History

Shen Kuo was a renowned government official and military general during the Northern Song period of China. However, he was impeached from office by chancellor Cai Que (蔡確; 1036–1093), who wrongly held him responsible for a Song Chinese military defeat by the Tangut-led Western Xia dynasty in 1081 during the Song–Xia wars. When Shen compiled and published the The Dream Pool Essays (Meng Xi Bi Tan, 《梦溪笔谈》) in 1088, he was living in retirement and relative isolation on his lavish garden estate near modern-day Zhenjiang, Jiangsu province. He titled the book after the name he gave to his private estate, the "Dream Brook". In English a full literal translation of the title is Brush Talks from a Dream Brook, and Shen Kuo is quoted as saying:

As the historian Chen Dengyuan points out, much of Shen Kuo's written work was probably purged under the leadership of minister Cai Jing (1046–1126). For example, only six of Shen's books remain, and four of these have been significantly altered since the time they were penned by the author. The Dream Pool Essays was first quoted in a Chinese written work of 1095 AD, showing that even towards the end of Shen's life his final book was becoming widely printed. The book was originally 30 chapters long, yet an unknown Chinese author's edition of 1166 AD edited and reorganized the work into 26 chapters. There is one surviving copy of this 1166 edition now in Japan, while a Chinese reprint was produced in 1305. In 1631 another edition was printed, but it was heavily reorganized into three broad chapters.

In modern times, Zhang Jiaju's biographical work Shen Kuo (1962) contains selected translations of the Dream Pool Essays from Middle Chinese into modern Vernacular Chinese. The Dream Pool Essays has also been translated from Chinese into various foreign languages. Various volumes of Joseph Needham's Science and Civilization in China series published since 1954 contain a large amount of selected English translations of the Dream Pool Essays. The Brush Talks from Dream Brook is the first complete English translation, presented in two volumes by translators Wang Hong and Zhao Zheng, and published in 2008 by the Sichuan People』s Publishing House, China. A Japanese translation of the 1166 Chinese edition was prepared by the History of Science Seminar, Institute for Research in Humanities (Jimbun Kagaku Kenkyusho) for Kyoto University, and printed by the author Umehara Kaoru in his 3-volume edition of Bokei hitsudan (1978–1981). Quoted excerpts from the Dream Pool Essays in French were printed in the written works of J. Brenier in 1989 and J. F. Billeter in 1993. A complete German translation is offered in Shen Kuo: Pinselunterhaltungen am Traumbach. Das Gesamte Wissen des Alten China, translated and edited by Konrad Herrmann, and published in 1997 by Diederichs Verlag Munich (Gelbe Reihe Magnum, vol. I).

Quotes

Geological theory

With Shen's writings on fossils, geomorphology, and shifting geographical climates, he states in the following passages:

In the Zhi-ping reign period AD a man of Zezhou was digging a well in his garden, and unearthed something shaped like a squirming serpent, or dragon. He was so frightened by it that he dared not touch it, but after some time, seeing that it did not move, he examined it and found it to be stone. The ignorant country people smashed it, but Zheng Boshun, who was magistrate of Jincheng at the time, got hold of a large piece of it on which scale-like markings were to be seen exactly like those on a living creature. Thus a serpent or some kind of marine snake (chhen) had certainly been turned to stone, as happens with the 'stone-crabs'.

In recent years 1080 there was a landslide on the bank of a large river in Yong-ning Guan near Yanzhou. The bank collapsed, opening a space of several dozens of feet, and under the ground a forest of bamboo shoots was thus revealed. It contained several hundred bamboo with their roots and trunks all complete, and all turned to stone...Now bamboos do not grow in Yanzhou. These were several dozens of feet below the present surface of the ground, and we do not know in what dynasty they could possibly have grown. Perhaps in very ancient times the climate was different so that the place was low, damp, gloomy, and suitable for bamboos. On the Jin-hua Shan in Wuzhou there are stone pine-cones, and stones formed from peach kernels, stone bulrush roots, stone fishes, crabs, and so on, but as these are all (modern) native products of that place, people are not very surprised at them. But these petrified bamboos appeared under the ground so deep, though they are not produced in that place today. This is a very strange thing.

