凡诊病之法，固莫妙于脉，然有病脉相符者，有脉病相左者，此中大有玄理。故凡值疑似难明
处，必须用四诊之法，详问其病由，兼辨其声色，但于本末先后中，正之以理，斯得其真。若不察
此，而但谓一诊可凭，信手乱治，亦岂知脉证最多真假，见有不确，安能无误？且常诊者，知之犹
易，初诊者，决之甚难，此四诊之所以不可忽也。故《难经》以切居四诊之末，其意深矣。陶节庵
亦曰∶问病以知其外，察脉以知其内，全在活法二字，乃临证切脉之要诀也。此义惟汪石山言之最
详，并附于后卷。
脉义之见于诸家者，六经有序也，脏象有位也，三部九候有则也，昭然若此，非不既详且备矣
。及临证用之，则犹如望洋，莫测其孰为要津，孰为彼岸，予于初年，亦尝为此所迷者盖屡屡矣。
今而熟察其故，乃知临
岐忘羊，患在不得其独耳。兹姑以部位言之，则无不曰心肝肾居左之三部，肺脾命居右之三部，而
按部以索脏，按脏以索病，咸谓病无遁情矣。故索部位者，审之寸，则似乎病在心肺也；审之关，
则似乎病在肝脾也；审之尺，又似乎病在两肾也。既无无脉之部，又无无病之脉，而病果安在哉？
孰是孰非，此难言也。再察其病情，则有如头痛者，一证耳，病本在上，两寸其应也。若以经脏言
之，则少阳、阳明之痛，不应在两关乎？太阳之痛，不应在左尺乎？上下无分，此难言也。又如淋
遗，一证耳，病本在下，尺中所主也。若气有不摄，病在右寸矣；神有不固，病在左寸矣，源流无
辨，此难言也。诸如此类，百病皆燃，使必欲以部位言，则上下相关，有不可泥也。使必欲以经脏
言，则承制相移，有不可执也。言难尽意，绘难尽神，无弗然矣。是可见诸家之所胪列者，亦不过
描摸影响，言此失彼，而十不得一，第觉其愈多愈繁，愈繁愈失，而迷津愈甚矣。故善为脉者，贵在
察神，不在察形。察形者，形千形万，不得其要；察神者，唯一惟精，独见其真也。
独之为义，有部位之独也，有脏气之独也，有脉体之独也。部位之独者，谓诸部无恙，惟此稍
乖，乖处藏奸，此其独也。脏气之独者，不得以部位为拘也，如诸见洪者，皆是心脉，诸见弦者，
皆是肝脉，肺之浮，脾之缓，肾之石；五脏之中，各有五脉，五脉互见，独乖者病，乖而强者，即
本脏之有余；乖而弱者，即本脏之不足，此脏气之独也。脉体之独者，如经所云独小者病，独大者
病，独疾者病，独迟者病，独热者病，独寒者病，独陷下者病，此脉体之独也。总此三者，独义见
矣。夫既谓之独，何以有三？而不知三者之独，亦总归于独小、独大、独疾、独迟之类，但得其一
，而即见病之本矣。故经曰∶得一之精，以知死生。又曰∶知其要者、一言而终，不知其要，则流
散无穷。正此之谓也。
虽然，然独不易言也，亦不难言也。独之为德，为群疑之主也，为万象之源也。其体至圆，其
用至活也。欲得之者，犹纵目于泰山之顶，则显者显，隐者隐，固若易中有难也；犹认针于沧海之
中，则左之左，右之右，
还觉难中有易也。然不有无岐之目，无二之心，诚不足以因彼之独，而成我之独也。故曰独不难知
也，而惟恐知独者之难其人也。独自有真也，而又恐伪辩者假借以文其僻也。真独者，兼善成于独
善；伪独者，毒己由于独人。独之与毒，音虽若同，而利害则天渊矣。故并及之，以识防于此。
大凡诊断疾病的方法，没有比脉诊更精妙的了，然而有脉象与病情相符的，也有脉象与病情相违背的，这其中大有深奥的道理。所以凡是遇到疑似难辨的情况，必须运用望、闻、问、切四诊合参的方法，详细询问病因，同时辨别患者的声音和面色，在探究疾病的本末先后中，以理法加以校正，这样才能获得真实的病情。如果不考察这些，而只认为单凭脉诊就可以依靠，信手胡乱治疗，又怎知脉证大多有真假之分，见解若不确切，怎么能不出错呢？况且经常诊病的人，了解病情还容易；初次诊病的人，决断起来非常困难，这就是四诊不可轻视的原因。所以《难经》将切脉排在四诊的最后，其用意深远啊。陶节庵也说：通过问诊来了解外在表现，通过察脉来了解内在病变，全在于“灵活变通”二字，这才是临证切脉的要诀。这一理论只有汪石山阐述得最为详尽，并附在后卷中。
脉学原理见于各家论述的，六经（太阳、阳明、少阳、太阴、少阴、厥阴）次序井然，脏象（脏腑生理病理现象）位置明确，三部九候（寸关尺三部，每部浮中沉三候）有法则可循，像这样清楚明白，并非不详细完备。但等到临证应用时，却如同面对汪洋大海，不知道哪个是关键，哪个是彼岸，我在初年，也常常为此所迷惑，次数很多了。现在仔细考察其中的缘故，才知道面对岔路忘记羊群（比喻迷失方向），毛病在于没有找到那个“独”字罢了。这里暂且从部位来说，无不说是心、肝、肾位于左手的寸、关、尺三部，肺、脾、命门位于右手的寸、关、尺三部，于是按部位去索求脏腑，按脏腑去索求疾病，大家都认为病情没有隐藏的了。所以探查部位的，审视寸口，似乎病在心肺；审视关部，似乎病在肝脾；审视尺部，又似乎病在两肾。既然没有无脉的部位，也没有无病的脉象，那么病究竟在哪里呢？谁对谁错，这很难说清。再观察病情，比如头痛这一症状，只是一证而已，病本在上，两寸脉应当有反应。如果从经络脏腑来说，少阳、阳明的头痛，难道不应该在关部吗？太阳经的头痛，难道不应该在左尺吗？上下不分，这很难说清。又如淋证、遗尿，只是一证而已，病本在下，由尺部所主。但如果气不摄纳，病就在右寸了；神志不固，病就在左寸了，源流无法分辨，这很难说清。诸如此类，百病都是这样，如果一定要用部位来解释，那么上下相关，有不可拘泥的地方；如果一定要用经络脏腑来解释，那么承制关系相互转移，有不可固执的地方。言语难以穷尽意旨，绘画难以穷尽神韵，没有不是这样的。由此可见，各家所罗列的内容，也不过是描摹影子，言此失彼，十不获一，只觉得越多越繁杂，越繁杂越失误，而迷津越深了。所以善于诊脉的人，贵在察神（精神气血的外在表现），不在察形（脉象的具体形态）。察形的，形态千变万化，抓不住要领；察神的，唯一且精专，独自见到真相。
“独”的含义，有部位之独，有脏气之独，有脉体之独。部位之独，是说其他部位无恙，唯独此处稍有偏差，偏差之处藏着奸邪，这就是“独”。脏气之独，不能以部位为拘束，如凡是见到洪脉的，都是心脉；凡是见到弦脉的，都是肝脉；肺脉应浮，脾脉应缓，肾脉应石。五脏之中，各有五种正常脉象，五种脉象互见，唯独出现偏差的是病，偏差而强盛的，就是本脏有余；偏差而虚弱的，就是本脏不足，这就是脏气之独。脉体之独，如经典所说，唯独小的为病，唯独大的为病，唯独快的为病，唯独慢的为病，唯独热的为病，唯独寒的为病，唯独下陷的为病，这就是脉体之独。综合这三者，“独”的意义就显现了。既然称为“独”，为什么有三种？却不知道这三种“独”，也总归于独小、独大、独疾、独迟之类，只要得到其中一点，就能见到疾病的根本。所以经典说：得到精髓，可以预知生死。又说：懂得要领的，一句话就能终结道理；不懂要领的，则流散无穷。正是说的这个意思。
