The most salient theme is that virtue and courage will prevail over craftiness and evil. In advancing this thesis, Stevenson uses the time-honored quest motif. After being kidnapped at the instigation of his wicked uncle and meeting with Alan, David must travel afar, fight battles, and even kill enemies.
Another thematic element is Stevenson's repeatedly exposed belief that there are positive and negative sides in nearly everyone. Several of the men on the ship where David is taken illustrate this belief. Second officer Riach shows some kindness to David, but his kindness is chiefly confined to periods of drunkenness; when he is sober, he tends to be mean. On the other hand, Mr. Shuan is the opposite: kind when sober and violent when drunk, as when he kills the cabin boy in a fit of drunken rage. Even Alan Breck, with all his bravado and tendency to violence, can be sensitive and caring. In a serious conflict between Alan and David, when tempers are flaring and David offers to fight Alan with swords, Alan pauses and refuses because "it would be murther" — he is a skilled swordsman, and David has shown little aptitude for this sort of combat.
In sum, the chief lesson in this novel is that one must learn and practice a valid moral code of behavior. While David begins his adventure as a good-hearted lad, he emerges at the close as a more sophisticated young man who understands, both himself and the world and more seriously appreciates the need...
(The entire section is 257 words.)