is everything that happened before the story begins. Every story has a predetermined period of time where its story telling occurs. In a movie, for example, that means from the moment the movie starts until it ends; for a book this includes everything from the first to the last page. Any event or fact that is referenced inside this period, but happened before that, or was established before that, is a preassumption to the plot.
No matter how insane, unreal or magical a preassumption is, it is usually assumed by the main characters to be true. But even on instances where the validity of preassumptions is questioned by characters, they do not have the ability to alter the main plot or the end result of the story. The main plot usually does not deviate from these pre-established facts during the story telling. When such a thing happens, the plot is considered to be inconsistent, leading to the possible creation of PlotHoles. On rare occasions, a good story will invalidate plot preassumptions in order to reveal a great turn of events, showing viewers that they were fooled into thinking something was true, when in fact it wasn't.
A PlotPivotPoint cannot be inside the preassumption. For all intents and purposes of this type of analysis, preassumptions cannot be changed, and cannot alter the course of the plot during the story telling. They are considered to be preestablished facts or events prior to the current period when the story happens.
!Examples of Plot Preassumptions
* '''Men In Black (1997)''' - The existence of aliens as well as a secret organization that monitors extraterrestrial activity on Earth are both preassumptions to the plot.
* '''Jurassic Park (1993)''' - The technology that allows dinosaurs to be cloned from ancient, somewhat well-preserved DNA is a preassumption.
* '''Back To The Future (1985)''' - The existence of the time machine, the clock tower getting struck by lightning, Marty's parents getting meet and get married, are all preassumptions to the plot.
* '''Dark Shadows (2012)''' - The existence of magic spells is a preassumption for the plot, used by the main characters.
* '''Eternal Sunshine of the Spotless Mind (2004)''' - The existence of a technological device that allows doctors to surgically remove a patient's memories at will is a preassumption to the plot.
* '''Memento (2000)''' - Leonard and his wife being violently attacked at home by robbers is a preassumption. The audience can see flashbacks to that event, but they are only references to something that already happened before the story began. [[spoiler:The fact that his wife died the night they were attacked is also a preassumption, but it turns out to be false one in a great revelation at the end of the film.]]
* '''Harry Potter series (2001-2012)''' - The existence of magic, wizards and prophecies are preassumptions to the main plot.