All the text-types overlap and it is conceivable to experience a narrative that engages in argument for example. Chatman distinguishes between tacit and explicit description. Tacit description takes place in film, explicit description mostly in written works. Diegetic narrative or diegesis involves pure narrative. When the poet narrates a narrative as himself, and not an assumed character, diegetic narrative takes place.
Mimesis occurs when there is imitation of character.
Chatman insists that all narratives have a narrator even if that narrator is non-human. Narration implies agency, although the word agent does not insist upon a human. Chatman rebuts Christian Metz s semiotical approach. He believes that verbal activity is not a sufficient model to analyze the visual.