No president who performs his duties faithfully and conscientiously can have any leisure.

True strength is not in the muscles, but in the heart.

The spread of liberal democracy around the world is not inevitable, but it is the most likely outcome.

举一个例子尚且不明白，就不要追求见多识广。 

A physical symbol system has the necessary and sufficient means for general intelligent action.

有时候，只要你坚持下去，活下去，就已经是非凡的成就了。