Early Heaven bagua: the Fu Xi arrangement of the eight trigrams

The Early Heaven arrangement (先天八卦, xiantian bagua) places the eight trigrams in a circle so that every trigram faces its exact opposite: Heaven across from Earth, Fire from Water, Thunder from Wind, Lake from Mountain. Tradition attributes it to the sage Fu Xi, but the diagram as we know it was published by the Song philosopher Shao Yong (邵雍, 1011–1077), who also gave the trigrams the numbers 1 to 8 that Plum Blossom divination still uses.

The text behind the diagram

The arrangement is built on one sentence of the Shuogua (說卦), the commentary on the trigrams among the Ten Wings:

天地定位，山澤通氣，雷風相薄，水火不相射，八卦相錯。

"Heaven and Earth establish their positions; Mountain and Lake exchange their breath; Thunder and Wind stir each other up; Water and Fire do not quench each other; the eight trigrams intermingle." The sentence names four pairs, and in each pair the trigrams are line-for-line opposites. Shao Yong read it as a description of a circle in which the pairs sit across from one another. The Shuogua never draws that circle; it is an interpretation, and a powerful one.

If you need a refresher on the trigrams themselves, start with the eight trigrams or the trigram pages.

The circle

Chinese diagrams put south at the top. In the Early Heaven circle:

• Qian ☰ (Heaven) is at the top, south; Kun ☷ (Earth) at the bottom, north.
• Li ☲ (Fire) is in the east (left); Kan ☵ (Water) in the west (right).
• Dui ☱ (Lake) is south-east, facing Gen ☶ (Mountain) in the north-west.
• Zhen ☳ (Thunder) is north-east, facing Xun ☴ (Wind) in the south-west.

Read it as a cycle of yin and yang. Start at Zhen in the north-east, with one yang line at the bottom, and climb the left side through Li and Dui to Qian: yang grows until it is complete. Then start at Xun in the south-west, with one yin line at the bottom, and descend the right side through Kan and Gen to Kun: yin grows until it is complete. It is the same picture as the yin–yang symbol, drawn in lines instead of curves.

Shao Yong's numbers

Shao Yong numbered the trigrams in the order 乾一、兌二、離三、震四、巽五、坎六、艮七、坤八: Qian 1, Dui 2, Li 3, Zhen 4, Xun 5, Kan 6, Gen 7, Kun 8. Around the circle, the numbers 1 to 4 run down the left side from Qian to Zhen and 5 to 8 run down the right side from Xun to Kun, and every opposite pair adds up to nine.

He derived this order from a line of the Xici: 易有太極，是生兩儀，兩儀生四象，四象生八卦 — "Change has the Great Ultimate; it gives rise to the two modes; the two modes give rise to the four images; the four images give rise to the eight trigrams." Split yang and yin, then split each again, and again, always putting yang first, and you get exactly Qian, Dui, Li, Zhen, Xun, Kan, Gen, Kun. Shao Yong applied the same doubling to all sixty-four hexagrams, starting from Qian and ending with Kun.

The binary pattern

Write a solid line as 1 and a broken line as 0, read from the bottom up, and the sequence is a countdown in binary: Qian 111 (seven), Dui 110 (six), Li 101 (five), Zhen 100 (four), Xun 011 (three), Kan 010 (two), Gen 001 (one), Kun 000 (zero). Shao Yong's number is simply eight minus that value.

This is why the arrangement is famous in the West. In 1701 the Jesuit Joachim Bouvet sent Gottfried Wilhelm Leibniz diagrams of Shao Yong's hexagram order. Leibniz had already worked out binary arithmetic, and he saw that the order matched it; he discussed this in his 1703 essay on binary numbers. The story, and what it does and does not prove, is told in Leibniz and the I Ching.

How Early Heaven differs from Later Heaven

The other classic arrangement is Later Heaven (後天), attributed to King Wen. The two use the same eight trigrams for different purposes:

• Early Heaven is about structure. Opposites face each other in perfect balance: a timeless diagram of how yin and yang are composed.
• Later Heaven is about process. The trigrams follow the seasons and directions in the order things actually happen: Zhen in the east for spring, Li in the south for summer, Dui in the west for autumn, Kan in the north for winter.

No trigram keeps its place: Qian moves from south to north-west, Li from east to south, Kan from west to north, and so on. A common saying sums up the relationship: 先天為體，後天為用 — "Early Heaven is the substance, Later Heaven the function." When you see a bagua diagram, check where Qian is: at the top means Early Heaven; in the north-west corner means Later Heaven.

How old is it really?

Song scholars presented the diagram as Fu Xi's own, transmitted secretly through Daoist teachers from Chen Tuan (陳摶) to Shao Yong. Zhu Xi printed it at the head of his Zhouyi Benyi, which made it standard for centuries. Qing scholars such as Hu Wei (胡渭) argued at length that these diagrams were Song creations with no basis in the early texts. Most historians now agree: the Shuogua sentence is old, the circle and the numbering are Shao Yong's. That makes it no less useful, but it is fair to know whose idea you are using. The debate belongs to the larger quarrel between the image-and-number and meaning-and-principle schools.

Where Early Heaven is used

• Plum Blossom numerology. The method attributed to Shao Yong turns numbers into trigrams with the Early Heaven sequence: a remainder of 1 is Qian, 2 is Dui, and so on to 8 for Kun. See Plum Blossom numerology; when the method turns to directions, it switches to Later Heaven.
• Hexagram order and symmetry. Shao Yong's square and circle of sixty-four hexagrams lay out every opposite pair, such as Tai and Pi, in a single geometric pattern.
• Feng shui and emblems. Many feng shui schools treat Early Heaven as the underlying pattern and Later Heaven as the working map, and the octagonal bagua mirrors hung over doorways often show the Early Heaven order.

Using it when you read

For an ordinary coin cast you do not need the Early Heaven circle at all: you read the hexagram text. It becomes useful in two moments. First, when you read a hexagram's two trigrams, the circle reminds you of each one's opposite, which is often the quality the situation lacks. Second, if you cast by numbers, as in Plum Blossom, memorise the sequence Qian 1, Dui 2, Li 3, Zhen 4, Xun 5, Kan 6, Gen 7, Kun 8 — it is the key that turns any number into a trigram.