We don't stop playing because we grow old; we grow old because we stop playing.
Words and deeds are not separate， but intimately connected.
Art is not what you see, but what you make others see.
下一代将根据我们在水中留下的东西来评判我们，而不是我们从中获取的东西。
The only way to deal with an unfree world is to become so absolutely free that your very existence is an act of rebellion.
我不考虑消极的事情。我只考虑积极的事情。
数学家的工作永无止境；总有新的问题要问，新的谜题要解。
The best picture books work on different levels for different ages.