How does the author, Dan Brown, use the thoughts of the characters to move the story along?

The author often uses the thoughts of his characters to interject history and back story. In Chapters 25 through 28, for example, Brown gives a history lesson on the speculation and rumors that surround the Mona Lisa by having Langdon recall an art history class he taught to prison inmates. Brown also uses Langdon's thoughts as an opportunity to recount Church history and its rejection of feminism. This adds more dimensions to the story.