Astronomy

When the Director of the Astronomical Observatory asked Shen Kuo if the shapes of the sun and moon were round like balls or flat like fans, Shen Kuo explained his reasoning for the former:

If they were like balls they would surely obstruct each other when they met. I replied that these celestial bodies were certainly like balls. How do we know this? By the waxing and waning of the moon. The moon itself gives forth no light, but is like a ball of silver; the light is the light of the sun (reflected). When the brightness is first seen, the sun(-light passes almost) alongside, so the side only is illuminated and looks like a crescent. When the sun gradually gets further away, the light shines slanting, and the moon is full, round like a bullet. If half of a sphere is covered with (white) powder and looked at from the side, the covered part will look like a crescent; if looked at from the front, it will appear round. Thus we know that the celestial bodies are spherical.

When the director of the astronomical observatory asked Shen Kuo why eclipses occurred only on an occasional basis while in conjunction and opposition once a day, Shen Kuo wrote:

I answered that the ecliptic and the moon's path are like two rings, lying one over the other, but distant by a small amount. (If this obliquity did not exist), the sun would be eclipsed whenever the two bodies were in conjunction, and the moon would be eclipsed whenever they were exactly in position. But (in fact) though they may occupy the same degree, the two paths are not (always) near (each other), and so naturally the bodies do not (intrude) upon one another.

On the use of the sighting tube to fix the position of the pole star, Shen Kuo wrote:

Before Han times it was believed that the pole star was in the center of the sky, so it was called Jixing (Summit star). Zu Geng(-zhi) found out with the help of the sighting tube that the point in the sky which really does not move was a little more than 1 degree away from the summit star. In the Xining reign-period (1068–1077) I accepted the order of the emperor to take charge of the Bureau of the Calendar. I then tried to find the true pole by means of the tube. On the very first night I noticed that the star which could be seen through the tube moved after a while outside the field of view. I realized, therefore, that the tube was too small, so I increased the size of the tube by stages. After three months' trials I adjusted it so that the star would go round and round within the field of view without disappearing. In this way I found that the pole star was distant from the true pole somewhat more than 3 degrees. We used to make the diagrams of the field, plotting the positions of the star from the time when it entered the field of view, observing after nightfall, at midnight, and early in the morning before dawn. Two hundred of such diagrams showed that the 'pole star' was really a circumpolar star. And this I stated in my detailed report to the emperor.

Movable type printing

On the methods of Bi Sheng's invention of movable type printing between the years 1041 to 1048 AD, Shen Kuo wrote:

Sheng took sticky clay and cut in it characters as thin as the edge of a coin. Each character formed, as it were, a single type. He baked them in the fire to make them hard. He had previously prepared an iron plate and he had covered his plate with a mixture of pine resin, wax, and paper ashes. When he wished to print, he took an iron frame and set it on the iron plate. In this he placed the types, set close together. When the frame was full, the whole made one solid block of type. He then placed it near the fire to warm it. When the paste the back was slightly melted, he took a smooth board and pressed it over the surface, so that the block of type became as even as a whetstone. If one were to print only two or three copies, this method would be neither simple nor easy. But for printing hundreds or thousands of copies, it was marvelously quick. As a rule he kept two forms going. While the impression was being made from the one form, the type was being put in place on the other. When the printing of the one form was finished, the other was then ready. In this way the two forms alternated and the printing was done with great rapidity.

Personal beliefs and philosophy

Of Taoism and the inability of empirical science to explain everything in the world, Shen Kuo wrote:

Those in the world who speak of the regularities underlying the phenomena, it seems, manage to apprehend their crude traces. But these regularities have their very subtle aspect, which those who rely on mathematical astronomy cannot know of. Still even these are nothing more than traces. As for the spiritual processes described in the of Changes that "when they are stimulated, penetrate every situation in the realm," mere traces have nothing to do with them. This spiritual state by which foreknowledge is attained can hardly be sought through changes, of which in any case only the cruder sort are attainable. What I have called the subtlest aspect of these traces, those who discuss the celestial bodies attempt to know by depending on mathematical astronomy; but astronomy is nothing more than the outcome of conjecture.

