Language in the public square is an "instrument of power," author and theologian Dorothy L. Sayers wrote, and it is an instrument few have been taught to handle aright.

The result, she warned, is a public ever in danger of succumbing to assault by the verbally skilled: "the demagogue who can sway crowds, the journalist who can push up the sales of his paper to the two-million mark, the playwright who can plunge an audience into an orgy of facile emotion, the parliamentary candidate who is carried to the top of the poll on a flood of meaningless rhetoric, the ranting preacher, the advertising salesman of material or spiritual commodities."

That danger loomed in 1942, when Sayers spoke of it as Nazi lies stained the mind of Europe. It looms today, too, albeit from different angles.

President Trump is a curious case. He straddles Sayers' line between "cynically unscrupulous" public orators and those who have "become the victims of their own propaganda," though his abilities in either mode are noticeably limited. He has rhetorical skill of an instinctive sort and often fits the description of the demagogue swaying crowds, the candidate winning on meaningless rhetoric, and even the ranting preacher. Rapid-fire promises are his weapon of choice, the bigger and less measurable the better. He'll fight for you, drain the swamp, make them pay, defend your "Suburban Lifestyle Dream," make America great again, keep America great, win so much you'll get tired of winning.

Aimed correctly, given the right audience and performance space, this onslaught downs its target. The president is a salesman and can hold his marks in thrall. But Trump's is the limited expertise of trial and error. He constantly floats new claims and slogans, often couched as innocent questions or something "people are saying" or an idea "I've heard." He keeps what works — whether by appealing to his base or infuriating his opponents or gaining him money or media attention — and tosses the rest. Under interrogation, Trump constantly tacks back to those known waters. If forced outside territory he has already explored, his inexpertise resurfaces.

A widely shared clip from Trump's new Axios interview, released Tuesday, showed this well. He launches from a comfortable port, this notion that the only reason the United States' COVID-19 caseload is the highest on Earth is that we do more testing than anyone else. Challenged by interviewer Jonathan Swan to consider another metric, Trump is helpless. "You can't do that," he sputters.

This revelatory tic of verbal incompetence appears throughout the interview. "You don't know that," he says at the 14:30 mark, when Swan asserts the COVID-19 death per population rate is substantially lower in South Korea than in the United States. At 19:30 he claims ignorance of what "arming the Taliban" means and responds to the report of Russia doing exactly that by denying he was ever told about it. At 33:30, he rejects the idea that he would have thought about racial disparities in police violence. "I don't know why [it happens]," he says. At 35:30 he has no opinion on the legacy of the late Civil Rights leader John Lewis. "I don't know. I don't know John Lewis," he says, adding that he "can't say" whether he finds Lewis impressive.

This doesn't read as an honest expression of human finitude and fallibility. That I'd welcome if it ever appeared in politics. It comes off, rather, as a man out of his depth and desperately paddling back to the firm, familiar footing from which he may demagogue again.

Yet Trump isn't alone in this eagerness to make public language his weapon. The public, invited by social media to become orators ourselves, can no longer anticipate assault from the relatively narrow category of people Sayers delineates. At any moment, anyone in our acquaintance may play the demagogue or playwright or salesman on our feed. Language is wielded as a weapon by Sayers' "experts who understood it perfectly against people who were not armed to resist it and had never really understood that it was a weapon at all." But now it is also wielded by the people against each other, none of them understanding it perfectly, like so many toddlers who have stumbled upon daddy's unlocked gun.

This may sound, I realize, like elitism. That was my first reaction to Sayers, too. It is not democratic to suggest, as she does, that it is "as dangerous for people unaccustomed to handling words and unacquainted with their technique to tinker about with these heavily-charged nuclei of emotional power as it would be for me to burst into a laboratory and play about with a powerful electro-magnet or other machine highly charged with electrical force." I realize, too, that to echo this argument as Sayers' fellow writer lumps me in her elitist company, if indeed the charge is fair.

But the opposite view — the idea that there isn't risk in making and entertaining public commentary without, in Sayers' phrase, a "wary determination to understand the potentialities of language and to use it with resolution and skill" — strikes me as simply untenable. Surely the Trump presidency or any casual scroll through Facebook or Twitter makes that amply clear. Until very recently, as I wrote earlier this year, we were exposed to and offered much less public opinion, and for many of us, that was a good thing.

Responsible and humane public use of language is indeed an expert skill. It is not something we are born knowing, nor is it something we are all taught, though it is certainly something anyone can practice to learn. Skip that step, however, and we can become a danger to each other and our common life.