自由とは、自分自身に責任を持つことだ。

When you think it's the most difficult, it's actually the closest you are to success.

计算机是我们想出的最了不起的工具。它相当于我们思维的自行车。

The study of mental processes requires both experimental and comparative methods.

经济学家的角色既是科学家，又是工程师。