And I wanted to show that common knowledge is not such an obvious a concept, as I've made it seem on the board.

我想让大家明白,共同知识并不是像我写在黑板上的,是一个想当然的概念

耶鲁公开课 - 博弈论课程节选

They are really a difficult concept to grasp when you have no base knowledge of it.

当你没有基础知识时，冠词确实很难掌握。

韩国人经常犯的失误 - SpeakingMax英语口语达人