Chinese religious and medical thought going back at least to the Warring States period holds that a living person is animated by two distinct kinds of soul rather than one, and the hun are the yang half of the pair, described as ethereal, cloud-like or breath-like, in contrast to the heavier, body-bound po. The hun are conventionally counted as three, the sanhun, and are associated with the higher faculties: consciousness, thought, and the capacity to travel independently of the body, most notably during sleep, when the wandering of a hun outside the body was offered as an explanation for dreaming.
Correlative cosmology, the framework linking bodily organs, seasons, directions and cosmic forces into a single interlocking system that underlies both Chinese medicine and much of Daoist body-cosmology, assigns the hun to the liver and to wood among the five phases (wu xing). This is not a metaphor within the tradition's own terms; a physician or a Daoist adept working from this framework treats liver function and hun stability as genuinely connected, so that disturbances attributed to the hun, restless sleep, vivid or troubling dreams, could be addressed through treatments directed at the liver, and vice versa.
At death, the hun are described as ascending, dispersing upward toward the heavens, which stands in direct and structural contrast to the po's association with the earth and the grave. This asymmetry, one soul-type rising and dispersing, the other remaining bound to the body and the ground, is foundational to how Daoism and Chinese folk religion together account for what happens to a person after death, and to why funerary and ancestral ritual in Chinese practice typically has to address the hun and the po by separate means.