The Li trigram (fire in the eight trigrams) is used in the middle school of Neidan meditation to explain the relationship between consciousness and emotion.
Li is recognized as “Shen” or the human spirit emerging from the heart. It is made up of two solid outside yang lines representing “Xing” or natural human consciousness and one broken Yin line representing “Qing” or emotion. In the Southern School document Understanding Reality, Zhang Boduan said “When the two natures (yin and yang) come together, Qing and xing are harmonized.” The middle school Theorist, Li DaoChun espoused the idea that if the Consciousness were kept absolutely still, the emotions would go into emptiness and the mind would revert to a state of pure Yang energy. Since Yang energy is considered to be generative in Daoism, then this is considered to be the correct method of practice. In other words, by submitting the mind to silence, it is possible to maximize yin energy, forcing it to go to its natural extreme and convert to yang energy, thus regenerating the body and mind.