If you read anything online these days, you’ll be familiar with the term ‘gaslighting’. It refers to the manipulation of one person by another, in a way that makes them doubt their sanity. It’s also been used to describe Trump’s campaign winning tactics, twisting and playing with our understanding of ‘facts’ until nothing seems quite concrete.

However, the term gaslighting comes from a play which you never read in school, and of which you probably never saw the movie either. It was the first play of a talented writer who failed to make it into our shared cultural history, and his name is Patrick Hamilton.

The play is set in 1880 in the upper middle class London home of Jack Manningham and his wife Bella. In the 1942 Broadway production Vincent Price played Manningham. You’ve heard of him, right? Manningham is a man who has purposely married Bella in order to be able to purchase a flat below the one where he murdered a rich heiress years before. He was searching for her rubies when the police arrived and fled and now, every evening he sneaks back in to resume his search. He refuses to tell Bella where he’s going (obvs) and promotes the notion that she’s mentally unstable so that, as she starts to get wind of the truth, she doubts herself. Bella begins to believe she is losing her grip on reality, because whenever he leaves, she thinks the gaslight is waning. The single truth is, the gaslight is waning, because Jack is upstairs with it on full blast as he searches for the jewels.

However, in this concept – the one single truth manages to support the untruth – that she is insane.

It takes Detective Rough’s intervention to work out the connection and uncover Jack’s actions.

So there you have it. It’s much more complicated than just Trump waving his hands around and saying the same few words over and over again. Gaslighting as a concept explains how truth can support fiction when we allow ourselves to doubt our perceptions or ignore physical reason.