Rabbi David Hartman, the American-born director of the Hartman Institute in Jerusalem, passed away on Sunday. He was 81.

Hartman was one of the world's leading Jewish philosophers and a promoter of diversity among Jewish theological trends.

The Shalom Hartman Institute, which was founded by the rabbi in 1976 and dedicated to his father, said Hartman died Sunday after a long illness.

Hartman was born in Brooklyn in 1931 and studied at the Yeshiva Chaim Berlin and the Lubavitch Yeshiva, before continuing his religious education under the auspices of Rabbi Joseph Soloveitchik. He was ordained as a rabbi at the Yeshiva University in New York, and received a graduate degree in philosophy at Fordham University.

Hartman held rabbinical posts in the U.S. and Canada, including serving as rabbi at the Congregation Tiferet Beit David Jerusalem in Montreal, and in the wake of Israel's 1967 Six Day War, Hartman decided to immigrate to Israel with wife Barbara and their five children in 1971. Hartman taught for more than two decades at the Hebrew University of Jerusalem as a Professor of Jewish Thought.

From 1977 to 1984 Hartman also served as an adviser to the education minister at the time, Zevulun Hammer, and was also an adviser to some of Israel's prime ministers on matters of religious pluralism in Israel and relationship between Israel and the Diaspora.

He was known for his efforts to promote understanding between Jews of various affiliations both inside and outside Israel.

In a 2011 interview to the Yediot Ahronot daily, Hartman spoke out against some religious groups in Israel for their strict interpretation of some aspects of Jewish law.

"It's insane, insane," Hartman said. "These people emphasize marginal issues. The important thing is loving kindness."

"They emphasize trivial things. We lost the deeper meaning," he said. "Do you think that people will want to enter a spiritual life made up only of what is forbidden, forbidden, forbidden?"

"A lot of young people come to me and say, 'If not for you, I wouldn't be religious'," he told the paper.

Menachem Lorberbaum, a professor at Tel Aviv University who worked closely with Hartman at the institute, said he "inspired a whole new generation of teachers in Jewish philosophy and theology."

Lorberbaum said Hartman will be known for his accomplishments on religious ethics, and as "a pioneer of interfaith dialogue."

"He was committed to the notion that morality precedes Jewish law," he said. 

Hartman was widely published and won numerous prizes. including the 1977 National Jewish Book Award, the Avi Chai Foundation Prize in 2000 the Guardian of Jerusalem Prize in 2001. Hartman also received the Samuel Rothberg Prize for Jewish Education by the Hebrew University in 2004 and the Liebhaber Prize for Religious Tolerance in 2012.

He was the recipient of an honorary doctorate from Yale University, from Hebrew Union College and from the Weizmann Institute of Rehovot.