Last night, I heard Robert Putnam, America's foremost social scientist, speak at Washington University on his latest research into American religion. His recent book, American Grace: How Religion Divides and Unites Us, is quickly becoming a definitive study on the subject. And his insights burst almost all the preconceived notions of what it means to be religious in America.

At the heart of Putnam's investigation (and his lecture) is what he calls the "puzzle" of American religion: How can America be simultaneously religiously devout, religiously diverse, and religiously tolerant, when history says these three social ingredients don't mix?

Coming out of the most religiously observant decade of American history, the 1950s, Putnam observed that we witnessed two seismic shocks in American public life. First, the social and political upheaval of the 1960s, during which time religious observance plummeted. Second, the social counterreaction to the 1960s that eventually coalesced in the Religious Right of the 1980s. (Although Putnam was adamant to note that this counterreaction began as a social and moral movement and not a political one.)

One of the striking realities to come out of this convulsive upheaval is that where previously religious identification did not correlate with political identification (in the 50s, you could find just as many Republicans as Democrats sitting next to you in the pew on Sunday morning), now people will change their religion to fit their politics, and not vice versa. Given the "stakes" of both religious and political belief, this is remarkably counterintuitive.

As examples, Putnam pointed to two demographic groups that had significant numbers in the mid-twentieth century that have now nearly vanished: unchurched conservatives and churched liberals. And this is a historical anamoly when you consider that virtually every progressive movement in American history started with religious roots.

Yet, this doesn't explain the puzzle. If anything, it makes it more puzzling.

The key, Putnam revealed, to how a religious America can nonetheless have a strikingly high tolerance for "other" religions lies on the personal level. In our personal lives, our networks of friends, family, and acquaintances have become increasingly interweaved among various religious backgrounds and traditions.

Case-in-point #1: intermarriage. Fifty years ago, a Methodist marrying a Jewish person would have caused scandal. Now its commonplace.

Case-in-point #2: change in religious identification. As opposed to a couple generations ago, a high percentage of religious adherents now claim a different religious affiliation than their parents.

What this means is that, to the extent our personal networks have become more religiously diverse, it has become increasingly difficult for us as individuals to look at nice old "Aunt Susan" (Putnam's moniker for the family member who fits one or both of the two cases-in-point above) and banish her to hell for not believing what we believe.

Ergo, a religiously devout and diverse America that is simultaneously tolerant.

It still struck me that an unresolved tension still persists at that intersection. How does a populace that is increasingly identifying their religion according to their politics (with the polarization to match) at the same time maintain a personal life that is becoming increasingly intermingled with "others" who do not fit their politics or their religion? Could it be that our personal and social lives aren't as angry or mean-spirited as the spectacles of the Tea Party, Occupy Wall Street, or any session of Congress make us out to be?

In which case, perhaps there is also a paradox at the heart of the puzzle that is American religion. And perhaps that is why religion can simultaneously "divide" and "unite" us.

On a final note, Putnam also made the convincing case that religious Americans are overwhelmingly more "nice" (i.e. more generous, more voluteering, more communally-involved, more blood-giving) than non-religious Americans. As Putnam said, it turns out "church friends" are perhaps the best friends to have. But that's another story for another time.