Final answer:
The theme of trusting in one's own knowledge and not second-guessing oneself is developed through Varick’s character in Mark Twain’s story, as he faces the challenges of running a crossing under pressure. Varick's responses to external pressures and his ultimate success or failure in handling the crossing illustrate this central message.
Step-by-step explanation:
The theme in the referenced passage from Mark Twain's story, presumably 'Life on the Mississippi' where Twain recounts his days as a steamboat pilot under the tutelage of Mr. Bixby, revolves around the idea that one must trust in their own knowledge and training instead of succumbing to doubt. This is illustrated by Varick's diminishing confidence as he faces the challenges of navigating the steamboat under increasing pressure. The character's resilience or lack thereof and the consequences of second-guessing one's abilities further develop this theme. It is through the resolution of the conflict, namely, whether Twain can successfully run the crossing despite the pressure, that the theme of self-reliance and the dangers of doubt is explored.
Throughout the story, the ways in which Varick responds to the added pressure—either by faltering or by overcoming his doubts—can signal to the reader a message or lesson about the importance of self-confidence and trust in one's skillset. If we look for repeated elements to suggest a theme, the increasing number of onlookers and the escalating nervousness of Varick showcase the main message around the importance of inner belief over external distractions and the significance of personal preparation and expertise.
As for the other themes, it's common for stories to have multiple layers, and readers might discern themes related to learning, the mentor-mentee relationship, or the journey from insecurity to self-assurance, all of which are relevant to both the narrative and the development of character in the story.