The problem is that over the past 40 years or so we have gone from a culture that reminds people of their own limitations to a culture that encourages people to think highly of themselves. The nation’s founders had a modest but realistic opinion of themselves and of the voters. They erected all sorts of institutional and social restraints to protect Americans from themselves. They admired George Washington because of the way he kept himself in check.

But over the past few decades, people have lost a sense of their own sinfulness. Children are raised amid a chorus of applause. Politics has become less about institutional restraint and more about giving voters whatever they want at that second. Joe DiMaggio didn’t ostentatiously admire his own home runs, but now athletes routinely celebrate themselves as part of the self-branding process.

So, of course, you get narcissists who believe they or members of their party possess direct access to the truth. Of course you get people who prefer monologue to dialogue. Of course you get people who detest politics because it frustrates their ability to get 100 percent of what they want. Of course you get people who gravitate toward the like-minded and loathe their political opponents. They feel no need for balance and correction.

Beneath all the other things that have contributed to polarization and the loss of civility, the most important is this: The roots of modesty have been carved away.

President Obama’s speech in Tucson was a good step, but there will have to be a bipartisan project like comprehensive tax reform to get people conversing again. Most of all, there will have to be a return to modesty.

In a famous passage, Reinhold Niebuhr put it best: “Nothing that is worth doing can be achieved in our lifetime; therefore, we must be saved by hope. ... Nothing we do, however virtuous, can be accomplished alone; therefore, we are saved by love. No virtuous act is quite as virtuous from the standpoint of our friend or foe as it is from our standpoint. Therefore, we must be saved by the final form of love, which is forgiveness.”