Being a Taijiquan  student and teacher, I, of course, can say something about what Taiji is. Being involved in Taijiquan, invariably on many occasions I have also heard of the term Wuji. However, in spite of the fact that I have heard of Wuji many, many times and have come across this term and its definition in numerous Taiji books I have read, I still was never able to understand what the term Wuji really means and the relationship between Taiji and Wuji. So recently I thought to myself why don’t I use my own knowledge from 14 years of studying Taiji to try to understand what Wuji is and the relationship between Taiji and Wuji. Instead of relying on what others have written about this subject, why don’t I try to explain this subject using my own words, knowledge, and experience. This article describes the outcome of that thinking process.
Taiji and Wuji: The word Taiji (太極) in Chinese means “Great Poles” or “Grand Ultimate.” The word Wuji (無極) in Chinese means “without pole” or “without opposite” or “the ultimate of nothingness.” Taiji was invented as a martial art; so in this article I try to explain Taiji and Wuji from a martial arts perspective, instead of from a philosophical perspective. In Taiji one tries not to oppose an opponent’s attacking force head on, because then whoever is bigger and stronger will win. The opponent’s attacking force is called a Yang force, usually associated with a strong force. Instead of opposing the opponent’s attacking force head on, the defender first deflects the attacking force by applying a small force at a small angle from the attacking direction; this can successfully deflect the attack (i.e., an effective defensive movement) because this small deflecting force has a component that is perpendicular to the attacking direction and the attacking force has no component along this direction . This small deflecting force is called a Yin force. Furthermore, the component of this Yin force that is along the direction of the attacking force, if enlarged, can use the attacker’s momentum to get him off balance (i.e., also an effective offensive movement). The fact that the Yin force is a defensive movement that also can lead to an offensive movement means that there is a component of Yang in Yin (and vice versa).
In addition, Yang and Yin are not static, and they evolve into each other. For example, in the above example, when the opponent senses that his attacking force has been deflected and he is being pulled off balance, he changes direction and tries to pull back and move his attacking arm in the opposite direction. In that instance, he changes his attacking Yang force into a retrieving Yin force. On the other hand, upon sensing that the attacker is trying to retrieve his arm and move in the opposite direction, the defender also changes direction and attacks with a Yang force along the direction of his opponent’s retrieving movement. Thus, the original attacker now becomes the defender, and the original defender now becomes the attacker, with corresponding changes of Yang and Yin forces.
In the above discussion, the attacking Yang force of the opponent and the complementary Yin force of the defender can be considered as two opposite poles. Similarly, the retrieving Yin force of the opponent and the now attacking Yang force of the original defender can also be considered as two opposite poles, except that the poles associated with the two people have reversed. Furthermore, in order for each person to be able to change direction quickly, there has to be a small component of the Yin force residing in the Yang force. Likewise, there has to be a small component of the Yang force residing in the Yin force. The revolving nature of Yang and Yin and the fact that each contains a small component of the other are clearly illustrated in the traditional Taiji symbol:
The black and the white parts represent, respectively, the Yang force and the Yin force. If you rotate the above diagram, the Yang force becomes the Yin force, and the Yin force becomes the Yang force. Saying it in another way, the Yang force tapers to a Yin force, and the Yin force tapers to a Yang force. Furthermore, residing in the Yang force (the black fish-like part of the diagram) is a small Yin force (the white dot), and residing in the Yin force (the white fish-like part of the diagram) is a small Yang force (the black dot).
This simple discussion of a small set of movements already captures the essence of Taiji, and it is already reflected in just the second form, “Wild Horse Shakes Its Mane,” in one of the simplest Taiji form sets, the Simplified Yang Style 24 Form Set.
If “Wild Horse Shakes Its Mane” is Form #2 in the Simplified Yang Style 24 Form Set, what is Form #1 “Opening Form”? The beginning part of “Opening Form” is when the Taiji practitioner just stands upright with hands by his side, with both his body and mind relax. His weight is equally distributed between his two legs. He is still, and not moving in any direction. He is not in a defending position or an attacking position. There are no poles associated with his body. His mind is relax and empty. He can be considered to be in a Wuji state, i.e., no poles and no opposites, in a state of nothingness. So the beginning of the Opening Form corresponds to a Wuji state. As the Taiji practitioner proceeds with the rest of Form #1 and into Form #2, he changes from a Wuji state to a Taiji state. The rest of the movements in this Form Set has the Taiji practitioner moving from one Taiji state to another Taiji state, until he gets to the last form, “Closing Form.” At the end of the Closing Form, he changes back to a Wuji state. This transformation, from a Wuji state to a Taiji state then to various Taiji states and finally back to a Wuji state, occurs in every Taiji form set in every Taiji style.
