Rabbi Kushner was a young father, still new to his ministry, when he learned in 1966 that his 3-year-old son, Aaron Zev Kushner, had a rare genetic condition known as progeria. The illness, which affects an estimated 1 in 4 million children, causes rapid aging and is invariably fatal.

Aaron died in 1977, two days after his 14th birthday. His death and the random, seemingly senseless nature of his illness submerged Rabbi Kushner in grief and upended the most fundamental elements of his religious faith.

“What I felt … was a deep, aching sense of unfairness. I had been a good person and always tried to do what was right,” Rabbi Kushner recalled. “I had assumed my side of the bargain, so how could this be happening to my family? If God existed, if He was minimally fair, let alone loving and forgiving, how could He do this to me?”

For centuries, theologians have argued over the question of theodicy, or how a god who is good can coexist with a world of suffering and evil. For Rabbi Kushner, and for the readers of all faiths who turned to him for guidance, the matter was not one of intellectual abstraction but rather of visceral pain and personal religious crisis.

Rabbi Kushner channeled his pain into the drafting of “When Bad Things Happen to Good People.” Several publishing houses turned it down before Schocken Books, a small Jewish press, agreed to publish the volume in 1981. It quickly lodged on bestseller lists.

Rabbi Kushner rejected traditional explanations for tragedy — the notion, for example, that God employs suffering to teach a lesson, or that God has a plan unknowable to mortals. Such arguments, as he saw them, served more to defend God than to help the person in pain.

Rather than imploring of God, “Why me?,” Rabbi Kushner argued, the sufferer should ask, “How do I go on?” He urged his readers to continue to seek refuge in their faith. He had managed to do so, he wrote, by amending his earlier conviction in God’s almighty power.

“If I, walking through the wards of a hospital, have to face the fact that either God is all-powerful but not kind, or thoroughly kind and loving but not totally powerful, I would rather compromise God’s power and affirm his love,” Rabbi Kushner once told NPR.

“The theological conclusion I came to is that God could have been all-powerful at the beginning, but he chose to designate two areas of life off limits to his power,” he continued. “He would not arbitrarily interfere with laws of nature, and secondly, God would not take away our freedom to choose between good and evil.”

Some theologians, while commending Rabbi Kushner for the comfort he brought to his readers, objected to what they regarded as his minimizing of God’s power. He responded: “Your God wants the earthquake to happen, the little boy to die? Which one of us is diminishing God?”

Such was the demand for Rabbi Kushner’s counsel that he eventually stepped down from his formal ministry at his synagogue in Natick, Mass., to become a full-time writer and lecturer.

He wrote more than a dozen books, among them “When All You’ve Ever Wanted Isn’t Enough” (1986), “How Good Do We Have to Be? A New Understanding of Guilt and Forgiveness” (1996) and “Living a Life That Matters” (2001).

Harold Samuel Kushner was born in Brooklyn on April 3, 1935. His mother was a homemaker, and his father ran a store that sold children’s books and toys.

Rabbi Kushner enrolled at Columbia University, where he was president of a student Zionist organization, and where he studied psychology and later literature under the Pulitzer Prize-winning poet Mark Van Doren. He received a bachelor’s of arts degree in 1955 and a master’s degree in the social and philosophical foundations of education in 1960.

During his studies at Columbia, Rabbi Kushner enrolled at the evening program of the Jewish Theological Seminary in New York. He was a college junior when he decided to pursue the rabbinate.

As a student at the seminary, Rabbi Kushner received a bachelor’s degree in religious education in 1955, was ordained in 1960, and received a doctorate in Hebrew literature in 1972.

In 1960, Rabbi Kushner married Suzette Estrada. He volunteered with the Army Chaplain Corps before becoming an assistant rabbi in Great Neck, on Long Island, and then rabbi at Temple Israel, a Conservative congregation in Natick.

The Kushners received the diagnosis of Aaron’s illness 12 hours after their daughter was born.

“We learned that our happy, outgoing son would look like a little old man while he was still a child,” Rabbi Kushner told The Washington Post in 1982. “He would never grow beyond three feet in height and he would die in his early teens.” By the time Aaron turned 10, he was physiologically in his 60s.

Rabbi Kushner’s wife died last year. Besides his daughter, of Wellesley, Mass., survivors include two grandchildren.

In addition to his works of spiritual counsel, Rabbi Kushner’s books included “To Life! A Celebration of Jewish Being and Thinking” (1993). Along with novelist Chaim Potok, he was a principal contributor to “Etz Hayim,” the official commentary on the Torah of Conservative Judaism, published in 2001.

Nearly half a century after it was first published, “When Bad Things Happen to Good People” remains Rabbi Kushner’s most famous work. He had written it, he said, to “redeem my son’s death from meaninglessness.”

“If I could choose, I would forgo all the spiritual growth and depth which has come my way because of our experiences, and be what I was” before Aaron became sick, “an average rabbi, an indifferent counselor, helping some people and unable to help others, and the father of a bright, happy boy,” Rabbi Kushner wrote. “But I cannot choose.”