The narrator is confined to reporting what she or he could realistically know. More than that, although the narrator may certainly interpret actions, deliver dictums, and predict the future, these remain the fallible opinions of a human being. We are not bound to accept them as we are bound to accept the interpretations, truths, and predictions of the omniscient author. You may want us to accept the narrator's word, and then the most difficult part of your task, and the touchstone of your story's success, will be to convince us to trust and believe the narrator.

Janet Burroway, Writing Fiction, Tenth Edit…, loc. 533