Jesus starts teaching in the temple midway through the feast and the Jews are asking for His credentials much as we would ask for a Dr. to present his credentials. Jesus responds indicating His doctrine was not His invention, but that it came from another source. Dr. Sproul discusses what Jesus knew and did not know both as a baby and as an adult explaining about Christ's dual nature.

http://www.ligonier.org/account/dashboard/sermon/136/download/