"In Wang, Zong-Yue’s Taiji Classic he states “What is Taiji? It is generated from Wuji and is a pivotal function of movement and stillness. It is the mother of Yin and Yang. When it moves, it divides. At rest it reunites.”
"According to Chinese Daoist scripture, the universe was initially without life. The world had just cooled down from its fiery creation and all was foggy and blurry, without differentiation or separation, with no extremeties or ends. This state was called “Wuji” (literally “no extremity”). Later the existing natural energy divided into two extremes, known as Yin and Yang. This polarity is called Taiji, which means “Grand Ultimate” or “Grand Extremity,” and also means “Very Ultimate” or “Very Extreme.” It is this initial separation which allows and causes all other separations and changes.
"Taiji is the hidden force which is able to lead Wuji into the division of Yin and Yang, and also to lead the divided Yin and Yang to the unity of Wuji. In humans, this hidden force is Yi. Yi is intention and the motivation to action and calmness. Yi is the force which divides Wuji into Yin and Yang, and Yi is also the force which combines Yin and Yang into Wuji. When this hidden force is applied to natural Qi or energy, it is the EMF (electromotive force) which is building up or diminishing. In one sense, Taiji is the first cause of Wuji and of the division into Yin and Yang.
"When Yin and Yang theory is applied to man, its root of action is your Yi (wisdom mind). It is your mind which decides if you will change your Wuji state into the Yin and Yang state, or if you will lead yourself from Yin and Yang into Wuji. This means that your Yi is the EMF which determines the entire situation: your Yin and Yang strategy, actions, or the Qi movements in Taiji Qigong." *
* Dr. Yang, Jwing-Ming, The Essence of Taiji Qigong