The greatest obstacle to being heroic is the doubt whether one may not be going to prove one's self a fool; the truest heroism is to resist the doubt, and the profoundest wisdom to know when it ought to be resisted, and when it be obeyed.

The mind can be considered as a physical symbol system.

唯一真正的发现之旅不在于寻找新的风景，而在于拥有新的眼光。

每一种材料都有其智慧。