《淮南子·道应训》
无始回答说： 说不知道的恰恰说明他知道的深奥，说知道的恰恰说明他知道的肤浅；说不知道的恰恰说明他知道了它的实质，说知道的恰恰说明他只知道它的外表；说不知道的恰恰说明他知道了它的精粹，说知道的恰恰说明他只知道它的大概。 
无始曰： 弗知之深而知之浅，弗知内而知之外，弗知精而知之粗。 
Wushi replied by saying, “To say that you do not know is precisely to show the profundity of your knowledge, to say that you know is precisely to show the superficiality of your knowledge; to say that you do not know is precisely to show that you have grasped its essence, to say that you know is precisely to show that you only know its external appearance; to say that you do not know is precisely to show that you have understood the quintessence of the Dao, to say that you know is precisely to show that you only know the general idea.”