As Qi moves from Yin to Yang and back again, its flow is charted using three-line diagrams called Trigrams. Since there are two polarities, and three lines in a Trigram, there are a total of eight Trigrams. In Chinese, these Eight Trigrams are called Ba Gua.
The Ba Gua is a mathematical model of the universe, and combines a representation of directions, the Five Phases, Yin and Yang, numerology and the Eight Trigrams into one image. All classical Feng Shui principles originate from or are related to the Ba Gua.
In a Gua, Yin is represented by a broken line, and Yang is represented by a whole line. Each line of a Gua is called a Yao.
Two lines can be grouped together to form the Si Xiang, or Four Images. A pair of Yin Lines is known as Greater Yin. A Yang line on top of a Yin line gives us Lesser Yang. A pair of Yang lines forms Greater Yang. Finally, a Yin line on top of a Yang line yields Lesser Yin.
The Four Images are used to describe basic changes over time. They represent rhythms of nature, like the phases of the moon, the four seasons and the stages of life. A full moon demonstrates Greater Yang. As it wanes and reaches the first quarter it demonstrates Lesser Yin. At the new moon phase, it reaches Greater Yin, then it waxes until it gets to the last quarter, where it demonstrates Lesser Yang.
Similarly, summer (and the summer solstice) represents Greater Yang; autumn (and the autumnal equinox) represents Lesser Yin; winter (and the winter solstice) represents Greater Yin; and spring (and the spring equinox) represents Lesser Yang. The presence of the astronomical associations with the seasons indicates that the Four Images may have originated as astronomical markers of the four mega-constellations in relation to the celestial equator. These mega-constellations are the Dragon, Tiger, Turtle and Bird.
The Four Images can also be correlated to the He Tu as depicted in the diagram below. Click the diagram to download full-size. Here, the Four Images gain associations with the Five Phases. 7 and 2 represent Fire and the south direction. This is associated with Greater Yang. 4 and 9 represent Metal and the west. This is associated with Lesser Yin. 1 and 6 represent Water and the north. This is associated with Greater Yin. Finally, 8 and 3 represent Wood and the direction of east. This is associated with Lesser Yang.
Adding another line to each of the Four Images brings us to the Eight Trigrams. The diagram above correlates to the Eight Trigrams in the Early Heaven Sequence as shown below. Click to download full-size. Here, the concept of change is expanded further. Each line is associated with a member of the Cosmic Trinity. The bottom line represents earth; the middle line represents mankind; and the top line represents heaven.
Two of the Trigrams are pure Yin or Pure Yang. The rest are made up of a mixture of Yin and Yang. Trigrams with one Yin line are considered Yin, while Trigrams with one Yang line are considered Yang.
Qian (pronounced “chee-en”) is made up of all Yang lines.
Dui (pronounced “dew-ee”) is made up of a Yin line on top of two Yang lines.
Li (pronounced “lee”) consists of a Yin line between two Yang lines.
Zhen (pronounced “jurn”) is composed of two Yin lines above one Yang
line.
Kan (pronounced “kahn”) is one Yang line between two Yin lines.
Xun (pronounced “soon”) is comprised of two Yang lines above one Yin
line.
Kun (pronounced “koon”) is made up of all Yin lines.
Finally, Gen (pronounced “genn”) is composed of one Yang line above two Yin lines.
Chad Dunham
8-White Star Feng Shui