Yang Tai Chi and Taoist Neigong
“In reality the essence of Tai Chi is not found in the external postures, but rather the internal principles, energy, and Qi. Yang is the trigram Chien (heaven), yin is the trigram Kun (earth). Inhaling and retreating represents the principle of the reversal of yin and yang. If we allow the fire (Li) to rise, and the water (kan) to descend, the two will separate. If, however we put the fire under the water, then their positions have reversed. This is called the principle of water and fire complementing each other, or principle of reversal”- Yang Cheng Fu from Self Defense Applications of Tai Chi Chuan [Tai Chi chuan shih-yung fa]