《Chapter 'Tian Xia' 》of the Zhuangzi states: 'The Book of Changes employs the Dao of Yin and Yang.' Indeed, Yin and Yang are the core concepts of the Book of Changes. Although the concept of Yin and Yang is not explicitly mentioned in the Book of Changes, the prevalence and transformation of Yin and Yang are indeed the most fundamental and core ideas of the Book of Changes.
The concept of Yin and Yang appeared and became popular as early as the Western Zhou Dynasty. In the Book of Documents, there are expressions like 'reaching Yueyang,' 'the Yang of Mount Min,' and 'south to Huayin.' Yang refers to the south side of the mountain, while Yin refers to the north side. In the Book of Documents, there is even the phrase 'discussing the way, managing Yin and Yang.' In the Book of Songs, it is said, 'Since the scenery is a hill, it reflects its Yin and Yang.' By the end of the Western Zhou Dynasty, Boyang Fu explained earthquakes in terms of Yin and Yang, believing, 'The qi of heaven and earth does not lose its order. If it loses its order, there will be chaos among the people. When Yin is hidden and cannot emerge, and Yang is pressing and cannot steam, then there is an earthquake.' (Guoyu: Zhou Yu Shang)
I
In the 16th year of Duke Xi of Lu (644 BC), a meteorite fell in the state of Song, and a bird flew backward over the capital of Song. Duke Xiang of Song asked Shi Xing, the interior minister of Zhou, whether it was auspicious or ominous. Shi Xing replied, 'This is a matter of Yin and Yang, not of auspiciousness or ominousness; auspiciousness or ominousness comes from people.' (Spring and Autumn Annals: Duke Xi's Sixteenth Year) Laozi believed that all things in the world are composed of Yin and Yang and are the harmonious unity of Yin and Yang. 'All things carry Yin and embrace Yang, they blend their life breaths to achieve harmony.' (Laozi, Chapter 42) In the late Spring and Autumn Period, Fan Li also had profound discussions on Yin and Yang, believing, 'The heavenly way is vast and grand, the sun and moon are constants, the wise take them as norms, and the subtle ones follow them. When Yang reaches its extreme, it becomes Yin, and when Yin reaches its extreme, it becomes Yang.' (Guoyu: Yueyu Xia) This idea is inherent in the Book of Changes.
The Commentary on the Book of Changes explains the Book of Changes based on the concept of Yin and Yang. The Tuan Commentary explains the Tai hexagram: 'Internally Yang and externally Yin, internally strong and externally gentle, internally the superior man and externally the inferior man,' hence auspicious; it explains the Pi hexagram: 'Internally Yin and externally Yang, internally soft and externally hard, internally the inferior man and externally the superior man,' hence not auspicious. The Tai hexagram has Qian below and Kun above, and the Pi hexagram has Kun below and Qian above, with the lower part representing the internal and the upper part representing the external. Qian represents Yang, strength, hardness, and the superior man; Kun represents Yin, gentleness, softness, and the inferior man. The Xiang Commentary explains the initial Nine in the Qian hexagram: 'A hidden dragon, do not act, Yang is hidden below.' It explains the initial Six in the Kun hexagram: 'Walking on frost, solidifying Yin begins.' The Wenyan Commentary explains the initial Nine in the Qian hexagram: 'A hidden dragon, do not act, Yang energy is concealed.' It explains the third Six in the Kun hexagram: 'Although Yin is beautiful, it is contained in serving the king, not daring to complete.' It explains Qian with Yang and Kun with Yin. All six lines of the Qian hexagram are Yang lines, representing pure Yang, so it is Yang; all six lines of the Kun hexagram are Yin lines, representing pure Yin, so it is Yin.
The Xici further explains the fundamental principles of the Book of Changes with Yin and Yang. Xici Xia says, 'Is it not the gateway to changes between Qian and Kun? Qian is Yang, Kun is Yin. When Yin and Yang are combined, there is virtue, and there is a blend of rigidity and flexibility, embodying the creation of heaven and earth, and conveying the virtue of gods and spirits.' Qian represents Yang, Kun represents Yin, the harmonious union of Yin and Yang gives birth to all things. Therefore, Qian and Kun are the gateways to changes, the keys to understanding the principles of the Book of Changes. In the system of the Book of Changes, whether it is the eight trigrams or the sixty-four hexagrams, the positions of Qian and Kun are like those of a father and mother.
II
In the 'Explaining the Trigrams' it says: Qian represents heaven, hence it's called father; Kun represents earth, hence it's called mother; Zhen produces a son with one throw, hence called the eldest son; Xun produces a daughter with one throw, hence called the eldest daughter; Kan produces a son with two throws, hence called the middle son; Li produces a daughter with two throws, hence called the middle daughter; Gen produces a son with three throws, hence called the youngest son; Dui produces a daughter with three throws, hence called the youngest daughter.Qian is father, Kun is mother; Zhen, Xun, Kan, Li, Gen, Dui are their six children, among which Zhen, Kan, Gen are male, while Xun, Li, Dui are female.
