Promises and Plot

I have always been drawn in by stories that make use of prophecy: O Brother Where art Thou?, Macbeth, and notably I, Claudius. The latter story is a fictional autobiography of the eponymous narrator, the Emperor Claudius, written by English author Robert Graves in 1935. My high school Latin class read it, and I still remember parts of its opening prophecy today. Per the story, various translations attribute the verses to the Sibyl, and this stanza predicts the fate of the narrator himself:

The hairy fifth to enslave the State,To enslave the State, though against his will,Shall be that idiot whom all despised.He shall have hair in a generous mop.He shall give Rome water and winter breadAnd die at the hand of his wife, no wife,To the gain of his son, no son.

What did it mean to be a "son, no son?" Why was Claudius the "hairy" fifth?I read happily, knowing two things: First, the story would answer my questions about the prophecy, even the seeming paradoxes. Second, if it did not, I would stop reading, and be a little ticked with Robert Graves for wasting my time.For a long time, I only knew that I liked these prophecies. After I watched a lecture about the importance of promises in a story, I understood why.Prophecies are a distilled example of promises. Prophecies contain promises in each line. "Here is what will happen in this story," they say. "Keep reading, because as you can see, this will be interesting."Throughout a novel, but especially early on, a writer makes promises to the reader. Prophecy is perhaps perhaps the oldest form of this. Modern stories still make promises, but in new formats. In The Secret History, the Prologue shows an event from much later: somehow, four friends, including the narrator, will come close to committing murder, they may even go through with it. In To Kill a Mockingbird, we know from page one that somehow Jem breaks his arm. In Harry Potter, a baby is dropped off on the front step of a house filled with something a woman who can become a cat calls "Muggles."Genre fiction comes with a set of built in promises. In a "Cozy Mystery," the investigator will be clever but not hardboiled, and there will be an absence of gore. In horror, the promises will be omens, and the characters are in real danger of gore. (Don't pick up that music box/old book/doll, put it down, c'mon.) In a mystery, the promises are clues.Writers give glimpses of the future even on the level of a scene. Whenever you read about a character's plans, that's a promise. Whenever you read about a character's expectations for what will happen, that's a promise, and often that's a promise that the characters expectations will be subverted.So in the above video, when Caligula breaks an actual promise to his mother on her deathbed, and follows up by claiming that a recent prophecy about the coming of God refers to him, the author foreshadows that Caligula will be arrogant, terrible, and borderline mad as emperor. And Caligula delivers. [embed]https://www.youtube.com/watch?v=Mk7T3qKrlgU[/embed]