虽然如此，“独”不容易说，也不难说。“独”作为一种德行，是众多疑惑的主人，是万象的源头。它的本体至圆融，它的作用至灵活。想要得到它的人，就像站在泰山顶上纵目远眺，显眼的就显眼，隐蔽的就隐蔽，本来好像容易中带有困难；又像在沧海中辨认针尖，向左就向左，向右就向右，反而觉得困难中带有容易。然而如果没有明察秋毫的眼睛，没有专一不二的心，确实不足以凭借他人的“独”，成就自己的“独”。所以说“独”不难知晓，只怕知晓“独”的人难以找到。自己要有真正的“独”，又怕伪辩者假借它来掩饰他们的偏颇。真正的“独”，兼善天下源于独善其身；虚伪的“独”，毒害自己源于孤立他人。“独”与“毒”，读音虽然相同，但利害却如天壤之别。所以一并提及，以此识别并防范于此。
In general, among all methods of diagnosing diseases, none is more exquisite than pulse diagnosis (Mai Zhen). However, there are cases where the pulse and symptoms correspond, and cases where they contradict each other; this involves profound principles. Therefore, whenever one encounters ambiguous or difficult-to-distinguish situations, it is essential to employ the Four Diagnostic Methods (Wang, Wen, Wen, Qie - Inspection, Auscultation/Olfaction, Inquiry, Palpation) to inquire in detail about the cause of the disease, while simultaneously observing the voice and complexion. By correcting with reason within the context of the root and branch, and the sequence of events, one can ascertain the truth. If these aspects are not examined, and one merely relies on a single pulse check, treating arbitrarily, how can one know that pulses and symptoms often have true and false manifestations? If one's understanding is not accurate, how can errors be avoided? Moreover, for those who diagnose frequently, understanding is relatively easy; for those diagnosing for the first time, making a judgment is very difficult. This is why the Four Diagnostic Methods cannot be neglected. Thus, the *Nan Jing* (Classic of Difficult Issues) places palpation (Qie) at the end of the four diagnostic methods, implying a deep meaning. Tao Jie'an also stated: "Inquiry reveals the exterior, while pulse observation reveals the interior." It all lies in the two characters "flexible adaptation," which are the key secrets of pulse diagnosis in clinical practice. This theory was explained most extensively by Wang Shishan and is attached to the subsequent volume.
The principles of pulse diagnosis found in various schools include the orderly sequence of the Six Channels (Liu Jing), the defined positions of Zang-Fu Manifestations (Zang Xiang), and the rules of the Three Positions and Nine Probes (San Bu Jiu Hou). These are clear and evident, seemingly detailed and complete. However, when applied in clinical practice, one feels like gazing at the ocean, unable to determine what is the critical point and what is the shore. In my early years, I was often confused by this many times. Now, upon careful examination of the