He used them to explain the differences between North and South.

VOA: special.2009.07.30

And try and explain to them why you think your program is doing what it's doing.

向别人解释你认为的程序作用,会给你带来很大帮助。

麻省理工公开课 - 计算机科学及编程导论课程节选

Even though they're ordinary and familiar, it still could turn out that we need to appeal to souls in order to explain them.

虽然我们对其早已司空见惯,但还是需要,诉诸灵魂来解释它们

耶鲁公开课 - 死亡课程节选