Why does Paul feel as though he doesn’t belong on the front lines?

Paul receives seventeen days leave to go home. His mother likes seeing him in them, but his father prefers he kept his uniform on. His father also barrages him with questions about the front; Paul gives him only a few anecdotes and refuses to talk about violence. Paul finds that others he meets have unrealistic expectations and ideas about war; at any rate, he feels he does not belong in this "foreign world." He spends much time alone; even if others understand him, it is "only with words," only with "half of themselves." He examines the books in his old room and attempts to think back on his youth, but nothing comes--he is only a soldier.