When the heaven and earth first opened, two poles of chaos arose: the pure air ascended to become the sky, and the turbid air descended to the earth. There is a wisp of air in the middle that neither rises nor falls, which is called "Yi Qi". This energy does not belong to heaven and earth, does not belong to yin and yang, and is outside the three realms and five elements. It is the medium for the flow of cause and effect in the world.
