Douglas Bovitt, Associated Press
A pedestrian walks passed an American flag at Del Buono's Bakery on Route 168, Monday, July 28, 2014 in Mount Ephraim, N.J.

Why is our public discussion so dominated by rancor and divisiveness? Why do our politicians increasingly resemble silly children throwing food at each other? Why do our “news” programs on TV so often consist of people dealing out abuse and accusations?

There are many likely causes of what a recent Pew Research Center study calls rising “political polarization” in American society, but one of them is intellectual, concerning not so much what we think as how we think. Let’s call this phenomenon polarized thinking, and let’s reflect on its dangers by understanding its features.

First, polarized thinking reflects the notion that only some values matter. What are the basic ethical concerns that human societies appear to value most? The psychologist Jonathan Haidt in his book "The Righteous Mind" points to six: care for others, fairness, liberty, loyalty, authority and sacredness. American liberals today tend to focus largely on care and fairness, while conservatives usually make more room for the other four. But polarized thinking goes further. It says that my preferred values are everything and yours are nothing. It’s like a right-handed person saying not only “I favor my right hand” but also “Left hands are no good.” It’s crude thinking. Try walking around one day using only one hand.

Second, polarized thinking is typically binary thinking, in which everything divides into two mutually hostile forces — left versus right, believers versus secularists, good people like me versus bad people like you. In his book "On Human Nature," the scientist Edward O. Wilson suggests that humans are hard-wired “to dichotomize, to classify other human beings into two artificially sharpened categories.” But this way of thinking should be resisted. As Wilson says, it’s artificial. It’s simplistic. The world is extravagantly plural, and thinking about it in binary categories just won’t do.

Third, polarized thinking undermines doubt. Many people today appear to view doubt as a weakness. Some religious leaders even suggest that it’s a sin, that doubt will endanger your soul. But the older I get, and the more I read and think, the more I’ve come to view doubt as my friend. Doubt can keep me honest. Doubt keeps me curious. By always reminding me of what I’m not completely sure I know, doubt can protect me from arrogance and self-righteousness. Yes, truth is objective, but we can only approach it subjectively — we see through a glass darkly. To treat doubt as a friend is to recognize this basic fact of our humanity.

I know there are plenty of people today who’ve already discovered the truth and whose main mission now is explaining it to others, but I seldom find them to be helpful. Or interesting. I’ll take a good question over a final answer any day.

Fourth, polarized thinking tends to replace the clash of ideas with accusations of bad faith. Instead of focusing on content, we get name-calling and speculations about wrong motives. It’s profoundly anti-intellectual.

From 2008 to 2011 my former teacher Michael Ignatieff was the leader of the Liberal Party of Canada. In "Fire and Ashes," his book about the experience, he describes how little it mattered what he actually said about the issues. What mattered were the personal attacks levelled against him. He describes them, correctly, in my view, as attempts to deny standing. The charge is not “What you say is wrong” but “You’re so personally flawed that you have no business saying anything.”

Ignatieff, a professor who’s written widely on politics and political theory, was genuinely shocked by the brutality and effectiveness of this procedure. I’ve been in the public debate myself — most controversially on the issue of gay marriage — and when the same thing happened to me, I too was genuinely shocked. And distressed.

Finally, polarized thinking turns opponents into enemies. It says not only “I disagree with you” but also “You and I have nothing in common” and “You are a threat to me.” The result of this transformation is that civic engagement itself becomes pointless and the normal practices of democracy fall into disuse. Why bother? Why listen to someone from whom you can learn nothing? Why compromise with those whose only aim is to cause harm?

Here we get to the heart of the matter. There’s a reason why we call it “culture war” and why one of the most frequently used words in politics today is “fight.” It’s harsh and aggressive and intended to be so. It works well enough in times of actual war. But it’s no way for citizens to treat one another. It’s no way to participate in civil society. It’s no way to run a democracy.

David Blankenhorn is president of the Institute for American Values. You can follow him on Twitter @Blankenhorn3.