The World Trigram and the Month Trigram

《周易》雖無八宮之別，而世應仍所不廢。惟《周易》之世應，但以爻論，而京《易》則特重在卦。京氏曰“卦有八世爻分六位，配乎人事，以定吉凶”者，固不僅為占筮言也。《易乾鑿度》曰：“三畫以下為地，四畫以上為天。易氣從下生，動於地之下，則應於天之上。動於地之中，則應於天之中。

The Zhou Changes (I Ching) does not distinguish between the eight palaces, but the system of world and response lines has not been abandoned. The Zhou Changes discusses world and response lines only in terms of lines (yao), while the Jingshi Yi particularly emphasizes the trigrams. Jing Fang said, "Trigrams have eight worlds, lines are divided into six positions, matching human affairs to determine fortune and misfortune." This shows that this system was originally not only for divination. The Yi Wei · Gan Zao Du says: the first, second, and third lines belong to the earth, while the fourth, fifth, and sixth lines belong to the heavens. The energy of the Yi arises from below and moves upward, so if a line moves at the lowest position of the earth, it corresponds to the highest position of the heavens; if a line moves at the middle position of the earth, it corresponds to the middle position of the heavens.

動於地之上，則應於天之上(此以上下二象分天地，故不曾人。人秉天地之氣以生，一身之陰陽之氣亦有感必應。言其精則水火升降，言其粗則脈絡之交布，穴氣之分行。與夫一身外相所表見者，無不各按其位，而上下相應。如人身上部口面耳目間有痣者，下部相應之位亦必有之，毫釐不爽。此上下相應之最顯而易見者也。一卦六爻亦如一身上下相通，如有否隔，即為疵病。天地人物，因無二理也。)。”

The moving line is at the topmost position of the lower trigram, so it should correspond to the topmost position of the upper trigram. Here, only the upper and lower trigrams are used to distinguish heaven and earth, so there is no separate position for humans. Humans receive the qi of heaven and earth to be born, and the yin and yang qi within the body also respond to each other. In terms of the subtle aspect, it is the rising and falling of the water and fire of the heart and kidney; in terms of the obvious aspect, it is the interweaving of meridians and the distribution of qi at acupuncture points. As for all the manifestations on the body's surface, they all correspond according to their respective positions, with upper and lower parts corresponding to each other. For example, if there is a mole on the upper part of the body, such as the mouth, face, ears, or eyes, there must be a corresponding mole on the lower part, exactly the same, which is the most obvious and visible example of upper and lower correspondence. A hexagram with six lines is also like the human body, connecting top to bottom. Once there is an obstruction, it becomes a disorder. Heaven, earth, humans, and things all follow the same principle. The above is from the "Qian Zao Du."

初與四，二與五，三與上，陰應陽，陽應陰，二氣感應以相與，此其正也。蓋天地之氣有終始，六世之位有上下，故《易》始於一(《易》本無體，氣變而為一，故氣從下生也。)，分於二(清濁分於二儀。公武曰：奇偶相與，據一以起二，而為主之相者，謂之應是也。)，通於三(陰陽氣交，人生於中。天地氣通，故三陽成泰，而泰為通。)，交於四，盛於五(二壯於地，五壯於天，故如盛也)，終於上(上則數極，極則反也)。故六爻皆有應，而世取其一。與世對者，則為應也。

The first line corresponds with the fourth line, the second line with the fifth line, and the third line with the top line. Yin goes to respond to Yang, and Yang goes to respond to Yin. The two energies interact and are close to each other, which is the correct example. Because the energies of Heaven and Earth have a beginning and an end, and the six lines have upper and lower positions, the Book of Changes begins with one (the Book of Changes originally has no form; when the energy changes, it becomes one, so it is said that energy arises from below), divides into two (the clear and turbid energies split into the two principles. Zhao Gongwu said: odd and even are paired, and from one comes two. The line that supports the world line is called 'response,' referring to this), connects through three (the energies of Yin and Yang meet, and a person is born in between. The energies of Heaven and Earth connect, so three Yangs arise and form the Tai hexagram, 'Tai' meaning connection), combines at four, reaches its prime at five (the second line is strong in the earth, the fifth line is strong in the heaven, so it is called strong), and concludes at the top line (when the top line is reached, the number has reached its peak, and at the peak it must return). Therefore, each of the six lines has a response, but the world line selects only one among them. The line that is directly opposite the world line is called the response line.

水火既濟，初陽而四陰，二陰而五陽，三陽而上陰，所謂六爻當位、上下皆相應者者也。既濟屬坎宮三世卦，三之應在上。火水未濟，既濟之反也。六爻皆不當位，而上下剛柔相應，屬離宮三世卦應亦在上。

The hexagram Water over Fire, named Ji Ji, has the first line as yang and the fourth line as yin, the second line as yin and the fifth line as yang, the third line as yang and the top line as yin. This is called the six lines each occupying their proper position, with the upper and lower trigrams corresponding in pairs. Ji Ji belongs to the Kan palace's third generation hexagram, with the world (shi) located at the third line, so its corresponding line (ying) falls at the top line. Fire over Water, named Wei Ji, is the reversed hexagram of Ji Ji, with all six lines not in their proper positions, yet the yin and yang lines still correspond in pairs. It belongs to the Li palace's third generation hexagram, with the world (shi) also located at the third line, and the corresponding line (ying) also falls at the top line.

月卦非月建，由世卦生，亦由十二月闢卦生者也。世分陰陽，陽世起子月，陰世起午月，以數不以氣。雖以闢卦為綱，而不去坎離震兌，仍以六十四卦配八宮之屬也。乾為本宮，上爻六世，陽爻陽世，從初爻子月起數至上爻為巳，故乾為四月卦。豐為坎宮五世卦。五陰爻陰世，從初爻午月起至五爻為戌，豐為九月卦。餘類推。

The "month卦" is not the same as the "month builder." It is derived from the world卦, or alternatively, from the twelve great trigrams. The world line is divided into yin and yang: if the world line is a yang line, it starts counting from the month of Zi; if it is a yin line, it starts counting from the month of Wu. This counting is based on numbers, not on solar terms. Although the twelve great trigrams serve as the framework, they are not like the卦气 system which removes Kan, Li, Zhen, and Dui. Instead, all sixty-four hexagrams are still assigned to the eight palaces. For example, Qian is the original hexagram of its palace, and the world line is on the top line, which is a yang line, belonging to a yang world. It starts counting from the month of Zi, Zi, Chou, Yin, Mao, Chen, Si, and reaches the top line at Si, so Qian is the fourth month卦. The hexagram Feng is the fifth hexagram of the Kan palace, and the fifth line is a yin line, belonging to a yin world. It starts counting from the month of Wu, Wu, Wei, Shen, You, Xu, and reaches the fifth line at Xu, so Feng is the ninth month卦. The rest of the hexagrams follow the same pattern.

