What are the motifs in Soldier's Heart by Gary Paulsen?

Maturity is a recurring idea in the book. The book is a study of the maturing of Charley Goddard. His maturity is in small steps and takes place over a year or more. He is certain of himself during his boyhood, and yet as he does mature, he becomes less certain of himself and questions his maturity, at times seeing it as training, not the growing of his inner self.