What is Qi

Qi includes the qi of mind and the bodily qi of the material four great elements. The qi of mind manifests as the breath/energy of the manas; it is the mental factors (caittas) of the manas, such as being arrogant and haughty, full of spirit, dignified in bearing, high-spirited and vigorous, having backbone, ambition, pride, and so on. Bodily qi includes kidney qi, lung qi, stomach qi, spleen qi, liver qi, and heart qi; all the five viscera and six bowels have qi, and indeed qi pervades the meridians throughout the entire body. Qi can carry the blood as it circulates, which is called blood-qi; the body relies on blood-qi for nourishment and operation. Once the supply of blood-qi fails, the six consciousnesses lose the strength to continue functioning and the activities of the five aggregates weaken; or if the circulation of blood-qi becomes disordered, the six consciousnesses become disordered, and one may even go mad. 

The qi of mind can drive and influence bodily qi, and bodily qi can elevate and influence the qi of mind; the two influence each other, and their impact on meditative concentration (samādhi) is considerable. When the qi of mind is not calm and balanced, samādhi will not arise; when bodily qi is not harmonized, samādhi will not appear. Therefore one must regulate the qi of mind and bodily qi. Regulating the qi of mind relies, first, on principle—reasoning things out so that the mind's qi becomes calm and stable—and, second, on good physical constitution with unobstructed circulation of qi and blood; only then can samādhi appear. Regulating bodily qi relies, first, on an ample supply of the necessary nutrients of the four great elements; second, on adjusting the breath and engaging in exercise; and third, on regulation through the qi of mind and mental intention—when the qi of mind is calm and balanced, bodily qi will gradually become calm and balanced as well; this is called "a calm mind and harmonious qi." If bodily qi is disordered and insufficient, the qi of mind will also become disordered and insufficient; the two complement and support each other.

Besides the qi of mind and bodily qi, there is also the qi of karmic obstructions. What is called the qi of karmic obstructions is in fact a force of karmic actions from past lives, or one might call it the inertia and power of karma; this is the most difficult to regulate and overcome, and in most cases one can only passively endure it. If a person has a relatively strong capacity for awakening and discovers where their karmic obstructions lie and discovers their own bad habits, they should find ways to turn them around and overcome them: first, through repentance, to repent away karmic obstructions; second, through making vows, to suppress the karmic obstructions; and third, by cultivating new good habits.