世之所位，而陰陽之肆者謂之飛，陰陽肇乎所配(乾與坤，震與巽，坎與離，艮與兌)，而終不脫乎本(以飛某宮之卦，乃伏某宮之位)，以顯應佐神明者謂之伏。故有卦之飛伏，有爻之飛伏。

The position where the World Line resides is clearly visible and is called "Flying." The beginning of yin and yang is connected to its paired trigram (Heaven pairs with Earth, Thunder pairs with Wind, Water pairs with Fire, Mountain pairs with Lake), yet it always remains within its own palace (any trigram that flies out belongs to a particular palace, and what is hidden is the position of that palace). This hidden element, which supports the divine and allows the visible manifestation to take effect, is called "Hidden." Therefore, flying and hiding can occur at both the level of the entire hexagram and at the level of individual lines.

《文言》曰：“同聲相應，同氣相求。”飛之與伏，聲氣相通，或顯或隱，各以類求。《中庸》曰：“莫現乎隱，莫顯乎微。”此精義入神之論也。後儒以經學自誇，謂孔子未嘗言此，指為術數小道，不知《十翼》之言飛伏者多矣。奈學者瞠目視之，皆未見耳。《雜卦傳》“兌見而巽伏也”，是明言飛伏之一例。《說卦》“坎為隱伏”，而《離·象》“飛鳥”，亦飛伏之見端。而六十四卦《彖》、《象》言之者，更不勝枚舉也。

The Wenyan of the Qian hexagram says: "Those with the same sound respond to each other; those with the same qi seek each other out." The flying and the hidden are originally connected in sound and qi, one appearing and the other concealed, each seeking according to its category. The Zhongyong says: "Nothing is more visible than the hidden, and nothing more apparent than the subtle." — The more hidden something is, the more it reveals itself; the more subtle, the more it becomes evident. This is precisely the argument of "refining the profound meaning to the divine." Later Confucian scholars boasted of their mastery of the classics, claiming that Confucius never spoke of flying and hiding, and thus classified it as a minor branch of divination. They did not realize that the Ten Wings contain numerous references to flying and hiding, but scholars simply looked past them with their eyes wide open, failing to notice anything at all. The Zage Zhuan says, "Dui appears while Xun hides," which clearly presents an example of flying and hiding. The Shuogua Zhuan says, "Kan represents concealment," while the image commentary of the Li hexagram mentions "flying birds," both of which are hints of the concept of flying and hiding. As for the mention of flying and hiding in the Tai and Xiang commentaries of the sixty-four hexagrams, they are countless.

《京氏易傳》以爻直月，從世起建，佈於六位(惟乾坎二卦從初爻起)。乾起甲子，坤起甲午。一卦凡六月，計一百八十日。積算以爻直日，即從月建所止之日起，如姤卦月建起庚午至乙亥(姤初爻庚午，上爻乙亥)，積算即從乙亥起。上九為一日，周而復始，一卦凡百有八十日。

The Jing's Tradition of the Changes assigns each line to represent a month, starting from the World Line and proceeding sequentially to fill the six line positions (only the Qian and Kan hexagrams start from the first line). Qian begins with Jiazi, and Kun begins with Jiawu. Each hexagram governs six months, totaling 180 days. "Accumulated Calculation" assigns each line to represent a day, starting from the day the month builder stops: for example, the Gou hexagram's month builder starts with Gengwu and ends with Yihai (the first line of Gou receives Gengwu, and the top line receives Yihai). Accumulated Calculation then begins from Yihai, with the Nine at the Top counted as the first day, continuing in a cycle, with each hexagram also totaling 180 days.

今占家用《火珠林》術，大半出於京氏。惟月建積算，罕有傳其法者。後人或以月為直符，日為傳符，指六爻所見之支當之，非其義也。此為京氏占法，詳晁氏《別錄》，說繁不贅錄。八純卦外，一至六世，皆以本宮納甲為伏，而變宮遊歸以爻論。詳下章。

The method used nowadays in divination with the Fire Pearl Forest is mostly derived from Jing Fang. Only the calculations of month builder and accumulated numbers are seldom passed down. Later people sometimes take the month as "straight symbol" and the day as "transmitted symbol," using the existing earthly branches in the six lines as substitutes, which is not the original meaning of month builder and accumulated numbers. The above is the method of Jing Fang. Details can be found in Chao Gongwu's "Bi Lu," which is complicated, so it is not copied here. There is also a general rule: except for the eight pure trigrams, the first to sixth generations of trigrams take the stem assignment of their original palace as "hidden." As for the trigrams of wandering souls and returning souls that have changed palace, they should be discussed according to the lines, which will be explained in the next chapter.

《說卦》“帝出乎震”，及“神也者”兩節，皆言後天八卦之用者也。術家言後天八卦皆居旺地，語雖俚而所見甚精。蓋帝出乎震之帝，非專屬震卦。帝者主也，主權所在，即王也。術家曰旺，即土之用。

In the "Sayings on the Trigrams" (Sayi Zhuan), the passages "The Emperor arises from Zhen" and "The divine is the one who subtly governs all things and expresses it through words" both discuss the functions of the Later Heaven Trigrams. Numerologists say that each of the Later Heaven Trigrams sits on its own prosperous ground. Though this statement is crude, its insight is quite profound. Because the "Emperor" in "The Emperor arises from Zhen" does not specifically refer to the Zhen trigram; "Emperor" means the ruler, the center of authority, which is also "King." The "prosperous" mentioned by numerologists is actually the function of this "King" (the original text's "earth's use" is likely a miswriting of "King").

《大平御覽·五行休旺論》曰：“立春艮旺(艮居丑寅之交，立春之候也)，震相，巽胎，離沒，坤死，兌囚，乾廢，坎休。立夏巽旺(巽居辰巳之交，立夏之候也)，離相，坤胎，兌沒，乾死，坎囚，艮廢，震休。

The "Five Phases Prosperity and Decline Theory" cited in the "Taiping Yulian" states: At the beginning of spring, the Gen trigram is in its prime (Gen is located at the boundary between Chou and Yin, which is exactly the time of the beginning of spring), Zhen is in its auxiliary phase, Xun is in the fetal phase, Li is in decline, Kun is in death, Dui is in captivity, and Qian is in decline. At the beginning of summer, the Xun trigram is in its prime (Xun is located at the boundary between Chen and Si, which is exactly the time of the beginning of summer), Li is in its auxiliary phase, Kun is in the fetal phase, Dui is in decline, Qian is in death, Gen is in captivity, and Zhen is in decline. (The original title is written as "Daiping Yulian," which refers to the "Taiping Yulian.")

