《抱朴子·内篇·论仙》
懂得自己所疑怪的只是未曾见过的呢？常人能看到百步之远，尚且不能一一尽了，却要把自己所见到的那一点断定为有，把看不到的断定为无，那么天下所不存在的东西，也必定太多了。
目察百步，不能了了，而欲以所见为有，所不见为无，则天下之所无者，亦必多矣。
Do you know that you only question things you have not seen? Common people can see a hundred paces ahead, yet they cannot comprehend everything. But they insist that the little they see exists and that what they cannot see does not exist. In that case, there must be so many things in the world that do not exist.