Taijiquan as a “martial art” is essentially an art of being aware of one’s self in time and moving from a place of stillness, maintaining it in the midst of movement. I understand this place of stillness as “Wuji,” which has many definitions among various philosophical sources: “state of undifferentiated (non)being,” “standing like a mountain,” “unselfconscious oneness,” “empty, yet alive, changeable, agile, quiet.”
“Taiji is born out of Wuji,” the classic states, and it returns to Wuji. Taiji is movement, wuji is empty and still. It is infinity, where one returns to one’s self. Stillness to movement to stillness…. Yin to Yang to Yin and so on. This suggests leaving and returning. Too often we leave and neglect to return. But it is possible that Taiji never leaves Wuji and Wuji is always present in every movement. This is stillness in movement. Your awareness never leaves Wuji even while your body flows in and out of Yin and Yang.
Dragon Journal of Taijiquan 