Your opponent’s center, towards which you should direct your attack, is united with the principle of everything in man’s body and spreads into its many parts, which can be divided according to the distinctions of Samjae, Yin and Yang, and In and Out.

When we say that centers are spread throughout the body we are referring more specifically to what are termed kyongnak in Korean traditional medicine. These also constitute the centers of your attack in Taekwondo, thus they are the centers of the opponent’s life and motion. Here we can discern the interrelation between medicine and Taekwondo, and how the methods of saving and killing a man are no different. Who would deny its mysteriousness! This sort of principle finds its origins in the contradiction that the entirety contains each part and every part contains the entirety. This in turn implies a constant tension, which is another aspect of life. This constant tension is both the infinite support of life’s growth and the source of endless threats against life. Life already contains a lethal weapon in its core.

We can discern the body’s centers according to Samjae (Haneul, Tang and Saram). The head, which controls every motion through will, is the Heavenly (Haneul) center. The abdomen, which produces physical vigor, just as the earth is the mother of all things, is the Earthly (Tang) center. The breast, which expresses a vitality between Heaven and Earth, is the center of Man (Saram). There are spots in the center of each of these three where vitality converges. As a result, each of them has been termed high-Danjon, middle-Danjon and low-Danjon respectively. These are vital and highly vulnerable spots.

Heaven regulates every change, thus you can control your opponent’s motion by catching hold of his Heavenly center. The earth is the source of nourishment for of all things, thus you can control your opponent’s vigor by catching hold of his Earthly center. Man is the arbiter of his own life, thus you can catch your opponent’s vitality by catching hold of his center of Man. So it is that when you suffer a blow to the head you collapse and lose consciousness; when you receive a blow to the abdomen you lose your strength and vigor and collapse; and when you receive a shock to your solar plexus the pain immediately interrupts breathing and movement. On the other hand, as the Heavenly center is sensitive to change it is difficult to catch; as the Earthly center lies hidden deep beneath one’s pose it is difficult to reach; and as the center of Man is protected by two arms and a spinning body it is difficult to catch even though one may succeed in touching it.

A center is naturally concealed beneath a surface. However, it is also true that all things possess a path to their center from their surface. Likewise, life’s entirety and each of its parts are intimately interrelated to each other so that the center reveals itself outwardly, manifested in the previously mentioned kyongnak, or vital points of Hyeol.²⁾ Therefore, the targets of a Taekwondo attack upon an opponent’s center may be divided into two main categories: the three centers and the infinite number of vital points that branch out from them.

The system of important kyongnak are grouped into the twelve maek of Jeonggyong³⁾ and the eight maek of Kigyong⁴⁾, all of which correspond to yin and yang. Corresponding to the principle that yin is concealed in shade while yang is exposed to light, the twelve maek of Jeonggyong, which accord to yang, reveal themselves outwardly running along the Ki-hyol and Jeongmaek and connect the inner and outer changes, while the eight maek of Kigyong, which correspond to yin, are concealed within and are not related to any specific department but manage all physiological processes.

A yang kyongnak is exposed while a yin kyongnak is concealed. Just as the core of a toy top regulates its spinning so does the center of a thing naturally control its changes. Thus, what manages change is concealed within near to its center as a yin kyongnak while that which is exposed and in contact with other things and presenting its changes on the surface is a yang kyongnak. Therefore, each of the eight maek of Kigyong manage the changes of vitality that comes from its breaks and connections and its strong and weak, while each of the twelve maek of Jeonggyong reveal them outwardly and deliver their shocks from the outside to the inside so that the eight maek of Kigyong accept them. This is so because, if turned inside out, yin and yang proceed in an inverse manner.

The externally exposed twelve maek of Jeonggyong are spread about every part of the human body to create various vital points. When themselves categorized into their corresponding yin and yang, the twelve maek of Jeonggyong form yin kyongnak along the interior and yang kyongnak along the exterior of the arms and legs. The yin kyongnak concern the functioning of the five viscera⁵⁾ while the yang kyongnak are connected with the functioning of the six entrails.⁶⁾ The five viscera, under the influence of yang kyongnak, continue their functioning without break while the six entrails function intermittently. The center which regulates all change is by nature hidden, while that which is exposed outwardly results from changes in function and breaks in the harmony of the ceaseless inner change. A yang kyongnak is relatively distant from the core of life whereas a yin kyongnak is near. For this reason, you can more easily subdue your opponent by attaining his vital points along the yin kyongnak.

At the point where the flow of vitality stops to become a hyeol, it avoids what is hard and firm and seeks what is soft and flexible, avoiding cold and seeking warmth, shunning the flat for the rugged, and avoiding bumps to seek out the valley between them. This is due to the fact that vitality is the generative power of life, which flows along continuous change.

The hard and firm is more difficult to alter than the soft and flexible. Since change and warmth are different aspects of the same thing, a life seeks out warm spots. Since a change stands out of the shape it avoids lumps. Thus, between a hard and a hard lies a soft, between a flow and a flow exists a stay, and between a strong and a strong is a weak, and all of these are the principles that rule the structure of a life’s body in ceaseless motion. And this is also the appearance of Nature’s body itself. If you observe in the correct way, your eyes can discern your opponent’s weak points with ease, and by moving against according to the correct principles your attacks will reach his weak points as naturally as water by nature flows downward to gather in a low spot.