Dissertation on the Timberwork Manual

Below are two passages from Shen's book outlining the basics contained in Yu Hao's Timberwork Manual. Yu Hao was a Chinese architect of the earlier 10th, and Kuo was one to praise his work. In the first quote, Shen Kuo describes a scene where Yu Hao gives advice to another artisan architect about slanting struts for diagonal wind bracing:

When Mr. Qian (Wei-yan) was Governor of the two Zhejiang provinces, he authorized the building of a wooden pagoda at the Fan-tian Si (Brahma-Heaven Temple) in Hangzhou with a design of twice three stories. While it was under construction General Chhien went up to the top and was worried because it swayed a little. But the Master-Builder explained that as the tiles had not yet been put on, the upper part was still rather light, hence the effect. So then they put on all the tiles, but the sway continued as before. Being at a loss what to do, he privately sent his wife to see the wife of Yu Hao with a present of golden hair pins, and enquire about the cause of the motion. (Yu) Hao laughed and said: 'That's easy, just fit in struts (pan) to settle the work, fixed with (iron) nails, and it will not move any more.' The Master-Builder followed his advice, and the tower stood quite firm. This is because the nailed struts filled in and bound together (all the members) up and down so that the six planes (above and below, front and back, left and right) were mutually linked like the cage of the thorax. Although people might walk on the struts, the six planes grasped and supported each other, so naturally there could be no more motion. Everybody acknowledged the expertise thus shown.

In this next quote, Shen Kuo describes the dimensions and types of architecture outlined in Yu Hao's book:

Methods of building construction are described in the Timberwork Manual, which, some say, was written by Yu Hao. (According to that book), buildings have three basic units of proportion, what is above the cross-beams follows the Upperwork Unit, what is above the ground floor follows the Middlework Unit, and everything below that (platforms, foundations, paving, etc.) follows the Lowerwork Unit. The length of the cross-beams will naturally govern the lengths of the uppermost cross-beams as well as the rafters, etc. Thus for a (main) cross-beam of (8 ft) length, an uppermost cross-beam of (3.5 ft) length will be needed. (The proportions are maintained) in larger and smaller halls. This (2/28) is the Upperwork Unit. Similarly, the dimensions of the foundations must match the dimensions of the columns to be used, as also those of the (side-) rafters, etc. For example, a column (11 ft) high will need a platform (4.5 ft) high. So also for all the other components, corbelled brackets, projecting rafters, other rafters, all have their fixed proportions. All these follow the Middlework Unit (2/24). Now below of ramps (and steps) there are three kinds, steep, easy-going, and intermediate. In places these gradients are based upon a unit derived from the imperial litters. Steep ramps are ramps for ascending which the leading and trailing bearers have to extend their arms fully down and up respectively (ratio 3/35). Easy-going ramps are those for which the leaders use elbow length and the trailers shoulder height (ratio 1/38); intermediate ones are negotiated by the leaders with downstretched arms and trailers at shoulder height (ratio 2/18). These are the Lowerwork Units. The book (of Yu Hao) had three chapters. But builders in recent years have become much more precise and skillful (yen shan) than formerly. Thus for some time past the old Timberwork Manual has fallen out of use. But (unfortunately) there is hardly anybody capable of writing a new one. To do that would be a masterpiece in itself!

Botany and zoology

Shen Kuo described the natural predator insect similarly shaped to the gou-he ("dog-grubs") which preyed upon the agricultural pest infestation of zi-fang, the moth Leucania separata:

In the Yuan-Feng reign period (1078–1085), in the Qingzhou region, an outbreak of zi-fang insects caused serious damage to the crops in the fields in autumn. Suddenly another insect appeared in swarms of thousands and tens of thousands, covering the entire ground area. It was shaped like earth-burrowing gou-he (dog grubs), and its mouth was flanked by pincers. Whenever it met a zi-fang, it would seize it with the pincers and break the poor beast into two bits. Within ten days all the zi-fang had disappeared, so the locality had an abundant harvest. Such kinds of insects have been known since antiquity and the local people call them pang-bu-ken ("not allowing other insects to be").

