Narrative Theories

 Tim O'Sullivan believed that all media texts produce a narrative. He believed that to make a narrative, a story and a plot both had to be present in the text. Story+Plot = Narrative. He believed that the story is made up of what is inferred (what happens),  the plot is what is presented by the text (how we are shown what happens) and that these added with non-diegetic material produced a narrative. The diegesis of a text is the fictional world where the narrative occurs.
Tim believed that narratives offer a set of ideas of us as a society, and how we are represented. This is why we find narratives interesting. Tim also argued that the narrative had to have a degree of verisimilitude (how real/true the story is). 

Tzvetan Todorov's theory of equilibrium can be used to back up the statement: "Linearity of cause and effect within an overall trajectory of enigma resolution." His theory for narrative structure explains how a narrative starts with a state of equilibrium, where the protagonist and antagonist are in their own diegesis and everything is in balance. The "enigma" occurs in the next stage of the narrative, which Tzvetan labels as a state of disruption. This disruption is often where the meeting of the protagonist and antagonist occurs. This then leads to the next stage which is the quest. This is the main [art of the narrative where the protagonist tries to overcome the obstacle which is the disruption. This overcoming then leads to the final stage of the theory, which is where a state of re-equilibrium is found as the diegesis and protagonist are back to the normal balance.

Claude Levi Strauss  came up with the theory of binary oppositions. He claimed that within a narrative, either the protagonists or the protagonist and antagonist are binary opposites. Examples of these oppositions are good V's evil, black V's white, rich V's poor etc. This opposition helps to fuel the narrative and give the audience a clear indication of which characters are fighting for which cause.