What is the main difference of the protagonist at the beginning of the novel vs at the end

Philip thinks that war is a joke. He used to play with Hendrik that they were soldiers in war. This soon changes when Philips ship going to Miami is torpedoed by a german U boat. He is alone on a raft with an old man and they get on an island . The old man, Timothy, teaches Philip how to catch fish,build a hut, travel alone even though he is bling, and climb a really tall coconut tree. Timothy later dies and Philip is blind and alone, after a while a ship passes and Philip is rescued. Philip never played with Hendrik about war and felt he was a man and was very mature