不可以同井底的青蛙谈论大海的辽阔，因为有空间的拘束；不可以同夏天的小虫谈论冰冻的寒冷，因为有时节的局限。

自守形式的研究是数学对称性之美的反映。

Language is the key to understanding higher mental processes.

It seems to me that if you or I must choose between two courses of thought or action, we should remember our dying and try so to live that our death brings no pleasure to the world.