cause, I realize that the problem of losing one's way at a fork in the road lies in failing to grasp the concept of "Uniqueness" (Du). Let us speak briefly of positions: everyone says that the Heart, Liver, and Kidney occupy the three positions (Cun, Guan, Chi) on the left hand, while the Lung, Spleen, and Mingmen (Gate of Life) occupy the three positions on the right hand. Thus, by position, one seeks the Zang-Fu organs; by Zang-Fu organs, one seeks the disease. Everyone believes that no disease can hide. So, examining the Cun position seems to indicate disease in the Heart and Lungs; examining the Guan position seems to indicate disease in the Liver and Spleen; examining the Chi position seems to indicate disease in the two Kidneys. Since there is no position without a pulse, nor a pulse without disease, where exactly is the disease? Who is right and who is wrong? This is hard to say. Further observing the symptoms: for example, headache is just one symptom. The disease originates above, so the response should be in the two Cun positions. But speaking from the perspective of meridians and Zang-Fu, shouldn't Shaoyang and Yangming headaches correspond to the Guan position? Shouldn't Taiyang headaches correspond to the left Chi position? With no distinction between upper and lower, this is hard to clarify. Similarly, strangury and enuresis are just one symptom. The disease originates below, governed by the Chi position. But if Qi fails to secure, the disease is in the right Cun; if Shen (Spirit) fails to consolidate, the disease is in the left Cun. Without distinguishing source and flow, this is hard to clarify. Such examples abound in all diseases. If one insists on explaining by position, the interconnection between upper and lower makes rigid adherence impossible. If one insists on explaining by meridians and Zang-Fu, the shifting of controlling and controlled relationships makes dogmatism impossible. Words cannot fully express meaning, and paintings cannot fully capture spirit; this is universally true. Thus, it can be seen that what various schools list is merely tracing shadows, saying one thing but losing another, capturing only one-tenth of the truth. One only feels that the more there is, the more complex it becomes; the more complex, the more erroneous it becomes; and the deeper the confusion. Therefore, a skilled pulse reader values observing Shen (Spirit/Vitality) over observing Xing (Form/Shape). Observing form yields thousands of shapes, yet misses the essence; observing Shen is singular and refined, uniquely revealing the truth.
