没有孩子的民族将面临无望的未来；没有树木的国家将面临更加无望的未来。

知识的增长是解决问题的关键。

I can never be safe; I always try and go against the grain. As soon as I accomplish one thing, I just set a higher goal. That's how I've gotten to where I am.

Most men die at twenty or thirty; thereafter they are only reflections of themselves.

“唯一真正普遍的是人类的经验。”