Natural phenomena

Around 1078, Shen Kuo wrote an accurate description of the damaging effects of lightning to buildings and to the specific materials of objects within. Taking an objective and speculative viewpoint, he stated:

A house belonging to Li Shunju was struck by lightning. Brilliant sparkling light was seen under the eaves. Everyone thought that the hall would be burnt, and those who were inside rushed out. After the thunder had abated, the house was found to be alright, though its walls and the paper on the windows were blackened. On certain wooden shelves, certain lacquered vessels with silver mouths had been struck by the lightning, so that the silver had melted and dropped to the ground, but the lacquer was not even scorched. Also, a valuable sword made of strong steel had been melted to liquid, without the parts of the house nearby being affected. One would have thought that the thatch and wood would have been burnt up first, yet here were metals melted and no injury to thatch and wood. This is beyond the understanding of ordinary people. There are Buddhist books which speak of 'dragon fire' which burns more fiercely when it meets with water instead of being extinguished by water like 'human' fire. Most people can only judge of things by the experiences of ordinary life, but phenomena outside the scope of this are really quite numerous. How insecure it is to investigate natural principles using only the light of common knowledge, and subjective ideas.

"Strange Happenings"

A passage called "Strange Happenings" contains a peculiar account of an unidentified flying object. Shen wrote that, during the reign of Emperor Renzong (1022–1063), an object as bright as a pearl occasionally hovered over the city of Yangzhou at night, but described first by local inhabitants of eastern Anhui and then in Jiangsu. Shen wrote that a man near Xingkai Lake observed this curious object; allegedly it:

...opened its door and a flood of intense light like sunbeams darted out of it, then the outer shell opened up, appearing as large as a bed with a big pearl the size of a fist illuminating the interior in silvery white. The intense silver-white light, shot from the interior, was too strong for human eyes to behold; it cast shadows of every tree within a radius of ten miles. The spectacle was like the rising Sun, lighting up the distant sky and woods in red. Then all of a sudden, the object took off at a tremendous speed and descended upon the lake like the Sun setting.

Shen went on to say that Yibo, a poet of Gaoyou, wrote a poem about this "pearl" after witnessing it. Shen wrote that since the "pearl" often made an appearance around Fanliang in Yangzhou, the people there erected a "Pearl Pavilion" on a wayside, where people came by boat in hopes to see the mysterious flying object.

Swords

Around 1065 Shen Kuo wrote about the assembly methods for swords, and the patterns produced in the steel:

Ancient people use chi kang, (combined steel), for the edge, and jou thieh (soft iron) for the back, otherwise it would often break. Too strong a weapon will cut and destroy its own edge; that is why it is advisable to use nothing but combined steel. As for the yu-chhang (fish intestines) effect, it is what is now called the 'snake-coiling' steel sword, or alternatively, the 'pine tree design'. If you cook a fish fully and remove its bones, the shape of its guts will be seen to be like the lines on a 'snake-coiling sword'.

Chinese clothing

Shen Kuo observed that the Chinese since some centuries prior had entirely adopted barbarian fashions.

中國衣冠，自北齊以來，乃全用胡服。窄袖、緋綠短衣、長靿靴、有鞢帶，皆胡服也。窄袖利於馳射，短衣、長靿皆便於涉草。胡人樂茂草，常寢處其間，予使北時皆見之。雖王庭亦在深荐中。予至胡庭日，新雨過，涉草，衣褲皆濡，唯胡人都無所沾。帶衣所垂蹀躞，蓋欲佩帶弓劍、帨、算囊、刀勵之類。

The clothing of China since the Northern Qi 550–557 onward has been entirely made barbarian. Narrow sleeves, short dark red or green robes, tall boots and metal girdle ornaments are all barbarian garb. The narrow sleeves are useful when shooting while galloping. The short robes and tall boots are convenient when passing through tall grass. The barbarians all enjoy thick grass as they always sleep in it. I saw them all do it when I was sent north. Even the king's court is in the deep grasses. On the day I had arrived at the barbarian court the new rains had passed and I waded through the grass. My robes and trousers were all soaked, but the barbarians were not at all wet. With things hanging from robe and belt they walk about. One perhaps might want to hang items like a bow and blade, handkerchief, coin purse or knife from the belt.