立秋坤旺(坤居未申之交，立秋之候也)，兌相，乾胎，坎沒，艮死，震囚，坎廢，離休。立冬乾旺(乾居戌亥之交，立冬之候也)，坎相，艮胎，震沒，離囚，坤廢，兌休(《唐典》：王、相、胎、沒、休、廢為八卦之氣)。”王充《論衡》亦同。蓋立冬之候也，得地為旺，旺之沖死，旺所生相，相之沖囚，胎之對廢，沒之對休。

At the beginning of autumn, the Kun trigram is in its旺 (prosperous) phase (Kun is located at the boundary between Wei and Shen, which is exactly the time of the beginning of autumn). Dui is in its相 (auxiliary) phase, Qian is in its胎 (nurturing) phase, Kan is in its没 (decline) phase, Gen is in its死 (death) phase, Zhen is in its囚 (captivity) phase, and Xun is in its废 (waste) phase. At the beginning of winter, the Qian trigram is in its旺 (prosperous) phase (Qian is located at the boundary between Xu and Hai, which is exactly the time of the beginning of winter). Kan is in its相 (auxiliary) phase, Gen is in its胎 (nurturing) phase, Zhen is in its没 (decline) phase, Li is in its囚 (captivity) phase, Kun is in its废 (waste) phase, and Dui is in its休 (rest) phase. The Tang Dynasty's "Six Canons" refer to the phases of Wang, Xiang, Tai, Mei, Xiu, and Fei as the energies of the eight trigrams. Wang Chong's "Discourses on Weights and Measures" also describes this in the same way. This passage is specifically discussing the beginning of winter. In summary, the trigram in its own position is called "Wang", the one opposite to the旺 position is called "Si", the one generated by the旺 position is called "Xiang", the one opposite to the相 position is called "Qiu", the one opposite to the胎 position is called "Fei", and the one opposite to the没 position is called "Xiu".

《淮南·墜形訓》曰：“五行：木壯，水老，火生，金囚，土死。火壯，木老，土生，水囚，金死。土壯，火老，金生，木囚，水死。金壯，土老，水生，火囚，木死。水壯，金老，木生，土囚，火死。”

The Huainanzi · Zui Xing Xun says: The waxing and waning of the Five Phases cycle in this way: When wood is strong, water is old, fire is born, metal is restrained, and earth is dead; when fire is strong, wood is old, earth is born, water is restrained, and metal is dead; when earth is strong, fire is old, metal is born, wood is restrained, and water is dead; when metal is strong, earth is old, water is born, fire is restrained, and wood is dead; when water is strong, metal is old, wood is born, earth is restrained, and fire is dead. In this context, "strong" means being in command and dominant. The Phase that nourishes me has achieved its purpose and retires to be "old." The Phase that I nourish is rising and is called "born." The Phase that restrains me is restrained and is called "restrained." The Phase that I restrain is overcome and is called "dead."

春令：木王，火相，土休，金囚。夏令：火王，土相，金休，水囚。秋令：金王，水相，木休，火囚。冬令：水王，木相，火休，土囚。土王四季，金相。

This is a flat chart showing the waxing and waning of the Five Phases across the four seasons, with each row listing the four states of "Wang, Xiang, Xiu, Qiu" for the current season: in spring, wood is Wang, fire is Xiang, earth is Xiu, and metal is Qiu; in summer, fire is Wang, earth is Xiang, metal is Xiu, and water is Qiu; in autumn, metal is Wang, water is Xiang, wood is Xiu, and fire is Qiu; in winter, water is Wang, wood is Xiang, fire is Xiu, and earth is Qiu. Earth does not rule a single season but is Wang for eighteen days at the end of each season, during which metal is Xiang. "Wang" means being in power and dominant (later writers often use "Wang" instead of "Xing"), "Xiang" refers to the element that is generated by the dominant element, which is secondary to Wang but about to rise, "Xiu" refers to the element that generates the dominant element, which has achieved its purpose and retreats into rest, and "Qiu" refers to the element that overcomes the dominant element, which is restrained and confined.

地支藏用，分晰陰陽，最為精密。周天三百六十有五度四分度之一，歷三百六十五日四分日之一而氣周，即六十卦三百六十爻之爻周。坎離震兌，分主二至二分，共三百八十四爻。陰陽錯綜，消息盈虛，無不合矣。藏天干於地支者，即乾體坤用。乾之用九，用於坤六，學者以術家言而忽之。是猶悅琢玉之精美，而賤斧鑿為匠器。《十翼》造化之筆，因無斧鑿之痕。然不知斧鑿之用者，又安識良工之心苦哉！

The hidden use of the Earthly Branches refers to the heavenly stems concealed within each branch and the number of days each stem rules. Yin and yang are distinguished with extreme precision. The entire cycle of the heavens is 365 and 1/4 degrees, and it takes 365 and 1/4 days to complete one cycle of the five elements, corresponding exactly to the 360 lines of the sixty hexagrams. Then, the four trigrams Kan, Li, Zhen, and Dui are added to represent the twenty-four nodes of the solstices and equinoxes, bringing the total to 384 lines. Yin and yang interweave and interact, waxing and waning, with no place not perfectly aligned. Embedding heavenly stems within the Earthly Branches follows the principle that "Qian is the body and Kun is the function": the "use of all nines" in Qian can only be seen when it falls upon the "six" of Kun. Scholars often dismiss this as mere numerology, just as they admire the beauty of a polished jade without recognizing the importance of the chisel and hammer. The Ten Wings are written by the natural hand of creation, leaving no trace of artificial craftsmanship; yet those who do not understand the purpose of the chisel and hammer will never comprehend the sincere effort of a master craftsman.

