Introduction to the I Ching: What are the Eight Trigrams?

Introduction

The Eight Trigrams (Ba Gua) are the core symbolic system of the I Ching (Book of Changes) and one of the most ancient and profound conceptual tools in all of Chinese culture. Using the simplest of lines, they construct a language for interpreting the operational laws of all things in the universe. For those new to the I Ching, understanding the trigrams is like obtaining the first key.

1. From Yin-Yang to the Eight Trigrams

The starting point of the Eight Trigrams is Yin and Yang.

The ancients observed nature: day and night, cold and warm, male and female, movement and stillness... It seemed that all things exist in a state of unity of opposites. Therefore, they used an unbroken line "—" to represent Yang, and a broken line "--" to represent Yin. These are the Two Forms (Liang Yi).

Building upon the Two Forms, adding one more level introduces another dimension:

  • Two Forms (Yin, Yang) → 2 combinations
  • Adding one line (Yao) to each of the Two Forms → Four Symbols (Old Yang, Young Yin, Young Yang, Old Yin) → 4 combinations
  • Adding one more line to each of the Four Symbols → Eight Trigrams → 8 combinations

This is what is stated in the I Ching - Appended Judgments (Xi Ci Zhuan):

"In the Changes there is the Great Ultimate (Tai Ji). This generates the Two Forms. The Two Forms generate the Four Symbols. The Four Symbols generate the Eight Trigrams."

Each of the Eight Trigrams is composed of three lines (Yao)—arranged from bottom to top, they symbolize the Three Powers (San Cai): Earth, Humanity, and Heaven.

2. Names, Symbols, and Meanings of the Trigrams

Each trigram has its own name, form, and symbolism. Zhu Xi of the Song Dynasty compiled a "Song for Remembering the Trigrams" (Ba Gua Qu Xiang Ge) for easier memorization:

| Name | Pinyin | Symbol | Mnemonic | Nature | Family | Attribute | |---|---|---|---|---|---|---| | Qian | qián | ☰ | Three unbroken | Heaven | Father | Strength | | Kun | kūn | ☷ | Six broken pieces | Earth | Mother | Receptivity | | Zhen | zhèn | ☳ | Bowl facing up | Thunder | Eldest Son | Movement | | Xun | xùn | ☴ | Broken below | Wind | Eldest Daughter | Penetration | | Kan | kǎn | ☵ | Full in the middle | Water | Middle Son | Abyss | | Li | lí | ☲ | Hollow in the middle | Fire | Middle Daughter | Clarity | | Gen | gèn | ☶ | Bowl overturned | Mountain | Youngest Son | Stillness | | Dui | duì | ☱ | Open above | Lake | Youngest Daughter | Joy |

Mnemonic Details:

  • Qian San Lian (Three Unbroken): Three unbroken Yang lines ☰, like the sky, whole and unbroken.
  • Kun Liu Duan (Six Broken Pieces): Three broken Yin lines ☷, like the earth,包容承载 (accommodating and supporting).
  • Zhen Yang Yu (Bowl Facing Up): Resembles an upward-facing bowl ☳ (two broken Yin lines above, one unbroken Yang line below).
  • Xun Xia Duan (Broken Below): Broken below ☴ (two unbroken Yang lines above, one broken Yin line below).
  • Kan Zhong Man (Full in the Middle): Full in the middle ☵ (broken Yin lines on both sides, unbroken Yang line in the middle).
  • Li Zhong Xu (Hollow in the Middle): Hollow in the middle ☲ (unbroken Yang lines on both sides, broken Yin line in the middle).
  • Gen Fu Wan (Bowl Overturned): Resembles an overturned bowl ☶ (one unbroken Yang line above, two broken Yin lines below).
  • Dui Shang Que (Open Above): Open above ☱ (two unbroken Yang lines below, one broken Yin line above).

3. Arrangements of the Trigrams: Prenatal and Postnatal

There are two classic arrangements of the trigrams:

Prenatal (Xian Tian) Arrangement (Fu Xi Bagua)

Traditionally attributed to Fu Xi, this reflects the inherent order of the universe:

  • Qian (Heaven) above, Kun (Earth) below.
  • Li (Fire/Sun) on the left (East), Kan (Water/Moon) on the right (West).
  • Dui (Lake) upper left, Xun (Wind) upper right, Zhen (Thunder) lower left, Gen (Mountain) lower right.

The Prenatal arrangement deals with Opposition and Balance—Heaven and Earth take their positions; Mountain and Lake exchange energy; Thunder and Wind arouse each other; Water and Fire do not combat each other. It is static, oppositional, and ontological.

Postnatal (Hou Tian) Arrangement (King Wen Bagua)

Traditionally attributed to King Wen of Zhou, this reflects the cyclic flow and transformation of all things:

  • Li (Fire) in the South, Kan (Water) in the North.
  • Zhen (Thunder) in the East, Dui (Lake) in the West.
  • Xun (Wind) in the Southeast, Kun (Earth) in the Southwest, Qian (Heaven) in the Northwest, Gen (Mountain) in the Northeast.

The Postnatal arrangement deals with Process and Cycle—The Emperor (vital energy) emerges from Zhen, becomes orderly in Xun, becomes visible in Li, is devoted to service in Kun, speaks joyfully in Dui, struggles in Qian, labors in Kan, and completes its work in Gen. It is dynamic, cyclical, and applied.

Simple Understanding: The Prenatal arrangement is the "Way of Heaven," while the Postnatal arrangement is for "Human Application." Practices like Feng Shui, destiny analysis (Bazi), and Traditional Chinese Medicine primarily use the Postnatal arrangement.

4. How to 'Calculate' with the Trigrams?

By superimposing the eight trigrams upon themselves (8x8), the 64 Hexagrams of the I Ching are formed. Each hexagram consists of six lines (the upper three lines are the "Upper Trigram" or "Outer Trigram," the lower three are the "Lower Trigram" or "Inner Trigram").

During divination, methods like yarrow stalk manipulation (shé shī) or coin tossing are used to determine the Yin or Yang nature of each line, ultimately resulting in a six-line hexagram. One then consults the corresponding Hexagram Statement (Gua Ci) and Line Statements (Yao Ci) in the I Ching to gain insight.

But the I Ching is far more than a divination tool—it is a philosophical system dealing with the laws of change and the wisdom of timing and position.

5. How Can Beginners Get Started?

  1. Memorize the Eight Trigrams: Use the "Song for Remembering the Trigrams" to first recognize and draw them.
  2. Understand the Symbolism: The natural phenomena corresponding to each trigram are the most intuitive entry point—Heaven, Earth, Thunder, Wind, Water, Fire, Mountain, Lake.
  3. Learn the Arrangements: Draw a Postnatal Bagua diagram and refer to it often.
  4. Read a Good Book: Start with recommended texts like Zhou Yi Yi Zhu (Huang Shouqi, Zhang Shanwen) or Nan Huai-jin's Discourses on the I Ching.
  5. One Hexagram a Day: Study one hexagram each day, aiming for gradual understanding rather than quick mastery.

Conclusion

The trigrams may seem simple—just eight symbols, three lines each—but what they carry is the fundamental understanding of the universe, life, and change developed by the Chinese people over millennia. They are not mystical speculation, but a way of thinking about the world: all things are in a state of change, and behind this change, there are patterns to be discerned.

Understanding the trigrams means you understand half of the I Ching. The other half lies within the 64 hexagrams, and even more so, within life itself.

Written on May 19, 2026