The meaning of "Du" (Uniqueness/Particularity) includes Du of Position, Du of Zang-Qi, and Du of Pulse Body. Du of Position means that while other positions are normal, this specific one deviates slightly; the deviation hides the pathology, which constitutes the "Du." Du of Zang-Qi is not constrained by position. For instance, wherever a Hong (Surging) pulse appears, it is the Heart pulse; wherever a Xian (Wiry) pulse appears, it is the Liver pulse; the Lung pulse floats, the Spleen pulse is slow, the Kidney pulse is stone-like. Within the five Zang organs, each has five pulse types. When these five pulses appear mutually, the one that deviates indicates disease. If the deviation is strong, it indicates excess in the respective Zang organ; if weak, it indicates deficiency. This is Du of Zang-Qi. Du of Pulse Body refers to what the classics state: exclusively small is disease, exclusively large is disease, exclusively rapid is disease, exclusively slow is disease, exclusively hot is disease, exclusively cold is disease, exclusively sunken is disease. This is Du of Pulse Body. Summarizing these three, the meaning of "Du" is revealed. Why is it called "Du" if there are three types? It is because these three types of "Du" ultimately return to categories like exclusively small, exclusively large, exclusively rapid, and exclusively slow. Grasping any one of them allows one to see the root of the disease. Hence, the classics say: "Grasp the essence, and you can know life and death." And again: "He who knows the essentials concludes in one word; he who does not know the essentials scatters infinitely." This is precisely what is meant.
Although so, "Du" is not easy to discuss, nor is it difficult. As a virtue, "Du" is the master of all doubts and the source of all phenomena. Its substance is perfectly round, its function is highly flexible. To attain it is like standing atop Mount Tai and looking out: obvious things become obvious, hidden things become hidden, seeming easy yet containing difficulty. It is like recognizing a needle in the vast sea: left becomes left, right becomes right, seeming difficult yet containing ease. However, without eyes that see clearly and a heart that is undivided, one certainly cannot use the "Du" of others to achieve one's own "Du." Thus, it is said that "Du" is not hard to know, but rather that finding someone who truly understands "Du" is hard. One must possess true "Du," lest hypocritical debaters borrow it to justify their biases. True "Du" achieves universal benefit through personal integrity; false "Du" harms oneself through isolation. "Du" and "Du" (poison/harm) sound alike, but their benefits and harms are worlds apart. I mention both to help recognize and prevent this.