There is Yin and Yang; Qian is pure Yang, Kun is pure Yin. Qian is father, heaven; Kun is mother, earth. With heaven and earth, father and mother, then there are all things between heaven and earth, there are offspring born from father and mother. 'Explaining the Trigrams (Part 1)' says: The Dao of Qian becomes male, the Dao of Kun becomes female. Qian knows the beginning, Kun brings things to completion. It also states: Qian, in its tranquility, is firm, in its movement, is straight, hence great things are born from it. Kun, in its tranquility, is yielding, in its movement, is receptive, hence broad things are born from it. Qian and Kun represent both heaven and earth and father and mother, and simultaneously embody Yin and Yang.
'Introduction to the Trigrams' states: With heaven and earth, then all things are born. Among what fills the space between heaven and earth, only myriad things exist... With heaven and earth, then there are all things; with all things, then there are male and female; with male and female, then there are husbands and wives; with husbands and wives, then there are fathers and sons; with fathers and sons, then there are rulers and subjects; with rulers and subjects, then there is hierarchy; with hierarchy, then there is propriety and righteousness.
From things between heaven and earth to human affairs, all are naturally produced by Qian and Kun, all are manifestations of Yin and Yang.
Regarding the nature and state of all things produced by Qian and Kun, 'Explaining the Trigrams (Part 1)' states: The Dao is the interplay of one Yin and one Yang, those who inherit it are virtuous, those who embody it are natured. The benevolent see it and call it benevolence, the wise see it and call it wisdom, the common people use it daily without knowing it, hence the Dao of the noble one is rare. What is the Dao of one Yin and one Yang? 'Explaining the Trigrams (Part 1)' states: That which is above form is called Dao, that which is below form is called utensil. Dao is spoken in relation to utensils, utensils are tangible, concrete objects.
Utensils are concrete, tangible, and specific, while Dao is abstract, formless, and cannot be explicitly identified. Dao is principle, not simply rules. Laozi said: The Dao that can be spoken is not the eternal Dao, the Dao that can be named is not the eternal name. The eternal Dao cannot be named, cannot be expressed, it can only be understood. The Dao of one Yin and one Yang is the fundamental concept of the Book of Changes. This fundamental concept mainly includes the following aspects of meaning.
III
Firstly, all things in the world can be simply divided into two aspects: Yin and Yang. Qian is Yang, Kun is Yin; heaven is Yang, earth is Yin; the sun is Yang, the moon is Yin; day is Yang, night is Yin; south is Yang, north is Yin; above is Yang, below is Yin; brightness is Yang, darkness is Yin; heat is Yang, cold is Yin; strength is Yang, gentleness is Yin; hardness is Yang, softness is Yin; male is Yang, female is Yin; noble is Yang, humble is Yin. Yin exists because of Yang, and Yin and Yang are mutually related.
Secondly, the basic nature of a certain thing can be Yin or Yang, but Yin is not purely Yin, and Yang is not purely Yang. Yin can be further divided into Yin and Yang, and Yang can be further divided into Yin and Yang. Within Yin, there is one Yin and one Yang, and within Yang, there is one Yang and one Yin.
For example, in the evolutionary sequence from Taiji to the eight trigrams, Taiji differentiates into Yang and Yin (the two polarities), Yang further differentiates into Taiyang and Shaoyin, and Yin further differentiates into Taiyin and Shaoyang (the four images), rather than Yang differentiating into Taiyang and Shaoyang, or Yin differentiating into Taiyin and Shaoyin. This indicates that Yang is not pure Yang, as it inherently contains Yin, otherwise, how could Yang give birth to Shaoyin; likewise, Yin is not pure Yin, as it inherently contains Yang, otherwise, how could Yin give birth to Shaoyang. Consequently, the evolution from the four images to the eight trigrams occurs.
Among them, Taiyang differentiates into Qian and Dui, Taiyin differentiates into Kun and Gen, Shaoyin differentiates into Zhen and Li, Shaoyang differentiates into Xun and Kan. In the evolution from the four images to the eight trigrams, each image produces one Yin and one Yang. Taiyang: Qian is Yang, Dui is Yin; Taiyin: Gen is Yang, Kun is Yin; Shaoyin: Zhen is Yang, Li is Yin; Shaoyang: Kan is Yang, Xun is Yin.
