I (Hsu Ai) did not understand the teacher's doctrine of the unity of knowledge and action and debated over it back and forth with Huang Tung-hsien and Ku Wei-hsien without coming to any conclusion. There I took the matter to the teacher. The teacher said: "Give an example and let me see. " I said: For example, there are people who know that parents should be served with filial piety and elder brothers with respect, but they cannot put these things into practice. This shows that knowledge and action are clearly two different things.

The teacher said: The knowledge and action you refer to are already separated by selfish desires and no longer knowledge and action into heir original substance. There have never been people who know but do not act. Those who are supposed to know but do not act simply do not yet know. …. Seeing beautiful colors appertains to knowledge, while loving beautiful colors appertains to action. However, as soon as one sees a beautiful color, he has already loved it; smelling a bad odor appertains to knowledge, while hating a bad odor appertains to action. However, as soon as one smells a bad odor, he has already hated it. It is not that he smells it first and then makes up his mind to hate it. A person with his nose stopped up does not smell the bad odor even if he sees a malodorous object before him, and so he does not hate it. This amounts to not knowing a bad odor. ….Or take one's knowledge of pain. Only after one has experienced pain can one know pain….