Final answer:
Mark Twain used a frame narrative in his memoir to highlight the theme of relying on knowledge over fear, to build tension through dialogue, and provide an intimate first-person perspective of his past experiences learning to pilot a steamboat.
Step-by-step explanation:
Mark Twain chose to write his story as a frame narrative in his memoir Life on the Mississippi because this structure allows him to explore the theme that it is essential to rely on knowledge and training rather than be swayed by fear. Using a frame narrative, Twain adds depth to the story by reflecting on the past from a present perspective, allowing readers to see how the past experience shaped his knowledge and character. In Twain's case, the frame narrative emphasizes the process of learning to become a riverboat pilot and how this experience contributed to his personal growth. Within the narrative, Mark Twain employs dialogue to build tension and define conflict, which supports the theme of his memoir. Dialogue conveys the narrator's transition from self-assurance to self-doubt, embodied in the tension of navigating a steamboat under scrutiny. This approach to storytelling grants authenticity to the account by placing readers directly in the moment of the experience. Furthermore, by organizing the story chronologically and narrating it from the first-person point of view, the narrative allows for a personal and intimate insight into the author's thoughts and emotions at the time of the event.