"The great secret that all old people share is that you really haven't changed in seventy or eighty years. Your body changes, but you don't change at all. And that, of course, causes great confusion."

To be happy is to be able to become aware of oneself without fright.

"The human heart is a battlefield of conflicting emotions."

计算复杂性的研究告诉我们，有些问题本质上是困难的，无论我们的算法多么聪明。

《在北京五族共和合进会与西北协进会的演说》，1912年9月3日。