Among those history, science and literature for teenagers, Sophie's World is definitely a classic. The defining theme （主题） of Sophie's World is, pretty clearly, philosophy. As the book moves along, Sophie Amundsen, a teenaged girl, learns important lessons in the history of Western philosophy from her teacher, Alberto Knox. Alberto, an intelligent man, guides Sophie through the history of philosophy.
It would take too long to summarize every philosophical system that Alberto reviews with Sophie—in fact, doing so would be beside the point. By the end of the book, Sophie certainly hasn't settled on any one system of ideas. There are things about Plato, Hegel, Kant, and Nietzsche that she admires, and a few moral issues that she's particularly interested in but she's not prepared to throw in her lot as a Kantian or a Nietzschean. Even after learning about 3,000 years of Western thought, Sophie continues to wonder what to believe.
The concept of "wonder"—both in the sense of questioning what is true, and in the sense of being continually amazed by the world—is the key to understanding Sophie's World. One reason why the novel doesn't end with Sophie arriving at an answer to her questions is that any such answer would be a little unsatisfactory, since it would make the universe seem "fixed", predictable, and dry. Alberto teaches Sophie about philosophy not to give her answers but to train her to ask questions—to think of herself as an outsider, trying to make sense of what's right in front of her nose. A good philosopher will never lose her sense of wonder at the universe's mysteries. One could even say that the goal of philosophy as Alberto understands it is to escape banality （平庸） and boredom.
In this way, Sophie's World arrives at the strange conclusion （结论） that although it's important to ask philosophical questions, it's not particularly important to choose definite answers to these questions. Philosophy is about preserving one's sense of wonder—this, it's suggested, is the only real wisdom.
