一个奇怪的事实是，根据从生物学或地球物理学的角度出发，对地球史前条件会得出完全相反的结论，这反映了我们目前知识的不完整状态。

The only way to deal with an unfree world is to become so absolutely free that your very existence is an act of rebellion.

Human kindness has never weakened the stamina or softened the fiber of a free people. A nation does not have to be cruel to be tough.

The key to solving complex problems is often to find the right abstraction that simplifies the problem without losing its essential features.

If you're lonely when you're alone，you're in bad pany。