Modern Physics and Cosmology: The transformation from a Wuji state to a Taiji state, or from a state of nothingness to a state with poles, actually has some analogs in modern physics and cosmology. In modern physics, there is a concept known as “vacuum polarization.” In quantum electrodynamics, the vacuum is no longer a simple concept, i.e., the nothing in the vacuum can be transformed into something. In particular, the vacuum can be thought of as a sea of equal number of electrons and positrons. The vacuum can generate a virtual electron-positron pair which can then annihilate each other. Since the virtual electrons and positrons are charged, in the presence of an external charged particle or electromagnetic field, the existence of these virtual electron-positron pairs affects, actually reduces, the charge or electromagnetic field of the external charged particle. Such effects have been experimentally observed, and the experimental results match the theoretical predictions. When these virtual electron-positron pairs appear, the vacuum changes from a Wuji state (without pole) to a Taiji state (with poles). When these virtual electron-positron pairs annihilate, the vacuum changes back from a Taiji state to a Wuji state.
In modern cosmology today, the most prevalent theory is the theory of an “Inflationary Universe,” which is very similar, except for two differences, to the traditional Big Bang theory, that states that the universe started from a small volume and then expands. One difference is that very near the beginning of the Big Bang, the universe underwent an enormous expansion (thus the term “inflationary”) for a small fraction of a second. Another difference is that unlike the traditional Big Bang theory, all the matter/energy of the universe did not have to be present during the original Big Bang, but most of the matter/energy can be created during the brief period of inflation or later during the expansion of the universe. Even though this theory might seem ad hoc, it does provide an explanation of several experimentally observed phenomena which otherwise could not be explained.
Astronomical observational data during the last 20 years also strongly suggest that not only that the universe is expanding, but the rate of expansion actually increases with time, and that the energy density of our universe is approximately 20 times larger than the traditional energy density associated with normal matter like galaxies, stars, planets, asteroids, inter-galactic gases, etc. To explain these surprising data, astronomers and physicists postulate that there is something called “Dark Matter” and “Dark Energy” that make up, respectively, approximately 25% and 70% of the universe’s energy density. Dark Matter interacts very weakly with ordinary matter. Dark Energy is especially unusual in that it is gravitationally repulsive. One possibility is that Dark Energy is a new kind of energy associated with the vacuum that is gravitationally repulsive. As the universe expands, more space, or more vacuum, is created, and thus more energy can be created. The vacuum is in a Wuji state, and when matter is created from the vacuum, it is in a Taiji state. Currently we still know very little about Dark Matter and Dark Energy. Hopefully with more theoretical and experimental advances, we can determine whether these postulates are valid.
Summary: Wuji means without pole or the ultimate of nothingness. Taiji means great poles. In Taijiquan, we usually start in a Wuji state, standing erect with equal weight on both feet, with body and mind relax; thus we are in a state with no pole. Then we move from a Wuji state to various Taiji states. In each Taiji state, weight is often non-uniformly distributed between the two legs, arms are usually raised or lower or extended, more emphasis is usually placed on exhaling or inhaling, and the mind is much more alert and focus. We are either in an attack (Yang) mode, or a defense (Yin) mode, or poised to move directly to an attack or defense mode. At the end of the form, we move back from a Taiji state to a Wuji state.
This has some analog in modern physics and cosmology. The vacuum corresponds to nothingness (Wuji state), but it can transform into particle-antiparticle pairs (Taiji state). In modern cosmology, the transformation of the vacuum to energy/matter (Wuji state to Taiji state) may hold the key to understanding modern cosmology in the form of an inflationary universe with accelerating expansion.
 Taijiquan is another name for Taiji. When more emphasis is put on Taiji as a martial art, the term Taijiquan is often used instead of the term Taiji. Taijiquan literally means the “fist of Taiji.”
 This is the meaning of the classic Chinese saying that “four ounces can deflect a thousand pounds.”