ARTICLE
Reading I Ching's hexagrams and practicing T'ai Chi Ch'uan are both the art of living as yin and yang qualities in eternal motion.
As yin and yang principles alternate in their expression, different qualities of chi or vital energy have been combined and represented in Fu Hsi's trigrams (kuas). By gathering trigrams, we have I Ching's hexagrams.
Main and nuclear trigrams create the structure of hexagrams, and we can appreciate those combinations in the roots of T'ai Chi's moves as well. It means we'll find specific parts of the body set in motion and following a specific path according to trigrams and the interaction of elements.
As chi's qualities change, trigrams change too, so each I Ching's hexagram comes out from some other preceding one as well as from the nuclear one, being part of different sequences. Similarly, T'ai Chi displays forms by gathering sequenced moves. And each sequence is a form related to a particular I Ching's hexagram, capturing some aspect of the motion that the sign represents. As we see sequences of hexagrams, each form follows a previous one too, like a continuous river flowing on and on, creating series of forms.
The lines of hexagrams acquire a functionality depending on the quality of related energies and the position in their structure (see figure below). The structure is like a growing tree, like a human figure reaching Heaven from Earth. The same principle is present inside of T'ai Chi's moves, as well as all parts of the body (feet, legs, torso, arms, hands, head) must be coordinated with our mind and breath.
Main moves
There're thirteen postures in T'ai Chi Ch'uan, and are usually divided in two groups. The first 8th ones are associated to trigrams, forming the Pa Qua, and they're the ancient Heavenly arrangements: the Four Primary Hands associated to the 4 seasons (main directions), and the Four Corner Hands (in between the main ones).
| eight main moves | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| name | action | orientation | kua | |||||||||||||||||
primary hands |
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corner hands |
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The other group includes 5 steps of more extensive moves of feet and legs. These ones, as a whole, are referred to as the Five Elemental Phases of Change, as their are also known in I Ching:
| Five Elemental Phases of Change | ||
|---|---|---|
| step | action | element |
| chin | advance | metal |
| tui | widthdraw | wood |
| tso ku | look left | water |
| yu pan | look right | fire |
| chung ting | central balance | earth |
As seen, all of them indicate different types of actions and orientations to make a move. For instance: an is one of the main moves resembling the waxing and waning of the Moon. It suggests pressing forwards, from the West (k'an, water) and looking at the left for interacting (since tso ku is the step associated to water). Another main move is p'eng or pulling back. Associated to kun (earth), it evades incoming energy by adhering to it, although keeping one's own posture (since chung ting is the corresponding step for keeping balance), also bouncing energy back like a large inflated ball.
Considering trigrams along with their positions inside of an hexagram, we may find more ways to associate the moves above to other situations and purposes, and even visualize a sequence to create a form for those specific qualities and interactions. Finally, the name of the form usually emerges as a combination of all of those relations and associations.
| kuas & associations | |
|---|---|
| chien | heaven, metal, head, turning, strength, light |
| kun | earth, moon, belly, receiving, hidden |
| ken | mountain, soil, leg, arm, hand, fingers, wing, tiger, monkey, temple |
| li | fire, sun, heart, eye, arrow, weapon, bird, horse |
| sun | wind, wood, cock, left, softness, willow tree, forward and backward |
| chen | thunder, wood, feet, moving, awakening, embracing, cut and leave |
| k'an | water, abyss, danger, bow, wheel, ear, fetters, forehead, kidney, rain, snake |
| tui | lake, metal, mouth, joy, right, golden, goat, oval-shaped, hurt |
Forms
We can see all of the moves above in the sequences of each T'ai Chi's form, for instance: both an (pressing forwards) and p'eng (drawing back) in Grasp the Bird's Tail, and mainly cai (pulling down) in Needle at Sea Bottom or lie (splitting) in Slant Flying.
There're several schools teaching different form styles1 but the following references are based on the series Da Liu explains in his book T'ai Chi Ch'uan and I Ching. A Choreography of Body and Mind, published by Routledge & Kegan Paul (1981)2. The art starts with the form called The Beginning of the T'ai Chi Chu'an, associated to Chin Progress (35) of I Ching.
The Beginning of the T'ai Chi Ch'uan & Chin (35)
"Stand erect, hands easily at sides, palms back. Heels are together, toes slightly apart. Sinking slightly with soft knees, shift weight onto right foot and step with left foot, toes straight forward, to the side so that feet are shoulder-width apart. Shift weight to left, and pivot on right heel to move right toes straight forward. Distribute weight evenly on both feet. Let arms rise upward to shoulder height in front; draw wrists toward shoulders, fingers slightly strengthening. Continue the circular movement, gently pressing hands down to sides again. The body rises slightly with the arms and sinks again as arms returns to sides."
Main kuas in Chin are upper Li (sun) and lower Kun (earth, belly), symbolizing the sunrise, the fire star slowly rising higher and higher above the earth.
Nuclear kuas are upper K'an (water) and lower Ken (legs), symbolizing a standing position with a flow rising in parallel, as arms move from the belly upwards and downwards.
Crossed Hands & Ming (36)
"Shift weight to right foot, turn left toes inward, and open hands wide over head. Continue the arms down and forward and then up to cross at the wrists, chest level, palms in. The right foot pivots on toes and steps back to original straight-forward position."
