母子关系是矛盾的，在某种意义上，是悲剧性的。它需要母亲最强烈的爱，然而这种爱必须帮助孩子离开母亲，变得完全独立。

What's left out is as important as what's included.

如果没有地幔对流的概念，大陆漂移理论将只是一种猜测。

一切人类知识都源于经验。

The writer's only responsibility is to his art.

Take long walks in stormy weather or through deep snows in the fields and woods, if you would keep your spirits up. Deal with brute nature. Be cold and hungry and weary.

我们想要一个人民可以自由的选择、犯错、持有宽容及同情心的社会。这就是我们所谓的道德社会；不是一个国家要负所有责任，而没有人须要为国家负责的社会。