壬五日三分半，癸二十日六分半，辛長生。癸九日二分半，辛三日一分，己十八日六分。戊七日二分半，丙七日二分半，甲十六日五分。甲十日三分半，乙二十日六分半，癸長生。乙九日三分，癸二日一分半，戊十八日六分。庚七日二分半，戊七日二分半，丙十六日五分。午丙十日三分半，己九日三分，丁十三日三分半。丁九十三分，乙三日一分半，己十分日六分。戊己共七日，壬七日三分半，庚十六日五分。庚十日三分半，辛二十日六分半，丁長生。辛九日三分，丁三日一分，戊十八日六分。戊七日二分半，甲七日二分半，未十六日五分。

This is a flat table of the twelve earthly branches' hidden heavenly stems. Originally divided into twelve rows, it is arranged in the order of Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, and Hai. Each branch lists the heavenly stems hidden within it and the number of days each stem is in charge. The seventh row contains only the character "Wu," which confirms the order of the entire table. Zi contains Ren water for five days and a half (originally ten days), Gui water for twenty days and a half, and Xin metal is born in Zi. Chou contains Gui water for nine days and a half, Xin metal for three days and a third, and Ji earth for eighteen days and a half. Yin contains Wu earth for seven days and a half, Bing fire for seven days and a half, and Ji wood for sixteen days and a half. Mao contains Ji wood for ten days and a third, Yi wood for twenty days and a half, and Gui water is born in Mao. Chen contains Yi wood for nine days and a third, Gui water for two days and a half, and Wu earth for eighteen days and a half. Si contains Geng metal for seven days and a half, Wu earth for seven days and a half, and Bing fire for sixteen days and a half. Wu contains Bing fire for ten days and a third, Ji earth for nine days and a third, and Ding fire for thirteen days and a third. Wei contains Ding fire for nine days and a third, Yi wood for three days and a third, and Ji earth for eighteen days and a half. Shen contains Wu and Ji earth together for seven days, Ren water for seven days and a third, and Geng metal for sixteen days and a half. You contains Geng metal for ten days and a third, Xin metal for twenty days and a half, and Ding fire is born in You. Xu contains Xin metal for nine days and a third, Ding fire for three days and a third, and Wu earth for eighteen days and a half. Hai contains Wu earth for seven days and a half, Ji wood for seven days and a half, and Ren water for sixteen days and a half (the last row reads "Wei sixteen days and a half," where "Wei" is a mistake for "Ren"). Within each branch, the three heavenly stems take turns in sequence, and the total days add up to about one month. This is what the divination masters refer to as "the heavenly stem governing the affairs."

積爻而成卦，故爻為卦之體。爻動而卦變，故爻又為卦之用。卦之體用，具在於爻。《說卦傳》曰：“昔者聖人之作《易》也，將以順性命之理。是以立天之道曰陰與陽，立地之道曰柔與剛，立人之道曰仁與義。兼三才而兩之，故《易》六畫而成卦。分陰分陽，迭用柔剛，故《易》六位而成章。”

The yao accumulate to form a hexagram, so the yao is the "body" of the hexagram; when a yao moves, the hexagram changes accordingly, so the yao is also the "function" of the hexagram. The body and function of a hexagram all lie in the yao. The "Commentary on the Hexagrams" states: the ancient sages created the Book of Changes to follow the principles of life and nature, thus establishing the way of Heaven as "yin" and "yang," the way of Earth as "flexibility" and "firmness," and the way of humanity as "benevolence" and "righteousness." They doubled the three categories of Heaven, Earth, and humanity, so the Book of Changes requires six lines to form a hexagram. Furthermore, because the six lines distinguish between yin and yang positions, and flexible and firm lines alternate, the Book of Changes requires six yao positions to establish order. This passage clarifies two points: the origin of the six lines comes from each of the three categories having two yao; the order of the six positions arises from the alternating combination of yin and yang and flexibility and firmness.

《繫傳》曰：“《易》之為書也，廣大悉備。有天道焉，有人道焉，有地道焉。兼三才而兩之，故六。六者非它也，三才之道也。道有變動故曰爻，爻有等故曰物，物相雜故曰文。文不當故吉凶生焉。”

The *Great Treatise* continues to say: The *Book of Changes* is vast and comprehensive, containing heavenly ways, human ways, and earthy ways. By doubling the three principles, it becomes six lines. This number "six" is precisely the way of the three principles. Since the way is changeable, it is called "yao" (line). The yao has distinctions of high and low, so it is also called "wu" (things). Different things intermingle, so it is called "wen" (patterns). When the arrangement of patterns is not appropriate, good fortune and misfortune arise from this. Thus, from "six" to "yao," from "yao" to "wu" and "wen," each term is established based on position and coordination. Good fortune and misfortune are merely the results of appropriate or inappropriate coordination.

又曰：“《易》之為書也不可遠，為道也屢遷。變動不居，周流六虛。上下無常，剛柔相易。不可為典要，唯變所適。”又曰：“爻也者效此者也，象也者像此者也。爻象動乎內，吉凶見乎外，功業見乎變，聖人之情見乎辭。”孔子之所以言爻者，詳且備矣。後世言《易》者，既昧於象數，而六虛六位之義，亦泛焉而莫知所指。每卦僅就所見之上下六爻，為承應當否，卦之情其何由見哉！

The Great Treatise also says: The Book of Changes cannot be separated from for a moment; the Dao it discusses is ever-changing, moving without stopping, circulating among the six empty positions; up and down have no fixed pattern, the strong lines and the yielding lines alternate with each other; it cannot be regarded as a fixed doctrine, but must follow the changes. It also says: The line represents the imitation of change; the image represents the imitation of change. The lines and images move within the hexagram, and the fortune or misfortune appears outside the hexagram; achievements are revealed through change, and the mind of the sage is revealed through the line statements. Confucius spoke about the lines in a detailed and complete manner. However, later scholars who interpreted the Book of Changes have become confused about the images and numbers, and are vague about the meaning of the 'six empty positions' and 'six positions,' unable to explain clearly what they refer to. They discuss each hexagram only in terms of the visible upper and lower six lines, considering their relationships of support, response, and whether they are in the proper position or not. In this way, how can the true situation of a hexagram be revealed?

