There are a number of prominent themes in Treasure Island. All of the traditional conflict themes of man vs. man, man vs. nature, and man vs. himself are present. Man vs. man is illustrated by the conflicts between Hawkins and Billy Bones and Long John Silver. Man vs. nature is presented in Hawkins's struggles to navigate the Hispaniola as well as Ben Gunn's small boat. Man vs. himself is evidenced in the difficult decisions Hawkins must make, such as when he must decide whether to desert his crew.
Honor is another important theme in the book, which applies to both the good guys and the bad guys. Even the pirates, who murder and steal as a matter of course, have an unwritten code of behavior which they must follow, or else they lose face in the eyes of their peers.
An overall theme which is prominent in Treasure Island is the achievement of maturity, or coming of age. Through his choices and experiences, Hawkins emerges at the end of the narrative a much more wise, confident, and courageous character than he was in the beginning.
Check out the enotes link below - it will provide you with a clear but comprehensive analysis of the themes in the book!