Yin and yang are symbolically represented by lines.
A solid line represents a yang quality. A broken line represents a yin quality.
Using one line to graphically illustrate the different qualities falls short when trying to describe different types of natural phenomena. That’s where the trigrams and hexagrams come in.
By adding another line to the existing yin and yang lines gives birth to four different combinations. These correspond with the directions of the compass.
Utmost yin corresponds with the north, utmost yang corresponds with the south, yin within yang corresponds with the east, and yang within yin corresponds with the west.
Adding another line gives birth to the eight trigrams. The eight trigrams symbolize the eight natural phenomena: sky, earth, thunder, wind, water, fire, mountain and lake.
To learn the different trigrams the Three Character song can be used. It goes like this.
Qian heaven’s continuous three
Kun earth’s broken six
Zhen thunder’s wide-mouthed jar
Gen mountain’s bowl overturned
Li flame’s center is empty
Kan water’s center is full
Dui lake’s top is lacking
Sun wind’s bottom is broken
Each trigram has a meaning that is useful for Chinese Medicine.
Heaven, the Creative
Creativity, Heaven, Light, Warmth, Sun, Drying, Male, Utmost Yang
Earth, the Receptive
Receptive, Earth, Dark, Cold, Female, Utmost Yin, Source of Myriad things
Thunder, the Arousing
Arousing, Shaking, Triggers Change, Destruction and Construction, Earth on top of Heaven. Earth affecting Heaven
Mountain, Keeping Still
Stillness, Earth towering towards Heaven, Forever
Fire, the Clinging
Consuming energy, Clinging, Radiance, Breaking Free, Departing
Water, the Abysmal
Abysmal, Gorge, Downward, Yang moves yin
Lake, the Joyous
Joyous, Open, Creation below Change
Wind, the Gentle
Gentle, Obedient, Ground, Heaven affects Earth
Richard Wilhelm has this to say about the trigrams.
From, The I Ching on Early-heaven Xiantian
Heaven and earth determine the directions. The forces of mountain and lake are united. Thunder and wind arouse each other. Water and fire do not combat each other. Thus are the eight trigrams intermingled.
He describes the trigrams in pairs.
Qian heaven Creativity is paired with Kun earth Receptive
Zhen thunder Arousing is paired with Gen mountain Stillness
Li flame Consuming is paired with Kan water Abysmal
Dui lake Open is paired with Xun wind Gentle
Zhen and Gen have two yin lines combined with one yang line, Dui and Sun have two yang lines combined with one yin line.
Utmost yin and utmost yang are paired with mixed yin and yang. Li flame has yin in yang, and Kan water has yang in yin.
The trigrams can also be organized by their yin and yang qualities.
From the Classic, True Transmission of Medical Principals, Of Qian and Kun’s six children, the youngest and the oldest are all imbued with biases of Qian and Kun. Only the middle male and female have received their natural disposition from Qian and Kun. People receive the cardinal qi of their original nature from heaven and earth and thereby come to life. Kan and Li therefore act as the root of establishing life.
Heaven and earth give birth to six children.
The three male offspring, Zhen thunder, Kan water, Gen mountain.
The three female offspring, Sun wind, Li flame, Dui lake.
Kan and Li are the most important because they act as the root of establishing life.
Kan water is a yang child of heaven and earth. Its original nature is yang. It is the yang nature of water that brings it to life.
Li flame is a yin child of heaven and earth. Its original nature is yin. It is the yin nature of fire that allows the flame to burn.