Regarding the eight trigrams, Qian, Zhen, Kan, and Gen are Yang, while Kun, Xun, Li, and Dui are Yin. Except for Qian and Kun as the incarnations of Yin and Yang, pure Yang and pure Yin respectively, the other six trigrams, although Zhen, Kan, and Gen are Yang, they contain Yin, each having two Yin lines and one Yang line; although Xun, Li, and Dui are Yin, they contain Yang, each having two Yang lines and one Yin line. Likewise, for humans, male is Yang, female is Yin, but within male, there is Yin and Yang, and within female, there is Yin and Yang. In the male body, there is up and down, with up being Yang and down being Yin. The female body also has up and down, with up being Yang and down being Yin. The body also has left and right, with left being Yang and right being Yin. In summary, Yin contains Yang, and Yang contains Yin; this is the fundamental understanding of the entire world in the Book of Changes.
Thirdly, the two forces of Yin and Yang are not static but dynamic, with constant interaction and fluctuation. The sixty-four hexagrams are composed of two symbols, Yin and Yang, and the different changes of Yin and Yang lines lead to different changes in hexagrams. When a Yang line changes to a Yin line, it is called consuming; when a Yin line changes to a Yang line, it is called resting. 'Explaining the Trigrams (Part 1)' states: Through the interaction of hardness and softness, changes are born.
Among the sixty-four hexagrams, there are twelve Transforming Hexagrams, also known as the Twelve Penetrations, which clearly illustrate the constant interaction of Yin and Yang, demonstrating the messages of Yin and Yang. Fu, Lin, Tai, Da Zhuang, Guai, Qian, from Fu hexagram to Qian hexagram, the Yang energy progressively rises, indicating a transformation from Yang to Yin, known as rest; Gou, Dun, Pi, Guan, Bo, Kun, from Gou hexagram to Kun hexagram, the Yin energy progressively rises, indicating a transformation from Yin to Yang, known as consumption. Qian represents the utmost Yang, and after Qian comes Gou, where Yin begins to rise; Kun represents the utmost Yin, and after Kun comes Fu, where Yang begins to rise. The constant interaction of Yin and Yang leads to changes in hexagrams, as well as changes in the seasons, hence the Twelve Transforming Hexagrams correspond to the twelve months of the year.
IV
"Fourthly, the two forces of Yin and Yang are not in opposition to each other. When the force of Yang strengthens, the force of Yin will retreat; when the force of Yin strengthens, the force of Yang will retreat. The theory of Yin and Yang in the Book of Changes is different from modern mechanics, which states that action and reaction forces are equal and opposite in direction. However, the Yin and Yang theory in the Book of Changes is not a theory of opposition; when the force of Yang strengthens, the force of Yin retreats, and vice versa.
In spring, Yang energy rises while Yin energy declines; in summer, Yang energy flourishes while Yin energy wanes. In autumn, Yin energy rises while Yang energy declines; in winter, Yin energy flourishes while Yang energy wanes. This forms the four seasons of the year. 'Explaining the Trigrams (Part 2)' states: When the sun moves away, the moon comes; when the moon moves away, the sun comes; the sun and the moon mutually push each other, bringing light. When cold retreats, heat comes; when heat retreats, cold comes; cold and heat alternate, and the year is completed. It is precisely because of the constant interaction of Yin and Yang that a cohesive whole is formed, and a stable situation arises. Otherwise, if Yin and Yang were in a state of opposition, it would inevitably lead to the collapse of things.
Fifthly, the two forces of Yin and Yang are not independent and solitary, but must interact with each other. If Yang only remains as Yang without any interaction with Yin, and if Yin only remains as Yin without any interaction with Yang, then Yang will always be Yang, and Yin will always be Yin, and they will remain in a state of separation. Without interaction, there can be no mutual response. The hexagrams are formed from lines, and the original meaning of 'line' is 'interaction.'
'Shuowen Jiezi' states: "Yao means interaction." Yao means interaction, that is, the intersection of Yin and Yang. Through interaction comes sensation, and through sensation comes response. The Taixi hexagram has Qian below and Kun above, where the energy of heaven ascends while the energy of earth descends, and the two energies intersect. Because of this intersection, there is harmony. 'Explaining the Trigrams (Part 2)' interprets the Taixi hexagram: Heaven and earth intersect, and there is harmony. 'Explaining the Trigrams (Part 1)' explains the Taixi hexagram: Heaven and earth intersect, and all things communicate; upper and lower intersect, and their aspirations are the same. Because in the Taixi hexagram, Qian and Kun intersect, heaven and earth intersect, upper and lower intersect, hence harmony. The Fuxi hexagram has Kun below and Qian above, where the energy of heaven ascends while the energy of earth descends, but the two energies do not intersect. Because of this lack of intersection, there is adversity. 'Explaining the Trigrams (Part 2)' interprets the Fuxi hexagram: Heaven and earth do not intersect, and there is adversity.
