In his 2004 book, "The Catholic Revolution: New Wine, Old Wineskins, and the Second Vatican Council," the Rev. Greeley wrote that the Vatican II reforms caused a rift between leadership and laity that resulted in a new generation of Catholics who have redefined the faith in their own terms.



These Catholics, the Rev. Greeley wrote, hold onto core doctrines and traditions even as they disagree with the rules in such areas as sexual behavior.



Robert McClory, associate professor emeritus at Northwestern University and a former priest, said the Rev. Greeley was one of the few Catholic scholars who was able to critique the Catholic Church without himself becoming a dissident.



"He was able to be critical of the hierarchical church while balancing that criticism with the sound sociological data that he had been working on for more than 40 years," McClory said.



"It's not as if he was dissenting. He would say, 'The figures are there, you can look at them and the church needs to decide what to do about that.' "



McClory said the Rev. Greeley also had the gift of making his data clear and interesting to the general public.



"He was not a scholarly sociologist," he said. "He had a popular approach to his writing which interested people on issues that they would not normally be interested in."



The Rev. Greeley possessed an unpredictable, sometimes volatile temperament which resulted in people following his columns to find out what he would say. He lashed out at the Bush administration in a series of essays that became a book entitled, "A Stupid, Unjust, And Criminal War: Iraq 2001-2007." Before the 2008 election, the Rev. Greeley wrote a column predicting Barack Obama would lose because racism would defeat him.



"He was gutsy. He was not afraid to take on the religious and political establishments," McClory said.



His muscular writing and straightforward opinions are evidenced in an excerpt from his 2004 book, "Priests: A Calling in Crisis," written after the church's sexual abuse crisis:



"In the worst-case scenario, the Catholic Church in the United States....may go down the drain, but not because of attacking infidels, not because of celibacy or homosexuality or sexual abuse, not because of secularism and materialism, but because of incompetence, stupidity, and clerical culture — all enemies from within."



The Rev. Greeley's research often contradicted commonly held opinions, according to the Rev. John Cusick of Old St. Patrick's Church in Chicago, who called the Rev. Greeley a mentor.