卦氣由下生，故以下為初。重三畫之卦為六畫，仍分三才。陽奇陰偶，陽剛陰柔。以配天地，中爻為人，曰仁曰義。上下進退，為內外兩象之中樞。孔子贊《易》，《彖傳》以內外兩象之陰陽剛柔，釋一卦之義。《象傳》則專取中爻，聯合上下象數，以人合天。

The energy of the hexagram flows upward from the bottom, so the lowest line is called "Chu." When three lines of a basic trigram are stacked to form a six-line composite trigram, it is still divided into the three principles of heaven, earth, and humanity: yang is odd, yin is even, yang is strong and firm, yin is soft and flexible. The upper two lines correspond to heaven, the lower two to earth, and the middle two to humanity, which refers to "ren" (benevolence) and "yi" (righteousness). The middle two lines can move up or down, advance or retreat, making them the key link between the inner and outer trigrams. Confucius interpreted the Book of Changes, using the Commentary on the Judgment to explain the meaning of the entire hexagram through the yin and yang, strength and flexibility of the inner and outer trigrams; the Image Commentary, on the other hand, focuses specifically on the middle line, connecting the upper and lower images through numbers and patterns, and using human affairs to align with heavenly principles.

六十四卦《象傳》，皆曰“君子以”或“先王以”者，即以人事明天地之道者也。天地之道往復不窮，而人事之千變萬化，皆在三四兩爻之反覆。孔子曰“其初難知，其上易知，本末也”，《大過·彖》曰“本末弱也”。明六爻之本末，而後一卦之體用可知。而元亨利貞，亦可以陰陽之升降上下而明其序也。

The Great Image commentaries of the sixty-four hexagrams all say "The gentleman uses... " or "The former kings use... ", which is using human affairs to explain the principles of heaven and earth. The principles of heaven and earth are cyclical and ever-repeating, without end, while human affairs change endlessly, all depending on the movement between the third and fourth lines, which represent the cycles. Confucius said, "At the beginning it is hard to know, at the top it is easy to know; this is about the beginning and the end." The first line is the root, so it is hard to know; the top line is the end, so it is easy to see. The Commentary on the Judgment of the Great Excess also says, "The beginning and the end are weak." Clarifying the beginning and the end of the six lines allows one to understand the nature and function of a hexagram. Furthermore, the four virtues, "origin, prosperity, benefit, and constancy," can be understood in order according to the sequence of yin and yang rising and falling.

端木氏曰：《易》太極含三為一，乾坤上下中，上天極，立在下地極，而中人極。離坎天地中，日月二人象，天地中人道，離坎交中，天地間生人。天地顛，乾下首，生人出。乾是坎，北極艮背。坤是離，南極巽高。而中極人道，震兌出入，天地大義人之終始。此六爻三極之道也。

Duanmu Guohu said: The Taiji of the Book of Changes encompasses three elements as one. The trigrams Qian and Kun divide into upper, middle, and lower layers: the upper is the Heaven's extreme, opposing and located below is the Earth's extreme, and in the middle is the Human's extreme. Li and Kan are located between Heaven and Earth, representing the sun and moon, which are also the images of human beings; the human way in the middle of Heaven and Earth is formed by the interaction of Li and Kan, thus human beings come into being between Heaven and Earth. Once Heaven and Earth are reversed, Qian descends to the lower position, and human beings are thus generated. In terms of the Later Heaven, the position of Qian in the Earlier Heaven is replaced by Kan, located at the North Pole, and the hexagram Gen speaks of "Gèn qí bèi" (keeping the back still); the position of Kun in the Earlier Heaven is replaced by Li, located at the South Pole, and Xun has the image of "gāo" (height). The middle layer represents the human way, governed by Zhen and Dui, which corresponds to the statement in the Commentary on the Judgment of the Hexagram Guīmèi: "the great principle of Heaven and Earth" and "the beginning and end of human beings." This is the reason for the distribution of the six lines among the three extremes of Heaven, Earth, and Humanity.

分陰分陽，迭用柔剛，故《易》六位而成章。六位者，初爻二爻為地位，三爻四爻為人位，五爻上爻為天位。以乾卦例之，初九在地之下，故曰“潛”。九二地之上，故曰“田”。三爻為人之正位，故曰“君子”。四爻不當位，故曰“或”。五爻天位，故曰“在天”。上九在天之上，故曰“亢也”。

The "Commentary on the Hexagrams" says, "By dividing yin and yang, alternating the use of soft and strong, the Book of Changes forms its six positions." The six positions refer to the first and second lines as the position of earth, the third and fourth lines as the position of humanity, and the fifth and sixth lines as the position of heaven. Taking the Qian hexagram as an example: the initial line, which is below the earth position, is described in the line statement as "the dragon remains hidden and should not be used," referring to "hidden." The second line, which is above the earth position, is described as "the dragon appears in the field," referring to "field." The third line, which is the proper position of humanity, is described as "the gentleman remains diligent all day." The fourth line, which has left the proper position of humanity but has not yet reached the heaven position, is in an improper place, hence described as "perhaps leaping in the abyss," referring to "perhaps." The fifth line, which is the heaven position, is described as "the dragon soars in the heavens." The top line, which is above the heaven position, is described as "the dragon reaches its peak and incurs regret," referring to "peak."

位有一定，而爻則變動無常。學者必先知有定之位，定其為陰為陽，為上為下，而後爻之奇偶當否，可得而言也(偶居陰，奇居陽，為當，反之為不當)。分陰分陽，迭用柔剛。惟既濟一卦，為陰陽柔剛各當其位，故曰“既濟定也”。定則不動，不動則不生，而《易》道或幾乎息矣。

The positions are fixed, but the lines are changeable. Scholars must first clarify these fixed positions—determining whether they are yin or yang, and whether they are upper or lower—before they can discuss whether the lines are appropriate or not. Even numbers correspond to yin positions, and odd numbers correspond to yang positions, which is called "appropriate"; the reverse is called "inappropriate." The six positions are divided into yin and yang, alternating between soft and strong. Among the sixty-four hexagrams, only the hexagram "Already Achieved" has every yin and yang, soft and strong in their proper positions, so the "Zagua Transmission" says, "Already Achieved is stability." But once something is fixed, it no longer moves; without movement, there is no generation, and the way of the Book of Changes almost comes to a standstill.

故荀虞均以乾坤成兩既濟為凶。《序卦》曰：“《易》不可窮也，故受之以未濟終也。”此以陰陽之位言之也。若以用言，則一卦六爻，惟中四爻得用。初未用事，而上則失位。故《乾·上》曰：“高而無位”，《需·上》日“位不當也”。王弼曰“上下無位”者，指此也。

Therefore, Xun Shuang and Yu Fan both regarded the transformation of Qian and Kun into two instances of Ji Ji as an ominous sign. The Xu Guatuan says: "The Book of Changes cannot be exhausted, hence it is followed by Wei Ji to conclude." This is speaking from the perspective of the positions of yin and yang. However, if we consider it from the perspective of 'use,' among the six lines of a hexagram, only the middle four lines truly have a role: the first line has not yet come to the point of action, while the top line has already gone beyond its position. Therefore, the line at the top of Qian, line 9, says "high but without position" (the original text in Wenyan reads "honored but without position, high but without people"), and the line at the top of Xu, line 6, in the Xiangzhuan says "though not in the right position." Wang Bi's reference to the first and top lines as "without position" refers precisely to this.

