If you read about the I Ching for long, you will keep running into three terms: Tai Ji, Liang Yi and Si Xiang. In short, they are a chain of creation that describes how the universe takes shape. Tai Ji (the Supreme Ultimate) is the original, undivided whole. It gives rise to Liang Yi (the Two Forms, Yin and Yang), the Two Forms give rise to Si Xiang (the Four Images), and the Four Images give rise to the eight trigrams (Ba Gua). This is the I Ching's foundational cosmology, and the root of why there are 8 trigrams and 64 hexagrams. This guide walks through it one layer at a time.

What Are Tai Ji, Liang Yi and Si Xiang? Definition and Basic Idea

The I Ching is more than a way to cast a hexagram. Before there are any hexagrams, it offers a view of how the world comes to be.

At the core is a chain of successive births. Each layer splits the one before it in two, moving from simple to complex.

The order of the chain looks like this:

Layer	Name	Number of states
1	Tai Ji (the Supreme Ultimate)	1 (the undivided whole)
2	Liang Yi (the Two Forms)	2 (Yin, Yang)
3	Si Xiang (the Four Images)	4
4	Ba Gua (the eight trigrams)	8

The key point: this is the I Ching's foundational cosmology. Once you see the chain, the eight trigrams stop looking random. They come out of a clear logic, one step at a time.

Beginners often assume the trigrams are the starting point. In fact they are the result, sitting at the very end of this chain.

In short: Tai Ji, Liang Yi and Si Xiang are the first three layers of creation in the I Ching. From one undivided whole, things split into Yin and Yang, then into four states, which lay the ground for the eight trigrams and the 64 hexagrams.

How Creation Unfolds: From Tai Ji to the Eight Trigrams

Let us walk through each layer to see the logic.

Layer 1, Tai Ji. This is the original undivided whole, before anything has been separated. It is one complete state that has not yet split into two opposing sides. Tai Ji is the root of the whole chain.

Layer 2, Liang Yi. From Tai Ji, the world divides into two sides: Yin and Yang. These are the two most basic forces, opposite yet complementary. In the structure of a hexagram, they show up as the Yang line (a solid line) and the Yin line (a broken line). Liang Yi is the first split.

Layer 3, Si Xiang. Each of the Two Forms divides once more, producing four states known as the Four Images:

Image	Character
Greater Yang	Yang at full strength
Lesser Yin	Yin that is still young and weak
Lesser Yang	Yang that is still young and weak
Greater Yin	Yin at full strength

The Four Images show that Yin and Yang are not two rigid states. Each side comes in different degrees of strength.

Layer 4, Ba Gua. The Four Images give rise to the eight trigrams, the eight basic building blocks. At this point the foundation of the I Ching is complete, and these eight are the material from which the 64 hexagrams are built.

Looking back, you can see a very tidy pattern: one becomes two, two becomes four, four becomes eight. Every step is a doubling. That is why this chain is treated as the I Ching's foundational cosmology.

In short: Tai Ji is the original whole and gives rise to the Two Forms, Yin and Yang. The Two Forms give rise to the Four Images: Greater Yang, Lesser Yin, Lesser Yang and Greater Yin. The Four Images give rise to the eight trigrams, which complete the base for the 64 hexagrams.

The Eight Trigrams and the Five Elements

The trigrams are the last layer of the chain, and each one carries a natural image and an element from the Five Elements. This is the place where abstract cosmology connects to the system of generating and controlling relationships used when reading a hexagram.

Once the chain reaches the trigrams, each one is no longer abstract. Each is tied to a natural image and to one of the five elements.

Here are the eight trigrams with their elements:

Trigram	Image	Element
Qian	Heaven	Metal
Dui	Lake	Metal
Li	Fire	Fire
Zhen	Thunder	Wood
Xun	Wind	Wood
Kan	Water	Water
Gen	Mountain	Earth
Kun	Earth	Earth

One detail few people notice: Qian and Dui both belong to Metal, Zhen and Xun both belong to Wood, and Gen and Kun both belong to Earth. This is a common point of confusion for beginners.

Why do the elements matter? Because when a hexagram is read, the relationships between elements are part of the picture. In the generating order, Metal gives rise to Water, Water to Wood, Wood to Fire, Fire to Earth, and Earth back to Metal. In the controlling order, Metal controls Wood, Wood controls Earth, Earth controls Water, Water controls Fire, and Fire controls Metal.

Because the chain from Tai Ji to the trigrams exists, and each trigram carries an element, the I Ching has tools for analyzing a situation.

In short: The trigrams are the last layer of the chain, eight in all, and each belongs to one of the Five Elements. This is where abstract cosmology connects to the generating and controlling system used when reading a hexagram.

Putting It to Use: Learning the I Ching from the Root

Many newcomers jump straight to looking up what each hexagram means. They can recite the names of all 64 hexagrams without knowing why those hexagrams exist.

A steadier way to learn is to start from the root. Once you hold the chain of creation in mind, everything that follows makes more sense.

Understanding Liang Yi gives you the basis of Yin and Yang. It also explains why a hexagram is built from solid and broken lines, which is the foundation for reading any hexagram.

Understanding Si Xiang shows you that Yin and Yang come in many degrees, not just black and white.

Understanding where the trigrams come from means you no longer memorize the eight by rote. You see them as the natural outcome of repeated splitting.

One thing worth saying plainly: this chain is a way of looking at how things form and which way they tend to move. It is not a tool for declaring someone's fate. The I Ching speaks about timing and tendencies. It may help you understand a situation and give you something to think with when you are undecided, but it does not announce what will certainly happen.

Once you have this framework, the next step is to cast a hexagram yourself and observe. That is when you will see how the theory matches real experience.

In short: Understanding Tai Ji, Liang Yi and Si Xiang lets you learn the I Ching without rote memorization. You see why Yin and Yang exist, why there are eight trigrams, and you read a hexagram with a coherent frame instead of scattered pieces.

Conclusion

To sum up, here are the main points worth keeping:

• Tai Ji is the original undivided whole, and it gives rise to Liang Yi, which is Yin and Yang.
• Liang Yi gives rise to Si Xiang: Greater Yang, Lesser Yin, Lesser Yang and Greater Yin.
• Si Xiang gives rise to the eight trigrams, completing the base for building the 64 hexagrams.
• This is the I Ching's foundational cosmology, moving from one to two, to four, to eight.
• Understanding this chain lets you learn the I Ching with roots, not by rote.

The surest way to make it stick is to try it yourself. You can cast a hexagram on HOROS and see how Yin and Yang, the Four Images and the trigrams work together inside a real hexagram. Learning alongside doing is usually what stays in memory longest.