David's primary function in Kidnapped is to serve as a way for young boys—Stevenson's intended audience—to see someone like themselves going through great adventures. David is young and inexperienced, and so everything he describes everything he sees with unfamiliar eyes, just as his readers would.

The basic plot of Kidnapped follows David's growth from a naïve young boy to a heroic, experienced man. Through his association with Alan Breck, David learns much about the "real world," living in difficult conditions, and justice. By the end of the novel, he is able to outwit his own scheming uncle, and claims his inheritance. His adventure is a kind of rite-of-passage. When it is over, he has become a much wiser and mature person.

David, the Protestant Whig, is also an excellent character to interact with the Highland Jacobite, Alan Breck. By making David a Lowland boy, Stevenson is able to examine the clans of Scotland from a more curious and unfamiliar eye. Many of Stevenson's readers may have had a negative opinion of the Highlanders. David does too, at first, but by the end of the book he has come to understand and respect them. Since Kidnapped is, in many ways, a paean to the Scottish Highland way of life that was quickly vanishing, if not gone, by Stevenson's time.