Radio host Alex Jones speaks into a megaphone. (Brian Blanco/European Pressphoto Agency)
Contributing columnist

A recent whim prompted me to reread Stephen Ambrose's "To America," a collection of reflections on the historian's craft and many of the topics and individuals Ambrose wrote about during his prolific career. The book might have been titled "Second Thoughts," because virtually every chapter describes some significant issue on which the author changed his mind over the years: his estimation of presidents such as U.S. Grant, Theodore Roosevelt and Richard Nixon; Harry Truman's decision to use the atomic bomb; the "robber barons" who built the transcontinental railroad; the reality of Soviet tyranny; and several more.

In many cases Ambrose relates how he came to dispute conclusions that his university professors and advisers peddled to him in his younger years. Elsewhere, he takes issue with his own previous views. But in each instance, he explains the evolution of his thinking, and the grounds for it, without defensiveness or embarrassment.

When the book appeared, early in this century, one would not have found such admissions especially noteworthy. In 2017, they take on a more striking cast, because ours is an era when it seems no one ever confesses to being wrong. Moreover, everyone is so emphatically right that those who disagree are not merely in error but irredeemably so, candidates not for persuasion but for castigation and ostracism.

Social historians will need some time and perspective to determine exactly what led to the new closed-mindedness, but some of the causes seem plain. One is the effect of narrowcasting, in which people find the sources of information (or the sources’ algorithms find them) that fortify their existing viewpoints and prejudices. “Confirmation bias” has mutated from a hazard of academic research to a menacing political and social phenomenon.

Meanwhile, those institutions of higher learning — the adjective now almost needs quotation marks — that should cultivate and model openness to debate and refutation too often have become bastions of conformity and thought control.

John Maynard Keynes is frequently credited with the aphorism "When I find I'm wrong, I change my mind. What do you do?" Today, the problem may less be an attitude of stubbornness than that fewer people than ever recognize their mistakes in the first place.

In a well-documented fashion, steady doses of viewpoint reinforcement lead not only to a resistance to alternative positions but also to a more entrenched and passionate way in which thoughts are held and expressed. When those expressions are launched in the impersonal or even anonymous channels of today’s social — or is it antisocial? — media, vitriol often becomes the currency of discourse and second thoughts a form of tribal desertion or defeat. Things people would not say face to face are all too easy to post in bouts of blogger or tweeter one-upmanship.

So honest admissions of error are more eye-catching these days. In recent years, The Post's Bob Woodward has recounted how, a quarter-century later, he had come to a very different interpretation of Gerald Ford's pardon of Richard Nixon. And how he wasn't the only one; Sen. Ted Kennedy, who excoriated Ford at the time of his decision, joined Woodward in that assessment, and conferred an award for political courage for the act they had once deemed a corrupt bargain.

A few months back, the world lost Jay Keyworth, nuclear scientist and presidential science adviser to Ronald Reagan. Keyworth had assembled the evidence to advocate an anti-ballistic- missile (ABM) system, which establishment opinion of the time relentlessly derided as "Star Wars" — a fanciful and impractical notion, and one in conflict with the then-sacred doctrine of mutual assured destruction.

Now, with one rogue nation perfecting both weapons and rocketry capable of annihilating U.S. targets, and another perhaps only years from joining it, the conversation is all about the effectiveness of our ABM system and why the heck the government hasn’t made our national safety more certain. We’re still waiting for that conversation to include “Thanks, Jay. You were right, and we weren’t.”

Ambrose wrote his book near the end of his life. In fact, it is dedicated to his cancer doctor and nurses. Maybe such honest introspection comes more readily under the imminence of the great event. But our everyday exchanges, and indeed the life of our republic, would be greatly improved by the more common utterance of those three magical little words: “I was wrong.”