This is why we’ve seen the sudden re-emergence of the older culture war — the one between the religious right and the secular left that raged for so many years before the financial crisis and the rise of the Tea Party. When sacred objects are threatened, we can expect a ferocious tribal response. The right perceives a “war on Christianity” and gears up for a holy war. The left perceives a “war on women” and gears up for, well, a holy war.

In the film version of “All the President’s Men,” when Robert Redford, playing the journalist Bob Woodward, is struggling to unravel the Watergate conspiracy, an anonymous source advises him to “follow the money.” It’s a good rule of thumb for understanding the behavior of politicians. But following the money leads you astray if you’re trying to understand voters.

Self-interest, political scientists have found, is a surprisingly weak predictor of people’s views on specific issues. Parents of children in public school are not more supportive of government aid to schools than other citizens. People without health insurance are not more likely to favor government-provided health insurance than are people who are fully insured.

Despite what you might have learned in Economics 101, people aren’t always selfish. In politics, they’re more often groupish. When people feel that a group they value — be it racial, religious, regional or ideological — is under attack, they rally to its defense, even at some cost to themselves. We evolved to be tribal, and politics is a competition among coalitions of tribes.

The key to understanding tribal behavior is not money, it’s sacredness. The great trick that humans developed at some point in the last few hundred thousand years is the ability to circle around a tree, rock, ancestor, flag, book or god, and then treat that thing as sacred. People who worship the same idol can trust one another, work as a team and prevail over less cohesive groups. So if you want to understand politics, and especially our divisive culture wars, you must follow the sacredness.

A good way to follow the sacredness is to listen to the stories that each tribe tells about itself and the larger nation. The Notre Dame sociologist Christian Smith once summarized the moral narrative told by the American left like this: “Once upon a time, the vast majority” of people suffered in societies that were “unjust, unhealthy, repressive and oppressive.” These societies were “reprehensible because of their deep-rooted inequality, exploitation and irrational traditionalism — all of which made life very unfair, unpleasant and short. But the noble human aspiration for autonomy, equality and prosperity struggled mightily against the forces of misery and oppression and eventually succeeded in establishing modern, liberal, democratic, capitalist, welfare societies.” Despite our progress, “there is much work to be done to dismantle the powerful vestiges of inequality, exploitation and repression.” This struggle, as Smith put it, “is the one mission truly worth dedicating one’s life to achieving.”

This is a heroic liberation narrative. For the American left, African-Americans, women and other victimized groups are the sacred objects at the center of the story. As liberals circle around these groups, they bond together and gain a sense of righteous common purpose.

Contrast that narrative with one that Ronald Reagan developed in the 1970s and ’80s for conservatism. The clinical psychologist Drew Westen summarized the Reagan narrative like this: “Once upon a time, America was a shining beacon.

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