qi, in Chinese philosophy, medicine, and religion, the psychophysical energies that permeate the universe.
Early Daoist philosophers and alchemists, who regarded qi as a vital force inhering in the breath and bodily fluids, developed techniques to alter and control the movement of qi within the body; their aim was to achieve physical longevity and spiritual power.
Neo-Confucian philosophers of the Song dynasty (960–1279) regarded qi as emanating from taiji (the Great Ultimate) through li, the dynamic ordering pattern of the world. That tradition, whose ideas predominate in traditional Chinese thought, held that qi is manifest through yang (active) and yin (passive) modes as wuxing, or the Five Phases (wood, metal, earth, water, and fire), which in turn are the basic processes defining the cosmos. See also yinyang.