And the challenge then is, for us, if our goal is to become practical idealists is to understand what it is that brings about change and then do it.

困难在于，如果我们想成为实践理想主义者,就要理解是什么带来改变然后去做。

哈佛公开课 - 幸福课课程节选

It was practical books about fortifications, hydraulics, artillery, navigation, and shipbuilding.

而是实际的书籍,比如有关防御工事的,水力学,炮术,航海和造船的

耶鲁公开课 - 欧洲文明课程节选