When I was already advanced in years I undertook a journey into the wilderness of the eastern border regions. There I met a strange person who looked at me casually and then asked me:
“Did you also study medicine? Medicine is difficult; it demands the greatest conscientiousness from you!”
Whereupon I replied: “Although medicine is a petty teaching, its concern focuses on life. How could I dare not to be aware of (the necessity for) conscientiousness. I take note of your instructions with respect.”

The stranger became very angry and addressed me in a voice filled with disdain:
“In any case you do not belong to those who are familiar with medicine! If you claimed just now of your own accord that the aim of medicine is life, how can you say then at the same time that this is a matter of a petty teaching? The principle of life has its origin in the principle of the universe and is distributed over the entirely of all things. Not until life sprang forth did the five social relationships develop. Therefore creation constitutes, as it were, the forge of life, and the teaching of the principle is considered the guiding principle of life, and medicine and the drugs are the nurses of life. Thence it becomes evident that the significance of medicine is deeply rooted and that its assertions encompass a wide scope. Only superhuman intelligence has the power to advance to its most subtle details, and only the enlightenment to adhere to the middle position suffices to discern even the last details. An understanding of the basic traits and details of the medical principles corresponds to (an understanding of) the principles of peaceful government. An understanding of the effect and the failure of the medical principles corresponds to (an understanding of) the momentum of rise and decline. An understanding of the hesitation and of the urgency of the medical principles corresponds to (an understanding of) the mechanisms of attack and defense. An understanding of the change and the persistence of the medical principles corresponds to (an understanding of) the significance of social intercourse and private life. Whoever is penetrated inwardly by the principles and the influences can point to the changes and transformations (of all things) and calculate them. Whoever is in command of the connections of yin and yang to the point where he can play with them ‘on the palm of his hand,’ for him the walls of separation and the outside walls do not represent an obstacle to perceive (all things).
“Through the discipline of his body and his mind the Confucian scholar treats himself to complete honesty. The Buddhist and the Taoist treat themselves by purging themselves of faults in their previous lives through perfect observance of moral rules and (a life of) sincerity. Body and mind of other people and of oneself are unified by the principle. Hence whoever perceives that which is close by, perceives also that which is distant; whoever understands well that which is distant, also understands well that which is close at hand. Therefore it is said: “If there are truthful people, there is true knowledge; if there is true knowledge, there is also a true medicine.’ How is it therefore possible to say that medicine is trivial?

“But wherever we turn we find superficiality and commonness. (A patient’s) itching is eliminated by pepper and sulphur, onions and shallots relive [a patient] of his winds. Has anyone ever said: ‘This is not medicine’? If someone but wears a black coat or a yellow cap, he is immediately called Buddhist or a Taoist priest. And if someone speaks in an affected manner and displays pretentious mannerisms, what else could he be (in the eyes of the people) but a Confucion! Yet not even in the course of the same day would one speak of the mountains of t’ai-sha and of some small hills, of the streams and the sea and some ditches of water.
“Whoever has no understanding of yin and yang and meddles with symptoms of excess and conditions of deficiency without knowing about them, whoever is endowed with a careless mind and the nature of a daredevil, hides in a cave and is one-sided and ‘common’ will certainly not only fail to accomplish anything good, but on the very contrary he will cause harm (wherever he practices). Such people do not even reach the level of those who use pepper, sulphur, onions and shallots, not to mention that they deserve the designation ‘pretty teaching’ (for their activity). On what basis would one able to talk to them at all about medicine?
“Medicine is certainly difficult! Medicine is certainly sublime! It represents the earliest tradition of genuine supernatural and exemplary people, and the first duty of a people.
“My son you should not belittle it because it is apparently but a matter of herbs and trees. You should endeavor to penetrate to the realm where essence and spirit are joined, and proceed to the border regions, where the dark meets the mysterious. Once you understand the beginning and the end of all processes, and once you have grasped the origin and consequences of a result, it can be said that you have accomplished something in this filed (of medicine). You certainly have to take the greatest pains!”

I listened to this instruction and was profoundly disconcerted and greatly alarmed. I muttered some words in exchange and withdrew. My agitation lasted for several months. So as not to forget these admonitions, I have put them down in writing.¨