Nothing was thought permanent, and yet nothing was destroyed, only its form changed. All aspects of reality possessed within it elements of its opposite. At the heart of every process of change was the repelling-attracting flow between Um and Yang. It was the essence of change. As the Way of Heaven operates, the myriad things develop and grow.
Man receives it and thus possesses life.
The clear part of Chi becomes his vital energy, while the turbid part becomes his physical nature. The identical concept in Korean, Ki, was considered the essence of existence. In a sense Ki can be understood as an energy force of opposites in the same way that negative current and positive current are different, but the unity of these polar elements are required to produce electrical energy. Ki permeates all living things as a submicroscopic Life Force present in every living cell and tissue. The theory of acupuncture in oriental medicine is founded on the premise that the life process is activated and maintained by the flow of Ki.