入门统计学课本一开始讲的几个要点之一，就是相关性不是因果性。这也是最先被忘记的要点之一。
Libraries were full of ideas—perhaps the most dangerous and powerful of all weapons.
The rules of art are not arbitrary; they are founded in reason and in the nature of things.
The deeper you go into mathematics, the more you realize how much remains unknown.
Quality is not an act, it is a habit.
