Harvard Kennedy School professor of public policy, award-winning academic and prolific author Robert D. Putnam spoke Monday evening in Hewlett Auditorium to a packed audience of students and community members looking to hear about the changing role of religion in American society.

Putnam, who has also earned the London Sunday Times’ endorsement as “the most influential academic in the world today,” began by pointing to an apparent paradox in American civic society: while Americans tend to be both religiously diverse and religiously devout — a combination that has proven explosive elsewhere in the world — Americans also tend to exhibit high levels of religious tolerance.

“Although the culture wars are very real, Americans of all stripes are often very open-minded across religious lines,” said Putnam. “Places that are religiously devout, as we are, and religiously diverse, as we are — they tend to be places of mayhem.”

Putnam’s statistical and social science research has taken him from evangelical icon Rick Warren’s Saddleback megachurch in Orange County to “small, fading Episcopal churches in Boston” to Jewish synagogues in Evanston, Ill., to Mormon wards on the outskirts of Salt Lake City. He proceeded to highlight throughout his lecture a particularly peculiar facet of American exceptionalism.

“Compared to other industrialized nations, the U.S. has a high rate of weekly church attendance,” he said.

In fact, measured by attendance at weekly services, “the average American is more religious than the average Iranian.”

Nonetheless, warned Putnam, “religion, taken in high doses…can be toxic to democratic unity” — a prospect he went on to demonstrate by charting a wealth of religious data across the decades, beginning in the 1950s.

Weaving together strands of polling data on subjects from attitudes toward premarital sex to yearly Bible sales to individual attitudes toward adherents of different faiths, Putnam told a story of both declining religiosity and increasing polarization. He showed more and more Americans identifying themselves as members of no religion — whom he humorously termed the “nones” — and as members of right-wing, passionately evangelical movements.

The result: a historically unprecedented correlation between one’s politics and one’s religion, which have never before been connected in any statistically significant manner.

“Historically, there had been progressives in the pews, and a lot of un-churched conservatives,” Putnam said. But “especially after 1990, we saw a sharp increase in correlation between your politics and your religion…that, historically, is not normal.”

With increasing numbers of the highly religious voting Republican and the avowedly secular voting Democratic — a statistic that had been reversed or negligible as recently as 1965 — Putnam cautioned that religion and politics may be intersecting in the U.S. today to produce a highly polarized and divisive “God gap” in political allegiance.

“We’re in two camps: the grace-sayers and the non-grace-sayers,” he said.

Despite high levels of religiosity and political polarization, Americans tend to have positive views of religious diversity, to have many friends outside of their own faith tradition, to believe by an overwhelming margin that people of other faiths than their own can still go to heaven, and to hold that “there are basic truths in many religions,” rather than that “one religion is true, and all others are not,” he said.

“Americans are pretty open about other religions,” said Putnam, citing statistical evidence suggesting that Jews and Catholics, almost universally reviled a century ago by nativist Protestant organizations, are now regarded as the most well-liked faith communities in America today.

“Putnam’s emphasis on religious tolerance in America as compared to elsewhere was encouraging and enlightening,” said event attendee Josh Valdez ’13. “In demystifying other religions and viewpoints, we begin to embrace others and their differences.”

“I was surprised by the study results because they were totally contradictory to what I would have guessed,” said Jordan Limoges ’13. “With the prominence of religion in the media, I would agree that we are very polarized, but the fact that we are also very tolerant caught me off guard…I think it presented an optimistic view of the future.”