Tweet of the Day: Writing Excuses 6.18: Hollywood Formula
This trope activates the moment a character does something so horrible, so despicable and so unforgivably evil there is no turning back. Past this point the character (or group, race, family, etc) enter Complete Monster territory while taking a piss on every warning sign and sit at Lucifer’s side while her devours the wicked trapped in his frozen lake.
As bad as they come.
But what it is curious, at least to me, is what the Moral Event Horizon says about the story itself, or at the very least the morality within the story’s universe.
To wit, the event that marks the horizon also marks the very nadir of what is morally acceptable in your world and in doing so defines what is or is not acceptable. Remember that this is an act so bad that it sets the actor apart from not only the heroes but even other baddies. There is no redemption for this act except (perhaps) death.
In various ancient cultures hospitality to a stranger was sacred and breaking it was tantamount to crossing the horizon. Many gods tested humans by posing as strangers in their homes (Odin and Zeus among them) and granting boons or curses depending on how well they were treated. Paris biggest sin in the eyes of the Greeks was not that he raped (as in took her away from her husband, sex or consent be dammed) but that he violated his side of hospitality by being a bad guest. City states and clan societies built their political alliances on this bond, often exchanging family members (hostages) to cement such alliances.
Modern stories add an interesting twist to the Moral Event Horizon. The MEH is not what defines the villain of the story, whom we all assume is evil most foul, but the hero, or at least the modern anti-hero. That is, the anti-hero is willing to do a lot of morally questionable things, but unlike the villain he will not cross the horizon, whatever that may be, such as shooting a child in a hostage situation, or torturing a female prisoner or whatever other act the author has set up as the MEH.
So what is the Moral Event Horizon in your story?