Rite of passage/Loss of innocence
This novel is signified by a boy going through a rite of passage into adulthood. After David's father passes away, the protagonist strikes out on his own into the world at large. A loss of innocence theme results because of the growth from youth to manhood, a path to maturity through obstacles which will have to be overcome. These challenges and the realization toward their solutions is symbolic of a young adult's progress toward an adult understanding.
Duality of Scottish character
This theme revolves around the ancient prejudices roused in Stevenson's writing, where the Lowlander views the Highlander as a barbarian and the Highlander views the Lowlander as a conservative moralist. The Highlanders are usually romantic Jacobites whereas the Lowlander is a pragmatic Whig. The lines blur, which is also explored, but the duality of the Scottish heritage was intriguing to Stevenson and is embodied in the novel.
Duality of self
The critic, Kiely, describes this theme as "the problems of the body and of the practical intelligence, in clean, open-air adventure.'" David is looking for logical, straightforward ways of effecting an action yet he is often incapable of enacting them. He lacks creativity and romantic imagination. Alan, by contrast, knows that if he thinks about a problem for a long enough time, he will invent some way of solving it. He is inventive and enterprising, though impulsive and often irresponsible. These qualities wage war within each human body and soul.
Man versus nature
Man is stripped entirely of the material objects, such as the money and clothing, which made him recognize his humanity until he can come to terms with the very essence of self. The landscape is also pivotal in breaking down the brotherly dynamic between Alan and David. David begins to lose his sense of practicality and to hate the position he has been put in during this journey and during this novel. As doubles - as halves - the men crumble to the point of blindly entering an ambush. The landscape does not kill them or save them, only men are capable of these acts in the novel. However, the character of the landscape certainly aids, symbolically, in the disintegration of the sense of self and the questioning of duality.
