Cheng Jingtong was a scholar who was well-versed in principles and possessed pure Confucian virtues, yet he also had extensive knowledge of medicine. I had not originally studied medicine; however, upon hearing Mr. Cheng diagnose diseases through pulse-taking (Mai Zhen, 脉诊), I felt my previous understanding was incomplete (Mu Wu Quan Ren, 目无全人: literally "eyes seeing no whole person," here implying being overwhelmed by his profound insights). His subtle and lofty arguments emerged layer upon layer, presenting unheard-of knowledge and explanations that were difficult to comprehend. It seemed that Mr. Cheng’s mastery of medicine had almost reached the level of "Dao" (道, The Way/Principle)!

I further observed his practice: even when treating patients of the lowest status and extreme poverty, once he took charge, he would always maintain a dignified demeanor, ask detailed questions, examine carefully, and engage in repeated, precise reflection, never showing any sign of weariness or怠惰 (dai duo, laziness/negligence). For difficult cases, he might spend an entire day pondering, fearing even the slightest error, and only acting once his mind was free of doubt. If he applied this same diligence, when he eventually became an official through imperial examination and used this mindset to plan state affairs and entrust the welfare of millions to him, what achievements could not be attained?

The book *Waitai Miyao* (External Cabinet Secret Essentials) by Governor Wang of the Tang Dynasty went out of print after five dynasties. In the Song Dynasty, Vice Minister Sun collated and published it, but it has since become extinct. Mr. Cheng could not bear to see this work disappear from the world and mentioned this to me. I asked Mr. Cheng, "If one wishes to master medicine, what path leads to proficiency?" He replied, "One must be eager to learn." "What should one study?" "First, read books." "Can reading books help one learn medicine?" He said, "There are those who read books but cannot treat patients, but there is absolutely none who can become a good doctor without reading books." Alas! This applies to all matters in the world, not just medicine.

I then asked, "With your medical skills saving people, you may be too busy during your lifetime, but after your death, books cannot fully express words, and words cannot fully express intent. I fear your methods will not be transmitted. Why not find a suitable person to teach them directly, rather than writing a book?" Mr. Cheng said, "A teacher seeks students more urgently than students seek teachers. If someone comes to learn, I am willing to impart everything I know. However, current 'students' do not truly wish to learn; they merely seek permission to practice. This Dao requires ten years of bitter effort to attain. Yet these modern 'learners' arrive and immediately ask, 'I want to follow a master; teaching me for ten days is enough, right?' So urgent are they that although I wish to teach, where would I begin? Alas! Learning in the world is generally like this, not just in medicine.

Ancient gentlemen seeking the Dao first eagerly sought like-minded individuals. When such individuals could not be found, they resorted to books, hoping for their eternal existence. They did not necessarily write new books themselves but focused on uncovering hidden truths, continuing broken lineages, and preserving ancient texts. Many ancient texts survived because conscientious descendants ensured their circulation. Initially, it was not required that all descendants be conscientious, eager learners capable of reading them; rather, they could not bear for the books to perish, believing that if even one person, conscientious and eager, could read them, the books would not have been kept in vain. A hundred generations later, others will emerge to view today's Mr. Cheng, akin to how Mr. Cheng viewed Governor Wang of Tang and Vice Minister Sun of Song. Thus, for those who come to Mr. Cheng’s door expecting to learn everything in ten days, Mr. Cheng can refuse them without any sense of guilt."

Written by Jin Sheng, a native of the same commandery, who held the degree of Jinshi (Doctor of Scholarship), served as a Hanlin Academy Junior Scholar (Hanlin Yuan Shujishi, 翰林院庶吉士), assisted in military affairs by imperial decree, and was appointed Censor of the Shandong Circuit (Shandong Dao Jiancha Yushi, 山东道监察御史).