Purposive behavior in animals and men.

对一个人而言，只要谨慎自信 ，没有什么是高不可攀的。

Theorems are the milestones of mathematics.

I will tell you what I will do and what I will not do. I will not serve that in which I no longer believe whether it call itself my home, my fatherland, or my church: and I will try to express myself in some mode of life or art as freely as I can and as wholly as I can, using for my defence the only arms I allow myself to use—silence, exile, and cunning.

I'm not interested in playing the hero. I'm interested in playing the human.