Final answer:
Stevenson begins the chapter with a paragraph that creates interest in the reader through mention of undiscovered treasure and a mysterious character.
Step-by-step explanation:
Stevenson's reason for beginning the chapter with this paragraph is to create interest in the reader. The mention of still undiscovered treasure and the arrival of a mysterious character in the narrator's life serves to grab the reader's attention and generate curiosity about what will happen next in the story.
Learn more about Stevenson's reason for beginning the chapter with the given paragraph