Everything is an argument in a way it didn’t used to be, every article your friends and relatives link to a declaration of rhetorical war. Day after day, comment after comment, we live in a state of fractious, troubling doubt. The internet has always been a cozy home for partisans and pedants, conspiracists and crusaders, but gradually, their spirit has crept into the rest of our lives. The president conducts affairs of state over Twitter. More important, he has somehow taken up the chaos of the internet as a defining ethos of his administration, delighting in his ability to blithely shift course and keep people guessing. One day he is said to have described several foreign nations in foul-mouthed terms; the next day, people who were present deny it, or insist he used a different vulgarity to do it. The business of the country is now conducted like an argument on an unmoderated internet message board — an unceasing thread of squabbles, reversals and revisions.

A recent editorial in Foreign Affairs articulated the “credibility gap” this habit has created. In the prim terms of international relations, this is no small thing: Being seen as likely to act on your word is the basis of every threat, every diplomatic agreement between nations, and for America to abandon that credibility is a grave loss. During the Cold War, “credible” was a mainstay of nuclear-defense chatter, where it could be used to describe any weapon that actually worked. (If your weapon is operational — and you have the capacity to defend yourself against retaliation — you are said to have a “credible first-strike capability,” a point of leverage possibly more important than the missiles themselves.)

Credibility matters at home too. In the midst of bedlam over the three-day government shutdown, Senator Lindsey Graham complained of the administration’s moving-target negotiations for a border wall, which seemed to cost $18 billion one day and $33 billion the next. Graham, addressing a group of reporters, sputtered in disappointment: “That’s just not credible.”

Credibility really is kind of metaphysical: We have to take a little leap of faith to get there. The main root of “credible,” after all, is the Latin word for “belief.” Aristotle thought the best way to inspire such faith was to seem like a good person: “Persuasion is achieved by the speaker’s personal character,” he wrote in “Rhetoric,” “when the speech is so spoken as to make us think him credible.” The audience is inclined to trust someone it already thinks well of.