Why is Captain Brooks' and his crew's knowledge of the island of Juan Fernandez important in "Excerpt from Shipwrecked?"

"as one of our outstanding historical figures once said, ‘when a great democracy is destroyed, it will not be because of enemies from without but rather because of enemies from within.’" (paragraph 7) how does this quote reveal mccarthy’s point of view and advance the purpose of his speech?

Which of these authors wrote a story that revolved around a captains underwater adventures with his crew and a sub marine long before the submarine was actually invented

Samuel johnson believed that literature should appeal mainly to the scholar, to him the common man, to teach him the common man, to teach and him the king and the parliament