A classic study offered free research to ordinary Democrats and Republicans. People on both sides were eager to get intelligent arguments reinforcing their views, and somewhat interested in arguments for the other side that were so silly they could be mocked and caricatured (it’s very satisfying to dismiss rivals as libtards or bigots). Neither Democrats nor Republicans were interested in intelligent arguments challenging their own views.

Decades ago, a media expert at M.I.T. named Nicholas Negroponte foresaw the emergence of a news product that he called “The Daily Me,” with information tailored to a user’s needs. Negroponte was thinking of local weather, sports, particular interests and so on, but what actually arrived with the internet was a highly political version of “The Daily Me.”

There’s not an exact parallel in the way the right and the left seek out like-minded news sources. The right has spawned conspiracy nuts like Alex Jones who believe that the Sandy Hook school shooting was faked, and one study found that the more people watched Fox News, the worse they did on a current events test.

So I’m not advocating that you waste time on Breitbart propaganda any more than I’m saying that it was worth listening to leftists in the 1970s who praised Chairman Mao. But wherever we stand on the spectrum, there are sane, intelligent voices who disagree with us — and too often we plug our ears to them.

On the left, there has been some outrage at conservative voices on the Times Op-ed pages. But as a progressive myself, steeped in the liberal worldview, I must say that I often learn a lot — however painfully — from these conservatives with whom I utterly disagree, partly because they gleefully seize upon inconvenient facts that my side tends to ignore because they don’t fit our narrative.