《繫傳》曰：“上下無常，周流六虛。”六虛者，即初二三四五上之位也。爻實位虛，爻有上下，而位無變動。爻有柔剛，位有陰陽(一三五為陽，二四六為陰)，剛柔雜居(剛居陽，柔居陰，為當。或以剛居陰，柔居陽，則相雜而文生焉)，吉凶以著。《參同契》曰：“二用無爻位，周流行六虛。”二用者即九與六也。

The Great Treatise says: "Above and below have no constant position, flowing through the six voids." The term "six voids" refers to the six positions: initial, second, third, fourth, fifth, and upper. A line is real, while a position is void; a line has upper and lower parts and can move, but a position remains fixed. Lines are divided into flexible and strong, while positions are divided into yin and yang (the first, third, and fifth positions are yang positions, while the second, fourth, and sixth are yin positions); when strong and flexible lines are mixed within these positions (when a strong line is in a yang position and a flexible line is in a yin position, it is considered appropriate; but when a strong line is in a yin position and a flexible line is in a yang position, they are mixed and produce "wen," or culture), the manifestations of good fortune and misfortune emerge. The Zhou Changes Treatise on the Harmony of the Three says: "Two uses have no lines or positions, flowing through the six voids." Here, "two uses" refer to the "All Nines" used in the Qian trigram and the "All Sixes" used in the Kun trigram.

乾九坤六，上下升降，周流六虛，以成六十四卦。故觀象者不可僅觀所見之六爻。六爻之下，尚有六虛，皆與此所見之六爻相關。爻為飛，位為伏，實易辨而虛難知。必由實而究其虛，庶遇爻而知其用，於《易》之道思過半矣。

The nine of Qian and the six of Kun move up and down between the upper and lower parts, circulating through the six voids, thus generating the sixty-four hexagrams. Therefore, those who observe the images should not only focus on the six visible lines before them. Behind the six lines there are also the six voids, all closely related to the six lines in front. The lines are "flying," while the positions are "hidden"; the tangible is easy to recognize, but the intangible is difficult to understand. One must investigate the hidden aspects through the tangible ones in order to understand the function of a line the moment it appears. When one reaches this level, one has grasped more than half of the Way of the Book of Changes.

爻位六而卦有八，八卦於六爻，各有其當位之爻，曰正位。家人曰“男正位乎外，女正位乎內”，言九五與六二，則但以陰陽言也。陰陽以二五爻為得中得正，乾坤為卦之宗主，亦陰陽之純體。故乾以九五為正位，坤以六二為正位，坎離為乾坤之交(坎中之陽即乾爻，離中之陰即坤爻)。故坎離之正位，與乾坤同。震以初九為正位，艮以九三為正位，巽以六四為正位，兌以上六為正位。卦各有其正位，故六爻具六子之位。為圖如下：

The six lines of a hexagram are fewer than the eight trigrams. Each of the eight trigrams occupies a specific line within the six lines, known as the "correct position." The Commentary on the Judgment of the Hexagram of Family states, "The male holds the correct position outside, and the female holds the correct position inside," referring to the line nine at the fifth position and line six at the second position. This is based solely on the principle of yin and yang. Yin and yang consider the second line and the fifth line as the central and correct positions. The trigrams Qian and Kun are the primary trigrams of all others and are pure expressions of yin and yang, so Qian uses the line nine at the fifth position as its correct position, and Kun uses the line six at the second position as its correct position. The trigrams Kan and Li are formed by the combination of Qian and Kun (the central yang line of Kan is the line of Qian, and the central yin line of Li is the line of Kun), so the correct positions of Kan and Li are the same as those of Qian and Kun. In addition, Zhen uses the line nine at the beginning as its correct position, Gen uses the line nine at the third position as its correct position, Xun uses the line six at the fourth position as its correct position, and Dui uses the line six at the top as its correct position. Each trigram has its own correct position, so the six lines of a hexagram can accommodate the positions of the six subsidiary trigrams. The diagram is listed below:

端木氏曰：天地六爻，坎離既濟定位，五多功二多譽，位當也。離坎未濟居方，三多凶四多懼，不當位也。有當位而不正者，而正位未有不當者也。而《彖》、《象》之言正則以二五，故八卦惟乾坤坎離之為得中得正也。

Duanmu Guohu said: Among the six lines of heaven and earth, when Kan (Water) is above and Li (Fire) is below, they form the hexagram "Already Perfect" (Ji Ji). Each line is in its proper position, so the "Great Treatise" (Xì Cí) says "the fifth line brings many achievements" and "the second line brings much praise," precisely because they are in the correct position. Conversely, when Li (Fire) is above and Kan (Water) is below, they form the hexagram "Not Yet Perfect" (Wei Ji), with each line merely occupying its place, hence the saying "the third line brings many calamities" and "the fourth line brings much fear," because they are not in the correct position. Some lines may be in the correct position but still not qualify as "correct" (zheng). However, any line that is considered to be in the correct position is necessarily in the proper place. The "Commentary on the Judgment" (Tuàn Zhuàn) and "Image Commentary" (Xiàng Zhuàn) refer to "correct" (zheng) exclusively in terms of the second and fifth lines. Therefore, among the eight trigrams, only Qian (Heaven), Kun (Earth), Kan (Water), and Li (Fire) are both centered and correctly positioned.