Book chapters

On the humanities:

• Official life and the imperial court (60 paragraphs)

• Academic and examination matters (10 paragraphs)

• Literary and artistic (70 paragraphs)

• Law and police (11 paragraphs)

• Military (25 paragraphs)

• Miscellaneous stories and anecdotes (72 paragraphs)

• Divination, magic, and folklore (22 paragraphs)

On natural sciences:

• On the I Ching, Yin and Yang, and 5 elements (7 paragraphs)

• Mathematics (11 paragraphs)

• Astronomy and calendar (19 paragraphs)

• Meteorology (18 paragraphs)

• Geology and mineralogy (17 paragraphs)

• Geography and cartography (15 paragraphs)

• Physics (6 paragraphs)

• Chemistry (3 paragraphs)

• Engineering, metallurgy, and technology (18 paragraphs)

• Irrigation and hydraulic engineering (6 paragraphs)

• Architecture (6 paragraphs)

• Biological sciences, botany, and zoology (52 paragraphs)

• Agricultural arts (6 paragraphs)

• Medicine and pharmaceutics (23 paragraphs)

Humanistic sciences:

• Anthropology (6 paragraphs)

• Archeology (21 paragraphs)

• Philology (36 paragraphs)

• Music (44 paragraphs)

(Total number of paragraphs = 584)

書名

《夢溪筆談》自宋代開始就流傳有兩個名字，一則如《宋史》《通志》稱之為《筆談》，二則如《直齋書錄解題》《文獻通考》題之《夢溪筆談》，清代目錄學家周中孚認為前者或許是後者省稱，但也有人存在異論。目前已知年代最早的《夢溪筆談》版本為南宋乾道二年（1166年）揚州州學刊刻本，該本題跋明言題為《筆談》，沈括自己在《夢溪自記》中也稱本書為《筆談》，明代的孫孟在讀《讀書志》時候所見引文亦俱稱《筆談》，他據此認為「夢溪」二字系後人添附，而根據現代學者祖慧的考証，「夢溪」二字或系沈括別號，類似也有洪邁《隨筆》訛名《容齋隨筆》。

作者

《夢溪筆談》作者是北宋錢塘人沈括（1031-1095），其人以博學著稱，為飽學之士，以百科全書式的廣博知識聞名於世，曾任昭文館校勘、提舉司天監事、史館檢討、集賢院校理等職，得以博覽群書。沈括是有為的政治家，積極參與王安石變法，官至翰林學士、權三司使，主管財政經濟，又以察訪使名義到各地視察新政的實施情況，新法失敗後被舊黨列入新黨的黑名單，是30人中的第15名

。沈括注意發展農業，在參與變法前，曾主持沭水和蕪湖萬春圩的水利工程，在變法活動中又主持整治汴渠的工程，並察訪兩浙路和河北西路的農田水利。他掌管過司天監，創造新天文儀器，改革曆法，採用衛樸的《奉元曆》。他能加強戰備，抵抗侵略，掌管軍器監時，研究城防、兵器及戰術；出使契丹時，駁倒遼國的無理要求，談判得勝；擔任鄜延路經略使時，擊破西夏7萬兵力的侵騷。沈括晚年定居鎮江，在夢溪園將一生所見所聞及研究心得，寫成《夢溪筆談》。廖咸惠指出約成書於1088年前後，傅大為則認為約成書於1090年代早期。

篇目

《夢溪筆談》是筆記體作品，隨筆記錄見聞和心得，全書609條，歸入17個門類：1.故事（前朝掌故）、2.辯證（事物與詞語的論辯）、3.樂律（音樂與律數）、4.象數（現象背後的數字規律）、5.人事（文人性格）、6.官政（官場之事）、7.權智（急智）、8.藝文（藝文活動或評論）、9.書畫、10.技藝（技術與機巧）、11.器用（高貴或古代的器物）、12.神奇（神奇驚人的事跡）、13.異事（奇異與變化）、14.謬誤（常見的錯誤）、15.譏謔（機智與諷刺）、16.雜志（對邊緣或非正統事物的記錄）、17.藥議（對藥物的議論）。《夢溪筆談》知識分類上類似《太平御覽》的傳統，趨於朝廷與官方取向，比較關注現世。

