippines constabulary. Ramos, a graduate of the U.S. Military Academy at West Point and a relative of Marcos, said in an interview that the regime's policies on dissent "have grown more liberal after the first three months, which were strict."

Last week, Defense Secretary Juan Ponce Enrile warned dissident students that "if they want us to return to normalcy, they'd better behave. If not, I will order their arrest." Enrile also threatened to recommend that Marcos close down universities that allow demonstrations to take place on their campuses.

Last month, Marcos himself warned that while he intended to bring authoritarian rule to an end, he would not hesitate to "utilize force and violence to stop illegal force and violence utilized against the state."

This kind of warning has convinced some of the more radical members of the academic and church communities that violence is essential to correct what they consider to be gross social and economic imbalances.

"There are some people in the church who feel that violence is the only alternative," said Bishop Francisco Claver. "In a way, I feel that nonviolence is more dangerous because we open ourselves up to charges from the church hierarchy of being Communists and from the government for civil disobedience."

Claver, one of the most outspoken Filipino Catholic prelates, is a Jesuit who was ordained in Baltimore and holds a doctorate in anthropology from the University of Colorado.He met with me just before leaving Manila to attend a Vatican conference on "Dialogue Between the Church and Communists."

"I talk to Communists," Claver said, "but it's in order to understand what they're thinking about, not to plot overthrowing the government." Although he has come under frequent government attack for his open criticism of the Marcos government, Claver said he would not stop speaking out.

"Out best protection is to stay in the open, not to be secretive," he said. "The government knows this and in order to discredit us, they're constantly trying to link us - the small number of outspoken church dissidents - with the Communists."

Claver, 48, claimed that "frustration" may have led some priests and nuns to establish links with students and Communists advocating violence. He also predicted that a "growing offensive" among dissidents would continue "unless President Marcos cracks down very soon."

He speculated that the crackdown has not taken place yet because "he's caught in a dilemma created by his own claims of leniency in response to foreign pressures, mainly from the United States."

There are indications that some students and other opponents of the regime have taken courage from President Carter's emphasis on human rights.

Claver said however, that he was "regretfully saddened" by Carter's initiatives. "It seems a pity that a foreign government should take the lead in the cause of Philippines' human rights," he said. "The church leaders should have been in the forefront of this struggle from the beginning. But we lack unity and cohesiveness, particularly at the top."

Some observers are puzzled as to why the students have chosen the movement when Marcos has expressed his intention to ease restrictions to step up their opposition to martial law, basically there are two answers.

The first is that they do not believe Marcos. The second is that the more radical students and faculty believe that "normalcy" under Marcos would be martial law in everything but name.

The director of "People's Mass," Behn Cervantes, like the play's writers, a former political detainee, noted that Marcos has linked the end of martial law to "normal" security conditions, mainly in the southern province of Mindanao, where a Moslem insurgency has been going on for years.

"Despite the government's claim that it has the Moslem problem under control." Cervantes said after a performance of the play the other night, "There's no real solution in sight. We doubt that under these conditions Marcos will feel able to lift martial law. So we're making our statement for basic human rights with this play."

Asked if he feared government repercussions, the youthful director replied, "Let's leave the censorship to the official censors. That's what they're paid for. The most important thing is not to censor ourselves."