Richard Arens deplores what Israel has done in Lebanon.

And so he deplores the part in it played by his brother, Moshe Arens, the defense minister of Israel.

"I'm embarrassed," says Richard Arens.

Moshe Arens, 57, defense minister of Israel, the respected and well-liked former Israeli ambassador to the United States, is an Israeli hawk and a symbol for his country.

His brother, Richard Arens, 61, is an American law professor at the University of Bridgeport in Connecticut, a long-time human rights activist now representing a Palestinian he says is unfairly imprisoned at the Israeli-run Ansar prison camp in Lebanon.

For years, Richard Arens says of his younger brother, "I thought he was a lost cause." He smiles ruefully, adding, "I think he must have regarded me as a lost cause."

Today, Richard Arens is so disillusioned by Israel that he has renounced his religion.

"I cannot accept a religion that adopts, as a central symbol, a state," says Richard Arens. "I'm not Jewish by religion."

He says, "I'm shocked the Israelis have displayed some--though not all--the characteristics of the Nazis. No doubt about it at all . . . They proceeded with ruthless disregard of the lives of the occupied areas. I'm talking abut the West Bank and Lebanon."

Barely a month after Arens accepted the second most powerful post in the Israeli government and replaced Ariel Sharon, Richard Arens volunteered his services to the Arab American Anti-Discrimination Committee to help Sahmi El Yousseph, a 29-year-old West German resident who, Arens says, was visiting family in Lebanon last summer when the Israelis detained him on suspicion of terrorist activities in West Germany.

"I've been engaged in civil rights since the start of the civil rights period," says Arens, who is in Washington to publicize his case. He has long been active on behalf of Indian populations in Paraguay and Guatemala. "It seems very strange to say no when asked to represent another oppressed group."

The brothers rarely speak to each other. It's not surprising. They say such different things:

"We have a long tradition that the only guarantee for Israeli's borders is the Israeli Defense Forces," said Moshe Arens in an interview in February.

"The entire invasion of Lebanon poses extremely serious problems for peace of the world," says Richard Arens in a steady voice, his face calm. He is a gracious man with thinning gray hair and a pair of green framed reading glasses that he slips on and off. His hands are neatly clasped in his lap.

They spoke briefly in New York two years ago, Richard Arens recalls. He was talking about the Paraguayan Indians, a group about whom he has written and researched extensively. He has filed papers at the United Nations charging the government of Paraguay with genocide of the Ache Indians in Paraguay.

"I invited his attention to the fact that the extermination of the Paraguayan Indians was being helped by Israeli weaponry," says Richard Arens. "I asked if he could put his influence to helping bring an end to these tyrannical regimes. He could not have cared less. He shrugged his shoulders and turned to another subject. I have not had any contact with him since that time," he says succinctly. Then he amends: "I think he telephoned me once since then. I was not interested."

The gulf between them is like an ocean separating continents. The two brothers, born in Lithuania of Jewish parents, diverged strongly in opinions and experiences when they were barely past adolescence, Richard Arens says. Richard, the older, went to boarding school, St. Paul's, in England, and slipped into a life he savored. Moshe, the younger, went to New York City, joined Betar, the Zionist youth movement, and in the words of his brother, "regarded the U.S. as a way station to Palestine almost from the beginning."

They were never close here in the U.S. "I haven't seen much of him since he left for Israel or before that," said Arens. "When we were both in this country, we were in different universities." Richard Arens attended the University of Washington and graduated from the University of Michigan and Yale Law School. He taught at the University of Buffalo in the 1950s and practiced law privately here during the '60s, teaching part-time at American University and Catholic University. Moshe Arens graduated from the Massachusetts Institute of Technology before going to Israel, against his family's wishes, to fight for Israeli independence. Both brothers served in the U.S. Army during World War II.

A sister, the youngest of the family, lives in the United States but "would have gone to Israel at the drop of a hat," Richard Arens says. She lives somewhere in New Jersey, he says he doesn't know exactly where. "I haven't seen her in 10 years," says Arens.

On his one visit to Israel in 1973, Richard Arens, who called himself "mildly pro-Israel" at the time, came away feeling that Israel had inflicted itself upon "the indigenous population . . . The idea of Jewish scholars turning into soldiers and farmers seemed very good to me. I didn't realize the price paid by the Palestinians for this group therapy."

He says the Israeli attitude toward the Arabs in Israel was "racist." He talked to his brother, Moshe, at the time about it and found his response equally distateful.

But Richard Arens' views are as strong as his brother's, just on the opposite side. Richard Arens, supported by 10 other law professors, petitioned the U.S. Congress recently to cut U.S. military aid to Israel. The result was a flurry of threatening letters in his mail. "I became notorious as a result of the petition," he says, chuckling. "Newspapers carried reports of it which I haven't seen but have had quoted to me by irate members of audiences I address."

What happened here to push brothers so far apart?

"In eastern Europe, given the degree of anti-Semitism, the natural impulse was to get out," says Richard Arens by way of explaining the clash between him and his brother. "Those who could get out, did. I got out. Those who couldn't, could dream of a Jewish state in Palestine, not realizing it was already occupied by another people. It was normal to dream of another place. What was abnormal was this obsession with Palestine."

Whatever it was that flung them apart in viewpoint, it now places Richard Arens--and his human rights work--in a curious limelight.

"It is embarrassing to be approached this way because of the nature of our relationship," he says calmly. It is a relationship that, he says, "I don't go around advertising. I've been accused by some Jewish sources of capitalizing on it. That's not what I intended to do."

Does he ever wish he could discuss the Middle East with his brother?

Richard Arens smiles. "As far as my brother is concerned, this is not a subject for argument."