David P. Barash is professor of psychology emeritus at the University of Washington. His next book, "Through a Glass Brightly: Using Science to See Our Species as It Really Is," will be published this summer by Oxford University Press. With his wife, Judith Eve Lipton, he is currently writing a book about nuclear deterrence.

I gaslight, you gaslight, he/she/it gaslights. What can this mean? Isn't gaslight some sort of compound noun rather than a verb? But it turns out that gaslight is indeed a verb, one with an interesting history and, moreover, a troublesome relevance to the present.

In 1938, British playwright Patrick Hamilton's work, "Gas Light," was produced in London, and ran for six months. Then it was adapted into a 1940 movie, titled "Gaslight," directed by Thorold Dickinson and starring Anton Walbrook and Diana Wynyard. Four years later, it debuted as an MGM film, featuring Charles Boyer and Ingrid Bergman, with a budget that was an order-of-magnitude larger, and comparably less fidelity to the original play. (As part of the contract, MGM insisted on destroying all pre-existing copies of the 1940 film ... at which, fortunately, the mega-studio was unsuccessful.)

But what is "gaslighting," and what does it have to do with the year 2018?

In the story, a wealthy, psychologically "delicate" woman (Bella Mallen) has married a suave, debonair, controlling and decidedly creepy continental European (Paul Mallen) and purchased a multistory London apartment where, decades before, a rich old lady had been murdered and the place ransacked; she was known to have had some extremely valuable rubies. No one had been willing to live in the apartment until its current occupants. Soon it is apparent that Bella is having a hard time: she repeatedly misplaces items, is blamed - by her husband - for taking things when she claims innocence, seems to imagine events that aren't real, and increasingly comes to doubt her own sanity.

It also becomes clear that she isn't crazy after all, but is being craftily manipulated by the nefarious Paul Mallen, who wants to have her "committed" because she accidentally encountered evidence that, unknown to her, could be used against him. The story is set in 1880 London, and in those Victorian times, a husband could have his wife committed simply on his say-so (#MeToo didn't exist.) 

Paul regularly prowls about the attic, searching, we discover, for those rubies which he – the murderer – hadn't been able to find when he committed the crime. As he searches, he turns on the attic gas lights (explaining the movie's title at last), which causes the lights in the rest of the house to dim and flicker; after all, this is 1880, before electricity. Poor belabored Bella notices this, but others – including her well-meaning maid-servant – attribute it to yet another flight of her over-stressed mind.

Eventually, all is set to rights, thanks to the intervention of a retired Scotland Yard detective, who – among other things – confirms the reality of Bella's perception and the guilt of homicidal, perfidious Paul. The film's major contribution to popular culture, as well as to the psychological literature, has been to introduce the verb "gaslight," meaning to induce someone to question their sanity and grasp of reality by malevolently manipulating his or her perceptions.

In the film, especially the 1940 original, which, despite its over-acting and comparatively poor production values, is far superior to the 1944 remake, Paul Mallen is frightening in his malignance, narcissism, lack of empathy, and overall creepiness. But he isn't one half as scary, or creepy, as the current occupant of the White House.

Readers of HNN are doubtless sufficiently well informed that they don't need a recitation of the continuing slurry of deceptions, misrepresentations, and outright lies that have emanated from and continue to disfigure the Chief Executive and his administration. Moreover, when caught in these lies, Donald Trump has unfailingly blamed the truth-tellers and doubled-down on his own mendacity, with a self-righteous insistence that makes Paul Mallen look like the mythically Honest Abe Lincoln, or George "I cannot tell a lie" Washington.

I doubt that Trump, unlike the fictional Mr. Mallen, is consciously gaslighting the country, in the sense of deliberately trying to drive us insane; as many have commented, he may actually believe his prevarications, in at least some cases. But the effect of his behavior is more important than his intention. Many veteran journalists and seasoned political observers have noted the extent to which Trump's obvious lies, his self-serving, dishonest claims of "fake news," as well as the unending barrage of positions taken only to be disavowed immediately afterward have been not only confusing but downright disorienting, so much so in fact that the victims are at risk of becoming as unstable as the perpetrator.

In his March 5 column, the New York Times's Charles Blow put it with characteristically accurate acerbity: "People used to dealing with a sane, logical person who generally doesn’t lie and generally makes sense are left scratching their heads, wondering whether to believe what they have heard, whether to make plans and policies around it. Believing anything Trump says is a recipe for a headache and heartache. The old rules no longer apply. We see the world as through a window — as it is, even if we are a bit removed from the whole of it. But Trump sees it as if in a house of mirrors — everything reflecting some distorted version of him. His reality always seems to return to a kind of delusional narcissism."

At the end of "Gaslight," Paul Mallen gets his comeuppance, and I am not alone in hoping that Donald Trump gets his, too. Be warned, however: when this happens in the movie, the cinematic sinner goes more than a bit crazy himself – decompensating, as psychiatrists would put it. But unlike Mr. Trump, the malignant Mr. Mallen didn't have nuclear weapons at his disposal.