The Tai Chi Chuan Classic（太極經） was written during the Ming Dynasty (1363-1662 AD) by a Tai Chi Chuan master named Wang Chung Yueh（王宗岳）. In the Classic he discussed the concepts of ‘Tung Keng’（懂勁）and ‘Sheung Chung’（雙重）. These are respectively the right way and the wrong way of applying the theory.
a) The Right Way - Tung Keng（懂勁）
Literally Tung（懂）means to understand while Keng（勁）refers to focused power. The ability to understand and freely apply focused power requires a great deal of thought and practice, and is the stepping stone to mastery. There are three main stages of development we must pass through before we can be said to possess Tung Keng. Firstly, we must through training acquire the ability to detect where our opponent’s Keng lies. Secondly, we must learn how to divert and dilute our opponent’s Keng. Thirdly, we must develop our own Keng to the stage where we can use it to strike decisively at our opponent’s weak points. Once a man has passed through these three stages he can truly be said to possess Tung Keng.
These three stages are intimately connected. Thus, if our opponent attacks and we, having detected his Keng, then divert the attack and counterattack, he may, unless prevented, divert our counterattack and launch a fresh attack, By this time the distance between us will have been closed so that the exchange of blows has become so fast that, if we depend solely on our eyes to detect our opponent’s attacks, our response will be too late. This is where the sensitivity and reflex actions, developed by long training, are of great use to us in detecting, diverting and countering our opponent’s attacks. Events may not always follow this pattern as occasionally we may have to attack before defending. However, it is of vital importance that as soon as we have detected and diverted our opponent’s attack we immediately counter attack decisively, to prevent him continuing his attack.
Continuous practice will develop our awareness of the techniques, sensitivity, mental alertness, judgment, reactions and powers. It will also develop our sense of balance and teach us to destroy that of our opponent. This refers to the void and substantiality of steps in attack and defense. In other words, if we wish to move smoothly as we change from defense to attack or vice versa, we must follow the theory of Yin and Yang. If we move forward, our front leg will become ‘substantial’ meaning it will support our weight while our rear leg will become ‘void’ meaning no weight will rest on it and it will be free to move. The reverse is the case when we move back. ‘Void’ is the Yang, while ‘substantial’ is the Yin. If we are to achieve Tung Keng we must also master this concept. Tung Keng is the Right Way.
b) The Wrong Way Sheung Chung（雙重）
Sheung Chung is the very antithesis of Tung Keng. It is pointless to spend years practicing Tai Chi Chuan and learning all the techniques but remaining ignorant of when and how to apply them. Such a student will lose fight after fight because of Sheung Chung instead of winning fight after fight because of Tung Keng.
Sheung（雙）literally means double while Chung（重）refers to centre as in centre of gravity. The concept means the absence of Yin and Yang, neglecting the difference between the void and the substantial, the hard and the soft. How then could a relatively experienced Tai Chi Chuan practitioner fall into this trap?
Usually the answer is that he loses his temper or coolness of mind in the heat of a fight, becomes tense and uses hardness against hardness, instead of overcoming hardness with softness. Ignorance or neglect of the difference between the void and the substantial means that we will be unable to adapt to the changing circumstances of attack and defence. We will be unable to make the change from hard to soft and vice versa and will always be defeated by a stronger force, even if it is only a brute force, as we are unable to apply the Tai Chi theory of using our opponent’s own force against him.
If we are to avoid Sheung Chung we must ensure that when training we are careful not to use hardness to overcome hardness as sooner or later we will meet an opponent whose force is greater than ours, and we must then lose to him. Normally, whether we attack or defend, only one hand and one leg should be fully committed at any one time; the other hand and the other leg should be ‘void’ so that we are able to change our position as the situation dictates. The use of softness to overcome hardness will also help soothe our nerves, making us calm and collected and confident. It is a great temptation in Pushing Hands to use force to overcome our opponent, especially if we are having difficulty in applying the strategy and tactics, but, if we give in, we will live to regret it. If we persevere, we will improve with experience. In this way we can avoid the perils of Sheung Chung, come to achieve Tung Keng and attain mastery.