Final answer:
The theme of man vs. self in the passage is portrayed through Mark Twain's internal conflict of self-doubt, emphasizing the importance of relying on one's own knowledge and training. This reflects the broader literary theme of personal growth through overcoming internal struggles.
Step-by-step explanation:
The theme of man vs. self conflict is evident in the passage as it showcases an internal struggle within the character. Mark Twain starts with confidence but gradually begins to second-guess himself due to external pressures, highlighting the central message that individuals should trust their own knowledge and training over succumbing to doubt and fear. This theme is a common trope in literature where a character faces an internal battle of conscience, decision-making, or confidence, often resulting in a deeper understanding of the self or a significant transformation in the character's development. The excerpt implies that overcoming self-doubt is an integral part of personal growth, aligning with Thoreau's concept of living freely and authentically, which also explores the theme of man's rational mind triumphing over external constraints to enhance life.