In the I Ching two three-line kua, or trigrams as they are called in the West, are combined to make a hexagram.  There are eight trigrams altogether, each named for a specific attribute, and associated with specific corerspondences. The combination of 8 x 8 trigrams result in the sixty four hexagrams, and insights into the nature of a hexagram can be deduced by studying it's component trigrams.

It is traditionally stated that the trigrams were developed first, and then the hexagrams from them.  I read somewhere, it may have been the Russian researcher Iulian K. Shutskii (Researches on the I Ching (Bollingen Series LXIL 2, Princeton University Press), that the reverse is the case, the hexgrams were developed first, and the trigrams later as a simplification or idealisation of the original hexagrams. However, this theory, although intersting, even persuasive, is not yet proven.

To study the Yi Jing, we must have a good understanding of what Pa Kua is. How did it come about? Why do we called it Pa Kua? If we have a clear idea on Pa Kua, we will get a better grasp on the subject.

What is Pa Kua? In the direct translation, Pa means eight (8) and Kua means suspending or hanging. It is like hanging a picture on the wall, in the living room, to observe it. Actually, in Yi Jing, Pa Kua is telling us there are eight phenomena among us, suspending in the Universe. Instead calling them the eight phenomena, they were referred as Pa Kua.

Our ancestors were studying the Universe by observing the suspended objects (phenomena) on the universal wall. To the best of their abilities, they saw eight basic images. These images are sky, earth, thunder, wind, fire, water, mountain, and marsh (body of water).

Before any languages wre written , one of our ancestors developed a line symbol system to repsent the universal images. He used a solid line to represent motion, elevation, harden and strong images. And a broken line to represent motionless, depression, soft and weak images. In later times, people called the solid line yang and the broken line yin.

The two different lines were stacked (bigram) and this only has four combinations. The bigram cannot use to represent any images and serves no purposes. It is only a passive development stage. However, by adding one yang or yin line to the bigram it will become Pa Kua. Each Kua was assinged an ancient name to it. For simplicity and avoid confusion, these names will not mention here.

The following is a decription of each of the Pa Kua symbols:

1. Sky

Three solid lines were used to symbolize sky. The sky is strong and has divine power to provide infinite space to accommodate all. Using three solid lines to represent the sky is very the appropriate for its supreme being.

2.Earth

Three broken lines are used to symbolize earth. The earth is a gigantic object. It is a supporting body for human life and a burial ground for death. It is considered soft and receptive, because it can take a lot of punishments with tolerance.

3. Thunder

Two broken lines on top a solid line symbolize thunder. The two broken lines on top have the image of lighting and the bottom solid line symbolizes elevation. Thus, the image is lighting striking on the top of a mountain.

4.Wind

Two solid lines on top a broken line symbolize wind. The two solid lines represent the sky and energy. The broken line represents earth. Thus, this image is the sky and energy approaching earth. The wind is invisible and we can only justify its existence by observing the moving tree tops.

5. Water (Moon)

A solid line in between two broken lines symbolize water. The two broken lines represent the depression of earth (river banks). The solid line in the middle represents motion. This creates the image of water flowing in a river. In addition, this kua also represents the moon.

6. Fire (Sun)

A broken line inbetween two solid lines symbolize fire. The two solid lines indicate the movement of fire. The broken line is the center of the fire which is still. In addition, this kua also represents the Sun.

7. Mountain

A solid line on top of two broken lines symbolize mountain. The solid line represents elevation and the bottom two broken lines represent earth. Thus this image is a mountain elevated above the earth.

8. Marsh

A broken line on top of two solid lines symbolize marsh. The top broken line is water and the bottom two solid lines is sky. If we are looking down at a body of water anywhere on earth, we will see the reflected sky below the water surface. This seems to be a logical way to symbolize the Marsh Kua.

The are two version of Pa Kua arrangements. The first one is called the Earlier Version Pa Kua and the other is called the Later Version Pa Kua. In the western world, people referred as the Earlier Heaven Pa Kua and the Later Heaven Pa Kua. However, I must point out that this was an error of translation.

The reason is that in the Chinese language, one does not say either "Earlier Version Pa Kua" or "Later Version Pa Kua", but rather "Earlier Days Pa Kua" and the "Later Days Pa Kua", respectively. The terms earlier days and later days are used to distinguish the two different versions. Unfortunately, the day character has the same meaning as day, sky, and heaven. For a person not familiar with the language, it is easy to mistranslate the "day" character as "heaven". By the way, heaven is heaven, do we have two heavens, an earlier heaven and a later heaven? It does not make sense to anyone. There is only one heaven.

The Earlier Version Pa Kua

The Earlier Version Pa Kua indicates the overall structure of the Universe. One may notice that the kua opposite each other are the complement of each other. The sky kua (three solid lines) opposite to earth kua which has three broken lines. Notice their special arrangements. Wind is opposite of Thunder; Fire is opposite of Water; Mountain is opposite of Marsh.

The Later Version Pa Kua

The Later Version Pa Kua was rearranged to make it more effective for other interpretations, such as Feng Shui.

The following table lists the 8 trigrams or Pa Kua. Two trigrams combine to form a single hexagram, with the combinations of 8 x 8 the result is a  total of 64 hexagrams altogether.  Although it is usually thought that the trigrams preceeded the hexagrams, the reverse would seem to be the case - the hexagrams were developed (invented? discovered?) first, and the trigrams proposed later as a sort of simplification.  Although the trigrams are widely used in Chinese cosmology and philosophy, they do not seme to have the archetypal significance of the hexagrms.  They are however useful as an aid (one of a number of aids) to the interpreting of the meaning of the hexagrams.

trigram	chinese name	english transliteration	meaning	graphic symbol	family relationship (polarity)
	ch'ien	the creative	spirit, creative or fertilising seed, stength, circular	heaven	father (mature yang)
	chen	the arousing	coming into manifestation, sudden movement	thunder	eldest son (immature yang)
	k'an	the abysmal	generally misfortune (spirit (middle yang line)  trapped in matter (two yin lines)	water, the moon	middle son (immature yang)
	ken	keeping still	resting, inert	mountain	youngest son (immature yang)
	k'un	the receptive	receptivity, vessel, matter, devoted, yielding, square	earth	mother (mature yin)
	sun	the gentle	penetrationg	wind, wood	eldest daughter (immature yin)
	li	the clinging	light-giving, also clinging (spirit on either side of matter)	fire, the sun	middle daughter (immature yin)
	tui	the joyous	joyful	lake, body of water	youngest daughter (immature yin)

THE EIGHT TRIGRAMS - By R.C.L - An Excerpt from Chapter Eight of Laws of Wisdom - a personal interpretation of the eight trigrams