昔贤云∶观今宜鉴古，无古不成今。今古医学，均宜参考焉。考今古医书，不能尽述，姑略提其要者
言之，如《神农本草》，轩辕《灵》《素》，越人《难经》，长沙《玉函》，以及刘、李、张、
朱四大名家之书，皆可备读也。盖读《本草》者，可知其性有寒、热、温、凉、平之不同，其味有酸、苦、甘、
辛、咸之各异，何为补正，何为祛邪。读《灵》、《素》者，可以上明天文，下达地理，兼知人身脏腑经络
受病之因。读《难经》者，可补《内经》脉象病因及奇经八脉之未逮。读《玉函》者，可识伤寒杂病之源头。
此皆古圣之医书，必须玩索。至于四大家者，即河间刘守真，法多苦寒，温病、热病者，须参考之。东垣李
明之，法多升补，内伤脾胃者，须参考之。大积大聚者，须参戴人张子和攻下之法。阴虚内损者，须考丹溪
朱彦修清补之法。不特此四家以补先圣之未备，可参可考，而后贤所发之论，偶亦有超出于四大家
者。如云间李念莪，西昌喻嘉言，延陵吴又可，金坛王宇泰，会稽张介宾，长洲张路玉，吴郡薛立斋，慈溪
柯韵伯，携李沈目南，钱江张隐庵是也。以上诸公，各有著作，皆当采取，亦可以备参阅，考近时之医书，亦
不能尽述，如阅古吴叶香岩之《临证指南》，可知临时之圆变，用药之灵机。阅若耶章虚谷之《医
门棒喝》，可知名家之疵谬，醒医家之聋 。阅淮阴吴鞠通之《温病条辨》，可知寒伤于足经，温伤于手经。
阅吴门周禹载之《温热暑疫全书》，可知温热暑疫受病之源各别。此皆时贤之书，亦宜备考。至于长乐陈
修园，新安程观泉，盐宫王孟英，武进费伯雄，皆有着述所传，偶或有导 之处，亦宜参阅。窃思
书有古今，而人亦有古今，古人气体俱浓，今人气体渐薄，若执
古方以治今人之病，不亦重乎？故医家不可执古书而不读今
书，亦不可执今书而不读古书，参考古今，则医理自得中和之道矣。
古人曾说：观察当今应当以古代为借鉴，没有古代就没有当今。古今医学，都应当互相参考。考察古今医书，无法全部叙述，姑且简要提及其中重要的内容来说明，如《神农本草经》、轩辕氏的《灵枢》与《素问》、越人（秦越人）的《难经》、长沙太守张仲景的《玉函经》，以及刘完素、李东垣、张子和、朱丹溪四大名家的著作，都可以作为备读之书。
阅读《神农本草经》，可以了解药物性质有寒、热、温、凉、平的不同，药味有酸、苦、甘、辛、咸的各异，从而明白什么是补益正气，什么是祛除邪气。阅读《灵枢》和《素问》，可以上通天文，下知地理，同时了解人体脏腑经络受病的成因。阅读《难经》，可以补充《黄帝内经》在脉象病因及奇经八脉方面的不足。阅读《玉函经》，可以认识伤寒杂病的源头。这些都是古代圣人的医书，必须仔细研读探索。
至于金元四大家，即河间刘守真（刘完素），其治法多采用苦寒之品，治疗温病、热病者，需要参考他的方法。东垣李明之（李杲），其治法多采用升提补益之法，治疗内伤脾胃者，需要参考他的方法。遇到大积大聚的病证，需要参考戴人张子和（张从正）攻下的治法。阴虚内损的病证，需要考察丹溪朱彦修（朱震亨）清补的治法。不仅这四家可以补充先圣医书的未备之处，可供参考考证，而且后世贤才所发表的论述，偶尔也有超越这四大家的。如云间的李念莪（李中梓）、西昌的喻嘉言（喻昌）、延陵的吴又可（吴有性）、金坛的王宇泰（王肯堂）、会稽的张介宾（张景岳）、长洲的张路玉（张璐）、吴郡的薛立斋（薛己）、慈溪的柯韵伯（柯琴）、携李的沈目南（沈金鳌）、钱江的张隐庵（张志聪）等人就是如此。以上各位先生，各有著作，都应当采纳吸收，也可以作为备查参考。
考察近时的医书，也不能全部叙述，如阅读古吴叶天士（叶桂）的《临证指南医案》，可以了解临床治疗的灵活变通和用药的灵动机巧。阅读若耶章虚谷（章楠）的《医门棒喝》，可以知晓名医的瑕疵谬误，唤醒医家的蒙昧。阅读淮阴吴鞠通（吴瑭）的《温病条辨》，可以了解寒邪损伤足经，温邪损伤手经的区别。阅读吴门周禹载（周扬俊）的《温热暑疫全书》，可以了解温热暑疫受病的源头各不相同。这些都是当代贤才的著作，也应当备考。至于长乐陈修园（陈念祖）、新安程观泉（程国彭）、盐宫王孟英（王士雄）、武进费伯雄（费伯雄），都有著作流传，偶尔或有引导启发之处，也应当参阅思考。
我私下认为，书籍有古今之分，人也有古今之别。古人的体质气血浓厚，今人的体质气血逐渐薄弱。如果拘执古方来治疗今人的疾病，不也太严重了吗？所以医家不可只执着于古书而不读今书，也不可只执着于今书而不读古书，参考古今医学，那么医理自然就能得到中和之道了。
Ancient sages said: "Observing the present requires taking the past as a mirror; without the past, there is no present." Both ancient and modern medicine should be referenced mutually. Examining medical texts from both eras cannot be fully enumerated here; I shall briefly mention the essential ones. For instance, *Shennong Bencao Jing* (Divine Farmer's Materia Medica), Xuanyuan's *Lingshu* (Spiritual Pivot) and *Suwen* (Basic Questions), Yue Ren's *Nanjing* (Classic of Difficult Issues), Changsha's *Yuhan Jing* (Jade Box Classic), as well as the works of the Four Great Masters—Liu, Li, Zhang, and Zhu—are all worthy of study.