科技

科技知識佔《夢溪筆談》全書內容三份一以上，貢獻最大是天文、數學、物理、地理、醫藥和樂律等方面，也涉及氣象、化學、冶金、兵器、水利、建築、動植物等領域。

天文曆法

《夢溪筆談》翔實描述五星運行的軌跡和隕石墜落時的情景。書中記載沈括曾對北極星空，做了極精密而繁複的觀察與紀錄，連續三個月，每晚都作觀察記錄，畫出約兩百多張星圖描繪北天中北極星的運動，以定位出真正不動的北極位置，判定它離當時所謂的北極星其實有三度之遙。其實三度的結論是錯誤的，是沈括讀錯了儀器，混淆了圓周角與圓心角，結果大了一倍。書中反而批評祖暅較正確「一度有餘」的數字。《夢溪筆談》記述了沈括對晷漏進行的研究，第一次從理論上推導出冬至日晝夜一天的長度「百刻而有餘」，夏至日晝夜一天的長度「不及百刻」。針對傳統的陰陽合曆在曆日安排上的缺失，《夢溪筆談》提出新建議，主張使用「十二氣曆」，即以「十二氣為一年」，以立春為一年之始，「大盡三十一日，小盡三十日」，而傳統的月相變化僅作為曆注書明。這一建議既簡便又科學，比起現行公曆格列高利曆還要合理。當時這項建議招致批評，但書中指出他日必有人採納。

數學

《夢溪筆談》研究的數學課題有「隙積術」和「會圓術」。隙積術是一種計算有空隙物體的體積的技術，計算在一種特定堆棧法下，酒甕的總數目：以長方形為底，平鋪一層酒甕，再層層上堆，依次縮小每層的堆棧數，使成為類以跺的平頭截體。隙積術屬於高階等差級數求和問題，是求解垛積問題，具體提到累棋、層壇及酒家積罌等的垛積問題。會圓術是已知弓形的圓徑和矢高求弧長的問題，書中推導得求弓形弧長的近似公式。《夢溪筆談》也討論圍棋棋步，延續唐代名僧一行的問題，計算所有棋步變化的總數。在縱橫十九路所劃成的棋盤中，每個交叉點只有白、黑與無三種可能，因此棋步的變化是可以窮盡的。書中又用幾何學來解釋弩機上「望山」（類似瞄準器）的用法。

物理學

磁學上，《夢溪筆談》記述指南針四種裝置的方法，並比較優劣。書心指出磁針「常微偏東，不全南也」的現象，是關於磁偏角的最早記載，比西歐的記錄要早400年左右。書中視磁偏角為不穩定的異常現象，懷疑是否指南針本身技術上出問題，建議改用絲線來垂吊磁針，「則針常指南」。光學上，《夢溪筆談》記載了對凹面鏡成像所作的實驗，指出物件在凹面鏡焦點之內時得正像，在焦點上時不成像，而在焦點之外時得倒像。書中試圖用小孔成像的原理，解釋物件在焦點外成倒象的現象，但其解釋並不完全正確。《夢溪筆談》又細心觀察與研究透光鏡，透光鏡能反射背面的花紋，書中以鑄鏡時冷卻速度不同來解釋，其說不一定符合歷史事實（透光鏡的效果，從制鏡的技術史上看，較一致的看法是認為利用磨製的方法而成的）。聲學上，《夢溪筆談》記載了用紙人進行共振現象的實驗，證明弦線的基音與泛音的共振關係。沈括剪一個小紙人，放在基音弦線上，撥動相應的泛音弦線，紙人就跳動，彈別的弦線，紙人則不動。這個實驗要比歐洲人所做的類似實驗早幾百年。書中也探討古代扁形樂鐘的機制。

