The central message of this sermon is that true spiritual growth and maturity come from living in accordance with fundamental principles, rather than seeking to add external rules or rituals to one's faith. This idea is encapsulated in the phrase "port is left and starboard is right," which emphasizes the importance of understanding and applying core truths, regardless of how much additional knowledge or experience one gains. The sermon uses the story of Captain McGill and his mysterious book as a metaphor for this concept, suggesting that even those who excel in their fields often do so because they have internalized fundamental principles, rather than relying on external expertise or shortcuts. Ultimately, the message is an invitation to listeners to re-examine their own lives and ensure that they are living in accordance with the fundamental reality of salvation by faith, not works, and to beware of adding unnecessary rules or rituals to their spiritual practice.