'Shuowen Jiezi' interprets the Fuxi hexagram: Heaven and earth do not intersect, and all things do not communicate; upper and lower do not intersect, and there are no states in the world. Because in the Fuxi hexagram, Qian and Kun do not intersect, heaven and earth do not intersect, upper and lower do not intersect, hence adversity. The mutual interaction of Yin and Yang is the basis and prerequisite for the generation of things. Without this basis and prerequisite, Yin and Yang would always remain separate, and the world would forever be a silent one, with nothing happening.
Sixthly, the interaction of Yin and Yang promotes the emergence of new things and facilitates the movement, change, and development of things. 'Explaining the Trigrams (Part 2)' states: Heaven and earth interact, and all things undergo transformation. Men and women combine essence, and all things are generated. Interaction refers to the fusion and union of the two energies of Yin and Yang. Because of the interaction of Yin and Yang, there is mutual sensation, and mutual sensation is the starting point of the generation of things. The hexagram of Xian is said to be prosperous and beneficial for divination, and it is auspicious to take a woman. Why is the Xian hexagram prosperous and beneficial for divination?
'Explaining the Trigrams (Part 1)' explains: Xian means sensation. Softness is above and hardness is below; the two energies interact and harmonize with each other, and there is stability and joy. The male is below and the female is above; hence there is prosperity and benefit for divination, and it is auspicious to take a woman. When heaven and earth sense each other, all things are born; when sages sense the hearts of people, the world is at peace. By observing what they sense, the sentiments of heaven, earth, and all things can be understood! Because there is sensation, there is prosperity and benefit for divination; because there is the sensation of heaven and earth, there is the generation of all things; because there is the sensation of sages, there is peace in the world. Sensation is the initiator, and response is the recipient. With sensation comes response. Response is the mutual attraction and response between Yin and Yang of opposite sexes. With response comes auspiciousness; without response, there is no auspiciousness. The hexagram of Wu Wang has Zhen below and Qian above, and its hexagram says: great prosperity and benefit for divination. Why is this hexagram auspicious?
'Explaining the Trigrams (Part 1)' explains the hexagram of Wu Wang: Activity and vitality; hardness is in the center and responds
V
Seventhly, when things develop to a certain extent, they will inevitably develop in the opposite direction: reaching the extreme of Yang leads to Yin, while reaching the extreme of Yin leads to Yang. From stillness comes motion, and from motion comes stillness. In the divination method of the Book of Changes, 6 represents old Yin, 7 represents young Yang, 8 represents young Yin, and 9 represents old Yang. Since 7 and 8 are young Yang and young Yin respectively, their development prospects are old Yang and old Yin, making them unchanging lines. On the other hand, 6 and 9 represent old Yin and old Yang, which are the limits of Yin and Yang. Their development prospects are young Yang and young Yin, hence they are changing lines.
The developmental sequence in the Book of Changes is: 7-9-8-6-7, which means young Yang-old Yang-young Yin-old Yin-young Yang. Qian (Heaven) represents the extreme of Yang, and its subsequent hexagram is Gu (Biting Through); Kun (Earth) represents the extreme of Yin, and its subsequent hexagram is Fu (Returning). When things reach their peak, they will inevitably decline, which is the basic rule revealed and confirmed by the Book of Changes. 'Explaining the Trigrams (Part 2)' explains the Feng hexagram: When the sun is in the middle of the sky, it will set; when the moon is full, it will wane; the fullness and emptiness of heaven and earth change with the seasons. 'Explaining the Trigrams (Part 2)' also states: When change reaches its limit, it transforms; when transformation occurs, it becomes adaptable; when adaptability is achieved, it becomes enduring. Yang reaches its extreme and becomes Yin; Yin reaches its extreme and becomes Yang. Yin and Yang mutually originate from each other, which is fully consistent with Laozi's teaching that the movement of opposites is the way of the Dao.
Cheng Yi said: "The Dao is called the interaction of Yin and Yang, but the Dao itself is not Yin and Yang. Therefore, Yin and Yang are the Dao." (Chengshi Yishu, Volume Three) He also said: "Without Yin and Yang, there is no Dao. Therefore, Yin and Yang are the Dao. Yin and Yang are Qi. Qi is what is formed below, while the Dao is what is formed above." (Chengshi Yishu, Volume Fifteen) Yin and Yang themselves are not the Dao, nor is the transformation of Yin and Yang, nor is the orderly and regular nature of the transformation of Yin and Yang the Dao. The Dao is the principle manifested through the transformation of Yin and Yang.
"The interaction of Yin and Yang is called the Dao" has profound implications, which are difficult for ordinary people to fully grasp. Therefore, it is said: "The benevolent see it as benevolence, the wise see it as wisdom; the common people use it daily without understanding." Those who perceive benevolence and wisdom only grasp a part of it, hence there are various interpretations. While the common people follow this Dao in their daily lives, they do not understand its principles. However, the principles are inherent and should be followed by people.
