It's a difficult thing to do these things and that's why we need invention.

做这些事很难,这正是我们需要发明的原因。

耶鲁公开课 - 金融市场课程节选

Because writing a philosophy paper is a difficult thing to learn how to do.

因为写哲学论文,是不太好学的。

耶鲁公开课 - 死亡课程节选

That's a complicated thing that accountants figure out and accountants find it difficult to define the earnings of a company, but they do something and they come up with a number.

会计们会计算这个复杂的问题,他们还会发现公司收益很难定义,但是他们会想办法,得出一个数字

耶鲁公开课 - 金融市场课程节选