JERUSALEM — Rabbi David Hartman, a U.S.-born Jewish philosopher who promoted a liberal brand of Orthodoxy and created a study center that expressed his commitment to pluralism by bringing together leaders from all strains of Judaism, died Sunday at his home here. He was 81.

His son Donniel said the death came after a long illness.

Hartman, who was a professor at Hebrew University for more than 20 years, was a leading advocate of the idea that Jews are partners with God in a covenant, and that they should therefore adapt religious observance to modern values in a multicultural world.

A charismatic teacher and prolific author, he encouraged students to question tradition and urged people of different backgrounds and ideologies to pore over Jewish texts together, a practice more common in his native United States than his adopted country.

“At the center of his thinking was a kind of counter-religious idea, where religious life is a life of affirmation, not a life of denial,” said Moshe Halbertal, a professor of philosophy at Hebrew University and Hartman’s former son-in-law. “If human life is not denied by the force of revelation, but it’s actually a participant in revelation, then human life has to come to its full fledge, with its moral convictions, with its encounter with the world.”

The Shalom Hartman Institute, which Hartman founded in his father’s name in 1976, has become a theological and cultural landmark, particularly for the thousands of Diaspora Jews who attend frequent conferences or spend summers studying there. With an annual budget of $18 million and a staff of 125, the institute has sponsored two Jerusalem high schools, runs a research center, opened a branch in Manhattan and trained more than 1,000 Israeli military officers. In the last year, according to the institute, more than 5,000 people across North America participated in a Hartman learning series called iEngage.

But Hartman’s progressive, universalistic approach was embraced more in the United States than in Israel, where some challenged his status as Orthodox and shunned his open-mindedness as heresy. He received honorary doctorates from Yale and Hebrew Union College, a Reform institution with four branches in the United States, but not the coveted Israel Prize. His never receiving it was a source of painful regret, several people close to him said.

In recent years he had been highly critical of the growing influence of the ultra-Orthodox on public life. He described as “insane” an ultra-Orthodox boycott of a military ceremony in which women sang.

“What is happening today with religion is more dangerous than what’s happening with the Arabs — the Arabs want to kill my body, the Jews are killing my soul,” Hartman said in a 2011 interview with the Israeli daily Yediot Aharanot. “I want to return the Torah to the Labor Party, to the entire people of Israel. I don’t want religion to be the private property of certain people. I don’t want the length of the sidelocks to be the determining factor.”

David Hartman was born on Sept. 11, 1931, in the Brownsville section of Brooklyn, N.Y., one of six children of Shalom and Batya Hartman, Hasidim who had moved to New York from Israel. Donniel Hartman said that the family was poor — Shalom peddled sheets and pillowcases door to door —but that the four boys became rabbis and the two girls married rabbis.

Hartman was ordained by Rabbi Joseph Soloveitchik, perhaps the most important Orthodox thinker of the 20th century, and received a doctorate of philosophy from McGill University in Montreal. He was a pulpit rabbi in the Bronx and Montreal before moving to Israel in 1971 as part of a generation of Zionists inspired by the Israeli victory in the Arab-Israeli war of 1967.

Hartman published several books in English and Hebrew, including two about Maimonides, the Torah scholar of the Middle Ages; one on the theological legacy of Soloveitchik; and two about his own spiritual evolution. He was an adviser to Ehud Olmert, the former prime minister; Teddy Kollek, the longtime mayor of Jerusalem; and Zevulun Hammer, Israel’s education minister from 1977 to 1984.

“He was a public philosopher for the Jewish people,” said Michael Sandel, a professor of political philosophy at Harvard who has written about Hartman’s work. “As Maimonides drew Aristotle into conversation with Moses and Rabbi Akiva, so Hartman renovated Jewish thought by bringing the liberal sensibilities to bear on Talmudic argument.”

Avi Sagi, a professor at Bar Ilan University and a Hartman fellow who edited a two-volume set on the rabbi’s work, said of him, “He gave me the opportunity to think without any limitation.”