As Heidegger points out in this passage, that's a thought experiment which, if it can be done at all, derives from that prior knowledge.

海德格尔在文章中指出，这个思想实验，在可以实现的前提下，来源于之前的知识。

耶鲁公开课 - 文学理论导论课程节选

If you try to imagine a smile with no body at all, it can't be done. Why?

如果你要相信一个没有身体的微笑,那是根本做不到的 为什么呢

耶鲁公开课 - 死亡课程节选