Instead of opposing force by force, a Gung Fu man completes his opponent's movement by accepting his flow of energy as he aims it, and defeats him by borrowing his own force. In order to reconcile oneself to the changing movements of the opponent, a Gung Fu man should first of all understand the true meaning of Yin/Yang, the basic structure of Chinese Gung Fu.
Gung Fu is based on the symbol of the Yin and Yang, a pair of mutually complementary and interdependent forces that act continuously, without cessation, in this universe. In the above symbol, the Yin And Yang are two interlocking parts of 'one whole', each containing within its confines the qualities of its complementary. Etymologically, the charters of Yin and Yang mean darkness and light. The ancient character of Yin, the dark part of the circle, is a drawing of clouds and hill. Yin can represent anything in the universe as: negatives, passiveness, gentleness, internal, insubstantiality, femaleness, moon, darkness, night, etc. The other complementary half of the circle is Yang. The lower part of the character signifies slanting sunrays, while the upper part represents the sun. Yang can represent anything as positives, activeness, firmness, external, substantiality, maleness, sun, brightness, day, etc. The common mistake of most martial artists is to identify these two forces, Yin and Yang, as dualistic (thus the so-called soft style and the firm style). Yin/Yang is one in separate force of one unceasing interplay of movement. They are neither cause nor effect, but should be looked at as sound and echo, or light and shadow. If this 'oneness' is viewed as two separate entities, things are 'whole' and cannot be separated into two parts. When I say the heat makes me perspire, the heat and perspiring are just one process as they are co-existent and the one could not exist but for the other. If a person riding a bicycle wishes to go somewhere, he cannot pump on both the pedals at the same time or not pumping on them at all. In order to go forward, he has to pump on one pedal and release the other. So the movement of going forward requires this 'oneness' of pumping and releasing. Pumping is the result of releasing and vice versa, each being the cause and result of the other. Things do have their complementary, and complementariness co-exist. Instead of mutually exclusive, they are mutually dependent and are a function of each other.
In the Yin/Yang symbol there is a white spot on the black part and a black spot on the white one. This is to illustrate the balance in life, for nothing can survive long by going to either extreme, be it pure Yin (gentleness) or pure Yang (firmness). Notice that the stiffest tree is most easily cracked, while the bamboo or willow survive by bending with the wind. In Gung Fu, Yang (firmness) should be concealed in Yin (gentleness) and Yin in Yang. Thus a Gung Fu man should be soft yet not lax, firm, yet not hard.