It is a Saturday, but as is the custom of Paulo Evaristo Ams, the cardinal archbishop of Sao Paulo is spending the morning in his office, attending parishioners which have asked for audiences.

Students, workers, professors, housewives wait patiently. A door opens, and from the cardinal's chambers enlarge a young woman and her child - the wife and daughter of a political outspoken Brazilian military officer who disappeared one day in 1974 and has not been heard from since.

"The situation here is actually getting better, "the cardinal tells his next visitor. "Three or four years ago my waiting room was always filled with friends of people who had been arrested for political reasons or who had simply disappeared without a trace."

They came to the cardinal then, as others come to him now, for one fundamental reason. In his eight years as head of the larget Roman catholic archidiocese in the world, Dom Paulo, as the 57-year-old Franciscan is known popularly, has earned a reputation as Brazil's most untiring and effective defender of human rights.

He has consisently spoken out against the torture of prisoners and is credited by many with being instrumental in forcing the replacement of an army commander here who condoned such practices. He has preached against the injustices and inequalities wrought by Brazil's "economic miracle," supported lay human rights groups, and called for a return to democratic institutions.

In recognition of these efforts, Arns was awarded an honorary doctor of human rights degree at Notre Dame university last year. Also honored in the same ceremony was Jimmy Carter. The two met then. Arns, in response to a White House invitation, will see Carter again in Rio de Janeiro on Friday.

"Carter's invitation to Arns is a symbolic gesture of great importance to Brazilians," says an opponent of the government here. "Many of us have been wondering whether Carter still cares about human rights, and there is no better way for him to show human rights still matter than to meet with the man the Brazilian people recognize as our leader in this field."

The fourth of 13 children of a saw-mill owner from the south Brazilian state of Santa Catarina, Arns has won this public esteem by playing an activist's role. Though he possesses a doctorate from the Sorbonne, his public image is that of a man of the people who has stressed the church's mission among the poor and the poweriess.

Brazil's authoritarian military government, however, views the cardinal as an unwelcome thorn in its side. Earlier this month, government censors prohibited the showing of a popular television show after two episodes had been taped in which Arns read a message explaining one of the church's current projects, a campaign demanding "work and justice for all."

Such attempts to silence Arns are nothing new. In 1973, the government suspended the license of the diocese's radio station, and even now the diocesan newspaper, "O Sao Paulo, a weekly with a circulation of under 20,000, is one of only three publications in Brazil still subject to prior censorship.

"Articles that are forbidden here sometimes are published elsewhere later without any problems," says the cardinal, holding up a copy of the paper to show the gaping white space where his "Meeting With the Pastor" column was to have appeared. "It is arbitrary and senseless. Even passages from the Bible have on occasion been censored."

Relations between Brazil's most powerful church spokesman and the Nation's military rulers have not always been so strained, though. In 1964, Arns, then a professor of theology at a seminary north of Rio, made a special trip by jeep to minister to the army forces in initiating the coup that ended civilian rule here.

He felt then that military rule was preferable to what he has called the "anarchy" of Joao Goulart's leftist rule. But his support soon turned to opposition.

"The main problem of the revolution today is the same as it was in the beginning," says Arns."They believe that all power belongs to the state, that what the government giveth, the government taketh away."

President Ernesto Geisels "great defect" is that he wants to resolve everything paternalistically," Arns said. "The Brazilian people continue to be marginalized, excluded from the process of determining their own future."

These bitter post-1964 experiences have left Arns skeptical of all politicians and their promises - including Jimmy Carter. "I liked Jimmy Carter's personality," he recently told a Brazilian interviewer when asked about the brief encounter, "though in many respects I don't approve of his policies."

"I have the impression that Mr. Carter's human rights policy set back rather than aided our own struggle here. Juxtaposing it with opposition to Brazil's nuclear program was not advantageous to us, because Brazil's pride was offended, and the two subjects became linked in the public mind."

Arns makes clear that he, like several other important critics of the government, supports Geisel's stand on the nuclear reactor question. "No Brazilian will accept restrictions in the nuclear field," he says. "Twenty other nations are using nuclear energy, so why not Brazil? There's no other way out."

President Carter's espousal of human rights has also had a positive side, he hastens to add. "It used to be that anyone who talked about human rights here was called a subversive. When President Carter picked up the banner, human rights could no longer be called Communist, and the movement gained new credibility among the Brazilian people."

In the meantime, the cardinal is meeting with leaders of the "Sao Paulo Commission for Justice and Peace," a lay group organized with church support, to find out what they would like him to tell the president and is initiating a campaign to pressure the government to improve the lot of the working class. "The high cost of living is the hot topic for us right now," he says.

To help draw attention to the subject, the diocese is underwriting a "cost of living movement" and helping circulate a petition, which it hopes a million people will sign, that calls for more equitable distribution of income and an end to economic exploitation.

"Somebody has to do something," says the cardinal in what may be the clearest statement of his credo. "There is a limit to what people can take."