Trigrams Qian (Heaven) and Kun (Earth)
Undivided, whole Fragmented, divided
Qian and Kun, either as trigrams or hexagrams, stand for Heaven and Earth, yin and yang. The trigram Heaven is made up of three yang lines and is pure yang, while the trigram Earth is made up of three yin lines and is pure yin. The trigram Qian is in command of bestowal; the trigram Kun is in command of receiving nourishment. Change refers to the change and transformation of yin and yang. As yin and yang act upon each other they create the six trigrams Fire ☲, Water ☵, Thunder ☳, Lake ☱, Mountain ☶ and Wind ☴. Heaven and Earth are seen as Father and Mother, or Husband and Wife, while the other six trigrams are seen as Sons and Daughters.
When the celestial (yang) is overcome by the mundane (yin), reality is obscured. This is like Heaven mixing with Earth; the yang in the middle of Heaven ☰ enters the palace of Earth ☷, so that the trigram of Earth is filled in and becomes Water ☵. When the mundane takes the position of the celestial, intellectual knowledge and emotions gradually develop. This is like Earth mixing with Heaven: the yin in the middle of Earth goes into the palace of Heaven, so the trigram of Heaven is emptied and becomes Fire ☲. Yin and yang are no longer pure and the true breath is lost. To return to pure yin and yang energy one needs to reverse this process in oneself. When one reverses the process, the trigrams Fire and Water are then seen as the medicine and Heaven and Earth as the crucible and furnace. They are the method or the tools to return to pure yang.