Reading *Shennong Bencao Jing* allows one to understand that medicinal properties vary among Cold (Han), Heat (Re), Warm (Wen), Cool (Liang), and Neutral (Ping), and flavors differ among Sour (Suan), Bitter (Ku), Sweet (Gan), Acrid (Xin), and Salty (Xian), thereby clarifying what constitutes tonifying healthy Qi (Zheng Qi) versus expelling pathogenic factors (Xie Qi). Reading *Lingshu* and *Suwen* enables one to comprehend astronomy above and geography below, while also understanding the causes of disease in the Zang-Fu organs (Zang-Fu) and meridians (Jing-Luo). Reading *Nanjing* supplements the deficiencies of *Neijing* (Inner Canon) regarding pulse diagnosis (Mai Xiang), etiology, and the Eight Extraordinary Vessels (Qi Jing Ba Mai). Reading *Yuhan Jing* helps identify the origins of Shanghan (Cold Damage) and Zabing (Miscellaneous Diseases). These are medical classics by ancient sages and must be carefully studied and explored.
Regarding the Four Great Masters: Liu Wansu (courtesy name Shouzhen) of Hejian employed many bitter-cold methods; those treating Wenbing (Warm Diseases) and Rebing (Heat Diseases) should reference his approaches. Li Dongyuan (courtesy name Mingzhi) of Dongyuan utilized many lifting and tonifying methods; those treating Neishang Piwei (Internal Injury to Spleen and Stomach) should reference his methods. For cases of massive accumulation and aggregation (Da Ji Da Ju), one should refer to Zhang Congzheng (courtesy name Zihe) of Dairen’s purgative methods. For Yin deficiency with internal depletion (Yin Xu Nei Sun), one should examine Zhu Zhenheng (courtesy name Yanxiu) of Danxi’s clearing and tonifying methods. Not only do these four masters supplement the incompleteness of the ancient sages' works for reference, but later scholars' theories occasionally surpass even these four masters. Examples include Li Zhongzi (courtesy name Nian'e) from Yunjian, Yu Chang (courtesy name Jiayan) from Xichang, Wu Youxing (courtesy name Ke-you) from Yanling, Wang Kentang (courtesy name Yutai) from Jintan, Zhang Jingsui (courtesy name Jiabin) from Kuaiji, Zhang Lu from Changzhou, Xue Ji (courtesy name Lizhai) from Wujun, Ke Qin (courtesy name Yunbo) from Cixi, Shen Jin'ao (courtesy name Munan) from Xielii, and Zhang Zhicong (courtesy name Yin'an) from Qianjiang. All these gentlemen have authored works that should be adopted and consulted.
Examining contemporary medical texts also cannot be fully listed. For example, reading Ye Tianshi's (Ye Gui) *Linzheng Zhinan Yian* (Guide to Clinical Practice) reveals flexibility in clinical treatment and agility in prescription. Reading Zhang Nan's (courtesy name Xugu) *Yimen Banghe* (The Gavel of Medical Gate) exposes flaws and errors in renowned physicians' practices, awakening medical practitioners from their ignorance. Reading Wu Tang's (courtesy name Jutong) *Wenbing Tiaobian* (Systematic Differentiation of Warm Diseases) clarifies that Cold pathogens damage the Foot Meridians (Zu Jing), while Warm pathogens damage the Hand Meridians (Shou Jing). Reading Zhou Yangjun's (courtesy name Yu-zai) *Wenre Shuyi Quan Shu* (Complete Book on Warmth, Heat, Summer-heat, and Epidemic Diseases) elucidates that the sources of infection for warmth, heat, summer-heat, and epidemics are distinct. These are works by contemporary sages and should also be examined. Furthermore, Chen Nianzu (courtesy name Xiuyuan) from Changle, Cheng Guopeng (courtesy name Guanquan) from Xin'an, Wang Shixiong (courtesy name Mengying) from Yanguan, and Fei Boxiong from Wujin have transmitted their writings; occasional insights therein warrant reference and reflection.
I privately believe that while books have ancient and modern distinctions, so do people. Ancients possessed dense and robust constitution and Qi (Qi Ti), whereas modern people have gradually thinner constitutions. If one rigidly applies ancient prescriptions to treat modern diseases, would it not be overly burdensome? Therefore, physicians must not cling solely to ancient texts while ignoring modern ones, nor cling solely to modern texts while ignoring ancient ones. By referencing both ancient and modern knowledge, one naturally attains the Way of Harmony (Zhonghe) in medical theory.