The mathematician does not study pure mathematics because it is useful; he studies it because he delights in it and he delights in it because it is beautiful.
什么都会的人,很少有自己所真正精通的东西,整天沉心思虑的人,往往遇事难以下决断。
天下的治乱不在于一个王朝的兴亡,而在于百姓的忧乐