自然和历史是地理知识的两个重要来源。

The natural effort of every individual to better his own condition， when suffered to exert itself with freedom and security， is so powerful a principle that it is alone， and without any assistance， not only capable of carrying on the society to wealth and prosperity but of surmounting a hundred impertinent obstructions with which the folly of human laws too often encumbers its operations.

I don’t like to be comfortable. I like to be challenged.

"I think that the only way to deal with life is to find something that you love and do it with all your heart."