地理學

地理學方面，《夢溪筆談》記載沈括對浙東地區的察訪，看到「峭拔險怪」的雁蕩山諸峰的地貌景觀，提出流水侵蝕作用的自然成因說，指出中國西部黃土地區「立土動及百尺」的地貌特徵，也是同一原因造成。書中又記述太行山麓的山崖之間，「往往銜螺、蚌殼及石子如鳥卵者，橫亙石壁如帶」，推斷昔日這是海濱，進一步指出此地「今距東海已近千里，所謂大陸者，皆濁泥所湮耳」，以泥沙的淤積作用，解釋了華北平原的成因。《夢溪筆談》記述沈括巡視各地時，沿途細心收集山川道路的地理資料，製成木刻地形模型；又記載沈括奉命編修天下州縣圖，共繪制全國大地圖1軸（12乘10尺），小地圖1軸，又全國十八路各一軸，共20軸。沈括把州縣相對方位的描述，由原先8個方位增至24個方位，同時十分注意兩地間水平直線距離（「鳥飛之數」）的測算，使州縣間的相對位置更為精確可靠。

醫學

藥物學方面，《夢溪筆談》根據實物，對一物多名或多物一名的藥物，進行證同辨異，校正前人的錯誤，如指明杜若即高良薑，赤箭就是天麻等等。對藥物的採集和使用，也多有糾謬正誤之處。「藥議」一門中所有條目，都是從沈括先前的著作《良方》中擷取的，該門附在全書最後，作為附錄。書中也記述了醫學理論「五運六氣」，沈括曾運用這個理論，成功占測久旱後的一場大雨，震動了京師。

工藝

《夢溪筆談》對古代的工匠技術，頗為稱讚，例如指出唐高宗時所造的「大駕玉輅」技術，根本不是宋代造輅技術所能望其項背的。對各種古代工藝技術，如古透光鏡、古照物鏡、各種古劍古刀、各種出土古弩機等，都常稱讚有加，而且因其奧妙之法已失傳，無法複制而深感惋惜。書中也忠實記錄當時的科技成就，如喻皓《木經》、畢昇活字印刷術、水工高超巧合龍門的三埽施工法，冷鍛瘊子甲和灌鋼技術、磁針裝置四法、水法煉銅法、淮南漕渠的複閘、蘇州崑山淺水中築堤法等等。

其他內容

政務

《夢溪筆談》記錄沈括仕途生涯中的所見所聞，一些他從事各種官職所學到的實用知識，如製作堅固堡壘的竅門，解決軍隊給養問題的方法，也談及作者在短暫處理北宋財政事務時，對財經政策的反省，如鹽和茶的各種交換機制、錢銀的供應與錢幣通貨的平衡，穀價政策等。《夢溪筆談》也檢視既有的政策，如陳恕的茶法、范祥的鹽鈔法、陶鑒的建制水閘（在運河中設置水閘，以便舟船通過）、范仲淹力主維持的商稅。書中也解釋了唐代劉晏所實行，可以知道全國穀價的方法。書中記下宋朝各時期所鑄錢幣數量，背後其實是作者對錢幣供應與平衡的看法。軍事方面，書中研究城防和陣法、行軍運糧之法，又講求改進武器，如弓弩、劍和兵車的製造，對煉鋼和鍛鐵甲也有所論述。

考古與藝術

考古學方面，《夢溪筆談》相關的有廿餘條，涉及石斧、殷周青銅器、戰國時玉器和金幣、漢代銅器、畫象石和印章、六朝時的古墓和玉臂釧、唐代的玉釵、肺石和銅錢。此外還有金屬武器銅弩機和鐵劍。書中也談到古器物花紋、古墓發掘，古墓和古城的考證，根據考古文物，指正宋初聶崇義《三禮圖》等書籍的謬誤。有關藝術，《夢溪筆談》討論如何摹寫正午下的貓和牡丹、演奏特定音符時琵琶的撥法、畫中所呈現音樂的節拍、佛像背光的形狀、為何畫牛虎皆畫毛而惟馬不畫毛、如何寫「藏鋒」的書法，如何鋪排筆劃的間架，解釋何以王維《袁安臥雪圖》中會有「雪中芭蕉」。書中批評論書法者多謂書不必有法，以為好的書法家可以創造自己獨特的標準與藝術，即「各自成一家」，其實學書法必須師法前人，忠實臨摹前人的法書範例。書中也計算出帝舜的兩個妃子在舜駕崩時已屆百歲，批評文人騷客將「黃陵二女」視為年輕仕女的說法，是瀆慢而不禮貌的。

