《庄子·内篇·大宗师》
正确的认识必须依赖于一定的条件，而这个条件却是不断变化的，何以知道我所说的出于自然不是人为的呢？
虽然，有患：夫知有所待而后当，其所待者特未定也。庸讵知吾所谓天之非人乎？
Correct cognition must rely on certain conditions, but this condition is constantly changing. How can I know that what I said is from nature and not artificial?