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.
历史是对于未来最好的老师。历史书中的答案价值万金。