奇聞

《夢溪筆談》記述了一些現代人看來不科學的內容，卻是作者的親證，如木中紋理變成顏真卿的書法、鴨卵生得「爛然通明」、生肉轉活成小牛、人患上奇症身形縮小如兒童、蛟蜃之氣變成人物車馬、蛇蜃蛻化成石、寶劍可屈伸自如、鱷魚卵卻孵化成魚或鼉黿、旋風望之插天如羊角、冰紋顯成花果林木模樣、雨雹看似頭顱形狀。書中記載僧人文捷有預知他人命運的能力，能清楚預言沈括從侄沈遘的仕途、年壽及死後在地下世界的任職，準確至可謂神奇的地步。《夢溪筆談》談到揚州有一能夠飛行的「張殼大珠」，光芒奪目，不能正視，「十餘里間，林木皆有影，如初日所照；遠處但見天赤如野火，倏然遠去，其行如飛，浮於波中，杳杳如日……熒熒有芒燄，殆類日光。」現代談飛碟學的著作，許多都會提到《夢溪筆談》這一條，名氣頗大。

《夢溪筆談》不會輕易批評一些古代奇術為欺誕，也沒有「迷信」觀念，論述《洪範》五行術、古卜者的繇辭術、揲蓍之法，八卦的過揲之數，各種《易》法（納音納甲）與易象之學、各種六壬學。書中討論「六壬術」時，檢討傳統對「十二神將」的詮釋（十二神將配對五行、十二地支），結果認為其實只有十一位神將，因為最尊貴的「貴人」居中，左右各有五位神將隨待，十二個中最後一個名叫「天空」，位居貴人正對面，「天空」就是天中空無一物的意思，所以只有十一位神將。書中不喜歡談鬼神，全書只談到鍾馗一隻鬼。

版本

《夢溪筆談》成書以後，在當時就有刻版和流傳。現今傳世的各種版本，都源自南宋1166年揚州州學刻本，其中有一個元代1305年茶陵陳氏翻刻本由於刻印精妙，孤本僅存，被譽為稀世之珍。《夢溪筆談》出版後，沈括繼續寫有筆記，後人據其原稿，編成《補筆談》3卷，現存最早刻本是明代萬曆末年《寶顏堂秘笈．匯集》本。稍後商濬以其所得《夢溪筆談》和《補筆談》以外的沈括筆記原稿11篇刻入《稗海》，題為《續筆談》。三者合共30卷，即《四庫全書》著錄之本。1956年，上海出版了胡道靜的《夢溪筆談校證》，次年北京出版了《新校正夢溪筆談》，都把全部30卷全文編號為609條。《夢溪筆談校證》是目前學術界使用的標準版本。1978年日文譯本出版，梅原鬱主譯，列入「東洋文庫」。

地位

在宋代文人圈子中，《夢溪筆談》是著名筆記，內容往往為其他筆記著作所採納，並加以辯論。《夢溪筆談》更是科技史上一部十分重要的著作，李約瑟視之為「中國整部古代科學史上的座標」，由此可以衡量科技史的成就。書中敘述各種創造與發明，提供第一手資料，具有非凡價值，介紹了畢昇的活字印刷術，木匠喻皓編寫的《木經》和他固定木塔的故事，磁州鍛坊的煉鋼、淮南漕渠的複閘和水中築長堤法。這些工匠的貢獻，在一般史籍上一字不提，只有在《夢溪筆談》中才有詳細記載，成為研究中國科技史的珍貴資料。

在「官政」門，《夢溪筆談》記錄了一些與王安石經濟政策有關的數字與金額，是宋代筆記中所特有的。如淮南漕渠在水閘設置前後，米運輸的各種數量、宋朝各時期鑄造錢幣的數量、京師所歲支吏人薪餉的最大值、對各種茶法實行後「茶收入」的絕對金額比較等等，所敘述的財政數字的精準性，即使是宋代以財政知名的士人張方平所寫的《樂全集》也比不上。書中所載類似《宋史·食貨志》中種種數字與金額，其歷史重要性很高。部份學者對《夢溪筆談》稍有批評，認為書中「夾雜著某些封建性、神秘主義的糟粕，如宿命論、因果報應說之類」。