When he talks about the soul being invisible, and invisible things being indestructible, maybe he means things that can't be observed through any of your five senses.

他谈到灵魂是无形的,无形的东西不会毁灭，也许他指的无形是通过五官,都无法觉察到的东西。

耶鲁公开课 - 死亡课程节选