Down in the bowels of the State Department, a car waits for Patricia M. Derian. She and two of her staffers are off to pay courtesy calls on several Latin American diplomats before she leaves on a working trip to South America. As she settles into the car, an aide begins to brief her on the diplomats and their countries' human rights positions. Suddenly Derian leans toward the driver, "Hello," she says brightly. "How are you?"

Until that moment no one else had acknowledged the man's presence, and it may have been simple politeness on Derian's part. But as Assistant Secretary of State for human rights and humanitarian affairs in an administration bent on integrating human rights issues into its foreign policy, Derian's personal attitudes are not inconsequential.

She sees Secretary of State Cyrus Vance privately once a week, usually a sign of influence in a city where access to the top translates into power. And as one of the architects of the Carter administration's human rights strategy, she has testified on Capitol Hill, coordinated the State Department's first review of human rights policy, and assisted in the writing of one of Vance's speeches on the subject.

Still, some veteran Foreign Service officers feel the human rights issue is not germane to foreign policy. "Derian is a competent, unsophisticated militant on the subject of human rights," says one observer at State. "But the administration is still working without a standardized definition of human rights. Derian seems to mean assassinations, crimes against an individual perpetuated by the government, but that definition leaves a lot to be desired."

Says Derian: "I operate on a very simple, elementary level. It's a matter of fairness.I think all children have that. It just gets dulled as some of us become adults."

Her friends say Derian's sense of human justice has never been dulled. "One of the reasons I supported Carter was Patt Derian," says feminist Gloria Steinem. "She's such a principled person that if she says a particular person is all right, then they're all right."

For all her adherence to simplicity, Derian is not exactly a newcomer to politics. Active early in the civil rights movement in Mississippi, Derian has held a number of important posts in the Democratic Party. She was a member of the Democratic National Committee in 1968 and worked to heal the rifts in the party after that year's presidential election. In 1972, she ran George McGovern's campaign in Mississippi. Last year she was the deputy national campaign director for Carter.

Robert Strauss, former DNC chairman, gives her high grades for her political acuity. "She and I disagree on a great number of issues, but she isn't the kind of person you fall out with.

Strauss recalls that when the party was attempting to select a city for its last convention, many women were concerned that a state be picked where the Equal Rights Amendment had been adopted. "Patt was one of them, but I thought they were making a political mistake. I went to her and said if you support the city we pick, every place we go we'll talk about ERA. We carried it nicely with her support."

Since her sppointment in April, the 47-year-old Derian's "simple, elementary" level of operation has delighted some veteran Foreign Service officers and annoyed others. Some have called her approach to foreign policy and the human rights issue naive and idealistic (a complaint heard about some other Carter aides), but no one has discounted her sincerity.

Perhaps it is Derian's sometimes elfin mannerisms that contribute to the impression of naivete.

During meetings at the State Department with foreign officials or U.S. government staffers, Derian is a quick study in ingenuousness. With her slight resemblance to comedienne Lily Tomlin, she will slump down in her chair a la Edith Ann.

She rivets her speakers with large, luminous blue eyes and punctuates their briefings with phrases like "Good grief," "Oh, shoot," "I think that's just swell," before ending the meeting with "I'm afraid we're going burst of sincerity that it never fails to have to stop. I just hate it." The interpections are delivered with such disconcert the visitor, often leaving him wondering whether he's just met an innocent lost in her job.

"She may be doing a bit of on-the-job training," says one policy officer, "but who wouldn't? The field is wide open and human rights touches everything that's done at State, from military assistance to foreign aid. The resources aren't the best either."

Derian operates her office with a staff of 30. Twenty-one deal with refugee problems, two with prisoners of war and those missin gin action, and seven with the human rights issue. "There are an enormous number of pieces in this," she says.

Yet Derian has faced formidable opposition before.

Born in New York ("I was only there a few minutes," she says), she was raised in Danville, Va. The double "t's" in her nickname were a gift from her grandfather, an architect who decided that a single "t" left the name unbalanced. "He squared it up," says Derian.

After high school in Virginia, Derian became a registered nurse at the University of Virginia's Nursing School, but not before making her mark on local pre-integration mores. Hospital wards were segregated and the general rule was that black patients were addressed by their first names. Derian wouldn't do that. She was called to the head nurse's office. She explained her way out of it. Then she was called to the head administrative office.

"I told them thay my mother had always taught me to call older people either 'Mr.' or 'Mrs.'," she recalls. "I told them that it would hurt my mother dreadfully if I went against her teachings. And they let me be."

Activism didn't stop. By then married she is now divorced), she and her orthopedis thusband moved to Jackson, Miss. There, in the early 1960s, Derian got involved in the civil rights movement, despite threats from the Ku Klux Klan. "I got into it at the beginning on a one-to-one basis," Derian explains. "I'm no hero. They were just people that I cared about."

Derian tells about a black woman friedn approaching her over a telephone bill that did not have a courtesy title on it.

"All the white people had courtesy titles on their bills, so I just went down and asked the company to do something about it. They did and then by word of mouth more people would come to me with problems."

What Derian can accomplish in her present job is another matter. "I can hardly think of a job which is more vulnerable to diverse policy considerations," says Joseph Grunnwald, a senior fellow at the Brookings Institution.

This appears not to disturb Derian. "I really like the ins and outs of government," she says. "One hundred per cent of human rights would be unrelieved sadness. I talk to my assistants who tell me the bureaucratic way that things are done and then I tell them what I want to do. They identify the roadblocks between what I want and getting it done."

She says it's a deliberate policy that neither her office nor the White House announce specific accomplishments in the area of human rights.

"We can't get anybody out of jail," she says. "It's the other countries. They do it themselves. For while we are rich and powerful and important, we are not the sole supplier of anything. We may have started out that way after World War II, but now we have to be very careful about not being arrogant. We're just trying to make other governments sensitive to the human rights issue."

Despite her schedule of meetings, foreign trips and testifying, Derian continues to put in time mothering her three college-age children long distance.

Before leaving her office to begin her current South American trip, she talked to her 19-year-old daughter, Brook. Roles were momentarily reversed as her daughter asked about Derian's work habits.

"No, I'm not tired," says Derian. "No, no, not that much. They turn off the air conditioning and you have to got home. Love and kisses," she signs off. "Same to Mike. Don't forget to see the doctor and remind Mike about the dental appointment."

Derian turns and says to a visitor, "I may not look it, but I'm a very simple person, which is not to say that I was born yesterday. It's mostly that I'm very, very straight."

She'll feel a sense of accomplishment, she says, if at the end of her tenure "there is functioning within the bureaucracy the feeling that human rights is just one of the givens."