六爻三極定位，天地定位。六爻上山澤，下雷風，中水火。六爻三極，下二初地爻地極，雷風恆，天地下極立心恆，坤地極立不易方，二初震巽爻是也，五上天爻天極，山澤損天上極員(損從員)，乾天恆無方，中日月斗，三人行，乾極與時偕行，五上艮兌爻是也。

The six lines of a hexagram belong to the three fundamental aspects of heaven, earth, and humanity, each with its own position, which corresponds exactly to what the "Commentary on the Changes" says, "Heaven and earth are positioned." Among the six lines, the top two lines belong to mountain and marsh (Gen and Dui), the bottom two lines belong to thunder and wind (Zhen and Xun), and the middle two lines belong to water and fire (Kan and Li). In terms of the three fundamental aspects: the second line and the first line are earth lines, belonging to the earth aspect. Thunder and wind combine to form the hexagram "Constant" (Heng). The lower extreme of heaven and earth is established by this "constant" — the "Image Commentary" of the hexagram "Constant" says, "The gentleman follows the principle of establishing a fixed position." Kun represents earth, and the earth extreme is precisely this "fixed position," referring to the Zhen and Xun on the first and second lines. The fifth line and the top line are heaven lines, belonging to the heaven aspect. Mountain and marsh combine to form the hexagram "Loss" (Sun). The upper extreme of heaven takes the meaning of "circle" ("Sun" includes the character "yuan"), Qian represents heaven, which is constant and has no fixed position, with the sun and moon and the Big Dipper suspended in the middle. The third line of the hexagram "Loss" says, "When three people walk, one is lost," and the "Commentary on the Judgment" of the hexagram "Loss" says, "Move in harmony with the times," referring to the Gen and Dui on the fifth and top lines.

四三人爻人極，水火既濟，天地中間人，於天地上下初終，首尾續終，中為人極。兼三才而兩之，定上下中極，四三坎離爻是也。六爻三極，天地南北居方，六爻辨物辨等。乾坤六十四卦終下坎北極，故曰“初難知”，曰“亦不知極也”。此《易》居方上下六爻三極之道也。

The fourth line and the third line are the human lines, belonging to the human extreme, and they combine water and fire to form the hexagram "Already Perfect." Humans are situated in the center between heaven and earth; they are in the middle of the beginning and end, the start and finish, of heaven and earth. In the beginning and end above and below heaven and earth, the connection and conclusion are made, and the middle part is the human extreme. "Combining the three elements and dividing them into two," thus determining the positions of upper, middle, and lower extremes, refers to the third and fourth lines, which are Kan (water) and Li (fire). The six lines are divided among the three extremes; heaven and earth are located in the north and south respectively, and the six lines are used to "distinguish things" and "distinguish ranks." The sixty-four hexagrams governed by Qian and Kun conclude at the lower Kan, which is the northern extreme. Therefore, the Great Treatise says, "At the beginning, it is difficult to know," and also says, "One does not know where it ends" (the original text says "also does not know the extreme"). This is the reason why the Book of Changes uses the six lines to determine positions and assign them to the three extremes.

右圖與前圖合觀，則知爻位之隱見變化，不但卦有飛伏交互，而爻之飛伏交互，亦與卦等也。向之說《易》家，能究心於爻位之義者甚鮮，而於爻位之分，更未有言之者。來知德氏，雖有八卦之正位一圖，而注中仍不能用，則以未明爻位之體用有別也。今合二圖而一之，並附以說，庶閱者可瞭然矣。

If you combine the above diagram with the previous one, you can understand the principle of the changing visibility of the lines (yao). Not only does the entire hexagram have hidden and revealed lines and mutual interaction, but each individual line also has hidden and revealed lines and mutual interaction, and their weight is equal to that of the entire hexagram. In the past, those who explained the Book of Changes rarely focused on the meaning of the line positions. As for how to divide the line positions, no one has ever discussed it. Lai Zhide of the Ming dynasty, although he drew a diagram of the correct positions of the Eight Trigrams, still found it difficult to apply in his annotations, because he did not clearly distinguish the 'essence' and 'function' of the line positions. Now, by combining the two diagrams and adding explanations, readers should be able to understand clearly.

六十四卦三百八十四爻，皆乾坤二用，周流六虛，至既濟而全卦之爻位相當。故曰“既濟定也”。爻位既明，二用斯章。然乾元用九，綱領全《易》。地道無成，坤之用皆乾之用也。乾無方無體，乾之用皆見於坤之用也。孔子《文言傳》曾發乾九用坤，坤六承乾之旨，已極詳備。大明終始，六位時成，乃非既濟而為未濟，其故可深長思矣。

There are sixty-four hexagrams and three hundred and eighty-four lines in total, all of which are governed by the principles of "use of all nines" and "use of all sixes" circulating through the six positions. When we reach the hexagram "Already Completed," each line corresponds perfectly, hence the "Commentary on the Miscellaneous Hexagrams" states, "Already Completed means stability." Once the positions of the lines are understood, the principles of the hexagrams "Heaven" and "Earth" become evident. However, "the use of nine in the Creative" is the overarching principle that governs the entire Book of Changes. The "Commentary on the Literary Meaning" of the hexagram "Earth" says, "The way of the Earth has no completion but is substituted by the finality of the Creative," indicating that the use of the Earth is actually the use of the Creative. Since the Creative has no fixed place or form, its use can only be seen through the use of the Earth. Confucius in the "Commentary on the Literary Meaning" has thoroughly elaborated on the principle that the nines of the Creative must be applied to the Earth and the sixes of the Earth must be supported by the Creative. The "Commentary on the Judgment" of the hexagram "Heaven" speaks of "great brightness from beginning to end, with the six positions formed in due time," yet the entire book ends not with "Already Completed" but with "Not Yet Completed," a point worthy of deep reflection.

乾六位，火本天親上。離五位，水本地親下。坎二位，而上下剛柔應位。山澤，艮上位兌三位。雷風，震四位巽初位。而上下六位，巽伏，震起，兌見，艮止，皆中離坎日月象。故曰“大明終始六位時成(下巽伏，上兌見，即坎象。下震起，上艮止，即離象。)。”

Heaven encompasses the six lines. Fire belongs to Heaven but is attached above, so Li is placed in the fifth position; Water belongs to Earth but is attached below, so Kan is placed in the second position—thus the yin and yang above and below are properly positioned. Mountain and marsh form a pair: Gen occupies the top line, Dui occupies the third line. Thunder and wind form a pair: Zhen occupies the fourth line, Xun occupies the first line. Thus, among the six positions above and below, Xun governs "concealment," Zhen governs "movement," Dui governs "appearance," and Gen governs "stillness," all surrounding the middle Li and Kan which represent the sun and moon. Therefore, the Commentary on the Judgment of Qian says, "Great brightness begins and ends, the six positions complete the time." (Below is Xun's concealment, above is Dui's appearance, together forming the image of Kan; below is Zhen's movement, above is Gen's stillness, together forming the image of Li.)

