The most important thing in mathematics is to understand the concepts, not just to memorize the formulas.

"Every saint has a past, and every sinner has a future."

你知道，在中世纪的英国，但你遇见一个非常穷苦的人，你会认为他“不走运”，直接地说，那些不被幸运之神眷顾的人。

The concept of progress is inseparable from the concept of catastrophe.

泽畔野鸡，宁愿走十步远去啄食，走百步远去饮水，也不希望被关在囚笼里。