Arguably the cruellest thing you can do to human beings is to rob them of faith in their own sanity. People can endure physical torment, even torture, so long as their minds are clear. If they feel sane, they can still make sense of what is happening to them and work out how to survive. But if you undermine somebody’s mental stability, they soon unravel. In the words of John Milton’s Satan in Paradise Lost, ‘Which way I fly is hell; myself am hell;/And in the lowest deep a lower deep,/Still threatening to devour me, opens wide.’
Chipping away at a person’s mental health is known as ‘gaslighting’, after Gas Light, the Patrick Hamilton play that in 1944 became a classic Hollywood melodrama. In the film, Paula, played by Ingrid Bergman, has a husband called Gregory (Charles Boyer) who wants her ‘sent to the madhouse’ so he can get his hands on some family jewels.