《上經》始乾坤終坎離，其往來卦十八。《下經》始咸恆終既未濟，其往來卦十八。十八為二九數，乃離坎二卦日月終始。離一九，寅數止戌。坎一九，申數正辰。此離坎二九，皆乾用九圓，日月為大明象。乾二九十八卦，《上經》始乾坤，終坎離，大明終始六位是也。

The Upper Classic begins with the trigrams Qian (Heaven) and Kun (Earth), and ends with Li (Fire) and Kan (Water). Within it, pairs of trigrams that come and go in relation to each other form eighteen groups. The Lower Classic begins with Xian and Heng, and ends with Ji Ji and Wei Ji, with pairs of trigrams that come and go in relation to each other also forming eighteen groups. Eighteen is the number obtained by multiplying two by nine, which corresponds exactly to the trigrams Li and Kan, which represent the sun and moon, their end and beginning. Li is paired with one nine: counting nine positions starting from Yin, it ends at Xu; Kan is also paired with one nine: counting nine positions starting from Shen, it ends at Chen. These two nines of Li and Kan are both the circular path of Qian's "All Nines." When the sun and moon come together, they form the image of "Great Brightness." The two nines of Qian make up eighteen trigrams. The Upper Classic begins with Qian and Kun and ends with Li and Kan. The phrase "Great Brightness begins and ends, the six positions are completed" refers precisely to this.

離坎二卦，南北終始，皆出入於震兌二卦，東西往來。震一九亥數止未，兌一九巳數止丑。此震一九離出震，兌一九坎出兌，皆乾用九圓。而上、下《經》各往來卦十八，始乾終既未濟，乾六位成而坤天下平。此離坎上下六位，南北居方卦大明日月也。

The trigrams Li (Fire) and Kan (Water) are positioned south and north respectively, governing the beginning and end. Their movement must pass through the trigrams Zhen (Thunder) and Dui (Lake), traveling between east and west. Zhen is paired with a nine: starting from the亥 position, counting nine steps leads to the 未 position. Dui is also paired with a nine: starting from the 巳 position, counting nine steps leads to the 丑 position. The nine associated with Zhen is the path by which Li departs from Zhen; the nine associated with Dui is the path by which Kan departs from Dui—both follow the circular path of Qian (Heaven) as expressed in "use nine." The upper and lower sections each contain eighteen pairs of trigrams in motion, with the entire sequence beginning with Qian and ending with Ji Ji and Wei Ji. Once the six positions of Qian are completed, Kun (Earth) achieves "the world is at peace." This is the reason why Li and Kan are placed in the upper and lower six positions, occupying the south and north respectively, symbolizing the sun and moon of the great day.

上下卦十八終始三十六，是為乾四九出入，南北上下為之極。其卦三十六，皆離坎首尾終之始之。而乾坤上下六十四卦六位，皆此離坎六位終始之。是乾用九乾圓象，而六十四卦以成終成始，乾大明終始，六位時成是也。

The upper and lower classics each contain eighteen, and when head and tail are combined, they make thirty-six. This is the four nines of Qian moving in and out, turning around, with north and south, up and down all based on this. These thirty-six groups of hexagrams are entirely opened and closed by Li and Kan at the beginning and end. The sixty-four hexagrams governed by Qian and Kun, and their six lines, are also concluded and begun by the six positions of Li and Kan. Thus, the "use of nine" in Qian is the image of the circular movement of the way of Qian. The sixty-four hexagrams are thus completed and begun through this. The "great brightness beginning and ending, the six positions formed in time" mentioned in the "Commentary on the Judgment" of Qian refers precisely to this.

六爻二極，尤重在人。天地之氣，以人而通。陰陽之道，以人而和。孔子贊《易》“立人之道”，以合乎天地之正。《京氏易傳》：孔子曰“陽三陰四，位之正也”，三者東方之數，日之所出也。四者西方之數，日之所入也。言日月終天之道。

The six lines of divination belong to the three ultimate principles, among which the most important is the human principle (the original text says 'two principles' but should be 'three principles'). The energies of heaven and earth depend on humans to connect them, and the way of yin and yang depends on humans to harmonize them. Confucius explained the Book of Changes by emphasizing 'establishing the way of humanity,' which is to enable humans to align with the middle and upright nature of heaven and earth. The Jing's Tradition of the Changes cites Confucius' words: 'Yang is three and Yin is four, which are the correct positions.' Three is the number of the East, where the sun rises; four is the number of the West, where the sun sets—this refers to the principle that the sun and moon traverse the sky throughout the day, moving around the heavens.

故《易》卦六十四，分上下象陰陽也。故奇偶之數取之於乾坤。乾坤者，陰陽之根本也。陰陽之道備著於坎離。坎離者，陰陽之性命也，而其樞要皆在於三四兩爻。於此求之，六十四卦之辭義可迎刃而解矣。圖附後。

Therefore, the sixty-four hexagrams of the Book of Changes are divided into the Upper and Lower Classics to symbolize the two aspects of yin and yang. Odd and even numbers are derived from Qian and Kun, since Qian and Kun are the fundamental principles of yin and yang; and the way of yin and yang is fully embodied in Kan and Li, because Kan and Li represent the nature and destiny of yin and yang—Qian and Kun provide the body of yin and yang, while Kan and Li manifest their function. And the key to all this lies in the third and fourth lines, which are the two positions where humans reside. By starting from here to seek understanding, the words and meanings of the hexagrams and their lines can be easily grasped. The diagram is attached below.

天地人六爻往復，天地上下，在人中爻三四迴轉。而上下天地爻，乃往復不窮。此乾坤六爻上下應位，二三四五同功異位，皆具此六爻往復中，皆在中人爻迴轉。人於天地上下，不見首尾，乃中間背脊，其道反覆不已。天地往復，其道不窮。孔子六十四卦大象，著六十四“以”字。“以”，古文作□，即結合上下兩卦往復迴轉之象也。

Heaven, Earth, and Humanity form a cycle of six lines that continuously turn and return. Heaven is above, Earth is below, and the entire structure relies on the third and fourth lines, which are in the middle and turn back and forth, enabling the lines above and below to move continuously without end. The mutual correspondence between the lines of the Heaven and Earth trigrams, as well as the "same function but different positions" mentioned in the Great Treatise, are all included within the continuous movement of the six lines, and they all revolve around the central line representing Humanity. Humanity is situated between Heaven and Earth, unable to see the beginning or the end, merely serving as the middle segment, its path continuously turning without cessation. The movement of Heaven and Earth is naturally endless. Confucius composed the Great Image Commentary for the sixty-four hexagrams, using the word "with" sixty-four times in a row. The ancient form of the character "以" (with), although missing in the original text, symbolizes the image of combining the upper and lower trigrams and turning back and forth.