Main kuas in Ming are upper Kun (earth, hidden) and lower Li (sun, heart), symbolizing the sun going down beneath the earth, as a fire remaining hidden behind hands before the chest.
Nuclear kuas are upper Chen (thunder, awakening) on Kun, and lower K'an (abyss, ear) on Li, symbolizing the dangers of raising what is hidden as hearing the light within.
Grasp Bird's Tail & Chien (1)
"The left hand reaches up, palm inward, to hold the bird's neck; the right hand moves down as though smoothing the long plumage of the bird's tail. Shift weight to left leg, pivoting on right heel, turn to right. Simultaneously, the right arm rises, elbow bent, with hand at shoulder height; the left arm rises and crosses body at waist level, palm up. The palms are approximately toward each other. Shift weight toward onto right foot and pivot on left toes to turn slightly to the left. Step left with left foot, straight forward and a little left. Simultaneously, the weight shifts forward on left foot, the left hand moves up to chin level, palm facing in; the right arm returns to right side, and as the body turns to left the right toes moves slightly inwards."
The form derives from Chien The Creative (1). 
The hands seem to grasp a bird's tail and head at the belly and chin of the practitioner. The bird is the dragon referred to in the nuclear lines of the main kuas (chien): the "field" (2°) is the abdomen, and the "heaven" (5°) is the chin.
Single Whip & Ko (49)
"The left hand resembles a single whip. The weight shifts to left leg, which slightly straigthens arms, while the right toes are lifted. Pivoting on the right heel, turn body 135°, arms still extended and moving with the body. Shift weight to right foot and pivot on left toes, turning body to face left. Simultaneously left arm moves across body at waist, palm up; right arm extends to right side of the body, fingers pinched, hand at shoulder height. The elbow points to the floor. With weight on right leg, pivot on left toes to turn left, facing forward, opening arms to front. Left foot takes a wide step forward and to the left. The weight moves to the left foot, the left hand turns palm over as it moves up to press with fingertips at throat height as the right toes move inward, pivoting on heel."
After 4 seasonal moves (Primary Hands), Earth has completed a revolution around the Sun. The form comes out of hexagram Ko Revolution (49) and follows the previous one (Grasp Bird's Tail, The Creative). 
Main kuas in Ko are upper Tui (metal, right) and lower Li (fire, horse), symbolizing a wide and wild expanding move. Nuclear ones are upper Chien (turning) on Tui, and lower Sun (wind, left) on Li, symbolizing a gentle 135° flowing motion in the opposite direction, like a soft wind of light.
For the full list of forms associated to I Ching's hexagrams inside of Liu's sequence, follow this link.
More about the art
T'ai Chi is considered as an "internal" martial art focused on developing chi (vital energy), by working in the dynamic relationship between yin and yang flows, reaching effortless action (wu wei), expressing naturalness and experiencing a no-mind state (wuxin).
Body and breath are coordinated in physical moves of deep relaxation rather than muscular tension, by attending inward and slowing the mind, as the pelvis moves and rotates in circles like the hub of a wheel, and arms and feet move as the spokes.
The art requires precise footwork and legwork, in form work, routines, and "push hands" exercises. But only when the body is balanced, aligned with gravity, it's possible to fully relax downwards through legs into the earth. Footwork develops five skills named wubu (wu = five + bu = step), which are quite relevante for body motion. The body follows steps to move, and only when the body can move to the right position (distance and angle), then the hand skills can work well.
There're six qualities of energies with a functional use: adhering, sticking, neutralizing, seizing, enticing, and issuing, always inside of T'ai Chi's endles quest for conservation of energy. Practitioners quickly learn how to read other people's moves, moments and intensities, and know what to do to keep themselves protected while looking for an opening. By constantly adapting moves to suit the environment and the person they meet, they develop the ability to adapt to ever-changing circumstances, since life is constantly changing at an ever-increasing tempo.
Practitioners also learn to put the full weight of their bodies behind every part of every move. Even if they are moving only one inch, they still have full power there. That power comes from connecting all the muscles together, not by isolating and training specific parts. As we see in I Ching's hexagrams, including the dynamic of all of the forces inside of a situation, is everything.
In the following video, master Yijiao Hong performs 24 forms of Yang Style as a single sequence of approximately 10', edited in a way we can appreciate moves from two simultaneous points of view.
1 The most practiced T'ai Chi Ch'uan styles are: Cheng,Yang, Wu Hao, Wu, and Sun.
2 Born in China, Da Liu has tought T'ai Chi Ch'uan for more than 20 years in US. Although he started learning in 1928 in East China with master Sun Lu-tang in the Sun style, he approached later the Yang style from the XIXth century, after travelling to Southwest Provinces. In the book of reference, all of the forms may be considered as a sequence representing the entire motion of the fire star from sunrise to sunset, between Chin and Ming of I Ching.
Sources: Wikipedia; Beyond Tai Chi forms and Tai Chi as a martial art, by Paul Chapman; Cloud Hands Taijiquan; T'ai Chi Ch'uan and I Ching. A Choreography of Body and Mind, book by Da Liu.
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